/diy/ - Do It Yourself

before I attach this usb cable to this device I just want to make 100% certain I've gotten the wiring down on the switch
does this look about right

>>1634058
>does this look about right
yes

I need metal cans to put some projects inside but I don't really know where to source them. I'm thinking like a cylindrical can that has pins on the base and I can put a circuit board inside. Not really large like a whole project box. But something around the size of a typical vacuum tube or very slightly larger. I'd like to use the cans for emi shielding of sensitive circuitry and for diy oven stabilized voltage and frequency references.

I briefly looked into metal vacuum tube shields as potential general purpose shield cans but the tops are typically open and they have a spring inside. I could probably modify them to suit my needs without too much hassle. Another plus is they fit a tube socket which means the base and the pins are already included. I also looked into metal centrifuge tubes which are also a good size and have a closed top. Downside is they are harder to find, are generally more expensive, and when you do find them they tend to be used and I don't exactly know what they've been in contact with. Plus I'd have to come up with a solution for the base and the pins myself.

I'm open to other suggestions but just don't tell me to machine my own because I don't have the tools to do that.

>>1634051
4051/52/53

>>1634002
Are you the continuous earbud bud?
So regardless of the highly advanced measurement techniques, do you have any idea how are you going to design an amplifier that would work over a wide range of impedances from 8 to 600 as you stated, and also sound good or at all? You would probably need to build 10 different amplifiers and switch between them dynamically. That should be your first task before you even start looking into the sensing and switching techniques.

>>1634077
Can you use a sample size paint can?
That would probably be the cheapest and easiest to get your hands on.

>>1634157
I was going for something a bit taller and thinner in form factor but it'll still work. It's on the table as an alternative option.

>>1633847
I am glad to see that. I almost suggested the 73871 but those aren't gonna handle 5V@2A and they aren't going to charge more than 2P without timing out

>>1633907
"Plan to throw one out - you will anyway"
t.Fred Brooks, _The Mythical Man-Month_
>custom footprint
y tho
>fix this
how thicc do you think the plating on a plated through-hole is, anyway?
quick fix: solder the drilled-out connections topside too
long term fix: check your connections and don't forget old Pythagoras when designing round holes for square pins
recommendation: get smaller wire for bodging (30AWG is great)

>>1634077
>EMI shielding
can you get copper pipe or tubing and end caps? or even just straight copper tubing which you could close with copper or aluminum tape?
you might ask the amateur radio guys, that sort of thing is their wheelhouse
>oven stabilized
you'd probably want to line the inside with something heat-retaining due to copper's excellent thermal conductivity
>what they've been in contact with
>not importing the highest quality Iranian yellowcake residue
fucking casual

>>1634051
>14.88n

are (lithium cell) battery charger/tender/power control units custom designed for the cells they're gonna use?

in other words, can I yoink a charging/power circuit from, say, a portable power bank and then hook up my own cells to it unmodified?

>>1634241
>designed for
yes
>yoink
it's your funeral

am i correct in assuming an opamp's output works somewhat like this?
for example if both inputs are the same(difference being 0), the output will be average between v+ and v-

>>1634273
Kind of, but the slope in the middle is so steep you can usually assume it's a vertical line, open loop gain is (usually) over 9000.

I'm wanting to have 50 or so buttons as peripherals for a single microcontroller, which will output digital data based on the arrangement of those buttons. Multiple buttons will be pressed at the same time. As I see it I have a few options:
Firstly is to use the ADC pins and some sort of resistor ladder like on a car's steering wheel console. Possibly more than one of these in order to stop noise from being an issue. Limited refresh rate.
Secondly is to use chains of PISO shift registers, which would have also a limited refresh rate but still might be the best method.
Thirdly would be some form of 1-of-x to binary encoder made from multiple ICs. The advantage of this method would be I probably wouldn't even need an MCU for encoding the data since it's asynchronous, the data would be output as-is to an MCU or raspi or serial port or something, where the real work would take place.
All options will encounter issues with switch bouncing if I don't plan ahead properly, but if I use a single ceramic capacitor per button and have each button be a SPDT tied to both Vcc and GND, I don't think I'll have any bouncing unless the contacts somehow bounce from one contact to the other and back.
Thoughts on which path to pursue? The project is some form of musical keyboard to test with custom waveform generating software of some kind.

>>1634309
What's wrong with multiplexing exactly?

>>1634314
You mean time division multiplexing with the PISO shift registers? Nothing much, but the delays could turn out to be significant with so many chained together. Not sure what data format to turn them into before transmitting either, keeping them as the serial output of the shift registers and having the two clock-lines' timing done off-board could work. Compared to a resistor ladder and ADC it uses a lot more ICs but less passives.

Also the 1 of x encoder would need to be a 4+ of x encoder since multiple notes would need to be played at once.

There's 12 keyboard keys per octave, so 4 octaves would mean 48 keys and therefore 6 shift registers. Which sounds like a reasonable count, but a prototype would likely only use half of that.

>>1634273
yes indeed, the ideal opamp is modeled as Vout = (V+ - V-) * Av
in reality, the zero point can be offset by several factors (including but not limited to input bias current * the difference in input resistance, input offset current * input resistance, input offset voltage) which you can mostly neglect when dealing with ac-coupled signals at moderate gains but which become a source of error to be compensated or tolerated where dc precision needs require it

>>1634314
rollover, I'd imagine

>>1634309
>which would have also a limited refresh rate
tens of thousands of times per second should be fast enough for an electronic music or HID application
what the 74HC595 does for output expansion, the 74HC165 does for input expansion. the only additional part required is a shared inverter for the ~PL inputs (which should be the inverse of ~SS). then you can stream the entire panel status into memory with a single, multi-byte SPI read cycle
debounce in software, you'll be able to see the rising edge that much quicker

>>1634320
>debounce in software
Will I need debouncing at all with pic related? Capacitance set such that the edge is quick but it retains a voltage for the time it takes for the contacts to move. The 74HC165 was what I had my eyes on. Assuming 100ms as this contact movement time, the maximum input current of 1µA for the shift register, and a 1V shift to stay mostly within the CMOS specs, results in a needed capacitance of 100nF. Might be able to cut that 100ms down closer to 10ms. Shorting 100nF at regular intervals wouldn't be awful, would it? I might want an extra 1µF across the rails for each switch.
Also I didn't know you could debounce multiplexed data in software, but I guess it makes sense. I don't plan on simply storing it in memory though, I want to send it straight to software to process it live and pump it out the speakers.

What is this rollover you were referring to?

>>1634320
>>1634324
Oh and as far as time goes, if I require that the whole system of 48 keys is updated 200 times a second, that requires a clock frequency (and bitrate) of 9600Hz, which is both easily viable and a surprisingly standard value for serial communications. Ignoring that extra pulse at the start/end to clock the registers in the first place, that is. I may setup some sort of more synchronous method of delivering that pulse.

This looks like the sort of SPDT button I'm likely to use:
https://www.aliexpress.com/item/32957920446.html
A tiny microswitch, likely with a pretty short contact-to-contact delay on it. But mounting might prove an issue. I don't want the whole thing to be mounted with a massive PCB, so I'd have to use those holes to mount the microswitches. Sounds like a waste of a hundred bolts, so I may see about cutting pins for that purpose on a laser cutter that fit into laser-cut brackets on either side. The switches are 6mm wide, so 12mm acrylic would make decent pins with room for 3mm acrylic stands on either end. The fit would have to be snug, meaning a decent amount of trial and error, especially with the variable kerf width on 12mm acrylic.

Also why aren't there any videos on youtube where people have taken switches apart to show the contacts bouncing in slow motion?

>>1634324
wouldn't you need a little bit of R for C to act as RC

>>1634338
It's not meant to, there's no schmitt trigger happening there. The capacitor is just there to hold the voltage of the previous state of the switch while the centre contact is floating, like in a sample+hold circuit. Otherwise, since there aren't any pullups or pulldowns, the value at the IC would be floating for a split second.

any idea what this chip is? It's on a portable tape recorder
CHMC S5702 D668

Is the forward voltage of a diode consirdered avanced knowledge? I'm currently doing a circuit design internship and the other intern that I work with didn't know what forward voltage was and didn't know what a mosfet was. Am I being harsh or is this dude retarded/shouldn't be a circuit designer?

>>1634343
>Is the forward voltage of a diode consirdered avanced knowledge
It really shouldn't be, but arguably if he's working only in circumstances where he'd never have to consider it it could be excusable. Same applies to the MOSFET but to a much lesser extent. How many years have you been studying for already?

>>1634342
Can't find shit, captain. What ICs are around it/wired into it? Do the lines coming from the motor(s), microphone, or write head go to it?

>>1634346
it is from a scrapped submarine.

>>1634346
Here's the full board.
All of the chips seem very obscure/Chinese
The top one seems to be an audio amplifier (D2622A), though it also seems to be connected to the driver motor for some reason.

The far left chip is an FM/AM radio IC, CD2003GB

>>1634345
We are building a device that uses LEDs to simulate different spectrums. I have one more semester of school left (3.5 years of study).

>>1634346
>>1634348
holy fuck 4chan compressed the shit out of that picture, I don't know what the fuck happened

anyway, that gray/white wire pair at the bottom seem to be connected to the record/write head. I don't know if it's some kind of playback controller or what because all of the control logic is handled mechanically by a series of levers and gears beneath the board, nothing electronic to control

>>1634342
CHMC are motor drivers
for example
https://www.ebay.com/itm/CHMC-D5954-SOP-28-4-CHANNEL-DRIVER-MOTOR-DRIVER-/401706327478

>>1634349
Like a VU meter, or something closer to a dot-matrix with something along the lines of a mock Lissajous pattern on it? Be funny if it was an autism meter, because you know, spectrum.
I'd wager he's not the most attentive person after 3 years of not learning what a MOSFET is.

>>1634358
You could say it's closer to the dot-matrix. I'm just kinda pissed because this guy has had two technician internships before but somehow knows nothing that an engineer would know.

>>1634324
correct, if you can get SPDT push switches you won't need debouncing
>contact movement time
unless you're gigging out in extreme temperatures, you can probably rely on the 25°C value of 100nA
>100nF
you would need to regulate the maximum current. they claim 1A 125VAC capability, I'd limit peak current thru the switch to 50% or less (so 10 ohm series resistor)
>Also I didn't know you could debounce multiplexed data in software
absolutely. it's a simple matter of saving the last n raw samples of the switches and combining each switch's past states somehow, say, with a simple logical-OR (for minimum key-down latency at the expense of maximum key-up latency) or a logical-AND (vice-versa), then sending that cooked set of key states to your voices. piss-easy if using 64-bit integer types to hold whole-keyboard states
>rollover
the number of simultaneously pressed keys a keyboard can detect without error
https://en.wikipedia.org/wiki/Rollover_%28key%29

>>1634332
>serial communications
I mean you *could*, just by adding extra '165s and manually placing framing bits where needed, and somehow distinguishing the first byte, but personally I'd rather generate the framing on the sw side than adjust to the keyboard's, so I favor SPI
>microswitch
nothing about operating life. that's disappointing
>mounting
consider boards for octave sections that end-stack using right-angle pin headers/sockets, Pic related. maybe a dowel, sized/turned to fit just freely through the holes, on which all the switches ride, with non-threaded spacers/plates between and springs/nuts at the ends to keep everything tight
>videos
thousands of frames per second at submicron scale? yeah nah. contact bounce is much more clearly viewed on an oscilloscope. bah just figure 10-20ms

>>1634348
is it variable speed? a simple transistor circuit inside the motor is usual for fixed-speed regulation

>>1634343
absolutely Brahmin

>>1634369
>pic related
>doesn't pic related

>>1634369
>regulate the maximum current
Yes now that I think about it it's probably a good idea to avoid switch arcing, even with 10nF. Just 2 resistors on the rails powering the switches would probably work fine, instead of having 2 for each switch. Still, I'd need to ensure they charge in significantly less time than the refresh rate, and don't inhibit the debouncing at all. Good thing I've an oscilloscope right next to me!
>keyboard rollover
Ah, that thing my laptop's built-in keyboard has a surprising amount of? Shouldn't be an issue since I'm not encoding a finite number of "which" keys are depressed or some other compactifying matrix, but rather reading out the state of every single key.
>extra 165s
Oh no I didn't mean like that, I meant more some sort of timing circuit such that I could send the "parallel in" command on a seperate line synchronously with the main clock, and have a circuit just wait for half the clock period and add a second pulse in there. Though now that I think of it, a standard computer serial port only has the one data output line, doesn't it?
>nothing about operating life
I don't exactly intend on jamming away on it for long periods of time, it's more of a proof of concept for the software side than anything else. It's the only reasonably priced momentary switch too.
>stacked boards
That might not be too bad. Plus it lets me construct a beta 2-octave board and have it not be a waste when I build it into a 4-octave board. Or I could have even and odd single-octave boards with 1 and 2 SRs respectively such that I can make an even smaller test board. Sounds like some fun PCB design. Hopefully I can use the 200*300mm of single-sided FR-4 I've got lying about, as opposed to the few rectangles of double-sided I'd rather save. I guess I'd have four pulldown resistors on the 2-SR board that you remove before connecting it to the 1-SR board, so it just sends zeroes.

>submicron
I figured they'd bounce at least 0.1mm with a beefy mains switch.

>>1634309

seems to me all your requirements can be met by using the control PCB from a computer keyboard (the PS/2 variety, not USB) from the thrift store. some ''gaming keyboard'' specs say they can handle 6 simultaneous keys. IBM's F and M keyboards can supposedly handle ALL simultaneous keys.

>>1634388
Ok with an SPDT switch in parallel with a voltage divider, I'm getting pic related, where the ~2.2V is where the centre contact isn't touching anything. Giving myself 10ms and 100nA does let me decrease my capacitance to closer to 1nF, which should be fine shorted through the switch, no? Kinda hard to measure those currents, but the period for which the current will be high and the total amount of energy will be low enough that I don't think I'll worry. And a single ~10µF across the rails at the start of each board should eliminate any ripple on the rails themselves.

>>1634400
The data would be a pain to process.

>>1634411
Tried testing with a 2.2nF I pulled off some other breadboard and the scope's 1M impedance caused it to not work as well as it could have. Using a 1µF cap I had lying about mostly worked, but it had some funny artefacts in the waveform, likely due to the cap not fully discharging on the bounces before final contact.
Also this analog scope's digital mode is proving very useful, great choice of mine. I've also figured out how to save a waveform, but not how to delete one from non-volatile-memory. And no I can't find my bag of capacitors.

>>1634400
>IBM's F and M keyboards can supposedly handle ALL simultaneous keys.
Not true, most of them are pretty standard scan grids, worst case 2 key rollover for most.

>>1634421
I could strategically choose keys that are unlikely to be pressed together or twice in a row for those ones, but it's still a pain. I can get the shift registers for cheaper than one of those IBM chips, and get more coherent data out of it.

>>1634388
>2 resistors on the rails
I thought about that for a long minute, but then I thought, what happens when the parallel-load pin goes high just as a key switch is making in the other state? possibly a very loud error depending on polyphony and the sustain level of your patch
>refresh rate
probably good enough to test a tone generator but could feel a hair laggy
>oscilloscope
not a filthy casual confirmed
>rollover
was telling the other anon why you were reluctant to multiplex
>async serial stuff
you need to frame your data if you expect async serial ports to make sense of it, Pic related (for real this time) shows 8N1 framing. each 8-bit byte requires a start bit (0, in positive-TTL logic) and a stop bit (logic 1, likewise) thus takes 10 bit times. a receiver won't start until it sees a 0 start bit and will raise a framing error if the stop bit is not 1. therefore for 4 octaves you must have at least 60 bits of SR. might be educational to fire up a terminal program, hold down a key, and watch it on the scope
>main clock
if there were a shared reference clock it would be synchronous
the interface circuit would have to supply some clock if one is not already available. le ebin 8-pin micro with a well-calibrated internal oscillator might be good enough, at worst, you add a xtal and load caps. plenty of pins/time left for an auto-scan feature
>even/odd
one of the few nice things about async serial is that senders can idle at will when not transmitting a frame. if your framed bytes don't take up a whole number of SRs, you can send 0 or more space (1) bits between characters, which you might if you just wanted to send 2 bytes/octave (80 bit times) and use the surplus 4 bits for non-scale switches, board ID, MIDI channels, modulation triggers, …

>>1634411
4ms break to make is decent. are those the actual switches?
>total energy
on second thought, I wouldn't worry if it were my test rig

>>1634428
then how the hell you gonna play the devil's tri-tone?

>>1634431
>what happens when the parallel-load pin goes high just as a key switch is making in the other state
With the resistors involved, I don't think the voltages on the other buttons would dive to Vcc, but you might be right, I'd have to draw it as a diagram and see.
>async
No I didn't mean asynchronous, just that I'd have a small delay in the keyboard circuitry itself to offset an extra clock pulse to clock the shift register with the parallel-load enabled. The 165 IC itself has the function that the CLK input is used both for L-shift and for parallel-load, depending on the state of a third pin, meaning the CLK needs an extra pulse in there aside from the regular refreshes. Kinda wish it didn't to be honest. Pic related.
I'll probably just feed the data into a raspberry pi with the pi itself outputting CLK and LOAD for testing, no MCU required. From there I'll see if either my software can be simplified to fit on an MCU or somehow build a desktop application via USB or something, which might require some more complicated synchronicity or lack thereof. And get that godawful RS232's ±12V out of my face.
>are those the actual switches
That was a SPDT toggle I had lying about. Since a momentary switch will have unidirectional springiness / the lever doesn't have to move past an area with no torque, I imagine this timeframe will be smaller with the microswitch. Might buy a similar microswitch for a few dollars from the local scumbags to test.
>I wouldn't worry if it were my test rig
What, so go with no current limiting? I'll bust out one of my 74HC04s so I can run the capacitor experiments with CMOS impedances and see what kind of results I get with and without current limiting. Assuming a time constant of 500ns with a capacitance of 1nF, that's a 500Ω resistance, with maximum current of 10mA. Which is easily passable for long-term use.

>>1634431
>>1634447
Shit, you're right. Resistor in series with each capacitor would make the next most sense. Before or after the line coming off to the register, not sure which one makes more sense yet.

>>1634421
>>IBM's F and M keyboards can supposedly handle ALL simultaneous keys.
>Not true, most of them are pretty standard scan grids, worst case 2 key rollover for most.

i double checked. the M keyboard is kinda normal, but the model F (which i own) has n-key rollover: it can handle ALL simultaneous keys.
https://www.youtube.com/watch?v=PaKzZc8KReQ

I have a light like this and i need to check if power is going into the socket into which the tube plugs in, but if i understand it correctly to start this kind of light there is some device there that generates thousands of volts. Does that mean that if i try to stick my multimeter probes into those light tube contacts, i will try to pump several kv through the multimeter and fry it and possibly me along with it?

>>1634453
Unlimited roll-over requires a diode per key. Which isn't an issue if you're already using a relatively expensive switch for every key. Once you reduce the switch to a plastic bubble, the diode costs more than the switch so most modern keyboards only have diodes for ctrl/shift/alt.

Without diodes, you're safe if only one key is pressed in each row and one in each column. A phantom key occurs if you press three keys (A,B,C), where A is in the same row as B and the same column as C, and A lacks a diode. It will appear from a scan that the key in the fourth corner (the same column as B and the same row as C) is also pressed.

>>1634452
Ok so there's basically no difference between whether the resistor is in series with the switch's middle pin, or in series with the capacitor to ground because of the large input impedance of the CMOS IC (pic related). I'll do whichever one looks better on the PCB.
Having any resistor will cause the charge/discharge time of the capacitor to be noticeably finite, leading to a curve of some sort at the CMOS IC's input. However, since I'm sampling into D-FFs, this analog imprecision will not propagate at all and won't cause any funky feedback issues, just cause the value of that bit to be chosen somewhat at random. This will be an issue if it happens multiple times in a row, but if the refreshing happens much slower than this time constant, this will never happen. To decrease the chance of this, I'll calculate the required resistor off the maximum allowable current, not off the maximum time constant. If the refresh rate (and by extension, the capacitor charge/discharge rate) is fast enough, the difference caused by this missed bit won't be noticeable at all.
So it looks like there's no reason aside from part count not to add these resistors, and it's not too many parts anyhow.

The only problem left is how large everything needs to be. 20mm-wide keys seems to be a fairly low value, but still an acceptable one. Same for 75mm long keys. Hence each octave will be 140mm wide, which fits comfortably on a mousepad if you happen to want a small keyboard. Since the ICs have a footprint of 10mm in width (including the holes) and the switches are 12mm deep, ideally I can make the PCB about 25mm long and 125mm wide. That latter dimension will depend on the pin-header reach, but will likely be closer to 135mm. The problem with such a narrow PCB is it means the frame and keys needs to overhang the PCB, so the PCB can't be a structural element in itself. Which isn't an issue particularly, but it will mean some thought will be required.

>>1634447
>needs an extra pulse in there
does it? the first bit would already be on the output when ~SS is low and (due to the inverter) ~PL is negated. you could use mode 0 (idle low, read on SCK asserting edge and write on negating edge) and read each bit correctly
also 100% compatible with a chain of 'HC595s in case you would care to combine output expansion on the same slave select
>toggle
micro switches are known for their snap action so probably safe to assume it's at least as fast, and size is on the micro's side
>desktop application
STM32F4* are pretty well-resourced. surely you'll like to have that FPU and SIMD and native USB so you can enumerate as a native MIDI device later. linking the key scanner and synth via the MIDI protocol (or callbacks similar to MIDI commands) might not be a bad idea, even virtually. it would make recording, engineering, and playing back pathological sequences easy in case you should need to
>no current limiting?
maybe go with no cap. if bounce time is less than the scan time, as here (<1ms), then the worst that happens is the possibility of a one-scan-cycle delay in that key being registered as down, so a simple pulldown would do, and maybe you can find SPST switches cheaper. metastability from bounce would resolve well within one scan cycle so wouldn't result in double triggering (i.e. a second key-down message). you could even turn up the scan rate. going from 200 to 500 puts you about 1m closer to the speaker latency-equivalent, where you could get some nice, tight chords if you needed to

>>1634461
don't guess. remove reflector/cover, probe power input directly
also /ohm/ RULE 0

>>1634461
Remove the tubes and measure the voltage you want to check for.

>>1634476
>the first bit would already be on the output when ~SS is low
Oh yeah you're right, that simplifies things a lot. Man I'd like to have been doing electronics back when chaining 165s and 595s was a done thing.
>safe to assume it's at least as fast
That's what I thought.
>STM32
Yes I was thinking about using a micro like that as the main driver for after all the testing is done, either just for USB interfacing, or for handling all the custom waveform stuff too. Problem with the latter one is I plan on having a fairly in-depth UI, where one manipulates individual points on a waveform, and the points on static filters (don't shift their corner frequencies with different notes) and dynamic filters (do shift their corner frequencies with different notes), and the points on sustain curves. There would also be a fourier toggle to see what your FFT will look like. So probably best done on a computer.
>FPU and SIMD and native USB
No clue what those mean, but yes being able to be a normal midi keyboard would be nice. As far as using the keyboard with custom software, would having it act as a midi keyboard be ideal? Custom USB drivers are even more out of my league than writing a GUI.
>maybe go with no cap
Would that be non much worse than cap+resistor? Reducing the passives on each board to just the decoupling caps across the ICs (and the unconnected slaves' pulldown) would be nice to see. I'll test what the output of my 74HC04 looks like now. Neither of the datasheets have a CMOS input diagram, but I imagine they're the same.

>>1634489
Ok with no cap I'm getting a bit of this shit going on with the falling edges (rising edges before the inverter). Looks like there isn't any glaring issue, as expected.

>>1634461
Pretty sure there's never a high voltage between each side's two pins, they're just supposed to provide heating. The HV only goes across side to the other, if I recall correctly. So probably see about measuring the two close-together pins' voltages. Is the ballast making a clicking noise?

>>1634490
I said this shit:

>>1634490
And here's an initial design, to be made with a laser cutter. A few fine changes, like making room for washers between the keys, adding a frame piece to keep the microswitches from bending on their pins, adding the headers on either side, making the black keys not tiny, possibly a few other changes. A wider shaft at the back would make the keys less-prone to rocking. I've no idea how to cut the keys from two directions. Now that I look at it, the resultant 3mm thickness of the keys would leave them pretty flimsy, so leaving them 6mm all the way through and just moving the shaft up would help. The PCB design will be a nightmare though.

>>1634489
life was slower and simpler back then. we (by which I mean the designers of the almost-scrap boards I bought at WeirdStuff Warehouse) used 'LS373s and 'LS374s and the narrower D latches when we had a onesie-twosie signal. sometimes we'd run the whole processor bus (tri-state buffered, ofc) up to the frontpanel
DATASHEETS
ON
WOOD
SONNY
and you ordered 'em out of Digi-Key's printed catalogue, from the "Books" section
Ctrl+F was learning to read quicker before you took a belt on the ass
ohh but we had the Bobs. Pease, and especially bless Widlar
anyway before that little ramble what I meant to say was YOUR TIME IS NOW. the micro hasn't killed us all yet. besides it sure beats the hell out of the lame, slow peripherals then-Philips was putting out for I2C
>best done on a computer.
the F4 series is a ~150MHz Cortex-M4 core. some of these have video accelerators, TFT panel output, built-in resistive touch sensing, and SDRAM controllers (also I2S). it could run linux if you were so inclined and you gave it enough RAM
>would having it act as a midi keyboard be ideal
sure. you can use the system exclusive messages to send private data and commands from your patch librarian on the PC side
>custom USB
if you're USB MIDI class-compliant you shouldn't need a driver. I don't know shit about windows though, you might need to write a device info file, depending on version
>no cap
the only drawback would be +1 frame uncertainty in which scan cycle the key will be sent as down
>no pulldown
now add the pulldown. if you were feeling especially creative you might use 1206 resistors or jumpers and turn them upside down for the white keys kek

>>1634505
I think I've seen some of those printed datasheet books at my physics lab, could trawl through them for hours, assuming doing so wouldn't destroy the binding. Be nice to get some of ebay or wherever, just because.
>TFT panel output, etc.
It might be viable then, though using bare-minimum for USB operation would likely be a bit cheaper. I guess it comes down to how much work the software end would be in either case.
>if you're USB MIDI class-compliant you shouldn't need a driver.
That's what I was thinking, and impersonating that standard in software (or with babby libraries) should be a fairly simple thing to do. Not like I'm missing any data by going through midi to the computer, though I think I would have to have the micro tell the computer what octave I'm in for casual use.
>the only drawback would be +1 frame uncertainty in which scan cycle the key will be sent as down
But I'd get that anyhow with a cap and resistor. I'm definitely going for path of least passives.
Adding a pulldown to each switch output would make little difference, right? There's bouncing either way without a capacitor to smooth things over. The pulldown I was talking about were for the secondary octave board, with only one 74HC165 on it. The primary board has two, and hence room for 16 channels on it, but only has 12 keys, so it has 4 extra terminals to one side in order to take the switch inputs from the secondary board. But if the secondary board isn't plugged in, those inputs will be floating, so I'd have 4 solder bridges or cuttable wires going to a pulldown resistor. Though now that I think about it I could just short them to ground, no need for a resistor. Using a DIP switch instead of the cuttable link or solder bridge might be a good idea, so you can more easily undo/redo the change.
Theoretically, with support on the software end, you could stack over 10 of these together, alternating primary and secondary. Of course there are barely 10 audible octaves in the first place.

>>1634499
noice digits
I think you'll want some kind of bearing on those switches, they might cut into the back of the key when you press on them. you would probably want them reproducible instead of e.g. bending the levers. I'm thinking a U-shape with the slot as thin as possible. you could modify the shape of the bottom to optimize the action if you gave enough of a fuck. delrin would of course be the optimum material for this, but I don't think you can laser cut it. I'd love to watch someone try :^)
>how to cut the keys from two directions
I don't think you do. I think you might want to borrow a drill press for that
>PCB design will be a nightmare
the support brackets probably won't mind a slot to accommodate the board, would they? esp if you're not putting components too near them

>>1634517
>some kind of bearing on those switches
There are microswitches with rollers on the ends, they're 2-3 times the price though. I figured wear wouldn't be an issue but at that angle it might be. Maybe a layer of delrin or ptfe on the underside of the switches would help, but I still wouldn't like that chisel-shaped piece of metal bearing on them. A lump on the bottom of the key to make it actuate against the side of the lever may be an option, with a slot in the face of the key to fit into. Actually microswitches with no lever and just the button would likely work fine for this, I don't exactly need the extra travel.
>drill press
Might be an option, have one at my folk's place, so the timing between that and being at uni with the maker space's laser cutter would have to be right. No actual drill press vice though, since it was mainly used for medium-sized woodwork.
I've seen someone laser cut a 90° bracket for something akin to a dial indicator holder, but in their case they were using 12mm acrylic to make a 12mm wide bracket, so flipping the part around and running the same pass again with the same cut settings was fairly simple. Worked pretty well, though I think the fit was a bit too snug.
>a slot to accommodate the board
This is what they look like by default, but I'm not too sure about the 4mm hole drilled all the way through them. I wouldn't want M3 screws or smaller, but it's too close to the walls and fairly long, making it a tough operation. The general idea is this will drill through the PCB too and clamp stuff together somehow, but it needs some refinement. The 4mm hole would be hell to route half a dozen traces around with my homebrew PCB technique. Not sure if I'd use a nut or just thread the bolt into the acrylic. Not even sure where to get this sort of roundstock either, I guess I'll check ali for brass tubing or something before the sale is up.
I'm starting the KiCAD file now, just to see how many jumpers a single-sided board will take.

I'm trying to find the feedback factor (β) for a transconductance feedback amplifier. iIve done the calculations for β (underlined) however I'm not very confident in the result and was hoping for someone to confirm/correct it for me.
Also, wondering if my calculations for R11 (-->) and R22 (<--) are correct as well.

how does a long tailed pair work on low voltages?
if the difference between Vin and Vee is under the Vbe of the transistor(0.7v) there shouldnt be any current and no output difference?
am i missing something?

>>1634531
0.7V isn't some hard cutoff point, it's an exponential curve, probably following the Shockley diode equation. Putting 0.1V into it will cause a very low current to flow, maybe in the realm of 10s of µA, through the base.

>>1634363
You may not like me saying this but it sounds like your friend will go further than you in life. You sound like a typical bitter ungrateful autist. Your friend sounds outgoing, friendly, and resourceful. He landed two internships with little knowledge, you landed nothing. Why? Because he will fit better into a company and can work with other people better than a bitter autistic show-off like you can.

Having knowledge and skills is important, sure but the social component is much more important and you seem to lack it entirely.

>>1634516
>simple thing to do
absolutely, but you may judge the chip you end up using by the libraries. MIDI at the data link level is pretty basic as you might expect from a 1970s creation: async serial, 31250bps, 3-byte packets, MSB=1 as start of packet marker, 4-bit command code, 4-bit channel, 14-bit parameters. meant to be easy for early microprocessors to parse
>micro tell the computer
9x nn vv - Note On/Off
x: channel
n: note (60 = middle C)
v: velocity (0=key up, 127 = full key down, and in between)
>Adding a pulldown to each switch output would make little difference
it's a floating input, you don't want it. you can't guarantee which way it will fall, and may differ from input to input and part to part. I don't think you'd want stuck keys. also if there is any concern about power from shoot-through, the pulldown would eliminate it
you wouldn't have to drill for 1206s on the bottom and you can fit 1-3 traces between the pads
>those inputs will be floating
I thought you liked floating inputs
without the cap the pulldown would be plenty to guarantee no note-ons from those channels. a double pulldown vs the switch would be no big deal and requires no configuration

>>1634523
>don't need the extra travel
but it's a convenient spring for the key. to use just the button part will require that you tighten tolerances for a usably even action, and also make the board positioning that much more critical
>no vise
that hurts. you're gonna want some kind of jig for side drilling
>maker space with no drill press
sad!
shift the middle bracket to the left a bit
>hell to route half a dozen traces around
if your fab isn't all that strong, give yourself some extra room. extend the board out toward the player if you need more traces
>round stock
hardware stores probably have at least aluminum and steel round stock. they might also have threaded rod with which (plus a big bag o nuts and star washers) you could stabilize all the switches

>>1634542
But they'll only be floating when the switch is in an intermediate state (i.e. being turned on or turned off), it's still going to be an SPDT that pulls itself both high and low, so it doesn't matter which way it falls during that short period.
>1206s
>1-3 traces between pads
>with my shitty etching setup
We'll see, haven't done a proper test on that stuff yet.

>a convenient spring for the key
Yes, but I'm also somewhat worried about permanent deformation from vigorous playing. The microswitch buttons themselves have a small spring in them that the lever bears on anyhow, so it shouldn't make much difference. I could probably take the lever out of these microswitches (I've had one apart before) and just use them like that. I'll test that tomorrow (pic related, but with tears) and make a decision afterwards.
>you're gonna want some kind of jig for side drilling
Yeah it shouldn't be too difficult. I'm more worried about the two sides of some of the white keys bending in on me, since they'll only be 3mm thick. Gotta jam something in there I guess.
>give yourself some extra room
Will probably do that seeing as I barely have enough room on either side for 9-pin 2.54mm pitch headers on the sides. But if I'm making jumper wires anyway, I might as go all the way and make the PCB a maze of uninsulated solid-core copper wires, so adding more to the bird's nest shouldn't be problem, at least not aesthetically. The real problem is how to add jumper wires in KiCAD's PCB view that don't disturb the netlist and without messing about in eeschema.
>round stock
Might purchase this: https://www.aliexpress.com/item/32949306406.html
gives me 300mm that can be cut into two lengths for one primary and one secondary. Should be sturdy enough, biggest issue might end up being color matching. I guess black acrylic will work with it.

>>1634535
Not him but I am not sure I understand the point of your banter. "Friendly and resourceful" may mean an idiot with connections. It is no secret that there are two kinds of people, those who get shit done and then there are others who get promoted. And even after landing two internships or whatever, it is still too early in the game and he might have gotten lucky and regression to the mean will eventually catch up with him.

>>1634523
>still SPDT
ah ok
>vigorous playing
I'd add a stop bar to the bottom of the key bed, maybe glue in acrylic round stock (if not hardware store, then try a sign shop) with a rubber sheet glued over it. that should keep the switch levers from being overextended. speaking of vigorous playing, on the other side be sure to make room for a key return stop somewhere to keep them from flapping about above home position
>Gotta jam something in there I guess
cut out a jig on the laser cutter of course
>jumper wires in KiCAD's PCB view
>without disturbing the netlist
sounds like you want another copper layer
>95.5% positive feedback
that tubing looks ok but is there no Hammer Hardware in the New Zealand outback? are there no local arts-and-crafts supply shops? no workhouses?

>>1634577
I believe that's a devotee of Jordan Peterson. afaik there's no good way fixing daddy issues on a blue board

Has anyone upgraded from LTSpice IV to VII? All schematics open fine but every single one of them fail to load the voltage source:
Couldn't find symbol(s) : voltage-
Are the old symbols compatible if I find them add them manually to this computer?

>>1634077
Other suggestion :
Use 2 layer PCB with ground plane on the bottom (or 4 layer if you need more routing). Cut some copper sheet into a rectangle with rectangular notches cut out the corner. Bend sheet into a cover. Solder cover to PCB.

>>1634106
Not him, but just make an amplifier which can deliver both the voltage for 600 Ohm and the current for 8 Ohm and power limit it so you don't blow someone's eardrums out.

Headphone amplifiers aren't impedance matched, it's purely the voltage/current limits inherent in the design which make them specialized to high or low impedance headphones.

>>1634531
The emitter voltage is biased down by Re, when the circuit is working linearly the Vbe of both transistors will always have to remain around 0.7V. That's why opamps have to use them in feedback, to keep the differential input voltage near 0.

The differential amplification of the long tailed pair is approximately Rc/re BTW (lower case r used for the inherent emitter resistance). Quickly googled doc explaining re :
https://www.pearsonhighered.com/assets/samplechapter/0/1/3/4/0134420101.pdf#page=6

>>1634610
>>1634106
And that's exactly how the amplifier is designed. There's a Class AB power amplifier output stage which is low impedance for the current drive. The VAS that drives it is a differential amplifier with different feedback networks that can be switched in for the different voltage gains. Keeping distortion relatively low at higher output levels will be a little tricky but shouldn't be too hard to tame.

>>1634462
>Unlimited roll-over requires a diode per key.

no diodes here, boss. the contacts are not physical switches but plates on both sides of the PCB that are capacitively coupled when a metallic key-tip approaches quietly in the night.

>>1634462
>Unlimited roll-over requires a diode per key.

no diodes here, boss. the contacts are not physical switches but plates on both sides of the PCB that are capacitively coupled when a metallic key-tip approaches quietly in the night.

Can relay that switches mains power fuck with IC that is 1 cm away from it?
Sometimes, not always, when the IC switches the relay it shits itself and reboots and i cannot figure out why
it only happens when the relay switches

>>1634535
Please go back and read. We are interning at the same company together. In fact we're working on the exact same project. This is my third ENGINEERING internship, this is his first. The company I work at doesn't normally hire Freshman because they don't know anything, but they took a gamble on this dude because he has two TECHNICIAN internships. It's just annoying because I have to explain the most basic things to him and he's not able to do anything well other than bitch work. No doubt he may be a great at something later, but I think he should probably be doing something other than circuit design right now if he doesn't know how a lot of basic circuits work.

>>1634688
>when the IC switches the relay it shits itself and reboots
If your relay is L1, do you have D2 connected?
magnetic field changes can cause electrical impulse in associated wiring.

>>1634688

could be
- the power supply voltage is weak, and you get a dip when the relay kicks in.
- the chip is CMOS and someone left some inputs floating.
- the flyback diode across the relay is missing or dead
- 1000000 other things

Redpill me on voltage controlled resistors, lads.
The more I read about it the more I think there is no practical solution. Even commercial designs use PWM and LEDs as JFETs are really hard to tame.

>>1634702

one pot or rheostat, a motor, a comparator: easy-peasy.

>>1634707
Excellent. And that looks like an IR receiver for a remote? Kinda confirms my guess then.

>>1634702
LM13700

>>1634719
Ah, I've looked into those transconductance amps. The datasheet confused me as it seemed too complicated. This seems to be a pic from the datasheet as I remember it.

>>1634702
they sell resistor ics which can be given simple commands over serial so you literally just send a number and it sets itself to that resistance

>>1634727
If you go digital just go all digital.

If you don't go digital, don't use the hugely overpriced ancient bullshit ICs ... what's the point? Your performance is already shit, not digital, so pick something which requires more experimentation and less copy/pasting.

https://vimeo.com/191507422

How would /ohm/ scale something like this up to hundreds of haptic elements? I'd like to try making clothing items like this for generalized inputs (not just sounds) as a kind of high-bandwidth BCI (one way), but ideally with much higher resolution. These guys' suits have like ~30.

I was thinking piezo elements. Like maybe making custom transducers with spaced out resonant frequencies so you could send out a single audio signal and each would act as both a bandpass filter and a haptic element. Less voltage and current draw too. Seems like it'd be a tough manufacturing job though.

Of course you could also do something simpler like having a bunch of these https://www.adafruit.com/product/1201 with an MCU and shift registers, addressable latches, or some other IO expander but that seems like it'd need too much power for a wearable which is probably why the guys in the video use so few in the first place.

>>1634727
>>1634738
my problem with all these fancy solutions including LM13700 is that unlike a true resistor you can't just plug it in between two random points in your circuit. I believe that's why the PWM through LEDs or optocouplers is so popular as a quick and dirty solution since you can stick it literally anywhere and regulate the average current through it and therefore change the effective resistance at that point.

>>1634741
I'd solve it with a hybrid solution. I2C bus, then a microcontroller to drive a bunch of MOSFETs to drive the piezos.

Main problem with piezo is that it's going to take a lot of voltage to get significant amplitude out of a piezo disc below their resonance frequency. Probably 100+ volt and even then you'll probably need to stack them. High voltage and haptic are not the best combination.

You can use an inductor to swing up a low voltage AC supply for each piezo disc so there's less chance of shock but then you're stuck with fixed vibration frequency.

>>1634746
For audio it's still the hand made LED-LDR coupler if you can tolerate the slow reaction. Another option is a JFET (pic).

>>1634077
Vintage mains smoothing capacitors from valve based equipment are cylinders just gut the insides.

I'm trying to control a portable cassette player's motor using a pot

It works. Kind of. I thought that pots at their extreme positions acted as dead shorts but that's apparently not the case, as it doesn't ramp back up to anywhere near the normal speed at the extreme position.

I can make it run at normal speed by essentially bypassing the pot with a jumper but that sort of defeats the purpose. Is there any way I can decrease the resistance of the pot without disassembling it? I thought jumping the holes with a 100 ohm resistor might allow it to draw a bit more current but it made no difference

>>1634817
Get the circuit diagram and look for the motor controller. Such pots are for signals, not for power.

>>1634826
earlier in the thread a few other folk tried to help me identify one of the chips as an anonymous CHMC driver, there isn't a datasheet for it to be found.

I'm essentially going to have to probe the pins of the IC with an oscilloscope to devise the pinout, aren't I?
Even then, how would I control the motor speed?

>>1634590
>hammer hardware
well shit there's one right next to the supermarket I go to

>>1634826
>>1634834
alright I think I found the pin on the main IC that outputs to the motor. At least, its waveform looks the most similar to that across the potentiometer.

>>1634499
Wait, just so I'm not being an idiot, would custom rubber domes with pulldowns or pullups be viable? Since the buttons aren't clocking anything I shouldn't have to worry about debouncing so long as the settling period is much smaller than the register-loading period. The only thing I can see myself worrying about is the travel distance, too short and the keys won't feel right. 2mm or so would be ok, anything up to 10mm would probably be fine, but 1mm is definitely out. So no normal tactile switches. But I'm looking at these conductive silicone tactile switches, which would be good for not having to worry about the underside of each key:
https://www.aliexpress.com/item/32824458218.html
But I can't find anything resemling a travel distance on the datasheet so I'd better not.
This listing for this similar product has "long travel" in its name:
https://www.aliexpress.com/item/32724698079.html
But it's still a little dubious. I'll look up how to interpret these actuation force ratings too.

>>1634854
>tfw there's no online catalog

hi... i'm new to this place...
how do i make heat (100C) with electricity?
just tell me what items i'll need... i'm really new to all this...

>>1634907
what is the heat going to be used for, how much do you need

>>1634908
portable water boiler... like an electric kettle... i own one but i would like to make one myself that i could wrap around my water bottle... and portable
maybe one liter of heated water...
i love tea... hehe

>>1634913
Let me say it this way. You can boil a canteen of water in a few minutes over a camp gas cooker with maybe a 10th of the gas contained in one of those small gas cans. Batteries are about a 10th as energy dense as LPG, so imagine lugging around a small gas-tank sized battery pack to bring one bottle to a boil. Better yet, if you know how many litres of water you want to heat up, you can calculate how much energy that will take via the volumentric heat capacity of water over a ∆T of 80°C or so, then see how many 18650s it will take to store that energy. For example, 1kg of water will take 4184J to heat up by one degree, or 4184J/kg. Since water's density is about 1kg/L, we can convert that to 4184J/L. So with 80°C to get from 20 to 100, that's 334,720J. A typical 18650 capacity is 2Ah, or 7.4Wh, or 26,640J. Meaning you'd need a bit more than 12 18650 cells to heat up your water, assuming ~100% efficiency. Such efficiency would require not a heater wrapped around your bottle, but one immersed in the water, with insulation around the outside.
At that point it's simply far more efficient to boil your water before going to work and keeping it in a vacuum flask.
If having access to mains power is still considered "portable", you could use an immersion heater instead, you can get them for $10 or so. But dunking one in the top of a bottle would be a little sketchy.

>>1634817
>>1634826
>>1634867
I've combed the annals of the electronics internet for roughly 8 hours now and can't seem to find a datasheet for this chip
>>1634348
The closest I can find, and it's pretty close, is https://www.digchip.com/datasheets/parts/datasheet/456/TDA7285-pdf.php

I don't know much about motor control, but I think this is the motor control out pin on the IC. At least, the waveform on the pin (bottom) matches with the impulses on the potentiometer I wired to the motor (top)

>>1634921
this was very informative... thank you... i didn't know it took so much fuell...

>>1634936
Yeah, water is a notorious pain in the ass to heat up.

Most materials have a specific heat (a measure of how much energy it takes to heat a material 1 degree C) of between .1 and 1.
Gold heats up very fast, its specific heat is 0.129. Aluminum heats up slightly slower, its specific heat is 0.9

Water?
Its specific heat is 4.18. Meaning it takes 418% more energy to heat up than most other substances.

>>1634945
I once used a bucket of salty water as a load to test high current transformers. Lots of salt (or baking soda) and aluminum foil on the opposite sides. 1000w at 50A? no problem. A bit messy though. I since bought a bunch of 100W automotive halogen bulbs. Haven't tested that setup yet. Thats a lot of heat to dissipate so might need a bucket of water still lol.

>>1634934
Are you sure it wants an analog speed setting voltage in the first place? It could be wanting PWM. Still, I don't think that could cause the issue described in >>1634817, since the maxima and minima will be the same. Though now that I look at it, shouldn't the pot be arranged as a voltage divider, not as a variable resistor? Considering that it's a tape recorder, the speed at which it rotates has to be pretty well controlled, do you think it needs some sort of timing or clock signal? I can't see a crystal on the PCB, so perhaps it uses an internal oscillator?
What are you wanting to do with this IC or circuit anyhow?

>>1634957
it's obvious at this point that it's a tape recorder.
It's mostly an experiment to see if I can't make it into a very lo-fi/shitty near-real-time sampler.

I want to try a few things. I want to splice an infinite cassette tape, and then have the write head constantly writing to the tape from its audio input, the read head then immediately reading it back out, and then the erase head erasing immediately right after.

Then, I want to be able to control the motor speed and possibly direction so I can chop and screw audio samples in almost real time on a low fidelity cassette tape. Granted I don't know how I could use a pot to speed it up, unless I give it extra voltage somehow.

it doesn't need to be surgically precise. I just need to be able to have somewhat fine control over the motor speed, and be able to read/write/erase at the same time. I don't know if those are mutually exclusive in the chip's circuitry, or if it's just a matter of mechanical control like the rest of the playback. It would be very helpful to have a datasheet but I'm almost convinced this thing is an anonymous specialized chip at this point/

>>1634968
>it's obvious at this point that it's a tape recorder.
Yes I got that, just it didn't look terribly broken and you didn't seem to be trying to remove the parts or fix anything.
>can chop and screw audio samples in almost real time on a low fidelity cassette tape
That's actually pretty interesting sounding. Perhaps a custom motor driver would be a better way to go?

>>1634968
granted, this leads into my next idea.
Eventually, when I'm learned enough, I want to be able to control the motor speed via a midi controller, so I can control the pitch of the sample on the tape itself like a monophonic synthesizer.

>>1634970
>just it didn't look terribly broken and you didn't seem to be trying to remove the parts or fix anything.
It actually flew out of my pocket at 80 mph when I was riding my motorcycle. I was astounded it still worked when I found it. Granted, the case was obliterated so I couldn't bring it with me anymore so now I have this crazy idea.

>Perhaps a custom motor driver would be a better way to go?
I thought of that briefly earlier and then promptly forgot about it, that's probably the best way to go since then it takes the weird chip completely out of the question. It'll also be easier to segue that into my above midi idea too

>>1634974
That begs the question, would doing away with the original PCB be more effort than trying to splice into it? I'm assuming the PCB isn't playing a structural part, but it might be I guess.

>>1634976
Most of the board is redundant, dedicated to the radio circuitry that I'm not going to be using. However I'm pretty sure the main IC has something to do with recording and audio playback. When I probe the IC with a sound playing, my oscilloscope does show the audio signal on multiple pins of the chip so it might still need to be kept. I've never tried to reverse engineer the pinout of an IC with just an oscilloscope so that'll be fun.

Otherwise, the board has no structural component at all, it's just screwed in.

>>1634978
It wouldn't be a gargantuan task to trace out the PCB, and doing so might provide some insight as to what you can keep and what you can toss. At the very least I'd want to keep the audio signal fully analog, but since I have no idea how the read/write heads actually work I couldn't say how easy that will be.

>>1634746
>you can't just plug it in between two random points in your circuit

>>1634986
Would this be more cost-effective than a JFET solution?

>>1634817
>dead shorts
±10%

>>1634874
>just a test rig
>custom rubber domes with pulldowns or pullups
well that escalated quickly
can't say as I've worked with them before. they might be more analog than you like (unless you feel like redoing the whole thing with analog muxes) and velocity sensitivity)
>silicone tactile switches
I was thinking of those too. as long as you can keep the actuating arm of the key on the straight and narrow (which might call for tilting the board around the long axis), those might even have better overtravel feel in context (they're silicone, they can squeeze a little)
>tfw
iktf

>>1634951
nobbad
a friend used a waffle iron as 8ohm dummy load. which is good as testing amplifiers always makes me hungry

>>1634978
>signal on a lot of pins
read heads deal in microvolts so it would be no surprise if they used a few stages to amplify to speaker volume

>>1634984
you should put down the board for a while and read up on the theory of magnetic recording. especially understand what a bias signal is, why analog recording needs it, and what to do with it. at which point you should be able to tackle each of the separate functions standalone (drive the write and erase heads, amplify the read signal, control the motor speed) and then work on making them adjustable
wait wtf kind of tape is this with separate read and write heads on the recorder?

>>1634988
dunno, haven't seen a dual-ended JFET resistor design yet that isn't dependent on the dc level in the channel, and discrete MOSFETs with the substrate broken out instead of connected to the source are a bit rare if you're not an IC designer
otoh, if signal levels, frequencies, and fidelity requirements allow, analog switches/muxes a la CD4066 or Harris' DGxxx are not ridiculously expensive

>>1635014
>well that escalated quickly
I was thinking pre-cut individual rubber domes that would be clamped onto the PCB with a piece of perspex, nothing like getting some manufacturer to make a custom membrane for me. But these silicone switches look like they'd be much easier to work with, not to mention allowing for a flatter end-product.
>as long as you can keep the actuating arm of the key on the straight and narrow
How so? I don't think the angle of the keys will ever get more than 5° (1mm depression at 25mm distance = 2.3°) so I don't think I'll need to worry about their force on the switches being a little on the oblique side, I bet computer keyboard keys are often depressed with consistant biases towards one direction or another.
>those might even have better overtravel feel in context
Even better, since I can just adjust the distance from the button to the hinge of the key (in a test rig for the test rig), I can change the travel distance with a fair bit of control. So all that would be required of me is to figure out what sort of actuation strength I'd want, since that will also vary alongside actuation displacement with distance from the hinge. I'm thinking 2-5mm travel, similar actuation strength to a slim rubber-dome computer keyboard, maybe a bit lighter.
I think I'll ditch the microswitches and just buy the silicone dome ones, I can tune the distance afterwards. They're cheaper, though I haven't factored in the pulldown resistors. Probably going to use 100kΩs.

Now the only other issue I haven't considered is what I'll be using to connect the boards together. I need right-angle board-mount connectors of both female and male varieties, and either with 2.54mm pitch or with 5.08mm pitch and two rows. Using D9 serial connectors is surprisingly tempting, considering they likely come in the right form-factors and 9 pins is my maximum (Vcc, GND, CLK, CLK_MODE, DATA, S1, S2, S3, S4 as between the primary and secondary boards).

>>1635027
>individual rubber domes
I'd be pleased to learn where these could be bought in <1000 lots if you happen to find a vendor
>I bet computer keyboard keys are often depressed with consistant biases towards one direction or another
side loads are usually borne by the bosses in which the key posts are mounted. also the domes in question have a bellows-like structure that accepts side loads, which those little switches do not appear to have
>1mm depression
I figured you were allowing for a lot more key travel than that, or maybe you're not accounting for the angle from rest to switch touch?
also consider the following https://www.aliexpress.com/item/10pcs-lot-no-sound-6-6-5-SMD-silent-benis-silicone-keypad-tactless-benis-switch-silicon-Switches/32807221477.html
>what sort of actuation strength
start with 100g applied 20mm from the near edge of the white key (based on the pleb-tier MIDI keyboard controller to my right), black keys might be a bit different
>100k
perfect. these probably won't bounce like the micros either, also, free jumpers
>DB9
yeah nah, Pic related, especially if you're cost-conscious

>>1635044
>I figured you were allowing for a lot more key travel than that
That's at the button 25mm from the root, not at the end of the key. At the end of the 75mm key that would end up as 3mm, which sounds decent. I don't need particularly high displacement, so I'd probably be fine with 1.5mm. Tuning to get the right actuation force will probably be what I'll care about foremost, with end displacement being more of an afterthought.
>100g 20mm from the near edge
A torque of 0.055Nm if you have 75mm keys. Assuming your keyboard's switches are 1/3 the way from the hinge like in that one pic from google images, that's an actuation force of 2.2N. Too bad I can't find any actuation force ratings for these switches online.
>Pic related, especially if you're cost-conscious
Yes I've decided those are the way to go. I'll likely add some mechanical support by way of the cases interlocking somehow, maybe with pins or something. Good thing about those is they can be trimmed to custom lengths, though less-so for the female ones without a bit of sandpaper.

I'm trying to simulate a voltage doubler and either the simulator is going full retard or I'm fucking something up. Is there anything obvious I'm missing? I'm putting 170VAC P-P into the transformer, getting 12VAC RMS out, fine, until I add my diodes and caps and then the scope voltage says about ~480VDC and the multimeter giving me bullshit like 1.3E-18V which is impossible. What the fuck is going on?

>>1635064
Shouldn't that diode D2 be going to the same node as the capacitor, not to ground?

>>1635068
Tried that, same result.

>>1635077

doesnt make any sense that the input and output should share a ground.

>>1635077
Circuit is correct. The output voltage is the peak-to-peak voltage of the AC source minus two diode drops. If you declare the center to be 0V (GND) you have a +/- dual supply.

>>1635077
Oh it's a two-sided one.

>>1635086
I know, but if I leave the generator floating, the simulator complains about a floating node and grounds it, though come to think of it the neutral line from the mains is tied to earth ground at the breaker panel from what I know.
>>1635088
With 12VAC in to the diodes, I should be getting about 32VDC, not 480. I know the circuit is fine because I used it many times before with tube amplifiers but I'm wondering why the simulator is not displaying the correct values.

>>1635097

since VM3 is in the 500V range, it would suggest your transformer is backward.

>>1635097
32V is right, I'm not familiar with your sim game though.

>>1635057
>25mm from the root
ahhhhhok, so the usual lever equations should work
>actuation force
for switches, usually specified in grams force. what's your key return mechanism? might be worth adding springs to tune the action if you can find some off-the-shelf that will do
>less-so for the female ones
true. you do lose a position when cutting but at less than a penny per pin I get over it quickly. I use nippers and a pen knife to remove the broken cavity, when I care enough

if i have lm317 and need it to be a constant current source for 1.2A, that means i need 1ohm resistor, so the resistor will then be dissipating
1.56watts of heat?
since voltage it drops is
1.2v = 1.2A * 1ohm
1.56 watts = 1.2A * 1.2V
am i calculating it correctly?

>>1635105
looks right, now calculate the dissipation of the LM317 itself and heatsink it accordingly

>>1635105

P=I*I*R
= 1.2*1.2*1
= 1.44W

>>1635106
the lm317 should be fine, i used a heatsink intended for a GPU, but i worry about the current setting resistor, the multiturn pot, since i think those are only made to dissipate .5W at most, so 1.5 will turn it into slurpie, but my hope is it will last long enough for me to try my stuff out, since i need it to only work for about 30 seconds

>>1635110

if you have a broken hairdryer, racing car speed controller, or something similar, you can use a section of the nichrome wire heating element. IIRC its like 6 ohms per 3 feet of wire.

>>1635110
yep at 3x rating it'll toast. why don't you parallel some fixed resistors instead?

>>1635112
because i need it as a laser driver and i need to find the current for the laser diode by slowly turning the pot to increase the current until i hit the sweet spot and the cunt turns on

>>1635110
The LM317L datasheet has an interesting suggestion if you want to adjust the current with a pot.

I want to turn a regular headset into a bluetooth one.
I don't want to just buy a bluetooth headset because i'm really fond of the one i have.

I've seen plenty of bluetooth modules on like aliexpress for next to no money (2-5 bucks) which seem like they would work fine, but as typical for such items, the documentation is lacking. The best i could find is some datasheets of the IC manufacturer, but they're vague and not really a guide as to how to turn such a chip into an actually usable thing.

I mean bluetooth needs pairing, right? And then the datasheet lists dozens of different bluetooth modes, audio formats supported and such, and i have no idea how to interact with the chip to actually use those.

I want low latency for the microphone transmission obviousy, high quality for the headset transmission, and i want to use some standard li-ion batteries like 18650 so that i can swap them anytime and charge them in some external charger.

I got *some* electronics experience from tinkering in the past, but no real solid education in the field.

Not looking for a step-by-step guide or anything, but maybe someone has tinkered with such chips/modules and has some advice or even some ressource with useful information i could read up on.

My google fu was very weak.

>>1635116

you're doing it wrong. BT speakers die after a few years coz the batteries go bad and they end up at thrift stores for a couple of bucks. same for BT headsets. so, just get a used unit for almost nothing, pull out the electronics, and replace LiPo.

datasheets not required. everything's already done for you.

>>1635115
What current range will the 500 ohm pot provide here if the r1 is say 2 ohms?
because if you have the 1k in paralel, then the 500 ohm pot would only adjust the range by few miliamps at most no?

>>1635116
You could just use something like that:
https://www.aliexpress.com/item/32963720133.html

I got one like that and just soldered an old cellphone battery on it to get better battery life.
You could solder a battery holder (and a small protection board) for your 18650 on it.

>>1635121

that circuit is fine if you're in the milliamp range. if you wanna use it in the amp range, you'd have to scale the 2 resistors down by 500 or so. so, forget it.

as for your multi-turn pot, the 0.5W rating applies over the entire surface area of the pot. but i'm guessing you have a large pot and are using just the very end of the range. that means the actual power-handling ability is way smaller than 0.5W and it will smoke in seconds.

>>1635104
>might be worth adding springs
I was actually thinking something more like set-screws to adjust the height of the PCB or the stopper-bar. This is the current iteration. I think I'll just increase or decrease the width of the bar where it stops the keys such that the keys are partially pushed into the spring-action of the switches. This will sacrifice a bit of my travel distance, but I think I'll have plenty of that anyhow. In other news, 25mm of PCB is likely too narrow thanks to the pullups taking up room between the switches, so I'll bump it up to 33mm (I'll be cutting them out of 150x100mm copperclad). If that's too small, I'll have plenty of room to cut out shapes in the boards to accomodate various features in the stands. Such as the gaps necessitated in the frames to make room for the switch pins.

>>1635114
>laser driver
I would control the voltage and limit the current. Makes it easier to find the right setting.

>>1635134
>voltage
every tutorial i ever read said to use constant current source for dirivng lasers or the diode will die instantly, so i am definitely using constant current

>>1635137
also i know the diode should be somewhere around 1.24A so that narrows the range down a lot

>>1635126
>you'd have to scale the 2 resistors
Reason? It acts on the effective adjust voltage.

>>1635140
>It acts on the effective adjust voltage.

ah, so it does. so, what exactly could we expect as the pot is varied from end to end? i'm too lazy to model it.

>>1635120
>>1635116

>you're doing it wrong. BT speakers

Speakers don't have a channel for microphone audio?

>they end up at thrift stores for a couple of bucks

No such stores where i live.

>>1635123
>>1635116
>You could just use something like that:
>https://www.aliexpress.com/item/32963720133.html

I've seen those. How does the mic channel work? I only see a 3 pin 3.5mm plug, not a 4 pin?

>I got one like that

How's the audio quality? Does it loose connection often?

>and just soldered an old cellphone battery on it to get better battery life.
>You could solder a battery holder (and a small protection board) for your 18650 on it.

Sounds good in theory. Hell they cost nothing, i should probably buy one just to try it out, but they take so annoyingly long to arrive.

>>1635151
>How does the mic channel work?
Has an internal mic. You'd have to desolder it for an external one.
I never used the mic.

>How's the audio quality?
I think it's fine but I'm not some audiophile.

>Does it loose connection often?
Only if I move too far away from the transmitter.
Range is okay-ish. Can't get through the thick walls of my house (but even my wifi router struggles with them).

I'm trying to drive one of these https://www.aliexpress.com/item/LM2596/32721507753.html
chink step-down converters with a 10k DPOT. I want to get a 19V to 5V(or less) range out of it with 24V source voltage. The DPOT seems to work fine when disconnected, and when connected, it works from 1.5V up to about 8.5V as you'd expect, then the voltage just stays at 8.5V for all consecutive steps of the DPOT. The output of the converter circuit is without any load, only have multimeter connected to it. Any idea what's causing this?
Diagram isn't exactly my converter but a very similar one.

>>1635158

Thanks, exactly the info i was looking for.
I really can't be arsed to decypher datasheets and figure out protocolls and pairing and maybe even get some USB-UART adapter to configure some module.
Especially if there is a working product i can modify that's 1.7 USD.

I use my headset a lot, and even tho i soldered in a 3.5mm plug so that i can use standard cables, i still shredd these cables at an alarming rate. I've got a dozen shredded cables, and i haven't found one that lasts longer than a couple of weeks. I found some half-way decent ones for 1.3USD a piece and ordered 20, but it still annoys the hell out of me so i wanna try wireless.

Gonna need some cheap replacable 18650 tho cause i use the headset like 16+ hrs a day.

>>1635127
looking good
>pullups taking room between the switches
c'mon mane, use hueg SMD on the flip side, you could put them anywhere and nobody will see them from playing position, even right under the switches if your board stock is thick enough

>>1635161
did you even read the datasheet for the part

>>1635137
Just to make sure i am not wasting time with the lm317, this driver really is dead right?
Basically when i connect the laser to it the fan on the laser spins but the laser doesn't work.
it should be ON when you short the TTL pins together and OFF when you leave them floating
It does not work like that for me, i sometimes get the fan to spin and it seems kind of random, but i am never able to measure any voltage across the laser output pins so i am assuming the driver is dead which would be actually really good because that would mean that my insanely expensive laser diode is probably fine

>>1635167
I'm not taking the SMT pill until I've got my etching technique sorted. It's going to take a while. In any sort of refined design I'd likely have the PCBs fabbed, and whether I use THTs or SMTs there is completely up to how user-friendly it should be.

>>1635171
naw, mane, they're HUEG

>>1635168
>when you short the TTL pins together
that's not TTL. TTL means you supply a 5V signal across them. are the two pins marked? yes, yes they are. put 5V on them, + to + and - to -, and the driver will probably work. did you even try that

>>1635175
>naw, mane, they're HUEG
They're still rigid parts which are a pain in the arse to desolder. Plus they make much worse jumpers. Also my ground plane is getting a bit choppy even with 0.3mm clearance and 0.5mm track width, which I suspect might be pushing my etch technique. We'll see.

>>1635176
fair enough. still, don't forget the jumpers inside the switches

>>1635167
>did you even read the datasheet for the part
I did, but I don't know what I'm supposed to take away from it. Is
>Voltage on VH/RH and VL/RL Referenced to VSS +-8V
causing it? I figured that since it's just a bunch of physical resistors inside, it should still work, or at least if it's failing, cause overheating or something.

>>1635179
>the jumpers inside the switches
The what? The SPST switches have 4 pins, and I'm pretty sure I know what their orientations are, but I'm just connecting diagonal opposites just to be sure. Also the long female header is getting in the way of the buttons on the secondary board, so I'll see about getting some 02x05s instead I guess.

>>1635175
of course i tried it, and as it says in the picture 5v is off so that doesn't help at all anyway

>>1635148
You can have a VR (R2) in the parallel path to increase the current beyond 1.25V/Rs. The calculation assumes R3>>R1 and ignores the small adjustment current. Verify before use.

>>1635180
yeah that's probably what's causing it, and if that rating was an absolute maximum, you may have damaged the chip by exceeding it. now if you put a couple of fixed resistors on the ends of your voltage divider to limit the voltage that the digipot sees (with respect to Vss) it should work
>just a bunch of physical resistors
what about the wiper switch? an input voltage in reverse of what it expects could turn one or more of those on
>overheat
not quite. in ICs, components are separated from the substrate by reverse-biased diodes. input voltages outside the power rails can forward-bias current paths and transistors that were not contemplated in the design, with unpredictable and usually undesired results. that's why most ICs require that voltages on their inputs stay between the power rails

>>1635184
>The SPST switches have 4 pins
shit, my bad, for some idiotic reason I thought the switches were being grounded. maybe I need to go eat a burger
curious, why the DIP switches instead of a second set of always-on pulldowns on the receiving board?
>long female header
if you replace that DIP switch with the fixed resistors you could pick up some space, or at least move some or all of the pulldowns to a less prime location
>filename
yes, yes I do

>>1635194
>why the DIP switches
To turn off the..
shit I could just have put the pulldown resistors on the receiving board in the first place
I guess I'll do that then

>>1635197
>>1635194
At least I don't have to change the schematic for the resistors, just move them from one side to the other. The DIP switches were an artefact from the high-impedance resistorless capacitor circuit, before I realised that I have no need for debouncing.
>if you replace that DIP switch with the fixed resistors you could pick up some space
I need space on the edges of the board for the headers to plug into, but the buttons want to take that space, and neither can be moved. The extra headers won't be too big of an issue.
>yes I do
Think it might be better to change to a 2.54mm grid once all the buttons are in place? The buttons are placed in 10mm intervals, hence the metric grid in the first place, but it's just tripping me up now.
Now I'm considering A: it may be better to have the male pin headers on the transmitting side since they'll always have something inserted in them when in use, and B: it may be better to have the transmitting side on the right, not the left, so your keys can be closer to your computer keyboard. B sounds like a pain, but I'll probably have to go through with A so you don't accidentally rip your hand off the side of the thing.
But aside from the requirement of 3 copper jumpers all the way across the back for the CLK, Mode, and Data, I don't see any problems that might stop me from pushing go on the order button. I can figure out the finer details later, once I've tested the positioning of the switches. The sale ends in under 20 hours, so I'll leave it to the last minute.

>>1635206
>space on the edges of the board
you've got room on the north side of the board, no?
>2.54mm
I usually don't, I just lock the other-grid part positions
>10mm
yes, you should definitely stick with the natural metric grid then
it looks like you have a full 3mm to the rear edge of the board to use, unless that's where the backplate/rest is going to sit
I would have routed the longer lines first
>transmit on right
that just means your top octave comes out first. shouldn't be a huge deal

>>1635014
alright you caught me I don't know how tape cassettes and magnetic tape reading/writing work very well
I thought there was a third head in here but I guess I was mistaken.

I know it's a really archaic and obscure subject now. Do you know of any resources where I can learn the theory behind magnetic recording? Or am I pretty much gonna have to just find and synthesize it all from disjoint sources

>datasheet for motor
>doesn't say if it's brushed or brushless
trying to keep me on my toes I see

>>1635263
cool thing
unfortunately, I picked it up in bits and pieces over the years. the short answers are:
>a high-frequency inaudible signal that is superimposed on the audio for writing to the tape
>because magnetic media isn't very linear and adding bias improves linearity of the medium
>just mix it in
Q.E.D.
>where can I
NEETS know everything. you can get an overview here
http://www.tpub.com/neets/book23/100.htm
iirc cassette recorders use the "direct" principle, which you would want to use for effects that require varying playback speed
you might need to drill down further than the doc shows. e.g. to understand the summing circuit, you might google "op amp summing circuit" which would show you a few examples and some basic equations for designing one
hmm, maybe this is a bigger project than I thought originally, depending on where you're starting from
actually, after reading that little overview, and understanding the major pieces and how they fit together, you might be able to better understand the all in one super chip and the existing board. you could probe around on it once more, maybe using a small speaker amp in addition to the scope. even better if you can get an FFT view so you can see the frequency responses of different stages of the process
then, when you find a discarded cassette player, you can try to add a third head with your own circuit, or just use the one that's in the new player
blah I'm babbling, I better sleep

>>1635027
>well that escalated quickly
yeah, should have created a separate thread

>>1635120
>everything's already done for you.
I created a thread about that recently. This is the real killjoy in this hobby.

>>1635299
>This is the real killjoy in this hobby.

some people enjoy the journey, others the destination. i, for one, prefer to play and not to sweat, so i'm always looking for the shortcut.

>>1635299
50 years ago, the typical electronics project didn't used to regularly involve programming, RF, networking, mechanical design of multiple mating parts, AND class D fire safety all at the same time

>>1635302
based anon gitting er done

>>1635306
>kids these days
but i imagine 50 years ago it was a REAL practical hobby where you'd build something you couldn't buy or it was too expensive and almost anything was a novelty. now you'd have to come up with crazy stuff like continuous impedance monitoring via remote web interface on your phone.

>>1635312
it's rather less hands-on with $2 prototype boards, FPGAs, microcontrollers, solder paste stencils and reflow ovens, and what appears to be a noticeable decline in spatial reasoning abilities after they took all the lead out of the paint
>screw you, copper, this is MEDICAL 60-40
back then you did build your own 7-segment displays out of cardboard and pilot lamps rather than pay $6 for one. there's still a lot to be done with the hands, it's just not quite as much on the electronics proper anymore
here's a blast from the past http://www.swtpc.com/mholley/PopularElectronics/Feb1969/PE_Feb1969.htm
it's interesting to compare their sense of perspective vs. ours today.
>The incandescent unit costs $10.90 per decade; the Nixie readout, while higher priced at $30 per decade, is still much less than equivalent commercial units.
for a pulse counter. holy shit it must have been refreshing to have the 744x decoder/drivers available a few years later
>Use a 25-watt soldering iron with a very narrow tip and thin solder (0.040" diameter) to install the ICs and transistors.
today I bitch that 0.5mm solder almost drowns my 0402s
>continuous impedance monitoring
kek, I think this meme has legs

>>1635372
if you've ever wondered where the hell Scientology got the idea for the e-meter, well, here you go

>>1635378
>here you go
The Original:
Illustrations accompanying US patent # 3,290,589, Device for Measuring and Indicating Changes in Resistance of a Living Body, awarded Dec. 6, 1966 to L. R. Hubbard. Filing date June 7, 1965.

>>1635101
I tried that already, no go.
>>1635103
Yeah, turns out that simulator isn't as good as LTspice. Took an hour to learn it and made the circuit, and it worked first try. It has nicer graphing too.

>>1635399
fuggggggg
shamefur of me

>>1635401
what simulator was that, just in case someone asks, so we can steer them away from the brain-busting results they will probably receive

>>1635463
>what simulator was that,

Tina

>>1635463
>what simulator was that

it's Tina, which has its problems, but i'm 100% sure this case was operator error. the dude characterized the transformer wrong.

What does this mean? Is it 3 volts logic or 5 volts logic?

>>1635493

are you kiddink me rite now? read the top line, burro.

>>1635480
>this case was operator error. the dude characterized the transformer wrong.

yep, the 3 after TR1 means it's a step-up of 3 when he wanted a step down of 10.

>>1635480 (You)
>this case was operator error. the dude characterized the transformer wrong.

yep, the 3 after TR1 means it's a step-up of 3 when he wanted a step down of 10.

>>1635493
looks like 5V TTL thresholds to me. should be plenty compatible with TTL or CMOS of any Vdd that the panel works at

>>1635521
sheeit

>>1635480
Ah fuck, I tried reversing the transformer out of curiosity, I forgot to reverse it during troubleshooting for the screenshot I guess; I couldn't understand why my scope voltages were correct but node voltages doing a DC analysis were way off. Being able to set the turns ratio as opposed to relying on proper orientation would be more intuitive, too bad I closed it without saving and tried a different sim instead of looking at it again in the morning. I feel as dumb as pic related, but at least I got results I want. I'll try again to see if I can get it to work in Tina as I like it for some things over LTSpice though both are pretty good.

Are there any single-IC's that does what pic related do? If not, what is the smallest way to achieve this kind of functionality?


Falstad link: tinyurl com / y2a3regh

>>1635553
it's not really that common of a function
both clock inputs are the same so you only need one OR. if you don't mind SOT-23, you could use a 74xx1G32 to implement the OR function, which saves a large footprint if you won't use the other gates

>>1635553
you can also get the little logic ICs in smaller than SOT-23 packages (SC70-6, 1.2x1.2mm QFNs) and the 74xx74 dual DFF is available in a 3.0x2.5mm QFN package. would not recommend unless you're pretty good with SMT already

I had this keyboard (Dell AT101W) for a few years and every time I try to use it on games it freezes after a few minutes or even seconds. I tried it on multiple systems, with a ps2 adaptor or straight into the ps2 port. Same results. It only happens while gaming. If I use it on the web or documents it works flawlessly. I was thinking that the IC chip or some electronic components might have failed. Maybe the capacitors can't hold the charge anymore while I keep that key pressed when moving in a game? What do you guys think? Did you have this problem with older keyboards?

>>1635566
I tried to order the IC (KKMPA40604) from Jotrin which is a Chinese supplier of components but they didn't have it in stock and couldn't find it elsewhere. Do you guys know of any replacement?

>>1635558
You're right. Removing one of the or gates gave me more room already. I'll get the 74xx74 in TSSOP-14, which is smaller than SOIC-14. Thanky ou.

trying to build a 555 pwm motor controller now. Circuit and schematic in the next post.

It's not working of course.
The collector of the transistor is showing this instead of a square wave. Does anyone know what might cause a waveform like this?

>>1635571
I should mention, the motor is buzzing but not spinning.

>>1635572

>>1635573
>>1635572
node: D2 anode / C
should be connected to
node: 555:6, 555:2, D1:C
all i can see thats wrong, no comment if your circuit works did you simulate it?

>>1635576
well now that I've corrected that mistake and connected the nodes, my scope does show a square wave with variable duty cycle.
The motor still doesn't spin though and the transistor gets quite hot (just burnt the shit out of my finger actually)

I don't know if it's my scope or the circuit, but changing the duty cycle of the wave causes the overall waveform on the screen to wander up and down. I think it might be an artifact or anomaly or something

>>1635592
I think my transistor might just not be up for it, the circuit just powered a smaller motor fine

>>1635537
>microwave time
>also known as minutes

>>1635599
what transistor and what motor? you might have a 100mA transistor trying to feed a 1A motor. not good.

>>1635592
Use a mosfet instead, the transistor might need bias for the base whereas a mosfet won't. IRF510 should do but make sure to heatsink it. Running it in your breadboard will melt it.

>>1635625
>>1635627
it was the transistor. I harvested a d882 off of another junk board and it's powering the motors fine.

>>1635633
For your further info, the 3055 might not have had enough base current for it to turn on hard enough. Ice is a function of Ibe and mosfets don't have that annoyance to worry about. No resistors to the base of the 3055 to set the voltage and base current are probably the reason why that schematic weren't producing results.

>>1635636
3055 is on the schematic but he is using a small one : >>1635572

>>1635642
>>1635636
Yeah, I wholeheartedly did not expect or anticipate a tiny little motor requiring a power transistor to power, until I burnt the shit out of my finger touching the little transistor like a dumbass

Looks like it's not an easy task to send keyboard or midi commands to a computer from an MCU without requiring drivers on the computer itself, but Atmel's V-USB seems like it might fit the bill. Computer keyboards (https://sourceforge.net/projects/uart2kbd/)) and possibly a midi keyboard (http://cryptomys.de/horo/V-USB-MIDI/index.html)) were made to be class-compliant without any drivers needed on the host machine. So this will be cheaper than getting a Teensy, provided I can get it working.
That guy who wanted to make a USB keyboard injector to streamline his workflow, if you're still around, take a look at obdev's V-USB project page.

I need a couple transistors for an old used transceiver. They're no longer made, so old stock would be well over $100. Or I can get the obviously counterfeit chinese ones for like $30. What are the odds the fake chinkshit ones would be close enough to spec that it would work?

>>1635748
lots of fake ones from ali. especially the power transistors. those are 100% fake. they might work under a very light load but will die on you as soon as you apply a little more current. what's also misleading is lots of positive feedback on the sellers' pages. either they fake the feedback or most buyers will never unbox stuff they receive and just rate 10/10 on delivery. i requested a refund and they agreed but refused to admit it was a fake. i was told i'd need to contact toshiba so they would confirm that particular part has been discontinued (yeah like 30 years ago). but if you claim it is defective then they will refund no questions asked. a bunch of scammers. i opened mine just for fun and of course the die inside of it was tiny, like 3-4 times smaller than the real one. i dunno how they do that. i'd rather try to find something comparable with similar parameters on digikey/mouser.

>>1635748
>I need a couple transistors for an old used transceiver
I may have a few still in my parts drawer.
In the 60s, 70s, and 80s I did radio repair.
What number are you looking for?
I'm not at the shop tonight so it will be tomorrow before I can check.

74HC logic outputs can source and sink current, right?

>>1635815
Yes, a few mA.

>>1635592
>changing the duty cycle of the wave causes the overall waveform on the screen to wander up and down. I think it might be an artifact or anomaly or something

the anomaly is you: switch the triggering to DC instead of AC.

>>1635592
>changing the duty cycle of the wave causes the overall waveform on the screen to wander up and down. I think it might be an artifact or anomaly or something

the anomaly is you: switch the triggering from AC to DC

>>1635836
the input coupling, not the triggering.

Are those 10-20 dollar USB logic analyzers any good? My only diagnostic tool right now is a multimeter and can't afford a scope

e.g. https://www.amazon.com/NOYITO-Analyzer-Device-Channel-Arduino/dp/B07C4DTWLV/ref=zg_bs_5011666011_5/132-6192221-2005631?_encoding=UTF8&psc=1&refRID=DB7WJENMNX1Z1WQ5BXDP

>>1635850
I bought one from ali for $7, it works fine. Pulseview is the free software you're likely to want to use with it. I'm assuming you're only working with digital electronics at TTL levels?

>>1635853
Yeah, I mostly want to intercept I2C and SPI communications between a few chips to help debugging

correct me if I'm wrong, but there's a way to use an opamp as a diode with no voltage drop, right?

>>1635911
from falstad's library of examples

>>1635911

https://en.wikipedia.org/wiki/Precision_rectifier

>>1635913
>>1635917
that's what I thought, I tried using another precision rectifier circuit in falstad earlier and can't/couldn't get it to work. I probably fucked something up.

>>1635917
es version still has the onda completa circuit, purged from en.

So, I'm looking into doing a solar panel setup. The panels would best be located around 300 yards from where my house and stuff are. How do I begin to go about figuring out if it's more worthwhile to put a switching setup and transformer to drop current to minimize conductor losses over that distance.

Are the calculations for switched DC through a transformer pretty much the same as AC through one?

>>1636051
>Are the calculations for switched DC through a transformer pretty much the same as AC through one?
Until you can answer that question yourself don't put any significant power into any transformer.

Solar panels are usually connected in strings, then you put that string on a string inverter, then you transport the mains voltage AC as normal.

>>1635920
that 10u may be shitting on the feedback loop or output stage of the first amp. I'd try to put some buffering in there

>>1636051
Pretty simple, just calculate the copper cost of the thick mains copper wires compared to the thinner HV wires, and see if that difference is less than the cost of the two transformers and all the fancy low-creepage mounting hardware. Not sure about losses in the transformers themselves, the datasheets probably have an efficiency rating with which you can see how much power you'd be wasting. Assuming you're not feeding power into the grid or storing it, you wouldn't really be losing money by wasting even 10% of the energy.

>>1636063
I think he's asking about first inverting it to mains voltage AC at the panels, then running it through a transformer to a few kV, then stepping it back down again after the 300m.

If i have a low side mosfet, i can normally use say 3V at the gate to allow 5V through the drain and the other pin, but will it also work if i use 5V at the gate an only 3V at between the drain and the other pin?

>>1636478
If it's lowside, then the drain voltage is always near zero because kirchhoff.

>>1636478
Should work, so long as there's not a maximum V_GD. I think that's how logic level shifters work in some orientations.

>>1636482
the drain is the collector analog bro

>>1636482
>>1636484
thanks
i got one more question
i need to connect 5V GPIO pin, to ic which has 3V gpio pins. And since the 3V ic has snapback protection on the pins, will it work if i use a single 10k resistor between the two pins?
I don't really want to use a level shifter since that is like 6 extra wires.

>>1636487
Is it in-only or out-only? If the data is only going one way then either nothing or a standard voltage divider respectively would likely work fine, otherwise a MOSFET level shifter would be required. I don't think snapback protection will protect against medium-impedance ∆V of 2V, unless you have some evidence to the contrary (i.e. an equivalent input diagram).

>>1636499
so voltage divider when communicating from 5V to 3V and a simple mosfet when going from 5V to 3V, where the 3V opens the gate and let's through 5V to the pin right..?
But, theoretically since the 5V ic register anything above like 2.5V as high, do i need the mosfet? Since if the 5V pin is set as input, then connecting it to my 3V pin shouldn't cause any damage right?

Anybody know what model or type of switches are being used here? I want to replace one of them since it's broken.

>>1636510
look like common 6 x 6mm microswitches

>>1636507
>theoretically
>anything above like 2.5V as high
lol no, 30%/70% of Vdd (for low max and high min voltages respectively) are usual

>>1636507
I assumed you knew earlier, but are you familiar with these? Bidirectional logic level shifters.

well the little 555 PWM circuit works well, now just to get a tape into the cassette player and see how fast it'll munch it up

The motor is making that classic PWM whine/hum. I'm considering bumping down the timing cap from 33nf to something lower but I don't 100% know what ramifications that'll have

I also have no way to rewind the tape using this circuit. Making an H Bridge controller seems a bit overkill though

>>1636635
alright one thing I'm noticing off the bat is that being driven by PWM seems to have completely neutered the motor's torque.

>>1636635
you would ideally like a frequency that will be swamped by mechanical momentum, but once you hear it you'll know more what to do with it
I commend you on your use of Dupont pins as alligator clip attachment points

>>1636637
I'm sure, there's no feedback loop

>>1636637
>>1636635
...and incidentally, going to a smaller capacitor for the timing cap has made it much more responsive and lets the motor spin at a lower rate

>>1636638
>Dupont pins as alligator clip attachment points
I like to keep it classy.
For real though is that a faux pas or something?

Nothing mentioned a feedback loop, what should I look up for a pwm feedback loop?

RF engineers, thoughts on http://scikit-rf.org/ ?

Can YOUR scope run half life?

>>1636653
Something about lab equipment running CE or even desktop Windows always bothered me.

>>1636639
legit beats clipping on to the lead of a random component or jamming an untinned stranded wire in there
>feedback loop
if you want to hold the motor speed steady against torque requirements and other variations, you'll need to sense the motor speed. I am 100% certain there are ways to do it without adding mechanical parts, by monitoring the ac component of the motor's current consumption which is at a frequency proportional to rpm, but I'm not up to working that out right now due to illness and if I had to make one of these right this minute I would probably opt for some sort of optical speed sensing
if you want MIDI control of tape speed with good temperament, there are two obvious ways to do it: analog (with freq-to-voltage converter, a logarithm circuit, and an error amplifier, applied to the CV input of the 555), or digital (with a spindle pulse input and a PWM output to the transistor, losing the 555 entirely). you will probably find it much easier to leave the analog domain alone and do the speed sensing, PWM signal generation, etc. inside the micro, alongside the MIDI command processing you would already be doing. depending on your ambition, you might make room in the circuit/on the board for a CV input with voltage divider to the micro's ADC. later, in case you should decide to interface the tape delay to other modules, you need only stuff those parts and add the feature in software

I'd like to build something funny, lads. Like a female head/torso with huge boobs and when you touch them she punches you. How powerful/what technology should the motor be to deliver a Mike Tyson's tier punch? Like maybe 200lbs? A simple servo not gonna cut it, right?

>>1636664
>>>/diy/ag

>>1634051

How do I design an LC oscillator?

What kinds of frequencies can you get out of one?

>>1636667
f = 1/(2*pi*sqrt(L*C))
all of them

what happens if you give this an ac input

>>1636677
it turns into a pumpkin

i'm making a shunt current meter and am wondering how low the voltages an lm358 off alibay can boost
datasheets say ~9mV but does that always vary or is it constant for each chip and can be mitigated by tuning the feedback loops
should i just get 0.01, 0.1 and 1 ohm resistors and see what works?

>>1636694
I don't see what you're looking at in my TI datasheet but I do see a low-level output voltage of 20mV max assuming an output load resistance of ≤10k. since you're working mostly near the - rail, you can give a little assist with a ~30k resistor to the - rail and pull it a little closer. I also see that the inputs are specified down to the - rail
so you should be fine with the standard non-inverting gain > 1 voltage amp circuit. if it doesn't zero well enough for your taste, you could try giving the 358 a - supply input a little below ground with additional batteries or a small inverting converter (ICL7660 is cheap and available), or (conversely) use a voltage reference to create a new "ground" node that's offset above V- by as much as 1V or so (not too high or you'll run out of headroom on the + side of the output), which you connect to the supply side of the sense resistor, the appropriate ground points for the sense amplifier circuit, and the - side of the meter output

help me remember the name of an old electronics book

It's from before 1990, maybe even 1980.
It's done in the style of, or might actually be handwritten on note paper.
It's a kind of "cookbook" type book, showing how to make from little knicknacks to full on pragmatic circuits
And it was supposed to be rather popular/seminal among electrical engineers from the era

>>1636712
Found it, it's "The Engineer's Handbook" by Forrest Mims

>>1636716
The Forrest Mims Engineer's Notebook

how is high voltage, low current switching done? Like several kV and at most a few milliamps?

>>1636818

this is what Dr. Frankenstein uses.

>>1636818

this is what Dr. Frankenstein uses.

>>1636916
what if doc wanted to switch it automatically via some uC?

>>1636921

one of these.

>>1636677
If I recall well, Crystals are -depending if working on harmonics or not- notch filters.
So, basically, it will filters out everything that is not 16MHz.

Is it possible to drop 120V to 12V by connecting 90-100 diodes in series? Did I just invent a transformerless power supply?

>>1634051
3102 fag detected

>>1637030
Depends on whether you put them in series or parallel/to ground. In series they'll be band-pass filters, to ground they'll be notch filters. Probably.

>>1637033
Not practical. First, dropping voltage just discards the corresponding amount of power, so dropping 120V to 12V discards 90% of the power; you consume 10W for every watt you use. E.g. if you draw 1A, you're consuming 120W but only getting 12W out. This is one of the main reasons switching regulators are preferred over linear regulators for non-trivial amounts of current or large voltage drops (also, you don't need a brick-sized heatsink to get rid of all the wasted power).

Second, dropping a fixed voltage makes the output voltage highly dependent upon the input voltage. If you drop 120V down to 12V, a 1% change in the input voltage equates to a 1.2V change which equates to a 10% change in the output voltage.

Finally, this all assumes that you're starting with 120V DC, and you probably aren't. Mains is AC and rectified-and-filtered 120V mains is 170V DC (120V is the RMS value, but rectification and filtering gives you the peak voltage). Dropping a fixed voltage from rectified-but-unfiltered mains would give you long periods with no output (when the waveform is below the dropped voltage) and and short pulses at the peaks.

>>1637033
Yes it is possible.

>>1636554
I have a bunch of them from chinks, but like i said i would like to avoid them since that is like 6 extra wires and i need only two gpio pin pairs one that goes 5v > 3v and one that goes 3v > 5v
But since i would have to use a divider for the first and fet for the second then it doesn't seem like i would be using any less wires or components in the end unfortunately
>>1636541
then explain why does i2c work between my 5v arduino and a 3v ic, when the 3v ic is doing the pulling up

>>1637108
30%/70% is a 74HC tolerance limit for acceptance. AVR I/O specifies ≥2.6V H and ≤2.1V L for the 328 5V version. Long discussion at
https://www.avrfreaks.net/forum/input-pin-voltage-threshold-and-hysteris-statement

What's the best datasheet website? I'm looking for:
>has easily accessible pdfs
>non-bullshit layout
>good selection
you can also post some obscure part numbers that I can search with to see which sites have them in stock if you feel like it

>>1637181
the manufacturers' websites, duh

>>1637183
I'd rather also have an aggregate source for when I'm looking for generic parts. Especially since I don't exactly have a cheat sheet of all the different little silkscreened logos found on the top of ICs these days. Didn't even recognise the Hitachi logo when I saw it a month ago.

>>1637184
every time i google a part the alldatasheet page comes up as a first result and they have tons of different versions of the pdfs too, the only annoying thing is it takes several clicks to get to the actual pdf file

>>1637185
datasheetcatalog.com is giving me a list of results that can be clicked, with the datasheet links actually sending me to the pdfs of the datasheets on the manufacturers' own servers, which is convenient enough for me. Not too fond of alldatasheet's in-browser pdf viewer, can't even find the damn pdf link half the time.

>>1637184
>generic parts
use a distributor website, like Digi-Key or Mouser. one, they extract the important figures of merit of each component and allow you to search parts on ranges and combinations of them. two, you aren't wasting time on data for stuff you can't even get
>logos
I had the same problem a while back. I found the vendor (some third-tier """"smart"""" metering chipmaker) by looking over the manufacturer lists and line cards on distributor websites

>>1637189
For some background, it's for Vivaldi's search engine customiser, where you can add search engines by adding your own urls and address bar shortcuts for any website. Defaults include standard search engines and wikipedia.
I've added:
>Texas Instruments (because they seem to have the most datasheets for ICs I'm using, especially THTs)
>Infineon (because they own International Rectifier for the common MOSFETs)
>Vishay (they also have a few common MOSFETs)
>Octopart (might be a bit inefficient but I find the site less laggy than DigiKey or Mouser)
>datasheetcatalog
and I'm considering adding a few other manufacturers.

>>1637196
ahhh
NXP is especially useful for discrete semiconductor types that start with B, and for formerly-Philips parts
and ofc Microchip for their analog and mixed-signal stuff as well as their micros
personally I just save about 3 of every 4 datasheets I read (for whatever reason, usually helping out some noob) locally, in folders by manufacturer. I keep telling myself that someday I will turn Apache Solr loose on the whole directory tree

>>1637203
Am I the only who still prints out datasheets and organizes them in binders?
Not even a boomer.

>>1637203
Oh yeah, Microchip/Atmel MCUs are something I probably look up often enough, at least more so than Vishay FETs. NXP sound good too.
How much space do all the datasheets take up? I want to store them but my SSD is in need of a clean up. Might stash some on my external 4TB tho.

>>1637204
I can see the appeal, especially when you have KiCAD or something open on your monitor and don't want to tab-out a bunch, but for that sort of thing I'd load it up on my tablet instead.

>>1637208
my datasheets-by-mfr directory tree contains 3000 files at 3GB. PDFs that are distilled from source documents are much smaller than those which are scanned. also I am less likely to save datasheets for components I definitely won't use anytime soon, that are straightforwardly rated and used, and for which I already have KiCAD footprints. so I've got a few collections of dc-dc converters, SMT inductors; some 74xxxG miniature logic and MOSFETs; a couple of mfrs' el-cap catalogues, not much on resistors or chip capacitors
>not running a triple monitor workstation with a dozen PDFs open in background windows
Bob Pease might approve but I don't think I would

>>1637204
I do have some basic reference tables printed out, like the E24-E192 series and capacitor codes. but ctrl+F is just too useful to give up

>>1637108
>when the 3v ic is doing the pulling up

I2C lines are pulled up by resistors on the SDA/SCK lines, and pulled low by chips communicating on the lines with an open-collector type design.
Some chips have built-in resistors on the SDA/SCK lines, but are still pulled low to communicate.

>>1637204
I don't print out full datasheets, just specifics that I need like pin outs. Sometimes its much easier to have a sheet of paper you can flip to and not load up a whole document.

roast my 3V3 plane

>>1637085
>Not practical.
Agreed. But suppose you are on a deserted island with 120V mains (just west of Guam) and there are no transformers and you found a box of 1A diodes that don't require heatsinks and 10000uF capacitors and you need to charge your phone.

> assumes that you're starting with 120V DC, and you probably aren't.
I mean let's say I added a bridge rectifier and a smoothing capacitor and now I need to convert 120V to 12V

Don't the other two drawbacks apply to conventional linear regulators as well?

>discards the corresponding amount of power
Where does it go? Does it get converted to heat in the diodes? Is that because I have 100 diodes? But what if I have a standard linear regulator with a transformer? I understand it is also inefficient but we can't apply the same brutal math in this chase, since I x V will be the same on both ends since transformer uses reactive power, correct?

>>1636382
>I think he's asking about first inverting it to mains voltage AC at the panels, then running it through a transformer to a few kV, then stepping it back down again after the 300m.

Unless you're way off grid and no one official will ever be near your shit, DIY'ing medium voltage distribution is insane.

>>1637274
Insanity is the normal case. Use cheap standard components you can collect after a storm.

>>1637274
>300m.
Just use an extension cord.

>>1636051
use thicc wire and add capacitance on the load end. or something like that. I may be missing details, my uncle set that up 40 years and dozens of addresses ago

I fucking hate my processor but my future and papers depend on him

>>1637331

congratulations on discovering that the secret to success in 2019 is to suck ass and to learn to love it. but not to worry, one day the tables will turn and someone who hates YOU will be licking YOUR butthole, and you'll have a good time, then.

>>1637270
The voltage drop across a diode varies quite a bit relative to the current drawn.
With minimal load on the string the voltage drop is very low.
As the load increases, the drop increases reducing the output.

How safe are Nimh batteries?

I have first generation Eneloop batteries I bought back in like 2008. I only charged them maybe twice and then they sat in a box to be forgotten.

Just found them, they still had some charge left so I threw them on the battery charger it came with.
Are they going to explode or anything from sitting 11 years?

>>1637609
Depending on the charger, it can explode or just recharge it.
If the charger apply a nice small current and is smart enough to see that the battery is old (like very discharged), it will be okay (don't expect full capacity tho. It will depend on how flat batteries were).
If the charger is a stupid "full power to fast charge durr durr", it may heat up. And destroy your batteries. And if really bad, make the batteries explode because of heat.

>>1637633
I thought NiMHs don't explode, just catch fire.

>>1637281
If a wire falls down on the ground why do they say it's dangerous to go near it, when it's literally shorted to ground?

>>1637728
Same reason cows sheltering under a tree die when the tree is struck by lightning?
Or perhaps because some of those wires are 3 or 4-core insulated wire that may not currently be shorting to ground? Especially if a few strands that were shorting blew themselves like fuses.
BigClive did a vid on those insulated overhead wires and the kind of clamping/crimping methods they use to terminate them if you're interested.

>>1637728
Wire lying on the ground is neither literally nor shorted, it's just lying there. Dry dirt doesn't conduct well.

>>1637747
Well usually wires fall down when it's stormy, hence it's likely to be wet. I agree with you for the most part though.

>>1637728

https://en.wikipedia.org/wiki/Stray_voltage

>>1637748
Even that cannot replace the neutral wire, it only goes to the green/yellow PE (protective earth). The N (neutral) is connected to the center of the 3 phase star, at least in my standard 3~/400/N/PE distribution.
>>1637751
Boots help.

I need to learn as much as possible about three phase power and three phase motors to keep a plant operational eg: asynchronous. Preferably books since I don't have a good internet connection.

Where should I start?

>>1637766
Principles of Electric Machines and Power Electronics
P.C. Sen

tried to make MOD 5/MOD 6 counter. Basically i want it to count 1-5, but it includes 6, i dont know why. NAND gate is connected to 2 and 4 outputs, 2+4 is 6, so at 6 it should reset, so why i still see 6 for good 2 seconds? If i connect NAND to 1 and 4 means to X2 and X4 PROBEs, 1+4 = 5, it counts 1-4 exluding 5, so why when i connect it to X2 and X4 it counts 1-6, including 6? Please help

>>1637879
because you're not clearing the LSB, of course
next time clean up your schematics a little before you post them for your own sake

>>1637762
No they dont. Stay the fuck away. If you're caught in one already, bunny hop away with your feet together.

>>1637748
Even wet dirt is likely to be 5k ohm to the lives return path. Earth return/single wire/farm systems have arrays of 6+ ground rods.

>>1637884
you mean Reset U2 from NAND output? Then i still get errors - it counts to 1-5 no matter if i NAND X2 (LSB) with X4 (5), or X2 with X5 (6). Sorry about schematics

>>1637890
oh I see now, 1-based not 0-based, unusual but I can work with this
logic designers avoid clocking registers or feeding asynchronous inputs from logic outputs because of the probabilty of glitches (and also, speed in real-world implementations). instead, try a synchronous design paradigm: use a single common clock, use logic to calculate the next state in terms of the current state, and set up the J and K inputs accordingly. the behavior of JKFFs when J=K=0 or J=K=1 can be exploited to simplify the counting logic

>>1637766
libgen.io

>>1637888
>hop away
good idea

>>1637910
thank you for schematics. Now there is different problem, if i NAND U2 output with U3 output it counts 1-5 (1+4), but if i NAND U1 out output with U3, it (2+4), it counts 3-6. Picture is snippet so you can open in MS if you want

>>1637929
correct, for the 1-5 case the second bit didn't need to be touched. knowing the behavior of a JKFF, can you determine what gate(s) need to be added to the second JKFF's inputs to make it reset whenever either desired terminal count is reached?

>>1637928
https://youtu.be/3hF5jHl48-U

>work for utility company. The only difference is we have high voltage blankets we can throw on the ground first.

>>1634219
Kek

>>1634219
>ask 4chan for circuit help

>the circuit works for purpose
>somehow its constantly screaming "you double nigger"
>you cant remove this section without disabling the entire circuit.

Never change 4chan

>>1637950
good info - thanks

>>1637937
i dont know i tried with NOT (there is only one input from U1?) but then it counts 1-4

>>1638016
hint: we want to reset U1 on terminal count. considering only J, K, and Q, there are three conditions under which the next state Q'=0: J=0,K=0,Q=0, J=0,K=1,Q=x, or J=1,K=1,Q=1
hint 2: we want to reset U3 on terminal count. considering only J, K, and Q, there are three conditions under which the next state Q'=0: J=0,K=0,Q=0, J=0,K=1,Q=x, or J=1,K=1,Q=1

>>1637888
>Even wet dirt is likely to be 5k ohm to the lives return path
Oh, nice to know.

>>1637649
One of mine exploded once.
It was violent, exploded in shrapnel and smells awfully.
It was a tiny 2S 100mA NiMh battery for a "pump to recharge" flashlight.
And I charged it with an intelligent charger, but I couldn't go below 10mA for the charging, and as the battery was old, it wasn't the best to do so.
It charges for like 2 hours and then exploded suddenly (no smoke, or bad smell before explosion).
So now, I place all my charging battery on a nice fat tile put on the floor to prevent chemical splatch and leave at least 1m around free to be sure not to damage anything.

I only have two explanations, either the battery was old and defective and something goes wrong, or the chinks put mercury non rechargeable battery wrapped in a nice "NiMh" label (the "charging circuit" of the flashlight was a single diode and a resistor. Not very preservative for battery life).

>>1638073
next time, pump slower

>>1638073
Some simple circuits do use NiMH cells like that as they're somewhat resistant to overcharging, at least when trickle-charged. How about using an explosion containment pie dish?

>>1638147
>explosion containment pie dish
You may run into patent infringement issues.
I'd ask Clive before doing that.

PCB for the midi keyboard concept one:
Not my finest work, that's for sure. Especially having to fold multiple traces right out of the way of the 2-row right-angle pin/socket headers to get "vias", which are actually just the thru-holes of solid core copper jumpers since it's a single sided board. But the copper jumpers are gonna look pretty neat, I hope red was a good colour choice for solder mask. Tying myself to 0.2mm tolerance and 0.5mm traces is just a precaution for my etching. Yes there are a few "aesthetic eccentricities" which might deduct from the efficiency of the layout. But it's a pre-test concept. If testing is promising, I may move those buttons down a few mm to get some more space between the headers. Might even put the black keys at different rows to the white keys if that would do anything useful.

https://youtu.be/hczjN9er9TI
ok 2 questions
anyone else seen this sort of lcd-based lightbox?
anyone else used a literal toaster as a reflow oven?

Looking into getting a fume extractor for soldering in small apartment bedroom with a ceiling fan and window.

Assuming i sit in front of the window to let the exhaust out and budget of around $40,
what is my best option for a fume extractor?

Option 1: use a Honeywell ht-900 or buy a different fan
then attach a carbon filter+vent hose

Option 2: buy a fume extractor+vent hose from amazon/ebay

Option 3: use some old PC fans and attach a carbon filter+vent hose

I'm leaning towards option 3 because i read that fume extractors at this price range just an overpriced PC fan setup.
Any alternative opinions and options would be appreciated.
Thank you for reading.

PC fans:
2x, 140mm, model: a12025-12cb-3bn-f1
1x, 120mm, model: a14025-12cb-3bn-f1

>>1638302
PC fans sound like the economical way to go. Any reason you don't shove some of that flexible foil ducting out your window and just do away with the filter? A water trap might also harvest the fumes without needing a filter, though you'd need a pretty big fishtank for that sort of air movement, so I don't think it's worth attempting as any more than a simple curiosity. Dumping your fumes down your toilet or sink's U-bend would also prevent you from inhaling them.

>>1638263
single sided board with soldermask, why?

>>1638348
because I have soldermask in a tube (for like $3) but soldering my headers and ICs without plated through-holes would be a nightmare

>>1638349
>nightmare
strange, never had any problems with that.

>>1638351
You need to solder on both the top and bottom without a plated hole to wet the solder all the way through, which is pretty tough when the top side of the board (i.e. the side that the parts are on) is completely obscured by something like a double-row right-angle pin header or DIP16 IC socket.
I could use 2-sided copperclad with connections only on one side, but KiCAD wouldn't take nicely to having different sized solder pads on each side, and I'd need to mess about with vias in order to get connections between the two sides.

>>1638353
>You need to solder on both the top and bottom without a plated hole

you do? why? i never do that, yet all my boards work A-OK.

>>1638288
>lcd-based lightbox
plot twist: it's a Wanhao Duplicator7 3D printer or clone
yep I tried this once. that machine demands a very particular 1440x2560@50Hz HDMI stream, and I never quite got the laminating step dialed in

>>1638353
>KiCAD wouldn't take nicely to having different sized solder pads on each side
pad stacks are coming in v6

>>1638263
good enough m8
if I were going to put more time into layout, I'd reconsider my connector pinouts to put layout efficiency first, and if you're using a home process make sure you neutralize the boards well to keep those acid traps from causing trouble

>>1638356
if you want to connect layers with the pin, you do

>>1638353
There are some tricks you can do, like threading a short wire through the hole or using copper rivets.

>>1638356
Well the whole point of a 2-sided board is to have traces on both sides of the board, if you can't connect those to the pins themselves you're not exactly doing yourself any favours. Going through all the trouble to etch traces on the other side only to use a bunch of copper wire as vias will results in the exact same footprint restrictions considering the jumpers I'm making. Plus they don't look as edgy. Naturally all my solder joints will look like that because it's the same as with a single-sided board.

>>1638361
>an SLA printer
The guy in the video looks like he's using a normal LCD panel with a removed backlight, looks like you could get it pretty cheap by hooking it up via HDMI to a computer. The most complex looking parts are the backlight LEDs, which have to have collimating lenses.
>reconsider my connector pinouts
I'm prioritising keeping the lower pins the same for both the single and double headers, but if I discard that requirement I could likely boost the board efficiency.
>neutralize the boards
You mean after etching?

>>1638362
I'm experimenting with THT rivets, but they're a right pain to punch properly if you don't have the proprietary $50 tool to keep the centres open. I'll try it with a $2 alibay leather punch instead when that arrives.

I finally got around to recording a sample (the amen break of course) to a cassette tape to warp on my circuit bent cassette player. If you're not big into jungle/dnb/breakcore it's going to sound annoying as fuck. But hey it works

https://clyp.it/qem5cmsb

next up I'm going to record just a single note from something like a sine wave synthesizer or a violin and then warp that sample with the cassette player

After that it's time for me to learn how to implement MIDI on an arduino, how to use the Arduino's PWM, and then how to link the two together

>>1638365
>SLA printer
note the Z-axis coupler and leadscrew at right. looking again, it's too small to be a D7 proper, but the general elements of the cheap direct-UV projection system are there
>collimating
in the D7's case, it's just a single 30W LED and a linear reflector. seemed to work well enough. a tiny bit of leakage isn't fatal to either process if loosely calibrated
>pinouts
got it. might have gained by placing the power pins to the edges tho
>neutralize
yes, to stop any etchant that might concentrate in acute angles. a thorough rinse should do

>>1638372
>how to implement MIDI
as a point of departure, consider the following https://www.hackster.io/janost/diy-usb-midi-to-cv-0a5469

>>1638361
>if you want to connect layers with the pin, you do

what layers, you said in >>1638263
> it's a single sided board.

>>1638392
It has now morphed into a 1.5 sided board.

probably/definitely more of a /ham/ question, but is it possible, or even feasible to DIY a wide-band (SW/AM/FM/HF/UHF...) receiver that's better than an RTL-SDR?

>>1638454
if you have to ask, the answer is "maybe but you're not there yet"
I recommend that you be able to pass your country's top-class ham license and build a few other RF projects first before attempting your own SDR or even a very sophisticated analog receiver. even if you don't take the exam, never apply for a ticket, and never transmit, you will begin to appreciate the fun and excitement (and math) that comes with high-frequency design, where the non-ideal nature of components (including wires) makes or breaks a project. ARRL publishes a magazine for radio experimenters called QEX and has placed selected articles on their website for free access. that should get you started on the summer's worth of reading you're going to need to do to make it happen
finally, remember the engineer's dictum
>good
>fast
>cheap
pick no more than two

I have a grounding question. Since the earth is neutral (it's overall charge is zero) but some upper layers of atmosphere are negative relative to the Earth, what would happen if someone connects the Earth with a copper cable to the stratosphere as a prank? Or better yet to the Sun which is positively charged. Will that screw up all grounding on Earth and millions of grounded devices will blow up?

>>1638483
>>>/sci/

>>1638483
Suspend your beliefs and look up 'global electric circuit'. You'll find a very dynamic sytem driven by the solar wind where nothing is 'neutral'.

>>1638507
But the solar wind is a rain of electrons washed out from the Sun. So it is negative. Which is why the Sun is positive.

>be me
>want to pick up some optocoupler masterrace for stock
>Digi-Key price for 10: $25.53
>LCSC price for 10: $8.75
>ali price for 10: $4.82 incl. shipping
any guesses what I am actually going to receive if I order from Mr. Ali?
>inb4 fuck-all

>>1638640
Solar wind has an excess of protons. The ionosphere is positively charged.

>>1638685
We live inside a spherical capacitor charged to about 300kV. The total charge of the earth's surface is about 1e6 As.

http://www.atmo.arizona.edu/students/courselinks/spring13/atmo589/ATMO489_online/lecture_1/lect1_global_elec_circuit.html

>>1638680
Only once have I not received an order from Ali, and even then, I got the envelope, it had just been partly torn and nothing was inside - it seemed to have just been mangled in transit so it wasn't the shop's fault, rather the transporter's fault.

>>1638685
Well after a little googling, the solar wind is pretty much electrically neutral as it contains both protons and electrons as it escapes the Sun. But I don't know what happens after that. So you are probably right since it can lose protons or electrons along the way and become either positively or negatively charged. The stratosphere is negatively charged if I remember correctly.

>>1638680
i never had any problems with ali except for power transistors. inexpensive/common/low current parts are ok.

>>1638693
that image looks like something from Made in Abyss

>>1638693
>tfw someone who jumps off a building is actually getting killed by the sudden transfer of charge at landing, not by blunt force
who knew

>>1638361
>pad stacks are coming in v6

God I have such a hardon for KiCAD

Please implement net classes so we can kill Altium already

>>1638706
Electricity in the Atmosphere
http://www.feynmanlectures.caltech.edu/II_09.html
not a comic book

>>1638730
I know, it was just because there was a similar description where the layers of the abyss were like a cloth stretched over you if you went too high

>>1638720
that might fall under
>Implement full featured constraint management system to allow for complex board constraints instead of netclass only constraints.
not much progress but it appears to be on their list.
http://docs.kicad-pcb.org/doxygen/v6_road_map.html
at this rate we just might get semi-autonomous routing by v7, enough to be fully automated by a Python script

>>1638732
Nut

I'm so glad we have nerds spending their free time on this so I can spend my free time using it for free

>>1638757
>free time
I still put some money in CERN's KiCAD tip jar from time to time, I suggest everyone do the same

>>1638288
Results looks nice.

I don't use toaster for reflow, but I already used it to unsolder a recyclable PCB.
I used the "vienoiseries" holder, which allows you to put something on top of the toaster and gets heat from both the slots.
It worked a bit too well and completely destroyed th bottom layer. But I could recycle the top components, which was what I wanted.

>>1639009
>Results looks nice.
Semiconductors have thermal limitations and the recommended temperature profile during production is carefully documented. The really important part is to find out whether yours are now 'toast' or degraded or still fully functional after recovery.

what book should I read if I want to truly understand the concepts of voltage and electrical current? Next time someone tells me stories about water-filled pipes like I'm 12 I will go on a homicidal spree

>>1639028
it's just an analogy meant to impart intuitive understanding of the interrelations between I, E, and R
try Horowitz and Hill, you might be able to find the full PDF floating around the interwebs

>>1639028
>like I'm 12
Mentally you are, tantrum boy.

anyone know where to buy these sexy little bitches in quantities of <100?

>>1639028
Physics for scientists and engineers by serway and jewett.

This is the book I had in my high school physics class and is 100% responsible for my doing EE in college.

Stupid question
Say I have a multimeter and I want to read the amperage of a phone charger. Will I only get a reading when a battery is connected? Confused because I'm getting 0 amps from a phone charger that actually works.

>>1639034
>>1639058
thank you

>>1639064
Oh. What do you even measure if nothing is connected to it? I hope you are not just measuring between the two output contacts?

>>1639065
You're welcome. Read all of part 4 though. The stuff on electrostatics in vacuum is important

>>1639067
I am. I figured if that's how I can measure voltage, I can do the same with amperage.
I'm an electronic retard. Sorry for polluting diy with my shit.

>>1639064
>I want to read the amperage of a phone charger
look on the label

>>1639071
Voltage is measured with the meter between the conductors, current with the meter in-line with one of the conductors. A meter set to read current is practically a short circuit, so you shouldn't connect it across a voltage source.

Hopefully the charger will protect against that; if not, the meter is dead (unless there's a fuse, which is quite common for the high-current range).

The charger might only supply power if it detects the presence of a suitable battery.

>>1639071
That's ok that's what this board is for to ask questions. I was just worried about your multimeter. You basically created a short circuit since it has almost zero resistance in the current meter mode. Check the fuse on the meter.

>>1639071
if it's any consolation, my newbie self did the same thing. Tried to measure the current on my nodemcu by inadvertently shortening it. Both the meter and the nodemcu survived