/diy/ - Do It Yourself

>>1715180
this thread's digits brought to you in part by the BTS5180 smart high-side power switch

How can I detect a signal from a laser at long distance? Example: need to send communications over a distance of a couple of miles, don't want the neighbors fucking with it. It doesn't need to be fast, it just needs to function so that the site has communications for, e.g., sending out an intruder alert, where cellphone coverage is unavailable.

>>1715220
>laser
>couple of miles
Scintillation will fuck you over. Use LEDs and lenses. Look up the Twibright Ronja for inspiration.

>breadboards

>>1714776
>>1714837
I have some ferrites from CRT... How do I make nice voltage multiplier fit in old cellphone sized enclosure?
I'm gonna cast everything in epoxy, because high voltage.

>>1715226
>Scintillation will fuck you over.
Would you be so kind as to explain this in more detail? I know what the s-word means generally but not in this context.

I want to network two Raspberry Pi's together across their GPIO pins. How fast can they detect pins switching between high and low? What sort of speed can I get across such a link?

I'm not looking for ethernet speeds. If I can communicate 100 bytes per second that's more than enough.

Electronics tech level: I've done most of the basic Adafruit tutorials but still can't solder worth a shit.

>>1715258
a rapidly oscillating pattern of visual distortions, often associated with migraine aura

>use a breadboard bro

>>1715264
Yeah, I've gotten scintillating scotomas twice in my life and the first time I thought I'd detached my left retina; it spread to almost my entire left eye and I thought I was going to be blind, then it just . . . went away after maybe half an hour.

But what is the problem with "scintillation" in the context of laser communications over ranges of a few miles, using electronics on both ends, in particular on the detector side?

I looked up that "Ronja" thing. I think it would be useful for fixed location installations, but I'm actually more interested in mobile. Can I use UV diodes for invisibility or do detectors not exist for that? The bright red LEDs are too visible for my application.

>>1715244
>>1715268
That's not keto. Zero carb for lyfe!

>>1715269
>But what is the problem with "scintillation" in the context of laser communications over ranges of a few miles

Different anon but variances in the air will fuck over modulation with a narrow beam laser past 1km unless you're top-tier at signal processing.

>Can I use UV diodes for invisibility

No, you can use infrared diodes though, the Twibright site even has an example model of exactly that if you read it properly.

>>1715262
why not let the hardware do it
http://www.pihome.eu/2017/10/08/enable-serial-port-gpio-raspbian-jessie/
https://www.instructables.com/id/Read-and-write-from-serial-port-with-Raspberry-Pi/

>>1715281
Won't work, I need to do it across the GPIO pins for what I want to do.

Still working on my 4017 switch reader interface circuit. It's based on the MC14017 datasheet example application. It reads and serialises up to 24 on/off switch inputs. I'm going to use it for interfacing a large number of two- and three-position rotary switches with a microcontroller.
The MCU toggles the clock input and inspects the state of the data output pin. If the corresponding switch is closed, the transistor pulls the data pin to GND. If it's open, MCU GPIO port pull-up resistor pulls it up to positive supply voltage.

>>1715283
those are GPIO pins
why haven't you written some test code yet? choose your favorite programming language, and try something like the "Centronics" strobe/ack handshake. I will say that 1000bps is a lot to ask from bit-banging from inside a multitasking OS
how about I2C https://raspberrypi.stackexchange.com/questions/76109/raspberry-as-an-i2c-slave

>>1715289
>I will say that 1000bps is a lot to ask from bit-banging from inside a multitasking OS
Seriously? These are gigahertz quad-core CPUs. I'm literally asking them to detect one bit change within 1,000,000 processor cycles or maybe more.

If necessary I'd CPU-lock all other processes out of one core, and leave my communications process as the only one on a single core. It's not like the system is going to be running anything other than my itty-bitty tasks.

>why haven't you done it already?
Seriously? I thought this was a discussion board.

>>1715274
Thanks. I'm not looking for huge bandwidth. Communication would be digital.

I found the IR diode version, thanks. Still a little worried about detection because even though they aren't bright red, the ones used for illumination for common cameras still show a red glow.

>>1712580
Why not use a 555 astable circuit, with a digitally controlled potentiometer for the external resistance?
Not sure if this provides adequate resolution for
your need, but it's a very affordable possibility.

https://www.arduino.cc/en/Tutorial/DigitalPotentiometer

>>1715294
there are a lot of layers that your single bit goes through from kernel to port register. there's the capacitance of the cable and the low drive strength of most SoC GPIOs to think about. unless you're completely sanguine about missing bits, handshaking is probably going to be a little slow, depending on how you have the scheduler configured, and the scheduler still hates you
speaking for myself, I'd much rather see finished projects, or half-finished projects, or just-started projects, than Pic related

>>1715303
there's an interesting protocol used in the automotive industry between ECUs and sensors called SENT (single-edge nybble transfer). as the name implies, it encodes 4 bits on a variable-width pulse on a power+signal line, without stringent requirements as to regular pulse frequency. if you were to use a similar encoding with a low enough duty cycle and an emitter/receiver pair that responds quickly enough, you might be able to keep the pulses sub-threshold on average
940nm might be long enough to allow a higher duty cycle while remaining sub-threshold. photodiodes are relatively cheap but power LEDs start to get expensive at much longer wavelength

>>1715256
>cellphone sized enclosure
Probably not, but if you have a few hundred metres of 0.1mm wire maybe. Have fun winding.

>>1715274
>unless you're top-tier at signal processing
Makes you wonder what the satellite-to-ground laser comms use.
>diodes
well there's your problem, semiconductor lasers have terrible finesse last I checked, meaning they spread out significantly past a certain distance. NdYAGs are probably a good choice for long-distance comms, but whether 1km is long enough isn't something I've done the calculations on. I can bust out the laser physics book if anyone's interested, but it doesn't have any practical examples for engineering reference, so I'd need the datasheets for whatever lasers you're potentially looking at.

>>1715310
Did you read what he needed it to do? Sine, square, triangle, sawtooth, reverse sawtooth, along with a precise back-and-forth frequency sweep. If he wanted something cheap that could just do square waves, then an arduino would at least have the benefit of a precise digitally adjustable frequency, throw in a DDS module to get probably all the features he's looking for.

>>1715323
None of those requirements were in the original post, also you can use a 555 to create almost any waveform.
http://www.learningaboutelectronics.com/Articles/Sine-wave-generator-circuit-with-a-555-timer.php
http://www.circuitstoday.com/saw-tooth-wave-generator-using-ne555
Whether or not it is practical to make each of these circuits yourself is up to you, it certainly would require a lower budget and have more learning potential than buying some chinese solution.

>>1715262
Use the serial pins like the other anon suggested; don't be a dolt.

>>1715350
>None of those requirements were in the original post
Here's the first post:
>I'm looking for the cheapest frequency generator or combined solution that meets the following.
>>bandwidth I'll be using is within low, up to 50KHz
>>output must be at least 0.5Vpp
>>must have a customizable sweeping function that not only sweeps from start to finish but will keep bouncing until I stop it from low to max frequency with configurable timer and mode linear-logarithmic
There's the sweep function in the original post. In the second post he says:
>I need the basics: sine, square, triangle, sawtooth and reverse sawtooth.

>more learning potential
555s are barely used practically these days, if he wanted modern learning potential he'd use a DDS or PLL. Which are also really cheap, if you didn't know, and don't have an abhorrent quiescent current of 3mA, or a "high" output voltage level of 1.4-2V lower than Vcc. And the "triangle wave" from a 555 is hardly a triangle wave at all, it would be better to use an op-amp integrator-based oscillator for that. Also 555s are terrible for changing frequency and duty-cycle independently, which the aforementioned integrator solution handles better. And don't even get me started on the 555's terrible pinout. If you want a learning experience better than any 555, I recommend you make your own positive and negative feedback circuits with comparators and op-amps respectively.

DIY CPU anon, here with a question about software multiplication

I've hammered out a preliminary 16-bit version of the ISA.
Since I'm implementing this with TTL, there's no multiply instruction.
I wrote a few shift-and-add software multiplication subroutines, and the fastest I could get was 90 cycles.
I realize this is kind of arbitrary, but does 90 cycles sound decent for software multiplication, or is that just really slow?
Instructions only take a single cycle, instructions with an immediate value take two cycles, for reference.

So I have this complex amplitude modulated signal and I'm looking to get it's smoothed envelope (as in not all chopped up by the local oscillator).

My problem is capacitors. Capacitor voltage increase according to a logarithmic function but discharges according to an exponential. I want to force the capacitor in my envelope follower to also discharge via a logarithmic function. I know I can use a current source to charge/discharge a cap linearly but I do not want that. Discharge needs to occur according to the natural log. How do I force that?

>>1715451
Both of those functions are exponential, they're just drawn as quarter circles in that image. The initial/maximum slope is a constant set by an instantaneous current V/R entering the capacitor, while as t approaches infinity the slope approaches 0. In other words: V_charge = Vcc(1-e^(-t/RC)), V_discharge = Vcc(e^(-t/RC)). Do the calculus yourself if you feel like it.

As far as getting a logarithmic curve, I don't know of any simple circuits with such a feature (not RC, LC, LR) so I think your only bet is to try to approximate it with a limited section of an RC circuit, or look into active devices. Last I checked there was something called a log amplifier, which has the relationship V_out = K*ln(V_in/V_ref). To turn this into a V_out = ln(X*t) you could use a constant-current capacitor ramp to get V_ramp = V_in = Y*t.

>>1715451
>>1715469
Log amps exist, taking advantage of the logarithmic curve of a diode or transistor, but they have a pretty limited voltage range.
For this diode based logarithmic amplifier, it saturates after about 0.7v input, and the curve is pretty sharp.

>>1715476
>>1715469
Log amps aren't a realistic solution. It's all analog devices parts that are like $20 a piece and log amps made with discrete components are nearly useless.

>>1715476
Wouldn't you use a voltage divider stage before the diode to expand the effective voltage range, followed by a gain stage afterwards? Seems a bit shortsighted to look at that circuit and say "can't use it above 0.7V". Though I imagine it may have other downsides. Could these be mitigated with a current-mirror feeding through two diodes somehow?

>>1715480
What?
The range of the amp is 0.7 volts, physically limited by the diode.
You can expand the input range by putting a voltage divider before the input, but the range of the amp is still just 0.7 volts, thus you must design around that.
Likewise, if you want an output range greater than 0 to 0.7, then you need to put an amplifier after the output.

So I gutted a couple old speaker systems I held onto and now have a bunch of loose drivers. Their old amp boards were junk, so I just salvaged some small parts from them. I also just got a nice old wine box that could fit quite a bit inside it, plus some old Chinese PC fans that I could use to cool the interior. My woodworking skills are decent, but I've only got a year of electronics classes under my belt with little audio system knowledge. Hope I'm in the right thread

Questions:
Is the stuff in pic related all I need to cobble together a new party speaker?
Would my 4 ohm drivers work together if I wired them all in series per L/R channel, despite the wattage difference?
Could I mix the larger sub with the smaller one?
If not, could I use the smaller one as a "center" by connecting it to both stereo channels?
Are the amp or power supply overkill for the stuff I'm trying to drive?
Is the sound going to be noticeably bad if I just mount every driver symmetrically on the sides and bottom of the box?
Would it be practical to add ports on the enclosure to plug in extra cabinets?

>>1715488
0 to -0.7V. Log amp is inverting.

>>1715488
>but the range of the amp is still just 0.7 volts, thus you must design around that
So if you can change the gain before and after it, what's the problem? Decreased SNR?

>>1715269
>Can I use UV diodes

No, the whole path would need to be transparent to UV and the lenses are probably not.

>>1715489
>Are the amp or power supply overkill

Power supply looks like a cheap Chinese switching PSU. You're better off with a regular transformer (ideally toroid ferrite core) found in most audio gear since you might hear switching noise artifacts.

>>1715441

90 cycles? You did better than the intel 8086.

As a performance-conscious programmer of your system would likely never use such a fluffy "vanity" instruction anyway though.

>>1715514
Jeez, the 8086 is that bad?
I've never done much x86 ASM, I mostly learned MIPS and AVR, with a tiny amount of 6502.

>As a performance-conscious programmer of your system would likely never use such a fluffy "vanity" instruction anyway though.
True, the best way to avoid the heavy performance penalty of multiplying two variables is to not use it at all, but I would like to try porting something like Wolfenstien 3D to it, and that will require multiplication between variables.

>>1715510
It's exactly a cheap Chinese switching PSU
https://www.amazon.com/gp/product/B01B1PRE6A/ref=ox_sc_saved_title_4?smid=A40NHWEFTZZNI&psc=1
but I haven't had luck finding any audio-specific transformers on amazon and I'm trying to keep the budget under $75-ish anyways

Would it be wiser to just buy pic related plus a small bluetooth reciever and separate sub amp? Or could I run that medley of speakers on the amp I already found using a 24v 5a laptop charger kinda power supply? End result doesn't need to shatter windows or anything

This seems like a good enough place for my dumb question.

When I do A - B = C with binary numbers, I convert B to 2s complement and then add it to A. Is C then in 2s complement or is it in regular binary?

Do those cheap $15 heat guns from ali work for smd soldering? i don't solder often so i don't want to invest into a quality hot air station

>>1715554
Others should correct me if I'm wrong, but C should be in 2s complement.
Think of it like this: if you calculate 2-4
You basically do 2+(-4) in 2s c , so if the result wasn't in 2sc, how would you ever get a negative result?

>>1715575
I never used one, but if you rarely use it and your and parts aren't easily heat damaged, go for it is what I'd say. If you do this more often, professionally or with expensive equipment, just invest in a decent one instead.

>>1715554
As an example:
2-6 =(-4)
In binary:
0010 + 1010 = 1100

And 1100 is (-4) in binary complement, but 12 in normal binary. That should answer your question better than I did in >>1715576

>>1715350
> you can use a 555 to create almost any waveform.

Things get a lot more complicated when you need a frequency sweep. That "sin" circuit you linked is just a low pass filter rounding the corners of a square wave. The amplitude and shape of the waveform will change as you increase frequency.

>>1712580
The ICL8038 will meet your requirements. It's obsolete but you can still find them for a dollar on eBay. There are also a lot of inexpensive microcontrollers with built in 8bit DACs that would work if a little bit of staircase is acceptable.

>>1715579
That's true, but you actually can add a 2's compliment number to an unsigned number and get an unsigned result.

6 + (-2) = 4
0110 + 1110 = 0100

You just need to keep track of your carries and overflows to make sure the operation is valid

>>1715554
>When I do A - B = C with binary numbers, I convert B to 2s complement
Don't think of it that way. It's all about representation. The nifty thing about two's complement is that the math works the same as for unsigned numbers.

Say you do:

1101 + 1101 = (1)1010

So, what was this really?

Was it 13 + 13 = 26?
Was it 13 − 3 = 10?
Was it −3 − 3 = −6?

It's all of them, or one of them, or none of them. That's what's so neat about two's complement, with just an adder you can do both signed and unsigned math seamlessly.

>>1715479
>posts a one-diode solution
>totally not realistic
wew

>>1715510
>powering a class D switching amplifier
>zOmG aRTiFaCtS

>>1715524
multiplying what size and signedness word by what size and signedness word?
for comparison, the 68000 unsigned 16*16=32 MULU instruction took 38 cycles
SPARCv7 had a "multiply step" instruction in its earlier iterations, see p83 https://www.cs.rochester.edu/~scott/456/local_only/sparcv7.pdf
only guessing here because of unpublished ISA, and programmer model but 16 reps of rotate-right/conditional-add/rotate-left should work. if you're not unrolling your loop, you are making the baby John Carmack cry

>>1715575
yes, but unless you're doing parts with hidden contacts (BGA, exposed pads, etc) a 936 clone with a 1mm bevel tip is better

>>1715582
>can
lol no, the result is still signed
5 + (-6) = (-1)
0101 + 1010 = 1111

>>1715586
>seamlessly
except for unary negation, if you have no carry input on your adder

>>1715441
Booth multiplication may be faster, particularly if you can quickly identify transitions. Booth multiplication uses both addition and subtraction rather than just addition. E.g. 240*x is calculated as (256-16)*x (2 terms) rather than (128+64+32+16)*x (4 terms).

>>1715576
>>1715579
>>1715586
Thanks anons, 2s complement just seems like a magic trick to be. It's so weird. So just to confirm, I should definitely be able to check for positive or negative by just checking the most significant bit of the result? 0 being positive, 1 being negative?

>>1715603
his is a 2-operand single-cycle machine with a small 2-read 1-write register file, all made of discrete logic, and cost constraints apply. therefore I would suspect he can't quickly identify transitions, and even if he could, he couldn't quickly act upon them. a full hardware multiplier seems expensive

>>1715630
it is a magic trick, a well-known, safe one available to any novice spellcaster, invented by a teenage punk and mathematician by the name of Galois and named in his honor
https://en.wikipedia.org/wiki/Finite_field

>>1715630
> So just to confirm, I should definitely be able to check for positive or negative by just checking the most significant bit of the result? 0 being positive, 1 being negative?
Assuming that there's no overflow. E.g. 127+127=254=-2. Most CPUs have an overflow flag which is set from the exclusive-or of the carries into and out of the most-significant bit.

yasssss it's working

my lgbt doggo will be so happy!
all the led collars they had at the store were dim pieces of shit that only do one color
so i made my own with 5050s and the great thing is that since it's a pixel strip i can program any pattern i want into that shit

>>1715656
LGBTQLEDRGBK9

>>1715656
absolutely fabulous
now you just need to waterproof the batteries n sheeit

>>1715656

wouldnt wanna be around when the wax paper falls off and the adhesive strip sticks to the dog's balls.

shit
it's TOO fucking bright
i just went into a dark forest to field test and my doggo looked like if he was being perpetually kidnapped by aliens
i could actually run around without any problems because the collar was illuminating so much environment around us
I have to tone it down a bit and use some nice mellow color transition and it will work out great
i also ordered a smol light lipo pouch from chinks so i can ditch the bulky aaa battery packs, since the doggo looks like a suicide bomber right now

>>1715676
when the lipo arrives and i am done with programming the IC i am going to encase all exposed contacts in epoxy and only leave two wires for charging the lipo

>>1715677
Later i am going to remove the paper and like rub the glue with cotton swabs or something to make it not stick

>>1715687
>rub the glue with cotton swabs

acetone is what you need.

>>1715687
Sure your HECKIN PUPPER can carry a bit more so it can react to his yappin' https://www.instructables.com/id/Sound-Reactive-LED-strip/

>>1715687
>encase all exposed contacts in epoxy

no need to do that. water is high resistance, and the voltage is too low to shock. the bigger risk is the LiPo which will burn if punctured.

>>1715687
>Later i am going to remove the paper and like rub the glue with cotton swabs or something to make it not stick

Really you should attach it around a regular collar so it won't fall apart so easily with time.

>>1715384
Not possible for this application. There are valid reasons for me doing it the way I've planned. Sometimes you guys just have to accept that.

>>1715826

>>1715826
What are the reasons? Explain and we might be able to help.

>>1715826
if you want free tech help you have to be willing to sate people's curiosity

I have this cheap coffee brewer (drip) with a heating plate. Thing is, it's on a timer, so it will turn off after a while and my coffee goes cold. Anyway to hack it into not turning off?

Really stupid question here, but what exactly am I looking for?

I've got a solar setup, and I run a few 12v things just right off the battery. Particularly a computer monitor that calls for 12v/8A but seems to only pull 3-4A at a reasonable brightness level.
But it will cut off as the voltage wears down through the night, especially with other loads, where I then have to lower the brightness all the way and it will then continue going.
So I'm looking for a voltage stabilizer is what I need?
I need 12-12.5V regardless of the input, 30v-10v input but always that specific output voltage.
Will this work? https://www.amazon.com/dp/B0711SDBFW

>>1715601
It's not about the number of diodes retard, there are other problems with discrete log amps
>This type of log amp has three disadvantages: (1) both the slope and intercept are temperature dependent; (2) it will only handle unipolar signals; and (3) its bandwidth is both limited and dependent on signal amplitude. Where several such log amps are used on a single chip to produce an analog computer which performs both log and antilog operations, the temperature variation in the log operations is unimportant, since it is compensated by a similar variation in the antilogging.
https://www.analog.com/media/en/training-seminars/tutorials/MT-077.pdf

So where does the whole "water pressure" analogy break down in electronics?

Any anons have racheting crimp tool recommendations for molex minifit-jr series of terminals?

>>1716079
Most semiconductor devices, mutual inductance, EM waves, the hall effect, possibly power transfer itself [does speed * pressure ( * constant) = power?]. I think negative resistance does work for when laminar flow breaks down however. Basically anything that relies on magnetism aside from simple inductors really, unless there's some method I'm overlooking. Basically the same as the mechanical analogy (drive shafts, torsion springs, and flywheels), only there I know the speed*torque = power, so it's arguably better. Haven't looked into the thermal analogy.

Man, sometimes it's really weird to see what chips are still in production and which aren't.
Loads of interesting and useful 74 series chips are long out of production.
But you can still buy many varieties of Bell 103 compatible modems on a chip.

>>1716102
MOS 6502 is still in production as well.
And it is fucking based.

>>1716103
If I wanted to experiment with wiring up 10s (or maybe hundreds) of microcontrollers for the lolz and for playing around parallel computing, would the 6502 be a good choice?

>>1716103
The 6502 is indeed great, still quite common as an embedded CPU, especially in medical equipment from what I hear.
Also, the Intel 8051 is hiding in everything.

That said, I can't figure out what a Bell 103 modem is still useful for, aside from packet radio on the HF ham bands, but I wouldn't think that's a big enough market to sustain multiple competing Bell 103 modems on a chip, especially with SDR around.
Oh well, I won't complain, I'll probably pick a few up to get talking with my TRS-80 Model 100.

>>1716104
How do you plan on each CPU communicating with each other?

>>1716104
>would the 6502 be a good choice?

nah. if you're trying to get petaflop performance, you dont do it with 20Mhz 8-bit CPUs but with 64-bit 1Ghz+ CPUs like the ARM Cortex-A53, and the like.

>>1716152
not him but, stm32?

>>1716116
>That said, I can't figure out what a Bell 103 modem is still useful for, aside from packet radio on the HF ham bands, but I wouldn't think that's a big enough market to sustain multiple competing Bell 103 modems on a chip, especially with SDR around.
Organized crime is keeping them in place maybe.

I’m getting tired of seeing videos on shit like EEVblog and Mr Carson’s Lab where they work on mains-referenced shit or high-voltage equipment like TV tubes and shit with large caps and just say “this is dangerous, you need to know what you’re doing” but then never show what safety precautions they’re fucking taking.

What do I need to know if I want to probe around in the back of a TV or on the primary side of a power supply? Is there a guide to this shit?

>>1716228

you cant generalize on a procedure coz each piece of equipment is different. the only advice that carries from one unit to another is ''know the equipment.'' you can use schematics and experience to determine where dangerous voltages are found. if, in doubt, measure with a DMM, or look at capacitor voltage ratings.

then avoid touching anything there. if you need to probe, turn power off, attach your probes, then power on.

then there's a whole complex story on whether you can connect a scope ground (or any grounded test instrument) to which parts of the unit . if in doubt, measure AC and DC voltage to ground with a DMM before connecting an instrument ground to that point.

>>1716228
Yes, common sense.

>>1716235
>then there's a whole complex story on whether you can connect a scope ground (or any grounded test instrument) to which parts of the unit
Right, I’ve read about that. It has to do with the BNCs on most scopes having continuity to chassis ground, and chassis ground in most electrical systems being connected to neutral, so there’s a full AC circuit through your scope if you connect your scope leads to something with AC on it.

I guess my frustration with it all is that they make it sound like if you’re even probing shit with your DMM you’re gonna blow yourself up. I’m guessing that’s generally not the case, situations like these being excepted: https://youtu.be/hfnEuRA7-vo (tl;dw: guy put his 600V-rated meter on a live 2.3kV industrial equipment circuit after bypassing a safety lockout).

>>1715981
looks ok

>>1716084
buy one of the chink tools with interchangeable dies, try your luck
or relax the ratcheting requirement, get Pic related for $50 and crimp just about any uninsulated open terminal by any manufacturer ever

>>1716102
Bell 103 is still used in payphones, vending machines, credit card terminals, alarm systems, etc. most hammers modem on a PC these days, or, for that matter, an MCU
5V discrete logic otoh has been a steampunk toy for at least 10 years and fully replaced in practice by MCUs, especially now that so may new devices come with a couple of LUTs on them

>>1716104
state your skill level and your plan
in general, the connectivity between/among the chips is the real problem to solve. at scale, multiple-access memory subsystems start to look a lot like packet networks. buy a stack of bluepills, or make lots of really tiny CPUs on $20 FPGAs

>>1716174
sure, ig. any sort of useful shared-memory system is going to be a bitch to implement with most external bus interfaces, which rarely include an external bus hold signal

>>1716228
life insurance
and respect

>>1716255
>5V discrete logic otoh has been a steampunk toy
Lol I’ve never heard that before but fuck me it actually makes sense.

Well, I’m not gonna avoid using ICs from now in.

>>1716259
ok hipster

>>1716274

>>1716275
It has to do with how the manufacturer measures nominal capacitance. This is Taiyo Yuden's method: https://www.yuden.co.jp/kr/product/support/faq/q006.html

The one you've selected is a Class 2 over 10µF, so the testing conditions are supposed to be, held at 150ºC for 1 hour, 0.5±0.1Vrms, and frequency of 120±10Hz (I think that may be an error, and it might be 120kHz±10%, based on the test conditions for other components and what the chart you have says). But I'm not 100% sure. Basically though, the lesson is that nominal capacitance depends on how the manufacturer defines it, since effective capacitance (what that chart shows) is affected by impedance.

Is lead-free/RoHS the onions of electronics?

>>1716300
no, 120Hz is standard (US mains half-cycle period). not especially applicable to present usage of 33µF caps but oh well

>>1716300
>nominal capacitance depends on how the manufacturer defines it
this is absolutely true. it also implies that nominal capacitance is not especially relevant
obviously this cap is best suited for ~200kHz noise

>>1716304
no, lead is for cucks who can't solder

>>1716308
>no, 120Hz is standard (US mains half-cycle period). not especially applicable to present usage of 33µF caps but oh well
Oh, good point. Yeah I guess Taiyo Yuden is just doing whatever the hell they want when they label those caps. lol

>>1716311
companies that serve automotive customers generally do not just do whatever the hell they want. I would suggest they have a reason for downshifting to 120Hz, possibly related to the range of their production testing equipment. for example, the E4981A capacitance meter https://www.keysight.com/en/pd-1452259-pn-E4981A/capacitance-meter maxes out at 100µF (nominal) at 1kHz

>>1716336
My point is that the chart anon posted in the last thread indicates that the cap hovers around 200 µF at most frequencies until about 100 kHz, when it starts its steady climb to resonance. I have no idea how they're getting their label value at 120 Hz with that chart.

>>1716152
Thanks, I was really just curious. I wanted to see just how much performance I could get out of a 6502, but maybe another project might be better just for testing low level optimized assembly or C. I am a programmer trying to learn about hardware.

>>1716255
Almost zero. I can solder, I have wired up small circuits on the past (timers, op-amps, etc.) and I have knowledge of electronics at a basic level.

>>1716116
I don't really know, I was hoping I could get advice on this board. Can't I wire the output from one to the input to another? Also, can I wire multiple 6502s to the address lines of another 6502 so it can act as a controller for those chips wired in parallel?

>>1716362
>Can't I wire the output from one to the input to another? Also, can I wire multiple 6502s to the address lines of another 6502 so it can act as a controller for those chips wired in parallel?
You really need to look at the datasheet. I feel like there would be weird timing issues. Especially if an interrupt happens to just one and the processors desynchronize. But I could also see problems on the signaling level.

I think it'd be better to implement a single-CPU setup before trying to tackle parallelization. There's a lot of specialized coding practices involved.

>>1716368
Yes, these are exactly the things I didn't know about. Would it be possible to "train" them like DDR RAM is trained? Perhaps timing could be set with a custom circuit with a tunable crystal oscillator. But I'll try it with a single 6502 or stm32 first.

>>1716378
I'm honestly not sure. I'm recalling lessons from computer architecture courses I took nearly 15 years ago.

>>1716381
So first: get a 6502 to talk to a character lcd display or small pixel display.

2nd: wire the output from one to another to see if they can talk to each other.

3rd: wire two chips into the input lines from another and see if they can be timed to deliver data in the right order.

>>1716390
I just looked up some lecture notes from the class I took back in the day. You might (or might not) find them interesting:
https://courses.engr.illinois.edu/cs232/sp2010/lectures/L20.pdf
https://courses.engr.illinois.edu/cs232/sp2010/lectures/L21.pdf

(this is from a few years after I took the same course, and unfortunately the links for video seem to be dead, and I don't have anything like a textbook—I'm not sure there was one—or my own notes from the class).

>>1716392
Also literally just found the book for that iteration of the class (it definitely wasn't the text when I took it, but it could be useful). Look for Computer Organization and Design on libgen.

>>1716392
Thanks anon, this is what I was looking for.

>>1716362
have you written any concurrent or multi-threaded programs on a real OS before? many of the same concerns (atomicity, data hazards, mutual exclusion, deadlocking, etc.) also apply at the hardware levels
>wire multiple 6502s
you could, but only one of them can control the bus at once. those ROMless 8-bit CPUs use the same bus to read memory for their instructions as well as to read and write data. at the very least you would want to give each device its own private memory for programs and data, and use some form of shared resource for inter-processor communication (dual-ported RAM chips, or some sort of bus interleaving like the CDC 6600 or various 8- and 16-bit home computers)
you should definitely spend some time reading up on existing designs from 20-50 years ago. the home computers had good to excellent hardware reference manuals that gave some nice detail about the operation of the system, especially in regard to how they shared graphics memory with the CPU

>>1716394
>CO&D
based Hennessy and Patterson
I also recommend the follow-on, Computer Architecture: A Quantitative Approach, in case anon decides they want to play around with designing their own ISA and CPU

>>1716435
God I loved taking computer architecture. Was the one last indication that I should’ve tried harder to do EE/ECE.

Building a tube preamp. Marshall 2204/plexi dual preamp.

Light turns on, tubes get filament current, but no sound except a hum. The master volume works too; I can turn the volume up and down. I seem to be getting sound but no actual preamp signal.

Is it my power supply? Or something else? The schematic didn't include a power supply so I tried to make my own.

I'll post pics, along with the schematic. Ignore the 4th tube socket

>>1716496
Schematic

Power supply. The rectifier diodes are connected to the caps under the turret board

>>1716500
whew
>just saying whew at the layout, can't say whether that's right or wrong lol

>>1716503
It's messy, I know lol. When it actually works, I'll clean up and move things to be more neat.

>>1716496
Well, most basic thing first: Did you let the tubes warm up?

>>1716511
Yeah I let them warm up. I warmed them up again for a good 20 minutes but still nothing

>>1716533
Well that oughta be plenty warm. I dunno from there.

>>1716392
based and illinoispilled

>>1716546
Honestly was the only pill for me to swallow. Mom and dad went there in the 70s. Sadly I didn't follow in their footsteps and marry someone I met there haha.

>>1716497
that's a child's art project, not a schematic
but ig it's what we got. post voltages

>>1716573
Yeah was gonna say myself, I’d much rather see the schematic in a conventional form if you have it.

>>1716573
Here's the standard schematic. Will post voltages later

I found boxes upon boxes of Motorola M-core related shit at home, they belonged to my dad, I will learn it just because

>>1716627

is the documentation in Latin?

>>1716631
Kek that's funny, got you.
More or less ;)

>>1716500
So you just got mains going in, being rectified and filtered right? Do you measure +170VDC on the output of the supply? If yes then it's working.

>>1716500
That is pretty unsafe senpai.

>>1716641
I imagine it's from the secondary side of a transformer.
shit nevermind those are 450V caps
also those diode-diode-wire solder joints look kinda dry

>>1716664
Yee. Those are pretty crusty.

>>1716664
Does he even have a transformer? You really need one in tube gear. You can rectify the mains directly. It may be somewhat safer to have one but it's not like it's a requirement.

>>1716683
*you don't really need one.

>>1716683
>You can rectify the mains directly
Well he's using a full-bridge, meaning his 0V rail will be riding down one half of the mains sine, which could be pretty noisy without input and output transformers. It also means that any shielding will need to be at that potential too, making it somewhat unsafe.
That's why I always use single-diode rectifiers.

Any good readings on power systems/transformers?

>>1716692
at what scale?

>>1716639
>170V
I... don't think a circuit designed for a B+ of over 300V is going to work very well on 170V

So, I'm looking at Dual Port SRAM for a project, but as you probably know, it's freaking expensive.
Looking at Digikey I was seeing prices of about $60 each, minimum order of 9.
In light of that, I started considering other options.
Currently I'm looking at using asynch SRAM and double pumping the bus.
Essentially, I'll make the asynch SRAM appear like synchronous SRAM, where the first read/write port is serviced while the clock is low and the second port is serviced when the clock is high.
This is what I managed to throw together, it works in the simulator.
Does this look like a viable solution?

>>1716781
Double pumping sounds like a reasonable solution, but why not just have 16 bit parallel output RAM instead? Like 32k x 16. Pretty sure you can get them, at the very least there are EPROMs where you can change from 8bit to 16bit modes. Or just have two 32k x 8 next to one another. What speeds are we talking about here? If it's just writing to 7segs I daresay a cheaper EEPROM or FLASH IC would work, then again if you're writing the damn thing on every clock cycle that probably doesn't apply.

>>1716300
>>1716336
thanks friends, maybe I can learn to cope with the ugly reality of practical components

>>1716781
yes, that is a good solution, if both ports are indeed synchronous
be sure to check the timing diagrams to ensure you meet access time, hold time, and all that other jazz. if you don't, you might see phantom writes

>>1716829
how's that dual-ported?

>>1716731
Haha honestly I don’t know. I was thinking general purpose shit, like you’d find in appliances and consumer electronics. Switched mode and linear power supplies and their design principles.

>>1716932
Pressman et al., Switching Power Supply Design. might need to work your way through The Art of Electronics first if you're not greybeard enough

Say I have a motor with 4 leads - red, black, brown and brown. The casing gets in the way so I can't see where they actually connect to on the motor. Where should I put suppression caps? Brown leads or other colour leads?

>>1716945
It’s been a few years (well more like 15) since I’ve done academic shit on electronics so yeah I might need to give myself a refresher. Thanks friend.

Is this doable: a brute force additive synth with a bunch of cheap low freq AD8xx chips? Lets say 64 of them? And a micro?

>>1716988
yes
can *you* do it? if you have to ask, probably not

>>1716994
i guess i asked a wrong question. is that a feasible/best solution for additive synth? even the cheapest AD9833 is like $2. perhaps there is a dedicated additive synth DSP chip that contains a few sine outputs. i found one but it is also pretty expensive.

>>1717000
i guess this is still not what i am trying to figure out. it sounds a lot simpler to do additive synth entirely in software. i am not sure if a general micro would do or i'd need a dedicated DSP or some other chip for that. in which case it wouldn't make sense to mess with physical DDS generators.

How hard and how expensive is creating a anti-thief alarm?

>>1717011
Depends on the design and specs. What's it do?

>>1717004
So I found these AD SHARC Audio DSP chips.
The cheapest is ADSP-21489 is $14. But that's just for one per voice so would need a lot of them for polyphony? Also they are very complicated and sounds like an overkill so maybe an FPGA would be a better approach. Has anyone done anything like that? For example, an additive synth with 256 time varying harmonics

>>1717013
Just a door and a sound system for scare Intruders

>>1717031

$5 gets you a simple but complete unit.

>>1717000
>feasible
lol no. any 50+MHz ARM MCU will be able to do at least one, if not several voices, depending on hardware math support. slap on a 16-24 bit DAC of your choice and rock your way to town
>has anyone else
http://zynaddsubfx.sourceforge.net/

>>1716829
The 7seg displays were just so I could quickly see the output.
>but why not just have 16 bit parallel output RAM instead?
I do, I just used the 8-bit RAM in Logisim to quickly bash together a proof-of-concept.
>What speeds are we talking about here
Probably around 15MHz.
I'll be using 20ns SRAM. Since the bus is double pumped, that gives me a max memory clock of about 25MHz. (1/(20ns+20ns)).
Naturally, I need to account for overhead from the selection logic, so let's say 20MHz max memory speed.
>then again if you're writing the damn thing on every clock cycle that probably doesn't apply.
Yes, I'll have two independent devices hooked up to it, each of which may make a read or write.
It's a shared memory region.

>>1716924
>be sure to check the timing diagrams to ensure you meet access time, hold time, and all that other jazz. if you don't, you might see phantom writes
Right, I'll have to check my delays on the selection logic to make sure everything stays in sync too.
I'm mostly banking on the fact that I'm not really pushing the SRAM as fast as it can possibly go to prevent any access or hold time problems.

>>1717067
for maximum reliability I'd recommend a 2x clock instead of DDR, if you can at all get it

>>1717084
Why's that?
I'd still need all the same arbitration logic, right?

I could try using a 2x clock, but routing just a single clock would be easier for me.

>>1717093
there's no arbitration per se in your design, just multiplexing. if one of the users were held off for a moment while the other one is allowed access, that would be arbitration
>Why's that
the logic is the same, but you could use the extra clock to enforce some dead time on the bus for addresses to setup etc

>>1717042
>http://zynaddsubfx.sourceforge.net/
cool, thanks. dang, all my inventions have already been invented. i did mess with a 100MHz STM32F4 at some point and i also have some F7's still in the package so I may give it a try. Somehow I remember there were some clock speed limitations but maybe I am thinking of other projects where I needed higher frequencies. These micros also have a 16-bit DAC but should be good enough.

>>1717117
oh no DAC is 12 bit. need an external DAC then
12 bit, really.

>>1717117
>STM32F4
hard-float, right? good for at least 3 voices imo
>12-bit
yeah, they're microcontrollers. 12-bits is plenty for most control applications. e.g. it would be just fine for feeding a control voltage to some part of an analog synth
the DAC is a part that allows many tradeoffs to be made, including cost, bits, linearity, power consumption, power output (e.g. integrated headphone amplifiers), etc. so the usual principle is to punt the DAC selection to the user
PT8211 is a cheap external 16-bit I2S-compatible DAC in SOIC-8

>>1717152
yes it has fpu. And I just checked and F7 is 216Mhz. Yea I think I probably have an external 16 bit one but this is mostly for the heck of it since even 12-bit is probably fine. Especially with F7 which gives extra room for oversampling at 216Mhz which would make it more like 14-bit. that be more than enough for my humble experiments.

How does a typical PCM player algorithm reconstruct/interpolate the signal that was sampled, at, say 2x nyquist like in the pic? I don't know if they do sinc convolution or zero-order hold or something else in software. Sinc sounds slow so it might be able to implement it in a PC but not in a micro.

>tfw you're wizard at soldering and pcb assembly but every electronics company around wants degrees in electrical engineering for basic entry level assembly positions and your 10 years of running a repair business means nothing to them

>>1717156
12 bits was enough for the Fairlight, so go for it

>>1717175
>typical player algorithm
>typical
lolwut
typically, it doesn't. you get a square wave whose harmonics get lost in the output filter

>>1717189
Yep. That’s how it is.
Go to night school lad. You can probably proficiency out of most of the classes if you are really that good.

>>1717189
>has the motor skills that can be easily automated
>none of the actual critical thinking skills

>surprised that nobody wants him.

>>1717189
>degrees in electrical engineering for basic entry level assembly positions
where is this? wtf

>>1717195
>implying an assembler needs especially strong critical thinking skills
>implying college is the only place one can get them
>implying you're a cuck
one out of three ain't bad

>>1717198
>where is this? wtf

Everywhere outside of mainland china

>>1717199
If your "repair business" was worth a fuck, you wouldnt be graveling for entry level assembly positions. Why do you think they would care about them?

>>1717201
>what is oversupply
>what is faith-based market cuckoldry
go back to /pol/ you fucking merchant

>>1717195
So why are they hiring for basic assembly positions if they're so easily automated? Talking to them, they don't want the assemblers doing that, they just drop components and send them to the tester.

>>1717201
>If your "repair business" was worth a fuck, you wouldnt be graveling for entry level assembly positions. Why do you think they would care about them?
>lasts 10 years
>isn't worth a fuck
Pick one. I only shut it down because I moved to an area that doesn't have a sustainable customer base.
I just love soldering and building shit, entry level assembly is perfect for that.

>>1717190
>you get a square wave whose harmonics get lost in the output filter
translation: do you mean it is an anti aliasing filter in hardware/DAC? not in software?

>lolwut
huh? i mean any kind of a media player, for example windows player. if you generate a wav it will happily play it. here is an example: sampling rate = 900, sine freq = 440, windows media player plays a pure sine but slightly muted.

int sps = 900;

double duration_sec = 2;
double freq = 440;

double npoints = (double)sps * (double)duration_sec;
short *wav = (short*)malloc (npoints*sizeof(short));
double amp = 10000;

fprintf (stderr, "npoints: %f\n", npoints);

for (int i = 0; i < npoints; ++i)
{
double t = (double)i / ((double)sps) ;
double y = sin (2 * M_PI * freq * t);
wav [i] = y * amp;
}


https://vocaroo.com/i/s1EvFdJj13iC

(it sounds distorted on vocaroo, you can hear beats but the wav plays fine on my PC so it may be due to their conversion algos)

>>1717205
>built supposed long term repair business
>on a whim decides to shut the business down
>on a whim decides to move to an area his "business" inst sustainable, before securing new employment

So you live with your parents, and nobody in your new city wants their Iphone screens replaced?
Sad

>>1717189
the dealio is, they're gonna take you on as a grunt, while making you do engineering work under the 'other duties as required' clause. this crazy bullshit keeps happening since they needed a hiring manager but would only offer a janitor's wage.

>>1717034
Where did you search it for that price?
Sorry I'm a newfag on this board

>>1717208
>windows player
with SIMD and an FPU, sinc ain't shit. FIR filters are a silghtly less intensive option

>>1717211
this is the correct answer

>>1717210
this is a larping cuck

>>1717215
>this is a larping cuck

I have made 0 claims. Im just trying to figure out your drivel as it doesnt make sense.

>>1717210
>hate living in a city
>hate the unpredictable wage
>get unrelated job and buy a house in a rural location
>still love the work, try to get a job doing it with reliable pay
If I wanted to replace phone screens, I'd go apply at the phone shop in the mall.

I still repair my old customers' stuff for free if they mail it to me, but I don't have the 5 or so secondhand shops paying me to make their tvs, stereos, and xboxes work again as a reliable base to build off of.

>>1717218
>trying to justify making a rash decision that is obviously biting you in the ass

Good on you, your mcdonalds paycheck will be nice and reliable.

>>1717217
>you have made 0 claims
kill yourself for shitposting

>>1717220
Hey now, im not the guy larping and blogposting.

>>1717222
>/diy/ is one person
you have to go back

>>1717215
>with SIMD and an FPU, sinc ain't shit. FIR filters are a silghtly less intensive option
OK, makes sense... but still, what do you think, is that the sound card's responsibility to apply a reconstruction filter in hardware, or is it done at a higher level in software, in some kind of a system DLL etc? I suspect that the media player just calls some kind of of a high level Play ("sound.wav") function and the rest is done internally but I am not sure where.

>>1717222
It is me actually but I am not him and not the anon larping and not the one typing this post but I am the other anon

>>1717224
I was thinking that you were playing it back at 2x Nyquist, so disregard the hw rationale
downsampling is probably done by the player or some underlying library, since it's something you would commonly need to do when playing back files of arbitrary sampling rates. but this is more like desktop OS shit and where it happens isn't really important from an electronics design standpoint

>>1717223
>you have to go back

Back to college to get a degree like everyone else?
Nah, I think I am entitled to job offers, in a rural place, without an education or formal work experience.

>>1717219
I have never worked in food service, and my retail management job is pretty reliable. I don't know why you care so much about my current situation, but you have some pretty severe projection going on right now and you should seriously look into your own life before someone else's.

>>1717230
> I don't know why you care so much about my current situation

I dont like whiny snowflakes

>>1717231
Self-hatred won't get you very far.

>>1717233
Slurp my cock you retarded faggot

>>1717233
Nope, it absolutely wont.
It takes some ambition and a little bit of understanding how your chosen job field actually works.

Thats why some people are on here crying that they wasted a decade of their life and cant get a real job. And then there are the rest of us.

>>1717237
>crying that they wasted a decade of their life and cant get a real job
I would argue that management is more of a real job than entry-level manufacturing.
Do you not want a job that you enjoy? Do you not wonder why companies list their jobs as entry level yet require a 4 year degree and discard any other related experience no matter its significance?

>>1717240
I wonder why my huge dick isnt sliding down your throat fag

>>1717241
KEK BTFO

>>1717237

>>1717240
>Do you not wonder why companies list their jobs as entry level yet require a 4 year degree and discard any other related experience no matter its significance?

I dont have to wonder why, it is what it is. Its something you have to accept when you pick a niche field like this.
Like it or hate it, its reality. And you should know that, everyone knows what.

You arent going to get your foot in the door any other way. But once you have the degree, and you get some experience with the entry level work, you suddenly have the opportunity to jump ship to bigger and better job titles.

Or you can play around with xboxs for a decade and then end up being a shift manager at dollar general wondering where it all went wrong.

diyaudio.com is a bunch of self appointed experts shitting on each other non-stop. it is fun to read for entertainment but pretty pointless otherwise. /ohm/ is the only true source i trust.

>>1717244
>t.cuck

>>1717244
>a shift manager at dollar general
but imagine being an employee managed by such a manager. there are always lower lows.

>>1717243
Its not really bait, its reality.
You think there arent people with EEs willing to put up with entry level work for job experience?
A company is going to pick that over "well I worked on tvs for thrift shops out of my moms basement!"

>>1717031
>a door and a sound system for scare Intruders
>>1717212
>Where did you search it for that price?
You're looking for a cheap alarm for your door.
Put: 'cheap door alarm' into any search engine and press enter for the results.

>>1717248
> there are always lower lows.

Of course, and if you arent a retard you make conscious decisions not to get into that position.

>>1717244
>I dont have to wonder why, it is what it is.
>I don't think, I just accept
No wonder you come off as insufferable and make wild assumptions likely based around your own life.

See also
>>1717250
>>1717254

>>1717253
>Put: 'cheap door alarm' into any search engine
Or, put it in Google and select [shopping] for direct viewing of prices.

>>1717250
>reality is whatever shitty game we're playing right now
listen up, you impudent little fuck. you do know that all you babby bootlicking yuppies can be genocide and that the world won't shed one fucking tear for any of you dead-weight leeches repeating whatever some rich merchant told you, right? your sophistry is not going to keep your head on your shoulders when it comes down to it
come back when you aren't just posting whatever Charlie Cuck told you to in order to (((earn))) your way through school
>>>/r/The_Donald
and stay there

>>1717011
This is really more appropriate for >>1701407

>>1717257
>>I don't think, I just accept

What else are you going to do?
Stick it to the man and not get paid? Thrive on NEET bucks?
What exactly are you going to fight and how are you going to do it when your peers will take advantage of you.

>>1717257
his breath has the distinct smell of shoe polish and cum

>>1717261
>says the guy who cant get employment

>1717265 no (You)

>>1717263
>no no, never question, always accept
The company I work at wanted to make me a cashier after I interviewed for shift management, if I hadn't questioned and just accepted, I wouldn't be their operations manager now.

I'd rather just be soldering, though, I really don't get to do it much anymore.

>>1717264
Employment itself is the definition of being a bootlicking faggot.
Its up to you how much money youll get for that sacrifice.

Or you can run your own business and try to be a little more free. But that wasnt good enough for this guy apparently.

>>1717269
>I wouldn't be their operations manager now.

Oh, you mean the sort of thing people get Bachelors degrees for?
Yeah, I believe you. That decade of no work experience is really what wooed them wasnt it?

Holy shit this repaircuck is seething. It’s like he thinks EE is a field you can just LARP into like coding.

>>1717271
>Yeah, I believe you. That decade of no work experience is really what wooed them wasnt it?
You're going on the assumption that I haven't worked there for years and jumped straight to the position.

>>1717278
>Holy shit this repaircuck is seething. It’s like he thinks EE is a field you can just LARP into like coding.

I'm coming short on explanations for how soldering a capacitor on a board requires an engineering degree, because I've been doing that for nearly 30 years. Is it only needed for chips with hundreds of pins? I've been doing those for years, though, too.

Do you need a mechanical engineering degree to put together a grill at the local walmart?

>>1717288
>been soldering for 30 years
ah got why you got rejected
you're already used up senpai
the new kids can solder a whole board two to three times faster than you

help
i think i'm becoming a voltnut
i've been looking for old weston cells lately

>>1717278
Not him but whats the difference between EE and coding? I know for a fact that 90% of soft eng are idiots and code monkeys. Which probably applies to EE monkeys as well.

>>1717288
>I'm coming short on explanations for how soldering a capacitor on a board requires an engineering degree

The better question to ask is, why would they hire you over someone with a formal education?

Its laid out right here for you anon
>>1717211

People come in educated with current, relevant information for the field.
They get paid nothing for a year or two wringing everything they can out of you.
Then they can get promoted to a better job title as someone worthy to the company, or they leave to a new company for a better job title.

Then the cycle continues.
There is no incentive to hire the likes of you, who clearly isnt going anywhere in the company when young people will leapfrog your with ease. Youd be dead weight.

>>1717319
ok boomer

>>1717319
know how I know you haven't had a job yet?

>>1717321
>i have been soldering and repairing VCRs for 30 years
>gib job pls

>>1717323
Go on mr dollar store shift manager who cant get an entry level job in this field. Tell me how everything works in the field you literally havent touched!

>>1717190
>Fairlight,
Holy shit thats a great idea, to draw harmonics on a touch screen of my tablet. No need for a pen, I can just use my finger! I need to build Fairlight in software.

>>1717318
in EE the math is more quantitative, and fluency with advanced math is critical. if you can't algebra don't even bother. in EE there's a lot of engineering arithmetic, and you need to be facile with scientific math involving units, sometimes disparate
a lot of CS is rote memorization of APIs and design patterns, and understanding of logic predicates and so on
either way, college is for suckers. just git gud and don't bother with careers. the western world is going to end in 10-20 years anyway and all these yuppie boomers are going to be on lamp posts or beheaded, and you're better off beating them than joining them

>>1717342
and you can use that second DAC to feed a VCA and maybe enjoy that little bit of presence that comes with not Nyquist filtering your outputs

>>1717346
top kek
based me going to law school will be one of the first magistrates in the new world

>see that /ohm/ has like 50 replies since I last checked
>think maybe some really interesting project got posted
>start reading thread
>stop reading thread

>>1717386
F

Is Ohm (as a man) overrated? Should Kirchoff get more credit? Your thoughts?

>>1717331
>Tell me how everything works in the field you literally havent touched!

>You've been reworking and repairing pcbs for longer than I've been alive, that means you know nothing about putting pcbs together

Remember when experience got jobs and not a piece of paper saying you paid money?

>>1717363
maybe. I don't think common law systems have a whole lot of long-term future except as performance art, but it might take its time dying out

>>1717399
Ohm did take important steps in quantifying electricity. (not that someone else wouldn't have if he didn't exist, in light of the historical pattern of simultaneous invention)

>>1717342
absolutely, drawing your own waveform is a wonderful thing. you can also flip back and forth between frequency and time domain easily, with the magic of FFT

>>1717409
I do, and I also remember when employers were willing to train promising applicants, but don't feed the /pol/acks

>>1717416
>maybe. I don't think common law systems have a whole lot of long-term future except as performance art, but it might take its time dying out
Actually if you look back at how the common law worked in medieval England, it's a beautiful system for bringing order to an agrarian society. The manorial courts, the assizes (particularly dealing with land disputes), the circuit justices, and the writ system! It brought tremendous order to how litigation needed to be brought.

>>1717420
I'm a fan of the civil law system, myself, from what little I know about it. judgment according to presentation is hopelessly bourgeois

>>1717429
>judgment according to presentation
I actually don't know what that's supposed to mean.

The real benefit of the common law system, especially in an agrarian society or on a frontier, is the policymaking authority (mostly procedural but sometimes substantive) of a jurist. Things don't need to be legislated with precision ahead of time as they do in a civil law system. Where there are gaps (particularly under the writ system but even to some extent in the modern code/rules pleading systems) the judge can mold the rules to arrive at a reasonable and just outcome, according to guiding principles and accepted standards. The problem with a civil law system, particularly in large countries, is that too often there isn't enough responsiveness of the judiciary to local conditions and prevailing customs.

I recommend reading Pollock & Maitland, The History of English Law before the Time of Edward I.

omg, what kind of a shitty lookup table is this, lads? i noticed the first point doesnt start with zero, and i have no idea why. i stole it from some arduino library. even if i use their largest 8k table, i clearly hear some beats and just overall horrible noise. checked the spectrum in audacity and got this. added linear interpolation and it made no difference, since the freq is 108Hz and this is a 8kb table sampled at 44100, so it is pretty accurate even with a fractional phasor step so nothing to interpolate. I am going to build my own lookup table tomorrow since it is trivial and I don't know why I even bothered with theirs but it is just weird that it looks so bad. Maybe it is intended to be used in a different way.

Business idea: Instead of /ohm/ call it /kvl/: Kirchoff's Voltage Lounge.

>>1717547
What's the lookup table supposed to be for? Is it originally in the time domain? What frequency is it supposed to be? Often considering the FFT with a linear frequency axis helps as it shows the data points being spread out evenly. I'm assuming that the 1.5Hz peak is just a single point, which I think would correspond to a sample duration of about 400ms, and the peak just represents a tiny amount of skew to the DC component. This may cause a little distortion when it comes to repeating the waveform, but shouldn't be terribly impactful. The 25Hz peak width at 108Hz however is likely the main source of noise, as that's at least 10 data points wide. I'd have to know what the FWHM is in order to judge what kind of timescale you'll run into incoherence within. Perhaps it's a lower sample number FFT that's been poorly extrapolated to many more samples? Either way I'd write your own lookup table, perhaps just generating it in something simple like python.

>>1717212
>Where did you search it for that price?

https://addison-electronique.com/en/products/alarm-security/alarm-system/keypad-alarm-system/

https://www.jbhand.com/retail/hardware/home-security/

https://www.maddison.ca/systeme-d-alarme/alarme/mad-027793.html

I want to pull my old acid battery from my bike and replace it with condensers.
The current battery is 6v5ah and the servie manual states that the bike generates 8v under high revs.

What's my optimal setup here, will 6v condensers explode when the bike administers 8v?
Also my bike has a kick starter so im not worried about the charge dissipating overnight.

>>1717627
>will 6v condensers explode
[F] = As/V, 5 Ah = 18 kAs, 18 kAs / 6V = 3 kF
Now get your 3 kilofarad 6 volt condenser and be the first to find out..

>>1717624
Thanks

>>1717627
What do you need 30Wh for anyhow? Assuming it's a kick-starting bike, it's not like you need that energy for starting the motor, three series 18650s would likely work just fine as a buffer for the electronics if you add some proper charging circuitry. Capacitors are very spatially inefficient, to store 30Wh (~100kJ) you'd need something around 5 litres of solid electrolytic capacitor. For smaller amounts it's viable, but still likely significantly smaller than the same amount of energy storage from lithium ion batteries (~50ccs worth). Though the capacitors will be much less voltage sensitive than lithium ions; they won't need a special charge circuit.

>>1717694
>As
shit's called a coulomb

>>1717742
Columb*second=Amp, not the other way around
Amp*second=Columb*second^2

... Hmm, is that like the charge acceleration then?

>>1717750
Er, oh wait, they cancel don't they? Disregard.

>>1717750
>>1717753
no amps is coulombs per second, current is rate of charge transfer

>>1717742
>coulomb
St. Ampère is my base saint.

>>1717570
>What's the lookup table supposed to be for?
It is from some arduino synth lib. I *assume* it is to generate sine harmonics for additive synth. At least that's what I am trying to use it for. But I just tested that table with a single frequency.

> Is it originally in the time domain?
Yes. I guess. It is a standard look up table, where you generate sin points in a loop from 0 to 2PI with a certain step depending on how many datapoints you need. Aren't they all supposed to be the same?
>a tiny amount of skew to the DC
Yes it looks like a DC offset and their table starts with -1:
-1, 3, 6, 9, 12, 15, 18, 21, 24, 28 etc.
(it is normalized to -128 +128 range)
So yea, it is a good point that I don't know what they needed that lookup table for, exactly.
>Perhaps it's a lower sample number FFT
Do you mean the spectrum in the pic? The window size is 32k points which is almost the highest setting in audacity. I wouldn't be too concerned about the spectrum in Audacity if it sounded OK. But the noise level produced by that table is just too bad.

Check this out. This is insane. I generated two tables: integers and floats. All integer tables sound like crap. Lots of rattling/hissing noise. But even the smallest table of floats sounds and behaves purer than most posters on 4ch!! Seriously, I cannot hear or see (in the spectrum) any difference between a 8k table of floats and a lowly 256 point table of floats!! Of course it is a low freq sample and this FFT is on a smallish window size but I did that on purpose to highlight the difference. Because thats exactly what it sounds like when I listen to both.

This is really interesting. So with a basic dumb linear approximation, I get decent results even on a tiny 128 point LUT, as long as it's floats not integers. And regarding the approximaton, the worst case corrected is 2.8 degrees. Is that a lot?

sine freq=16000
sample duration, sec:20
sps: 44100
table_size=128
lookup table phase_step: 46.439911
total samples in wav: 882000
max amp level (abs, normalized to 16 bit): 32766
total samples corrected within 0.001 rad: 817080
max correction, rad: 0.0491 ( 2.8113 deg)

How do I estimate the minimum size of a LUT so the linear approximation would give negligible results and I could drop it? For example for a 1k LUT,
sine freq=18000
sample duration, sec:20
sps: 44100
table_size=1024
lookup table phase_step: 417.959198
total samples in wav: 882000
max amp level (abs, normalized to 16 bit): 32767
total samples corrected within 0.001 rad: 561280
max correction, rad: 0.0061 ( 0.3515 deg)

The worst case is 0.35 degrees and the number of samples that even required correction is less than 40%. Is that good enough to drop approximation?

Nah screw that, the approximation is fucking awesome. I can keep the table as small as 128 points and still get audibly great results even on high frequencies. Whereas without the correction, the table would need to be at least 8k so there is no distortion on high freqs. And correction is very cheap to implement. SRAM is more expensive. Now I know I can keep a LUT of 256 floats in SRAM and thats all I need.

>>1717742
>three series 18650s
full charge 12.6 volts
two fully charged 18650s are 8.4 volts
two seems ideal
parallel more pairs for more capacity

I took apart a canon printer. Can someone tell me what a nec sgp d703107agj is?

>>1717811
>integer
are you sure you got the endianness right?

>>1717898
NEC had an implied uP prefix. try searching again with upd703107agj

>>1717849
>how do I estimate
with your ears

>>1717898
It’s a microcontroller.

>>1717898
>>1717952
Here’s your pinout.

>>1717951
I am testing on PC, both generating and playing samples, so there is no issue of endianness since WAV files are little endian.

>>1717956
>>1717952
>>1717951
fhanks bros

>>1715180
do these really chepa logic analyzers support voltages as low as 3.3v?
description says: "Input voltage:DC 7 - 14V"
https://www.ebay.com/itm/USB-Logic-Analyzer-Saleae-24MHz-8CH-With-Test-Hook-Clips-Kits-for-ARM-FPGA-M100/153650457162?hash=item23c647ea4a:m:mEYBV7ecYc3Ub10ImyHOnoA

>>1718021
>conversion efficiency
kek, it's copypasta
assume 3.3V only until you open it up and have a look around

For me lads? It’s the elite 6502.

>>1718021
Yes. Did that when debugging Bluetooth problems, the thing's powered with 3.3

How reliable is usb 5v. Im using the regulator from my teensy to power an analog to digital converter but my readings arent as accurate as I would like. I know that the voltage CAN vary from like 4.75 to 5.25 but are those worst case something happened scenarios or does the voltage from usb actually fluctuate a lot.

>>1718089
I think it's pretty reliable
bear in mind that it's mains earth referenced if the power source you're connected to is itself plugged into mains

>>1718089
maybe you're overdrawing the regulator. did you check the schematic to see whether it could handle it?

>>1717887
oh yeah, 6V not 12V

>>1718089
What's your voltage reference? Just the 5V from the regulator?

Feature creep is my favorite hobby. Instead of making progress with the synth, I decided to hack Audocity's FFT implementation by separating it from the code base and making it a separate little class. But their implementation is closely coupled with WxWidgets, the UI library. So much for code isolation. Why the hell would interaction with UI need to happen right in the FFT code?? They should have kept it a separate text only implementation of the FFT algorithm and pass input and get output and visualize it in whichever way they want in the UI code. What if they decide to switch to a different UI library in future versions? That is stupid.

>>1718232
Is there anything special about Audacity's FFT compared to existing standalone implementations/libraries? As far as DSP algorithms go it's hardly a terribly complicated one, probably within a hundred lines even with a few bells and whistles (cosine curves on the sample edges, other noise reduction methods, etc.). Of course if you want a proper UI then that complicates things, but it still shouldn't be terribly difficult.

>>1718232
>text based
>current year
how do you foresee doing anything live with a design like that without some serious iron? sometimes performance > making your comp sci senior advisor proud
mathematica is free with raspberry pi, if you want

OK potentiometers are kinda expensive, especially ones with more than 2 gangs. So looking at the bog-standard digital potentiometer ICs (X9C103) I noticed that they have two control pins; increment and up/down. So if I hook up a cheap 20-step rotary encoder with pulldowns/pullups, the quadrature will automatically work as the up/down counting. But turning a rotary encoder a bunch of times to get from one end to the other sounds like a pain, so I'm wondering how feasible it is to design a small circuit that pulses the "count" pin more times per rotation if you rotate the rotary encoder quicker. Even if it's only two or three different speeds instead of a continuous speed it would work fine. At the very least being able to use the built-in pushbutton for this would be acceptable in most cases, though using this button with an inverter to feed the chip-select pins of other digital pots means you can use the same encoder for multiple uses.

My guesses are to use a high-pass filter after one of the encoder's outputs to give an analog voltage proportional to the speed of the encoder, then compare that to a threshold voltage of some kind, that activates an oscillator, which interrupts the increment line of the digital pot with a mosfet a bunch of times. But that's like two comparators and a transistor or two.

also a digital pot that can handle higher voltages would be nice for audio stuff

>>1718330
wow you side-stepped that. There's absolutely no reason why algo should be mixed with UI in the world of multi-tasking OS circa 1993.

>>1718089
USB what? 1.0? 3.2? Are you using something that was built to USB spec? Are you using it from your computer?

how much power are are drawing total?

USB is spec'd for different power profiles. a "lower power" hub can drop to 4.4V and stil be to spec.

>>1718356
Wait, the high-pass method will require a certain number of turns to boost the voltage up to that threshold, which is probably too many turns. So I should either go for a rotary encoder with more poles per rotation, or a more digital method. Like an up/down counter or left/right shift register, where the up/right direction is being controlled by the encoder and the down/left is being controlled by a reference oscillator. When the turning frequency gets higher than the reference frequency, the counter/SR will increment to the other direction by two, triggering the extra kick or three to the pot. In other words, even more ICs, but it's much less prone to delicate tuning than the previous method. I'll look into other encoders.

I'm making one of those EMP guns, because it sounds fun, and it would be handy to have when I'm having an issue too intermittent to get the company to warranty it. What the hell would something like this be under on Digikey/Arrow? I want to go as overboard as possible. I can solder, but don't actually know much about electronics, I'm just following guides online.

i want to build a simple constant current source where i can set the current digitally

so i was thinking, use lm317 and replace the R2 with a digital pot which can be controlled from some IC or something, this would get me a constant voltage source and to turn it into a constant current i would add a shunt just before VOUT and use it to measure current and then the IC would raise or lower the R2 to maintain the desired current, would that work?

I know you can configure lm317 as constant current source directly by using just a single resistor, but the problem is that the load current passes through that resistor so i can't use the digital pot in this case since it would get fried as i need over an amp of current

>>1717742
Yeah I wasn't counting on 30Wh, just mentioning what I'm pulling from the bike.
>>1717694
I could actually simulate the riding conditions on my variable voltage generator, so I might just go ahead and order

>>1718392
>>1717742
>>1717694
Ive seen people use any big condenser from old PSUs and call it a day.
I have a few CRTs and old audio amps, what's the biggest I could stick in there without blowing any bulbs?
I mean I've always fixed audio equipment with overrated caps no prob, but this is kinda new for me.

>>1718385
That can be done but does the 317 make sense? I would draw a complete circuit including current sense, digital potentiometer etc. and think about it. Couldn't a transistor do the same? Note that digipots may have a 5V limit.

>>1718412
>dacia
based

>>1718280
I find that's the case for a lot of WxWidgets stuff. There's stuff like JSON parsing and SQLite libs that are specifically intended for use with Wx.

>>1718446
Whoops meant to quote >>1718232

>>1718413
I also found stuff like this which seems nice, but people complained about it resonating or whatever and i don't even know what that means

>>1715180
I took a high brightness led lamp, removed the mains converter and I want to use it as a bike lantern. I tried making a Joule thief but it did not have enough power. The lamp is a 20V led that takes about 10ma under nominal load. How do I increase the current a joule thief gives? What are some other alternatives to solve this? I don't want to buy a dc/dc converter from china. I've been using 2 AA in series to power the converter. It works nice as a warning light but can't put enough light to brigthen the road.

>>1718458
it doesn't resonate. It's a fairly stable circuit. (it depends on the opamp really). You can use a bipolar transistor because most mosfets these days are made for switching and you'd be wasting extra money buying one for that.

>>1718357
I didn't sidestep shit. I made the quite reasonable and arguable claim that your mode of design isn't applicable outside of academia or the DESIGNATED parts of the industry
seriously. text? take your Java VM and >>>/g/

>>1718356
>bog-standard
bari bari varu is not necessarily standard
>a bunch of times
it's not even two revolutions
>feasible
you could have written a program to do that in the time it took you to write the post, and put it into some random 8-pin micro by the time you finished the follow-up

>>1718385
no, but you can put the digipot across the load resistor. the downside is that the input codes are inversely proportional, and you also have to refer the logic to the high side somehow
>posting a stock schematic instead of what you're asking about
wew
what exactly do you need this current source for? must it be high-side or is low-side okay? if you don't know what that means, are you sure you should be doing this

>>1718464
>how do I make a meme work like something meant to be used

>>1718472
also you can add a touch of RC lag to the gate or base

>>1718474
>>how do I make a meme work like something meant to be used
Ok I'll just put back the converter, build another bike using 200 AA batteries and I'll have a functioning light. thanks /ohm/

>>1718485
Joule Thief is a toy with a cute pun as a name, like 90% of Node.js modules and software startups. it's not meant to be used
>don't want to buy from china
then buy one from some drone shop in your own country ffs. the era of component-level recycling is long dead
since you have restricted yourself to working with scrap (another shit-tier meme) better just add batteries until you get enough output to suit you. I think a total of 4 would about do it

So for plc's would sinking or sourcing be best for a basic bitch learning setup? What kinds of inputs and outputs do I need for testing out sensors and stuff like Air pressure, speed, etc.

>>1718502
>learning
>PLCs
why don't you ask the vendor or your instructor

>>1718514
Yeah, may have to ask the vendor.

>>1718495
epic meme bro. I bet you don't even solder things anymore, just keep up the good work!

>>1718474
Code isolation is definitely not just an academic exercise. You seem to be misreading his initial post where he said "text based" implying that the FFT functions should not directly rely upon the GUI infrastructure.
By the way, TUIs and CLIs are still very much used.

>>1718554
6/10 made me turn on the soldering station and dig out a component I wasn't going to place until this weekend

>>1718578
>definitely not an academic exercise
perhaps not, but it certainly is something that can be and is traded off when necessary, and it is definitely not the source of OP's problems
>text based
you seem to be reading his suggestion rather generously, but alright
>TUIs and CLIs are very much used
and thank Bob for that. but they have basically nothing to do with a GUI-centric audio file editor that tbqh wasn't all that high quality in the first place
righto, back to my very much text-based FORTH programming in vi

Check out what this anon made lads:
>>>/g/73631400
>>>/g/73631420

Is there a way to remove the DC component in LTspice when using .MEAS ? I'm trying to automate ripple measurements btw.

>>1718280
Probably nothing special, but there is some bloat there that makes it significantly more code than a typical lean implementation. There are like 10 or so different window functions, and multiple algos like spectrum, autocorrelation, cube root correlation, and some other bells and whistles. And Inverse FFT as well. But I don't really need anything other than spectrum. And the only window function they themselves recommend is Hann. I don't know what the autocorrelation feature is meant for.
I guess the main reason I am going this route is I can also reuse their UI screen calculations down to coordinates so I can plug it in almost as is in whatever control I am going to implement in Android. Plus hey it is Audacity, a peer reviewed source so to speak, not some noname github repo.
>>1718330
I don't understand what you are talking about. I am saying algorithms are supposed to do number crunching, they don't have anything to do with UI. Unless we are talking about a certain OS that has graphics built into the kernel. You are baiting me, right?

>>1718446
After taking a closer look, they do have some levels of abstraction but they also depend on WxWidges for other reasons: they use it as some kind of a generic wrapper library for things like concurrency and even custom string and character typedefs. Yuck.

>>1718661
yeah, Wx isn't strictly a UI lib. neither was GTK+ before glib and gobject were split out into their own packages. I think Qt has/had quite a bit of that sort of cruft too. not really unexpected when bridging the huge chasm between what the C libraries of 20 years ago offered and the screen

>>1718474
>it's not even two revolutions
It's 5 turns for the 100-step digital pots, so probably acceptable, but I may still want a fine/coarse button if the speed detection doesn't work.
>an MCU
Yes I could, but no I won't. This is an exercise in cost saving, and MCUs are more expensive than comparators. Also that would ruin the fun.

How do I reduce noise for a system. I cant get a stable voltage reading necessary for my experiment. The output to a phototransistor needs to be measured within .1mV but Im getting about .3mV of jitter. I dont know anything about capacitors and I read that it helps stabilize voltage. However while the voltage would be more stable, it would slowly increase or decrease over time.

>>1718695
Noise can come from a lot of places, be it directly through from the switching power supply, through capacitive or magnetic coupling form elsewhere, thermal noise, or even from switching transistors within your circuit. For the most part, noise on your rails will be mirrored as noise on what's connected to these rails, which is why it's important to isolate the noise produced by each part of your circuit with low-pass filters of some kind. For the most part, a single capacitor from Vcc to GND as close to those pins of each component will work, a so-called decoupling or bypass capacitor, but for your power supply itself you may want to consider an LC pi filter. To avoid magnetic noise, ensure that any inductors in your main circuit are toroidals or otherwise have an enclosed magnetic core, surrounding your circuit with iron shielding would also improve this. For long stretches of wire, put wire pairs as close to one another as possible, twisting the wires if possible, ensuring that the net current through the twisted pair is zero. For capacitive noise, which is probably more of an issue, you'll want to keep ground planes near to your wires, possibly even using coax for jumper wires that are above the ground plane. Consider building a grounded shielding box around your circuit.
As for the phototransistor itself, what's your pullup resistor's value? A larger value means more thermal noise, though this can be mitigated to some extent with an output filter (try an RC low-pass, assuming you're after low-frequency values from your phototransistor). A value that's too small will yield in a low signal-to-noise ratio in the first place, and 100µV sounds pretty low.

Finally, if you have an oscilloscope, you should be able to trace the noise in your circuit, especially if you're in a position to disconnect individual parts of the circuit to see where the noise is coming from.

I have a Perkins 130-10 diesel motor @ 1800 RPM running Mecc Alte 120/240V Generator sitting in a light plant. I want to use it to top up my offgrid battery bank during the winter months. I'm looking for a break down of components I would need to make this possible. Automatic start isnt a priority. My battery bank is 48V and the inverter I have currently does not have generator support. Google keeps trying to sell me gen sets for 10k plus or brings up very simple 2d diagrams.

>>1718713
not sure what "generator support" is but it sounds just like you need a 120 or 240 VAC to 48 VDC power supply. That ought to be retardedly easy to source.

>>1718727
I live in the Yukon, so let's hope so.

What's the cheapest place for a Canadian to get PCBs manufactured? I've been using DirtyPCB and the manufacturing cost is super low, but shipping is $30 and clearing customs is another $25.

>>1718734
Nice stack. What're you making?

>>1718735
"Special" LED panel that makes pictures humans can't see but show up on camera. It works by strobing pixels in a way that produces controlled rolling shutter artifacts.

>>1718734
JLCPCB is about as cheap as boards can be gotten afaik
failing that, check pcbshopper.com

>>1718737
Here's a prototype. In this one the pixels are hardwired so it can only produce the one picture. I think I can spin this concept as some sort of philosophical social commentary and get some art grants.

>>1718737
Oh that is nice. Is that some guerrilla marketing device in the works there?

>>1718746
it's digital photobombing. might not need to get too abstract with the sales pitch
otoh patent that shit right now so the merchants can't steal it

>>1718762
Yeah definitely look into patenting that shit. In fact, don't post any more about it until you've talked to somebody.

>Set Overflow (SOB)
>A negative transition on the Set Overflow (SOB) pin sets the overflow bit (V) in the status code register. The signal is sampled on the rising edge of PHI2. SOB was originally intended for fast input recognition because it can be tested with a branch instruction; however, it is not recommended in new system design and was seldom used in the past.
Can someone explain why being testable via a branch instruction would make that better for fast-input recognition?

>>1718794
In assembly the branch instruction can usually only operate based on the value of the accumulator. To branch based on some other register first you need an instruction to load that into the accumulator. That SOB pin automatically changes the accumulator value so a branch based on it doesn't require two steps.

>>1718794
it's like a pending interrupt without the interruption. it apparently saves all of one bit-test instruction every time you check it so 2-3 clocks. not all that compelling, is it

>>1718796
no, just the flags

>>1718794
This is from the 6502. That pin is used for things that need to poll very fast. The disk drive in the C64 used it.

Basically, you could run a polling loop in 3 cycles instead of 7 cycles. On a 1 MHz 6502 that's a savings of 4 microseconds per loop iteration.

>>1718781
I agree, it could be a great way of getting people to look at things through their phone cameras out of curiosity, only to see something really unusual (like a dog using chopsticks) and a QR code to scan or short website link to see. Even better if it's a two part advertisement where you can see the first part of the scene with the naked eye but have to use your cellphone to see the second part. Though that sounds as difficult as driving an electroluminescent dot matrix. Making advertisements interactive like this will really improve the mental retention of them.

Bonus points for using RGB LEDs, or even managing to find the bandwidth for a few different brightness settings per LED, but that's really getting into high bitrates for an entire display if you intend on having the processed data be entirely serial at any point.

so they don't sell flux here but i have some hard rosin, how do i turn it into a flux paste i can squirt on my smds like in rossman videos?

>>1718830
I've been experimenting with RGB. These all look blank white to the eye. To our eyes cycling R->G->B blends together into white just like PWMing the three channels in unison. On camera each stage of the sequence gets recorded at a different vertical position so you get rainbow.

>>1718844
Dilute it with a weak organic solvent. Isopropyl alcohol is probably preferable, ethanol and probably other alcohol types will work, and acetone will work but it will also dissolve solder mask and potentially other plastics. Also acetone's fumes are kinda nasty. Which solvent you use will determine the speed at which it dries up, which may or may not be a good thing. Then fill up syringes with the mixture, with a nozzle/needle diameter to match the viscosity of the mixture.

Good luck.

I was going to ask /sqt/ but one of you anons might know, do we know the name of the headers in the foreground? They are 3mm taller than a "normal" header pin (against back row for reference) but all I can find are the bog standard gold headers, likely because I have no idea what the fuck I am searching for. Cheers.

>>1718909
Those aren't pogo pins, are they? They're the spring-loaded ones. If they are solid, they look to be some variant of machined headers, possibly designed for wire-wrap, but probably just to serve as an extra-tall standoff.
Searching "machined standoff pin header" in google images gives me things like pic related, which are similar but lack the black plastic. In your case, perhaps the only reason for the plastic bit is to hold the row together. And maybe the stepped nature of those pins is to allow two seperate boards to be placed over them, each sitting at a different height. Though I suspect instead it's just a mechanical strength thing.

>>1718909
>>1718915
Oh and "mezzanine" might also be a keyword worth searching for.

>>1718917
>>1718915
They are not spring loaded, and you're right about the application, this is on the solder side of an accelerator board for an Amiga 2000, it needs the extra height to clear the components on the main board, which is why it is stepped. Searching for variants of machined header and standoff pin header give me similar looking DIL and SIL headers (which is closer than I was before I posted, thank you), but nothing with the extra 3mm I need to clear the chipset on the mainboard. Nothing relevant on mezzanine headers etc unfortunately.

>>1718925
Ackchually, further searches on mezzanine headers led me to PCB connectors, I might just replace the lot with a matched pair of pic related. That will give me the height, and while the 68000 CPU will not fit into the headers directly, the accelerator will never be removed so it's kind of a moot point. Might roll with this unless someone has sauce on the original headers. Thanks anon.

Is it normal for flyback converters to have such high losses in the diode? Teacher gave me the task of designing a 110/5v 50 w converter with a given duty cycle (???) of 62% (even though controllers don't go past 50% anyways). The output is 5V and 10A, but the diode sees about 16Arms and 30 A peak. Is there a way to lower this? (the sensible thing would be to design one like you're going to build one and not a silly academic exercise but I see no way of having 90% efficiency if I can't change the duty cycle.

>>1718935
Scratch that, it's 50A and 20 RMS.

>>1718830
>Even better if it's a two part advertisement where you can see the first part of the scene with the naked eye but have to use your cellphone to see the second part.
See, this is my idea: Do you watch baseball? Ever see those advertising displays they have behind home plate? They're sometimes green screens, I think anyway, so that they can change the ad for whatever TV network is carrying the game at that moment (or so they can rotate the ad during the game). If you had something that could display an ad for in-park viewers, and either a green screen or a rotatable ad for the TV cameras, they could sell the in-park ad space to local companies (and play like they're more friendly to local businesses) but still sell the on-TV ad space to national companies and make good money.

Another way of looking at it is that they can sell the same ad space twice.

>>1718906
Also most acetone available outside of lab supply will be adulterated with benzene, so working with it adds additional organic contaminants and a carcinogen to any process using it.

I want to make a keyboard-thing that you operate by tapping a stylus on bare copper, I plan to etch the circuit onto a copper clad board. The keyboard is then connected to an arduino.
So far I thought of three possible ways to do it, but I'd like your input since am noob.

The first one would be to just have a couple of decoders grounding / setting high individual keyboard squares, which would then be tapped with the stylus connected to the arduino which would then read the voltage. The problem with this however is that I need ~50 keys and that might be too many decoders.

Another way would be to just use a sensing columns/ driving rows kind of scheme and the stylus would act like a switch bridging rows and columns, pictured on the right. With this however I'd need a fat stylus and it would be hard to make legible legends.

The last way is the one I'd hope to make work, pictured on the left. Digital pins drive the columns high one at a time. The columns are copper squares bridged by resistors. The stylus would then ground and read the voltage of a square with an analog pin.

Would the last one even work as I think it would? Is there a better way?

>>1718963
>tapping a stylus on bare copper
hope you're factoring in oxidation

>>1718935
>even though controllers don't go past 50% anyways
lol
>50Arms
you can reduce losses with synchronous rectification. maybe an SCR would be worth a look

>>1718830
I'd patent it just to prevent that tech from being used for commercial purposes. fuck you amerifat merchants

>>1718963
use capacitive touch sensors. they're built-in on grownup MCUs

>>1718997
>I'd patent it just to prevent that tech from being used for commercial purposes. fuck you amerifat merchants
Implying patents are self-enforcing

>>1718997
What the fuck kind of diode do I use in this? They usually give me a pulsed rating based on
>Peak forward surge current 8.3 ms single half sine-wave superimposed on rated load
not
>big ass triangle wave
Should I just try to find onde where the foward rms current fits the datasheet? (Speed and frequency don't matter at all because it isn't going to be built anyway.)

>>1719005
Use a vacuum tube diode.

>>1718963
Got to try the one with daisy chained resistors and it actually worked as intended, who would have thought. Guess that solves my question probably.

>>1718964
Heh. Hopefully tapping it will just scratch it away. It's gonna be a meme device anyway.

>>1718997
I don't think the keys are gonna be big enough for a finger to tap accurately and I'd also need resistors with pretty big values which I don't have. Would it work like the resistor thing? Meaning chaining copper squares and resistors to get different values? I remember messing around with a capacitive touch library on the memeduino and it being pretty slow.

>>1718963
I mean, you're basically talking about a keyboard encoder aren't you? Why not look at how those work?

>>1719005
yeah, go by the forward rms current
>speed and frequency
should be considered because capacitance and delays affect efficiency

>>1719019
so use a capacitive stylus
>resistor thing
more like a matrix scanner https://www.ti.com/lit/ug/tiduaz5/tiduaz5.pdf

>>1719006
biodes are better

are there any crimp connectors which can be connected together and disconnected like a jack for example?
By crimp connector i mean something like ferrule, but it comes as a male and female so you can plug and unplug them together

>>1719053
all kinds of them. look up "wire to wire connectors" on your favorite search engine or distributor
for single-position connections, insulated spade connectors are common and easy to get at your local auto parts store

>>1719051
>yeah, go by the forward rms current
thanks
>should be considered because capacitance and delays affect efficiency
Yup, I know but not for this "project". I love building things, but my teachers like ""building""" things.
>"building" = simulating the equations you pulled out of your ass and calling it a day
>2019
>not using bidirectional biodes
top leek
>>1719006
see the biode poster

>>1719058
Yeah spades look exactly like what i need
thanks
which crimping tool do you recommend for them?
I have ferrules and use that one that creates a shrinking hole, but i don't think that will work with the spades

>>1719066
>which crimping tool do you recommend for them?

google it, nigger.
you can get 'em at the dollar store, or pay over $100. the 6th unit in the adjoining pic is dollar-store quality.
for low-current stuff, you can just use pliers or vice-grips. you can also just solder the wires.

what do you guys do with used solder
i press it down with a heatsink to form these blob things which are cool i guess
any better ideas?

>>1719079
I usually throw mine out or put it in the water supply

>>1719063
>400v mosfets have usually 0.3 ohm Rds
>power bjts for that same voltage and current have 0.5 voltage drop
>actually lower losses
hmmmmmm really makes me think

>>1719089
Remove MOSFET
Install IGBT

>can design complex analog circuits
>can't grasp thermal management
If
>Power ~ current source
>Voltage ~~ temperature
>resistance ~~ resistance
If you put a heatsink in series with the junction-ambient resistance why would that help? Woudn't that just be another series resistance??? Makes no fucking sense

>>1719079
Mix with jizz and flush.

>>1719122
thetaJA is thetaJC + thetaCA. the heatsink thetaHA, properly mounted, is in series with thetaJC, in parallel with (part of) thetaCA

>>1718909
if the board is 'through hole' for the concerned pads, put a 3 mm spacer under the 'normal' headers

>>1719161
So I should use the heatsink in parallel with the case-ambient resistance? It's the only way I can see to actually lower the temp and get to pick a heatsink.

>>1718909
you can get pin headers in different pin lengths. but those kinda look like free-standing machine pin sockets, which you might occasionally see on gaming keyboards for ez switch swaps

>>1719208
Pretty much.

In most cases, when you're using a heat sink, you can basically ignore case-ambient and replace it with the thermal resistance of your heat sink plus the thermal resistance of your thermal interface (insulation pads, thermal grease, etc)

Why do some memory/rom/eeprom chips have separate chip select, output enable, and write enable pins?

>>1719270
Sometimes those commands are coming from different ICs, it can just make sense and require less gates. Same reason some ICs have multiple enable pins that go to an internal AND gate. When everything's just interfacing with a single MCU it's not as apparent. And having a single output/write enable pin could cause some pretty terrible bugs if you get your propagation delays wrong.

>>1719270
sins of an ancient civilisation. removing it now would break backwards compatibility.

>>1719342
mmm juicy

>>1719270
simplicity and speed of decoding. ~CE can be taken from the address decoder which can be as simple as one of the address lines or a 74138 decoder output, or as complicated as some bank-switching PLA. ~OE and ~WE can be connected directly to the bus master's ~RD and ~WR outputs (or derived with just one inverter to create ~RD from RD/~WR on some buses), and they don't have to be gated by the address decoder. the address, or enough to decode it, is usually known before the operation in those kinds of buses
also, some RAMs have a secondary, non-inverted CE input ANDed with the other, which could be used to remove even more user logic from chip selection, OR was often used to protect contents of battery-backed RAM against the bus master running amok on its way down or up

just found a job ad for radio/gps electronics assembly in my hometown, wish me luck boys

>>1719342
holy shit I've always wondered about this

>>1719342
nice commieblock. 10/10 would sign lease tomorrow

>>1719349
luck, faggot. don't forget to bring your fake BSEE

>>1719351
>fake BSEE
Doesn't even mention any required degrees, I'm hoping my physics science degree will make a positive impact however. I'm more worried that it's asking for experience working with SMD components under a microscope, but hopefully I can overcome that.

>>1719353
ah, you missed the raid this weekend. good for you
as long as you have any experience with SMD passives of freedom size 0603 or smaller, you're probably trainable
the jkgamm041 youtube channel contains many erotic soldering masterpieces, have a watch at his SMD stuff if you haven't already

>>1719413
>any experience with SMD passives of freedom size 0603 or smaller
Nope, but I got a practice board on the way. I've reflowed pins on SOICs/QFPs however, and think my technique with tweezers and flux is sufficient.

Some comfy bedtime reading for you lads: http://www.tubebooks.org/Books/rider_VTVM.pdf

>>1719413
nice yt channel, it's pretty comfy watching

>>1719433
>scanned "pdf"
I'll be back in 30 minutes once it's loaded

>the virgin diode
>the chad triode

If i want to waterproof my project is turning it into an epoxy cube with just wires sticking out the best way?
How problematic is epoxy vs heat generated by the circuit?

can you explain to someone with 5 IQ what circuit oscillation means? I am asking for a dumb friend

>>1718963
What you're describing sounds a lot like a stylaphone.
https://www.youtube.com/watch?v=kWKzi28alcI

The simplest solution is a big row of resistors in series. One end connects to VCC, the other to ground. A copper pad at each of the points where two resistors meet. You get a different analog voltage at each of these pads. Your conductive stylus touches these pads and runs a wire to the microcontroller ADC.

>>1719441
the giga chad biode

>>1719519
Things that should stay quiet, shake and things and don't do. If your washer stopped spinning and your table startedjumpin for no good reason

>>1719517
>How problematic is epoxy vs heat generated by the circuit
Depends entirely on what your circuit is. Could do calculations for heat transfer if you want, but you could always slap a heat sink on offending parts and have it poke out of the goo.
Also I'd consider silicone instead of epoxy. It's probably cheaper, it's more flexible (which matters considering differing rates of thermal expansion and potential shattering on drop) and it's more hydrophobic. But it depends on what sort of enclosure you'll be potting it within. If it needs to be rigid to hold two boards at a certain distance apart then a resin would still be a good choice, and silicone while curing can be corrosive and also conductive, so watch out for that.
context?

>>1719519
A feedback loop with some form of hysteresis/delay and a net gain close-to or more-than unity. Probably.

>>1719544
i remember some schizo posting about these and the transistor equivalent
where do i find more info?

>>1719552
>context
The silicone isn't a bad idea, do i need to some special one, or do i just budy one of those cheap silicon guns?

basically the usage is generic water protection so i put the circuit say under the hood of my car, or on the roof of my house the circuit will be protected from nature shit, the circuit will almost always be some IC like an attiny with some extra stuff connected to it, all sitting on a home made pcb

found it
>>/sci/thread/S10309736#p10309736

>>1719558
More important question, how will it be mounted?

>>1719560
Oh man I remember this shitshow

>>1719558

a lot of chinese IP68-rated stuff is done precisely like that: put the PCB in case without any holes, inject silicone all around it, under and over it, and put the back of the case on, which gets glued and sealed by the silicone.

in your case, it's best to get a hand-squeezed silicon tube coz it's more maneuverable, and has a smaller tip.

and you gotta make sure any connectors (like USB) you use are also covered in paste, otherwise water will wick along the wire and make it all the way to the PCB to corrode it.

>>1719560
>anons make a $500 million deal
>youre all bitches and if you steal my idea youre dead. i have proof from a lot of people that my ideas have been around and in print in their possession for a long time. i have proof from universities that i had this idea in their hands over 1 and a half years ago. if you don't have anything nice to say, don't say it because i will shut you down quicker than you can say 'i'm sorry' if you ever try to take my credit. my patents are getting renewed right now anyways. see you fuckbags later, unless you wanna talk about my inventions in a kind way.
i almost feel bad seeing a mentally unwell person bullied this hard

>>1719560
Lol their paper is still up on dropbox

>>1719604
You should read the other documents about the secret power of melanin

I'm designing a PCB for a small bluetooth controlled tank

It's going to be an arduino-compatible, so I want to be able to program it via a USB port, however, I've noticed that linear regulators like AMS-1117 can conduct current from the output pin to the input pin via an internal diode, which is enough to enable the motors to be powered from the usb port alone, which is something I desire to eliminate compeltely in this version of the board, since turning the motors without a connected battery pack is enough to cause the board to be disconnected by the computer.

So, I'm thinking: can I use a n-mosfet to low-side switch the "motor power" part of my h-bridge circuit like this? The idea is to only let the h-bridge power the motors when the board has either a 6-AA battery pack or 2x3.7v li-ion cells connected to it

>It's going to be an arduino-compatible

>>1719711
why don't you just add a series diode on the input side of the regulator
>arduino

>>1719711
Where are the biodes?

>>1719729
Because it doesn't work

>>1719731
Actually, I think it would work, but I'd end up with 4 big ass diodes on the board

>>1719741
Solution using N-channel mosfet seems simpler

BTW, this is not a new development, I've designed and produced other versions of this board. They're supposed to be used by schoolchildren. In the next year schools will start receiving it, so I need to come up with a better plan for the near future

>>1719741
You could use thermionic diodes instead.

>>1719741
only three, or maybe two, and SMB isn't that big
>only let the h-bridge power the motors when the board has either a 6-AA battery pack or 2x3.7v li-ion cells connected to it
how about
>only provide power to the motors from a battery pack

>>1719745
if you don't mind your duino seeing high voltages from the H-bridge

>>1719747
shut the fuck up reddit

>>1719749
>le tubes are le reddit
Shut the fuck up cassie.

>>1719752
le tubes are le hipster shit, especially on battery power
your avocado toast is getting cold

>>1719749
The board has 2 connectors for 4xAA batteries, the h-bridge originally had 2 diodes so that you could power the board either with just 4xAA batteries or a wall-wart, or with 2 4xAA batteries packs. I even have a small injection molded holder just for the 4 batteries. Long story short, the wall-wart input was removed from the board, the 2 JST connectors stayed in. User can either use one extra 4xAA pack for the motors, or use 6xAA for both with a single JST connector. Works alright, but something I never intended was that the motors could turn evenwhen the board was connected just to the usb port. Turns out this happens because the linear regulator has an internal diode (why?). So I had to remove one of the diodes and the h-bridge will only work with its own 4xAA battery pack connected. Now I realize that if I had done as you drew, it would work as intended.

>>1719766
Actually no it wouldn't work the same, because the h-bridge would always get power from the logic battery pack, the diode in series with the motor battery pack wouldn't even conduct