/diy/ - Do It Yourself

Anyone got pics of beautifully laid out PCBs?

The kind where all the chips are laid out in one orientation, and every layer has all its tracks going along one axis.

Apparently this style of routing was very common back in the 80s when DIP packages were all the rage, but for some reason I'm having a hard time finding pics that feature a good-looking board without potato quality or poor cameramanship.

Hey /ohm/, a guy is selling this used oscilloscope (Tekronix 2205) for $100. I have never had my own oscilloscope before and was wondering about important things to considers/ if it is a good deal. The prices I see for it vary a lot.

>>836226
>Anyone got pics of beautifully laid out PCBs?

>still no art of electronics 3rd ed pdf

WHAT THE FUCK

>>836240
Tek generally makes really good scopes, just make sure it's in working condition and has suitable test probes.

Though you might want to consider getting a digital scope instead, they don't cost much more, I imagine. (unless of course you're looking for an analog scope specifically)

http://www.ebay.com/itm/USED-GW-Instek-Digital-Storage-Oscilloscope-GDS-2064-BARELY-USED-/261947008442?pt=LH_DefaultDomain_0&hash=item3cfd4225ba

>>836221
'ere ya are OP, spare parts mainboard for one of my lighting consoles.

someone please link the art of electronics 3rd edition...

>>836278
Go look in the last thread, or at any of the archived thread you simple git.

>>836240
make sure the range is what you want.
for instance, I have one from dick smiths I picked up ages ago for 100$.
its range is too low for it to be usable. for me.
also make sure you're not really after a bus pirate/signal analyzer.

>>836240

It probably needs to be calibrated; that process usually can be done yourself with a user manual (and a bunch of other calibrated test equipment, but can be fudged if you want it good enough). Just check it out to make sure it isn't out of whack before you start using it in serious use.

What are upir /ohm/ relevant go-to tech blogs?

>hackaday
>dangerous prototypes

Anyone used these things (snap domes) before? Especially in DIY/prototyping context. How do you attach them to PCB? Apparently you can't just solder them down because they need to flex around. Also how much do they actually cost?

It's so annoying that vendors can't just dump all their precious info on their web pages. I don't want to talk to your sales people, I just want to buy and use your stuff. Like e.g. Snaptron requires me to fill a frikking form and wait until their sales people wake up to get their Designer's Guide. Or like every vendor requires me to contact sales to get an quote to get any idea about the pricing when I just want to buy a hundred units or so. It is not just worth it.

>>836300
>DIY/prototyping context
But anon, that shit is for mass production.
A typical way to attach them seems to be to have a separate plastic sheet to keep them in position.

>>836304
>But anon, that shit is for mass production

I don't see why all the nice toys should be limited to stuff produced in the millions. I just want some nice cheap small/low-profile switches, domes seem like perfect fit.

> A typical way to attach them seems to be to have a separate plastic sheet to keep them in position

Do you know any details, plastic sheet covers fairly wide range of items. I suppose that it at least needs to be flexible enough not to interfere with the snap action.

>>836318
why not capacitive touch switches? they are no profile. as far as the switch itself goes. just a trace will do for the contact point.

or there's the old multi layered thing with traces mounted on little humps.

>>836300
>How do you attach them to PCB?

>>836226
i guess you hate my board then :P

>>836240
I used that model in college (yes, that was a while ago) (yes, we had nicer/newer Agilent ones in the main EE labs but these were in the physics labs). Good scope.

Does any of you know why the art of electronics 3rd edition isn't available for download yet on any torrent sites?

>>836221
This may be a question I should ask on the 3d printer general. Suppose I were to change my bottom plate to aluminium, make it conduct, and add a probe(or two) to the extruder assembly to calibrate and build a coordenate system upon the points collected, where it would record as soon as there's contact. How could I go about detecting the edge of the plate? I can define the axes of the volume, but I can't think of a way to define the size and positioning of the plate automatically without having to drag the probe(s) along the surface and scratch it.
The reason I'm going with two probes, is so one can be spring loaded and lowered onto the plate faster. The other one is fixed and placed slowly onto the plate.

I'm a bit of a tard when it comes to electronics, i'll admit. Could I get some assistance in identifying what the wires/connectors are? I know it's a high voltage transformer pulled out of a microwave

>>836407

there's 3 coils, one of which is has one side connected to the case. the black-white is the 120V input, the two thick red wires are the filament output, and there should be one other spade lug for the high-voltage output winding, but i dont see it.

>>836410

oh, i see it now, it's the one sticking up like an erect prick above the red wires.

>>836411
>>836410
This?

yeah, that.

>>836414
>>836411
>>836410
Thanks. I appreciate it. That answers it 100%

I tried asking /g/ but got directed here.

I got a 3,5 to 6,3 mm jack converter that's plated with gold. However, it's matte now as opposed to shiny when I got it like 4 years ago. I'd like to make it shiny again.

I had sort of the same problem with a copper bracelet which I fixed with a non-concentrated solution of acetic acid (the type you use to clean your sink and kettle to remove chalk), but I'm not sure this can work on gold, since the converter will be used for electric current.

Any ideas?

Pic related.

>>836443

>>836443

forget the brasso, just rub it with a pink eraser. it'll get rid of all oxidation on the exterior. for the interior, you need a thin rubber rod. work like you do with the dildo in your ass.

>>836300
>>836318
Yeah, we use these at work. They get attached to the back of the rubber button sheet that sticks out the front side. I'm sure the snap domes are cheap but the infrastructure around them is not.

Alternatively you could just tape them down. If you look inside Atari controllers that's what they did.

>>836463
>Alternatively you could just tape them down.

confirmed. have seen them in various items held down by scotch tape. which is good, coz if the switch starts to act up, you can remove the tape, rub it and the PCB pads with an eraser, and stick it back down: good as new.

>>836462
>>836443
>>836453

>gold
>oxidation

Nope

Gold doesn't readily oxidize. If it's lost its shiny-ness that's due to micro-scratches on the surface. You could try polishing it, but there's probably only 0.00003" or so of gold on that connector and you'll probably rub right through. Unless it's giving you issues, it should be fine as-is

>>836407
If you consider yourself a tard you should stay far away from microwave oven transformers (MOT). They are extremely unforgiving, as in you are dead if you fuck up

>>836495
>only 0.00003" or so of gold on that connector
that the base metal oxidizes through the pores of

Hello /diy/, my /g/ brethren can't help. I live in a shithole with tons of long power outages on winter evenings. Having no Internet drives me nuts. I have a smart phone and power bank, but the part of town I reside in has 2G coverage.

I get ADSL. I can still make calls with my landline during outages, so I guess the ADSL would work too. Now how do I power the modem? UPS? Expensive as living fuck, small capacity. So I though up some crap.

I have 2 modem/router/AP shits on me. The one I'm using now, I don't want to fuck with it (it runs on 9V) because I bought it. The one my company gave me runs off 12V, and if anything bad happens, I can claim spike in the mains.

I can get a 12V, 7Ah gel battery for literally nothing. Now, I know that battery voltage drops as the charge does, so I can't just hook that shit in and expect it not to fry after 4 hours when the battery's pushing 10V or some shit. So, what about soldering this little fucker (7 dollars);

http://articulo.mercadolibre.com.ar/MLA-567697111-modulo-lm2596-convertidor-step-down-dc-dc-in-4-40v-3a-max-_JM

Between the battery and the power plug? It takes a range of voltages in and spits out a specific voltage out, right? Would a battery + this mean I can run the modem off a battery?

If so, how the fuck do I charge the battery? I don't have a battery charger. I don't know shit about charging batteries either. Can I just use any 12V switching power supply, or would that melt my face and win me a Darwin award?

>>836273
>>836281
>>836285
>>836344
Thanks folks, just waiting to here back from the dude.

>>836496
Fair enough. The thing I want to do though is pretty hands-off. When I apply power, I'll be a safe distance away.

>>836505
Yeah, that module will work. Then get a SLA trickle charger.

>>836526
>SLA trickle charger
Kinda expensive, but I guess it's not too much.

>that module will work
I was sort of worried after posting that because I read the title again and it said "step down", and I interpreted that as in only lowers, does not regulate to a higher voltage. I know very little about this sort of thing, but are you sure?

>>836530
Oops, yeah, you're right. You can try to find a buck-boost. But it's also likely that the modem/router has its own step down converter inside and will accept a wider range of voltages.

>>836539
The batteries are pretty much super cheap. Two in series? 24V is within the acceptable rage. Would the step down simply draw less current as with the higher voltage, meaning I'd get (very roughly) double the run time?

>>836542
Sure, you can do that, if you can figure out how to charge them.

>>836542
I have a 2WIRE gateway from AT&T. (12v power)
When my power goes out for extended period (ice storm, etc) I connect to a regular lawn and garden tractor battery.
I do have a diode or two in series to drop the voltage a volt or two (depending on state of charge)
The tractor battery stays on a trickle charge / maintainer when not in use.

>>836530
Other options include using a 9V regulator and the other router, or using 2 batteries. Step-down converters tend to be more common and cheaper than step-up or either-way.

Either way, you need an actual battery charger. And it needs to allow for the fact that the router will be drawing current from the battery while it's being charged, so the charger needs to be able to push out enough to power the router and charge the battery.

In that regard, a dumb charger is better than a smart charger, as it won't be confused by the current draw.

>>836241
>>836275

I stood way too long watching at those beauty.

>>836546
Charge separately and then put them in series again. Or am I missing something?

>>836550
>Either way, you need an actual battery charger
Shucks. Well, I guess I could cut costs by getting more use out of it. I could upgrade to a buck-boost for really not that much more, and not only run the router but a USB car chargers, you know the kind. If efficiency goes to shit I can just slap on another battery in parallel to make up for the runtime, those are dirt cheap.

http://articulo.mercadolibre.com.ar/MLA-567260043-modulo-convertidor-dc-dc-xl6009-sepic-buck-boost-arduino-pic-_JM

According to specs it should be able to handle the load.

This is getting pretty nigger-rigged, but hey, a UPS which would power everything for a third of the time costs twice as much. Would have to charge batteries all day, don't mind though.

>And it needs to allow for the fact that the router will be drawing current from the battery while it's being charged

No. I just yank the phone line out of the one I always use, stick it in the backup, and turn on the backup. I can deal with the 30 seconds of downtime between doing that and the modem establishing the connection.
Going to bed, I'll check the thread in the morning. Thanks a ton /diy/, I ought to spend some time on here.

>>836587
Well if you can tolerate downtime that simplifies things.

Dunno if it's the right place for this but
My old technics amplifier has the right channel pretty much dead. Sound started to come and go at first, I thought it was a bad contact/rusty clip connectors, so I bridged some RCA connectors over them but problem persisted, and now it's dead. Left channel still works.
I don't know a thing about amps. Is it fixable or it's time to get a new one? I think this thing is over 20 years old.

>>836722
>signal injector
>work back from output -> input

>>836722

almost certainly that big chip connected to the heatsink, probably an STK4122, is dead. you can get a replacement amp at a thrift store for $8-$25 so no point in repairing it, coz it'll cost just as much.

>>836726
> almost certainly
Because a 20 year old amp is not going to be riddled with dry capacitors, is it?

>>836226
>dat spaghetti wire

>>836722
I guess the great thing about amps is that they're modular and symmetrical, so you can swap huge sections from one side to the other, and see if the fault travels with them.

Or if they blow up the good side too, I guess.

This is where a meter or a scope would come in handy: by following a signal all the way through the good side, you can see where it stops working in the bad side.

Anyone have the /ohm/ challenges chart?

Alright so, im making a coin mechanism that is designed to trigger a microswitch (on-on), which in turn will turn on a solenoid which will release a drawer (the solenoid acts as a lock), for a vending machine mechanism kind of thing.

Problem is, im thinking that the solenoid will only trigger when the microswitch is hit by the coin, which will only be a few milliseconds, and then once the coin has dropped the solenoid will go back to the 'lock' (off) position, not giving the person enough time to pull out the drawer before it locks.

So question is, how do i delay this, between when the button is pressed and the solenoid turned off, just for maybe a few seconds to give people the opportunity to pull out the drawer?

Is there like a 'timed switch' component i can buy that has maybe like a set 'on' time before it switches off automatically? I looked through the catalog at my local electrics shop and i couldn't find anything, but there probably is something hidden in there, its just everything is written in electronics jargon.

Also, if i did find such a switch, would it be possible to rig it up to turn on, not a human push, but an input from another button (the microswitch)?

>>836801
It sounds like you could solve your problem using a counter and some digital logic. Just hook the counter's outputs and the switch to an OR gate and the output of that gate to the solenoid. That way it'll only turn off once the counter hits 0. Loop the output of the OR gate back to the power (Tc) of the counter so it turns off once you get back to 0 and only triggers once input from the switch occurs.

I just bought an oscilloscope and I've been jerking around, I tested what noise my body had and I found this, a ~100V peak sine wave, it rises to around 150V when I stand barefoot. I guess it comes from the grid, but I wasn't touching anything connected to it except for the probe, I would like to find the explanation behind this. I sometimes feel little burn-like shocks at my fingertips when I touch things connected to the grid, like my laptop, I guess it must be related.

>>836808

I could do this, problem is im no good with electronics and figuring out how to integrate chips could be hard. Simplicity is best for me, currently what i have is a simple circuit with literally one component and a button.

Initially i was thinking of using a arduino to control the solenoid, as you can use inbuilt timers, use counters and have LED displays, but in the end i decided against it because it was complicated and more expensive than i would like.

Ill keep it in mind though, if its the best way to do it ill figure out how to do it.

>>836816
I'm more of a digital guy than an analog guy, but I think you could use the discharge of a capacitor to an NPN transistor to accomplish the same thing. It'd be less accurate though as capacitors do degrade over time.
Or if you're okay with using a 555 timer, you could look up simple timing circuits and make your own OR gate and use that as your timer.

>>836771

military class circuit boards are awesome.

>>836823
I was gonna say something about those pics, saw them a while ago. Isnt there more?

>>836831
yup here
https://www.youtube.com/watch?v=55z_0BYb5is

>>836823
> be Soviet 7th grader
> all schools dedicate a day per week for pre-professional learing
> boys have a choice between carpenter, mechanic, electrician, radioelectronics and IT technicians
> meanwhile, a factory manufacturing Polyvoxes and also parts for C300 anti-air defense operates in the town.
> mfw scrapped components from hundreds of boards like those during classes on welding and PCB repair.

>>836850
CДEЛAЙ ФOTO CPAЗУ!
or it didn't happen!

Is nail polish good to prevent copper from oxidizing?

>>836898
I can't see why not. So long as there aren't any exposure points, I'd say you're good.

>>836801
>opportunity to pull out the drawer?
I've worked on several cash drawers that operate in this manner.
They all had a 'push' spring behind the drawer that opened it a couple of inches as soon as the solenoid triggered.
The person could pull the drawer open as needed and the spring and solenoid were reset when the drawer was closed.

>>836894
It's all past tense dude. The factory got closed between '94-95 as the manager was selling pretty interesting equipment left and right using very grey schemes (damn, so many 'ol scopes, wave soldering, injection casting machines, galvanic basins etc etc just dissolved in general China direction)

>>836221

Pretty new to electronics so hopefully this isn't too stupid a question

Thinking of using reed sensors on a project I have in my head, was wondering if I expose them to a relatively weak magnetic field for long periods of time (hours?) is it likely that they will become magnetized (and thus stay in the connected position)?

Also is there an easy way to degauss them if they do pick up a magnetic field?

>>836266
for real :( please someone do this for my poor ass

>>836939
Reed switches are available in NO and NC configuration even SPDT
I've never encountered one that changed orientation.
>dat trans reedie

I have encountered a few that were 'welded' closed due to excessive current.

>>836822
rollen

>>836812
Get an outlet tester; you might have no ground or reversed hot and neutral. And get an isolation transformer for your scope.

>>836947
Okay sweet, thanks.

How hard is it to wind your own transformers?

>>836963
Probably about the simplest basic electrical component you can make next to resistors and capacitors.

>>836963

Not hard, just tedious.

>>836963

Here's a good page on it.

http://ludens.cl/Electron/trafos/trafos.html

>>836963
wrap layers of enamelled wire around a bobbin while counting the turns, stick it on a core. the hardest part is the boredom.
http://ludens.cl/Electron/trafos/trafos.html

>>836812
>>836812
The reason you see the sine wave is because your body acts like a antenna.
>150v peak to peak and burn like shocks
Sounds like something is wrong with the electrical wiring in your home.

Is it necessary to clean off the residue left by soldering? And if so, how should you clean it. I've seen iit happen with both soldering and desolderibg with a solder wick.

>>837438
Usually no, but your stuff looks nicer if you wash it. Alcohol (ethanol or isopropanol) + a toothbrush works well.

>>836976
>>836981
>that site
http://ludens.cl/Electron/chinverter/chinverter.html
holy shit I'm laughing my ass off.

>>836812
Probe ground is directly attached to earth ground. This would indicate that the voltage is coming from the ground prong of your outlet. Your time division is set to 20ms, so it is obviously 50hz/60hz. With what you said about the shocks, I would call an electrician immediately.

>>836898
You are talking about copper traces right? Coat them in solder.

>>837452
Just followed the link. This is comedy gold.

>>837438
Alcohol, an ultrasonic bath, and a toothbrush.

>>836812
I'm guessing the oscilloscope is not connected to a grounded outlet?

Anyone here burn themselves with the soldering machine yet? Burnt my dominant hand and now I can't do shit with it because

I just dropped my PIC. How do I know if this thing is still working?

Not sure how diy this is, but I've dismantled a tiny keyboard from an old em@iler telephone in hopes to use it for my laptop. However, the cable and the pins that attach to it are not usb to PS/2 (maybe it is but I cannot confirm), instead it has 4 pins aligned horizontally as in pic attached. Do I need a PIC and software/driver to go with this? is it salvageable?

>>836221
kjhuhjk
hi im a fucking idiot and would like someone to point me in the right fucking direction as to where i might be able to start learning about electronics and how to make electronic shit.
(i am a complete beginner and dont know shit)
thank

I have a battery charger and some 18650 cells from laptop batteries. I want to use them for flashlights and other things, so is there any way to test them and see which are working and which are dead?

till I can be bothered to but together a decent switch mode PSU, how terrible of an idea would making a variable power supply out of a laptop power brick and a buck converter module off amazon be? just starting to tinker with electronics at home and since I'm already spending a bunch on tools and shit I just want something cheap and simple for now

>>837608
If it's not too ancient there's a decent chance that it's actually usb or ps/2 with a different plug. Both have 4 wires. Finding Vcc and ground shouldn't be hard, and there might be silk screen on one or both ends that would help you find the pinout. If you're feeling reckless you could just hook it up to a usb port different ways to see if it works, but I'd put it after a hub for less risk of damaging your computer.

>>837608
Got a pic of the other side of the cable?

>>837620
Didn't read the first post, eh?

>>837564
I've done it a few times. If you have long hair make sure you tie it back before working on anything. Burning hair smells terrible..

I am currently making this device which has the .asm and .hex files on the website in a text format. The problem is I don't know how to convert them to make .asm and .hex files. Here is the link:
http://www.mindspring.com/~tomtitor/index.html#programcode
I am using MPLAB X IDE and a pickit 3 to put the code into a PIC16F628A

>>837644
To update:
I think I'm supposed to make an empty .asm file and then copy and paste the contents from the site to it. I've done so and, changing compiler to mpasm, it managed to build. However, now connection to Pickit3 is not working. I'm using one of these devices, but is there more I'm supposed to do?

>>837595
jist grab another from the drawer they cost pennies

>>837644
Lemme let you in on a secret: everything is text files. Just change the filename to end in .hex or .asm.
>>837649
That is a different problem, it probably has something to do with how everything made by microchip is completely broken in every way imaginable.

>>837664
Well darn I guess that's $70 wasted... Should I go with AVR?

>>837666
Not if you plan on using that code. You could try some combination of plugging and unplugging it repeatedly, DBANing and reinstalling everything or circumscribing it with pentagrams. It will probably randomly start working for no apparent reason about five hours in.

>>837664
>Just change the filename to end in .hex or .asm
Uhhh

>>837664
>Lemme let you in on a secret: everything is text files. Just change the filename to end in .hex or .asm.
You mean everything is binary files

>>836221
Nothing impressive but thought I would share anyways, just finished testing the new, larger battery in my sansa clip+. original battery was rated at 290mah and this new battery just measured out to 428mah. Feels good man.

>>837681
binary, text, it's all just data. all that matters is how you interpret it.
>>837679
both are human readable text based formats, no conversion is required

>>837689
>binary, text, it's all just data. all that matters is how you interpret it.
hexadecimal text is completely different from assembled opcodes.

>>837689
>both are human readable text based formats, no conversion is required

Hex is as far from human readable as you can possibly get, and it's not the same thing as assembly to a CPU. You need to run the assembly through an assembler to generate hex.

Say a line of assembly is NOP, and NOP has an opcode of 0 in the CPU architecture. If you gife the CPU 'N', 'O','P' is sees the Opcodes 78,79,80 (ascii indexes of the characters), not the opcode the line of assembly represents.

>>836841
>>836823
Is that conformal coating on those boards? It looks all sexy and shiny and chrome. Definitely going to spray that on my next project.

I'm having some trouble designing a boost converter for a project. I need to step up the 12V off my car battery to ~40-60V. Needs to drive a string of 10 blue LEDs. They will only go on when a voltage is applied to my radar detector's 3.5mm jack, it'll be controlled with a MOSFET, that's not the issue though. I don't really know how to pick values for the boost converter, what caps should I use, what inductance do I need, how do I find and set the duty cycle for the regulator?

I'm reading these:
http://www.ti.com/lit/an/slva372c/slva372c.pdf
http://www.ti.com/lit/ds/symlink/lm2585.pdf

but it's confusing. It's talking about switch and input currents and I don't even know what the input current is or how to find it? The boost converter IS the load for that part of the circuit since it's hooked straight to the battery, the input current is determined by the entire network right? Or is it just the max current the battery can supply? Or am I supposed to put it through a resistor to limit it first? Either way I don't need a lot, I was gonna use a voltage regulator set up as a constant current supply to push a few mA through the LEDs, maybe 15mA? I don't really know what the forward current for blue LEDs is.

>>837777
What do you need the 40-60v for? Is that what your LED string requires? Pre-made ones are almost always 12v, so why did you go out of your way to find one you can't power easily?

>>837779
It's just a bunch of blue LEDs in series, not a literal string like Christmas lights. I should have used better wording. I was under the impression that even if I used a constant current source to push ~15-20mA through the LEDs the voltage drop across 10 would be too high for just the 12V battery so I'd need to apply a higher voltage.

>>837781
Are these just "regular" LEDs in the 2v-3v, 20mA-30mA range or are you trying to use high powered (1W+) LEDs to light your car up like a rave?

You don't need a constant current supply unless your LEDs are high power; just some resistors. You can arrange them for 12v. Use this: http://led.linear1.org/led.wiz

>>837784
Regular. I'll look into redesigning the circuit without all the complexities then. I guess I was just doing it wrong.

>>837784
Okay, redesigned. A lot simpler now. It looks like it'll work as I intended now. Thanks.

>>836812
I have a rigol too. But its a 2 channel, very similar to yours. It did the same thing when plugged into an ungrounded outlet. A grounded outlet does the same thing but at much lower amplitude. I have yet to see it come through on any isolated circuit i have tested. only when i fuck around and poke the probe into my skin.

>>837790
Okay, this design is better but I'm getting some weird voltage spikes when testing in multisim. Is multisim just being stupid or am I forgetting something important?

Does anyone own a USB multimeter? Do they actually work well or are they basically gimmicks?

>>837935
The good old yellow bricks are cheap. I'd say gimmick.

>>836266
>>836940
>tfw bought 2e like a year ago

>>836963

I rewound and repair flybacks and HIGH VOLTAGE transformers and its not easy, maybe cause of the HV

very delicate process cause if you make one mistake, it will punch thru the isolation and short out,and your work is for nothing ,then you also have to dip them and so on ...

>>836950
Europoor here, plugs can be connected either way. Thanks for the isolation transformer tip.
https://www.youtube.com/watch?v=LbkCU-LBqKk
>>836982
>>837477
I don't know what could be wrong, I'll seek help anyways.
>>837489
>>837800
No ground, my house is grounded, but this particular outlet isn't, I'll try to run a cable to my room.

The shocks thing occurs sporadically I guess when the ambient conditions are met, they are barely noticeable only when I'm barefoot.

>>837980
With no ground, the case will float at half mains voltage.

>>837980

where in Europe ? which country ?

maybe you're close to me

AC question. I have a wire that is like pic related. I connected the red wire to live (from main) and before I connected the netural I just tested it with a tester and I could see voltage on the black wire!

How did that happen? It had nothing connected to it. Did the live wire transfer voltage to it just by being close to it?

>>838161
capacitive and/or inductive coupling
this is one reason why those expensive meters with their fancy gigaohm jfet inputs are shit for many practiacal applications

>>838161
Are you sure you know how to work a meter?
Serious question. I had a tech who said she was an electrician for 5 years but couldn't .

> capacitive and/or inductive coupling

translating this into terms the dude can understand, it means that a very weak charge is flying thru the plastic insulation from one wire to the other. if you were to put any kind of load on it, it would disappear like the Cheshire cat.

>>838214
yeah, just stick a resistor in there and try it again.

/g/ here, sorry for shitting up the thread with a retarded question but /g/ doesn't actually know anything about technology

I accidentally plugged in an old laptop using an AC adapter with reversed polarity for about 20 seconds, I didn't hear anything and no smoke came out, am I still fucked? I don't have a compatible AC adapter to test it yet.

I think it has a circuit to protect against damage from this kind of situation, but I'm not sure.

> I think it has a circuit to protect against damage from this kind of situation, but I'm not sure.

some do, some dont.

>>837649
ok now what is your problem? First of all what programmer are you using?

>>837845
why aren't you using parallel sets of 4 blue leds in series?

Need halp

Have a solenoid, need to be able to trigger it on in both forward and reverse, which means i need to switch the polarity in my circuit.

Problem is, i only have a normal switch with 3 pins instead of a DPDT switch, as the design i need for the switch is quite specific.

Can someone help me figure out a way to reverse the polarity? Is it possible to do with some creative wiring?

I have: 1 Battery, 1 Micro switch with 3 pins, 1 Solenoid.

Capacitor on my GPU somehow came off from handling
I looked up the cap and it seems to be fairly cheap off alibaba & co (2.5v 820ohm)
how hard is it going to be to replace it?
The only soldering equipment I have is a copper wick and a shitty craftsman iron, and a shitty craftsman gun, which gets ungodly hot

>>838357
forgot to add, I put a thread up on /g/
>>>/g/48916742

>>838355
This will do it, but the battery needs to have a voltage about twice as the minimum required by the solenoid. You also won't get much holding force, so not appropriate for things like solenoid valves.

>>838357
>(2.5v 820ohm)
Ohm is resistance of resistors. Capacitance of capacitors is measured in Farads. 820 means 82pF

> Capacitor on my GPU somehow came off from handling
Why don't you solder it back on instead of buying a new one?

> shitty craftsman gun
Don't use glue.

>>838369
>Ohm is resistance of resistors. Capacitance of capacitors is measured in Farads. 820 means 82pF
not at 100% right now
>Why don't you solder it back on instead of buying a new one?
it physically came apart

>>838072
Eastern Spain, I wouldn't mind having an electronics buddy.

>>838357
Depends on how much damage you did to the board. Your irons probably won't work very well, leadfree solder on a multilayer PCB requires a lot of power. Try desoldering the legs of the broken capacitor and see how that works out for you.

>>838383
the card seems to work fine without the cap
I'm going to stress test it and see if I can get some magic blue smoke

>>838386
>>838383
I should probably ask before I proceed
where would I get some of these caps?

>>838372
why not just get good capacitors and do the job right by recapping the whole thing with a known brand of capacitor with a preferable ESR.

just leaving the unneccesary capacitor off isnt really an option. its probably part of a bank of capacitors that stabilize the voltage for a particular part like the ram or GPU. in parallel, they add up.

or just replace it with cheap electrolytic whatever.

>>838388
>why not just get good capacitors and do the job right by recapping the whole thing with a known brand of capacitor with a preferable ESR.
I doubt my skills to recap the ENTIRE board
I'd fuck up somehow

>>838389
>>838388
http://thecapking.com/25820.html
would this be a good source?

Hey guys

I'm a newbie in this electronic stuff and getting into Arduino and shit

I want to build a midi controller that's just knobs, but Arduino only has 6 analog inputs and I would like to build one that has at least 16 knobs. How can I do this?

I already own an Arduino Uno, but most guides online for midi controllers suggest using Arduino Leonardo. I know this is because Leonardo acts as a usb keyboard/mouse/whatever, but is it possible to work the Uno around to work similarily? If the difference is too much I don't mind spending a bit on the Leonardo.

>>838455
You should use something better for the job than an arduino like this http://www.pjrc.com/store/teensypp.html

The first thing to learn in Electronics is to drop the arduino. It's fine as a tool, but early on it can easily become a crutch. Arduino isn't the best tool for the job in most situations. Think of it as a jack of all trades, master of none sort of thing.

>>838455
You can use an analog multiplexer IC like the 74HC4051 to select between multiple potentiometer outputs connected to a single analog input. This will mean you can't read the values as quickly because there's an extra step though.

Another option is rotary encoders. They can be read by the digital pins.

>>838472
Third option is to use an external ADC IC.

>>838455
The only way to make an Uno into a custom USB device is to reprogram the second chip that acts as the USB-serial converter.

The Arduino Zero would be another option.

>>838477
>>838474
>>838472
>>838465
I see.

I think the Teensy alternative would be the most practical, but I appreciate your inputs.

Do you think you could link me to some tutorials?

>>838465
I was reading about this and noticed it only has 8 analog inputs... I'm guessing you can expand them somehow? Sorry, I'm not very educated in the matter.

>>838215
>>838214
>>838177
Yeah, thanks! I get it now. When I connected the neutral it went away.

>>838188
I didn't use my meter. I used a tester screwdriver.

Low voltage here so I installed a stabilizer. It really fixed the voltage and it's bearable now (from 140 to 200) but there's a problem. The neutral it gives out as output shocked me. I can also measure voltage on its neutral.

Other problems include turned-off lights that blink every few seconds.

What do? Should I connect the stabilizer neutral to ground?

>>838505
Use two like this guy did.
http://m.instructables.com/id/A-Framework-For-Making-Affordable-Stylish-Modula/

>>838512
Use your meter.

>>838391

the cap you link to sounds fine, but the site where you found it sounds very dodgy. they're saying their 2.5v 820uF cap can replace a 6.3V 1500uF, cap which is complete nonsense.

pro-tip: do not use a solder gun, only a soldering iron, coz a gun can possibly kill every chip those capacitor contacts connect to. if you have difficulty removing the old capacitor pins, just leave them and run a short extension cable to you capacitor, making sure to isolate the wire and capacitor legs. (like the battery in pic, but shorter)

>>838465

>Think of it as a jack of all trades, master of none sort of thing.

AKA the ideal beginner board

>>838761
I suppose. The biggest problem is that arduino let's you do electronics without knowing electronics. You can do complex circuits using their shields and not know anything about circuit analysis.
It's like making a game with rpg maker. Yeah, you technically made something but it's lackluster and usually very empty with a few notable exceptions.

>>838689
thanks
I found that the card boots and displays just fine
I'm going to stress test it and hope for no magic blue smoke

I want to charge a capacitor from a low voltage, let's say around 4 volts.
In a normal case with more voltage I would use a 555 and a transformer in flyback mode, but in this case I don't want to rely on ICs, so I need info on any of the following:
·A way to produce an square wave around 10-30kHz (astable multivibrator or similar oscillators)
·A way to produce feedback from the transformer introducing a feedback coil or something like that.

I would really appreciate some info about winding small transformers with feedback coils, I would really like to make step up converters with just a transformer, a transistor and other passives...

(I know there's a low voltage 555, I just want to do it the hard way)

I read that you can short-circuit (non-stepper, non-servo) e-motors to make them hold their position.

DOes that simply mean if i connect the motors vcc and ground that it holds its position?
That would mean it wouldnt consume any energy to do so. Can this be true?

>>839011
It's a form of dynamic braking. That is, if the motor is spinning, it slows down faster.
It won't hold its position.

>>838989

Well, I've made some progress, this is a two transistor oscillator with one of the caps connected to a darlington transistor and then to a small transformer I made. You can see the green neon light which indicates the presence of high voltages. The voltage input is around 3 Volts.

How can I improve this circuit?

>>839058

i made a circuit similar to this that's worked quite well for powering Nixie-like devices. can deliver quite a nice bit of current. my circuit only uses 2 transistors, but it's the same principle: a relaxation oscillator driving a transformer in a push-pull configuration. this circuit adds a second set of transistors for buffering.
a voltage multiplier can boost the voltage if the transformer doesnt have the right ratio.

>>838989
What's the point of self-imposed limitations if you need other people's help to get around your limitations?
Well, whatever. If you go with separate oscillator and transformer, you could download LT1070 design manual. It tells you how to design flyback transformers and it is clearly and concisely written.

>>836822
rol

began laying out this thing today. Not sure if this design will end up being too dense for assembly. Have to take a look with fresh eyes tomorrow, gotta go sleep now.

>>839071
Nice, thank you, I don't plan to use a voltage multiplier since I won't be using more than 300 volts.
>>839073
The point is to learn, other people's help makes it easier to find good resources like the one you just posted, I probably would not have found it by myself. Thank you very much for the read.

>>839194
I'm guessing you'll use hand soldering? It looks doable, but you'll have to think about the order you solder the components. If your components are at all larger than the footprint you're fucked.

Sup /ohm/. I have a circuit like so (pic attached). I can change Rsense, but nothing else (Rsignal/Roffset are a single sensor with pretty much random AC signal and DC offset amplitudes of between ~100-10k and ~1Meg-10Meg respectively, and the voltage across the sensor has to be kept at Vctrl with very little leeway for offset).

I have Vout = V+ - V- = (Rsense*Vctrl) / (Rsignal * Roffset), but want Vout = C*Rsignal.

At the moment I'm thinking:
Analog divider taking Vctrl as numerator and Vout as denominator, i.e. V1 = Vctrl/Vout = (Rsignal * Roffset) / (Rsense)
Then just differentiating to get V2 = dV1 = Rsignal/Rsense and feeding it to my ADC.

The problem is that all the monolithic analogue dividers I've found are shit. Has anyone worked with them before? They're usually rated to ~1% of full scale input, but is it possible to calibrate that out, or do they drift?

What about just going log-amp -> unity-gain inverter -> VGA with V as signal and signal as control (i.e. the poor man's divider); is this going to be any better than a generic multiplier/divider IC? Are there any log amps with differential output/VGAs which take differential control input so I can skip the inverter?

Is this idea just too damn impractical?

>>839396

Forgot pic.

>>839396
>voltage across the sensor has to be kept at Vctrl with very little leeway
Re-check that assumption. Maybe it's incorrect, making your whole problem go away.
Another thing is that your sensor sounds like a piece of shit (pressure sensitive resistor?). You sure 1% accuracy in signal processing is not enough?

>Analog divider
Since you have an ADC, why not handle the division after it, digitally? That would be the usual way. Also, do you need sensor linearization in any case? If yes, then the reciprocal value might not be that bad starting point.

>poor man's divider
I'm not sure what you mean with that, but analog dividers are usually implemented with logarithmic amplifiers internally. Analog multiplier + opamp is another way to build a divider, but analog multipliers aren't that great either.
And no, I don't think you're going to get much better results by implementing the analog divider by yourself. Better consider ways to get rid of it completely.

I have one of these variable capacitors. I think it's a Sprague-Goodman GZC18100. I can't figure out which pin is antenna. I assume the middle pin is the ground. The manufacturers site doesn't seem to say and other variable capacitors have O-G-A labels.

Any ideas?

>>839410

>Re-check that assumption. Maybe it's incorrect, making your whole problem go away.

First thing I did, unfortunately it's part of a research project; the sensor behaves differently at different voltages and part of the experiment is trying to characterize that.

>Another thing is that your sensor sounds like a piece of shit (pressure sensitive resistor?).

It really is.

>Since you have an ADC, why not handle the division after it, digitally?

Because the smallest shift in voltage I'd want to measure would be on the order of ~100 microvolts, and I was hoping to avoid using an 18-24-bit ADC or externally adjustable gain.

>poor man's divider

A VGA typically has exponential gain on the control input; so a log-amp + inverter + VGA would divide the VGA's input by the log-amp's input. If the log-amp/VGA were both fully differential, you could just swap the differential lines and skip the inverter. The problem is that the minimum log-amp output voltage is necessarily tiny if you want high dynamic range and VGA gain is awfully inaccurate for small control inputs.

The datasheets I've read seem to suggest that modern monolithic multipliers are all current-mode input and use the translinear principle for multiplication directly, rather than via separate log-amps for the two inputs.

>Better consider ways to get rid of it completely.
I think I'll have to. Thanks anyway, anon.

>>839416
Get an ohm meter and measure pin to plates.

>>839416

if you turn it over, you should see two of the pins are actually tied together, so effectively it only has 2 pins, and it doesnt matter which way around you use it.

>>839497
Damn it I wasn't even paying attention. Thanks.

>>836221
I'm a monster.

hey guys
i have a pcb pretty darn close to some aluminum.

is there some kinid of anti static paper that i can put on top and around the pcb so that in case it does touch the aluminum, it doesn't short the pcb?

>>836343
some sort of arduino thingy?

>>839728
In a pinch, regular electrician's tape :D
Better way would be a plastic or mica insulator/standoff, or a plastic standoff.

Also, you don't need conductive or antistatic paper, you need an insulator!

So i want to build a music-box for my little brother.
Its supposed to be made of some nice wood and have two speakers and a plug for his mobile phone audio output.

So far i was thinking i need:
-some 12v Battery
-the smallest stereo-amplifier i find
-speakers
-wiring
-a plug to charge the battery

Now the amplifier and the battery are both around 110mm x 40mm x 60mm.

Now there is two things i dont know:
-are there smaller amplifiers? didnt find one so far, but dammit we make phones that fit in my nose, there have to be smaller amplifiers. Batteries as well..
-What is the consequence of using certain voltages on the amp. Is it just more volt = more amplification, up to the point where the current will burn some components? Or will it not work if i dont have the exact voltage.

Please halp. My generator keeps switching neutral. I had it hooked up to my main panel an everything worked fine but the generator input wire gave neutral on the live wire and live on the neutral wire so I switched it. And it's still the same.

Don't a generator have a constant neutral? I have switched the wires multiple times but still somehow it feeds live to the neutral wire and neutral to the live.

>>839755
thank you so much man
love your enthusiasm

>>839786
> I have switched the wires multiple times but still somehow it feeds live to the neutral wire and neutral to the live.

i'm curious as to how you are making this determination? it seems to me that a generator gives out a floating 120Vac supply, and so the neutral and live are interchangeable.

Does anyone in /ohm/ work as an electronics technician?

What do you think of the ETA certifications?

I'm thinking of sitting for the CETa because I have no education and no relevant experience but want something to put on a résumé.

>>839818
Im getting an apprenticeship as an electrical technician and I just got my CETa. It was a stupid easy test. FCC Element 3 is much more involved. But the place i'm going to work for loves certificates.

But yea if you know ohms law and how to find the resonant frequency of a simple LC circuit you're golden for the CETa.

>>839779
>What is the consequence of using certain voltages on the amp?

They normally just have a max voltage they can be powered with and a max wattage. So as long as you stay under it it will work, but only amplify up to a threshold under that voltage (80-90%)

>>839824
Do you need to be working as an apprentice to meet the requirements to take it?

The ISCET associate exam requires literally nothing. Would either be preferred by employers?

sup /ohm/ any of you got anything good/fun to do with a PSP? found one in the trash today [I dig through trash, okay?] and everything was there expect half the charger, I went home checked my "why the fuck do I keep all these cables that are like 20 years old with connectors nobody uses any more" pile. Only needed the end that plugged to the wall, found one and plugged in, it charges and holds charge, not too badly beat up, it is an earlier one, 1001. just dunno wth I'm gonna do with it. I already tried googling some things, and its just mostly emulator crap.

>>839837
I actually competed in SkillsUSA nationals in Kentucky for Electronics Tech. They gave us the test for the cert free. As well as the CSS cert ETA offers. The site says you need less than 2 years experience as a tech or in trade school to take it but I dont know if no experience counts. Worst comes to worst you could always take the SET, although i can't imagine how much easier it could be.

>>839871
PSPs are the go-to emulation machine, but you can do plenty of homebrewing with it.

>>839883
I see it has some sort of camera capability, wonder if I could wire up a DIY rear-view car camera/screen system. idk yet. no good uses have come to my head, it would prob sit on the shelf until I come up with something.

speaking of cameras. I got an older JVC camcorder. pretty sure the battery is dead on it, not chargeable any more, and I don't have the plug that goes into the camera to test if it works off of the mains power.

is there any other way outside of buying a new battery/plug to even test if the camera works?

>>839891
who cares, rip the NTSC viewfinder off of it.

>>839893
its quite a bit newer then that... say. about 4-5ish years old.

>>839895
Ignore me, I just googled that and I'm a fucking tard. I thought that NTSC view finder was the older ones where you put your eye up too the little lense shit... lmao didn't know it still applied to the flip out screens.

>>839895
oh well fuck the thing then, it's shit and useless. you said camcorder and got my hopes up fuckhead.

>>839900
lol! I got a few VCRs?.. I really need to throw away this shit.

>>839902
VCRs have useful parts too, but nothing like a ready-to-use video scope. You know how long I've wanted to put together an active infrared sight for my AK?

>>839903
you know the rarity of me finding those old cam corders in the trash has gone down the last 8 years or so... but every now and again, I find one in the trash, or at a yard sale for like 5 bucks. if I find one anytime soon ill post what it is here, and if its any good for your needs, you pay postage, and you can have it for free.

I don't really know where else to ask this question. I am moderately competent with electronics, but I don't get power regulation beyond the use of PWM and relays to dim lights. assuming I have an infinite budget, whats the best way to get multiple different voltage lines from a 11.1v battery? I want to be able to run USB electronics from it, but also 12v speakers and other stuff when necessary.

>>839996

https://en.wikipedia.org/wiki/Switched-mode_power_supply

All high-efficiency power supplies are switching supplies. Basic idea is to short out an inductor with the source, then cut it off some time before it saturates. The energy stored in the inductor is then recovered by a myriad of circuitry, filtered, and delivered to the load.

>>839999
wow. that sounds very intelligent, but i have no idea what any of it means. before you tell me to start googling, I tried, the parts that I got still didn't make sense. please explain what you care to.

After buying a new PC case, I decided to not use my old ODD drive, because it still used ribbon cables and I used it like once a year
Knowing that I'm too lazy to try, and no one would actually pay anything worth my time for it, I wondered if I could make a "burning" laser from it, as I've seen on youtube several years back
Now the question is what would it require and how hard would it be to make for a person with pretty much no electrical knowledge
I mean I have very basic understanding and whatever I learned from physics in school, but that's pretty much it
What tools would I need and what parts would I need

>>839873
Funny you should mention that. I'm from eastern Kentucky and was wondering about the job market for electronics techs in our state.

>>840018
>I tried, the parts that I got still didn't make sense
Which parts?

>>840020

dude, dont touch your optical drive, you're gonna be sorry when your HDD craps out and you need to re-install Windows. think of it like a fire extinguisher: even if you never use it, it's still useful.

>>839804
It gives out 220v. U1 should be live and U2 should be neutral, right?

>>840084
> Installing OS from slow optical media.
> Not using Rufus or similar tools to make faster bootable USB installer sticks.
> Being this pleb.

>>840084
fucking lol
I havent used optical drives in more than six years
who the fuck still burns discs

> who the fuck still burns discs

people who live in the real world, and have to deal with real world problems like
- I got a virus and have to re-install, how do I know my USB isnt infected also
- my sister wants to reinstall Windows but now I gotta phone that idiot for 20 minutes just to set the laptop to boot from USB
- my computer crapped out, so I gotta download the Win7 ISO, then burn the ISO to a USB. how do I do that without a working computer?
- that cute girl wants me to come to her house to fix her Windows, but she doesnt know which version, or which edition of Windows her serial # is good for. so now I gotta spend $120 to buy 10 USB sticks, instead of $5 to get 10 DVDs. or lose face.
- etc

>>840138
USB sticks aren't read-only media. Sometimes discs are safer.

>>840175
>- my computer crapped out, so I gotta download the Win7 ISO, then burn the ISO to a USB. how do I do that without a working computer?
Why the fuck do you only have one computer

>- that cute girl wants me to come to her house to fix her Windows, but she doesnt know which version, or which edition of Windows her serial # is good for. so now I gotta spend $120 to buy 10 USB sticks, instead of $5 to get 10 DVDs. or lose face.
Why don't you have that shit in a drawer somewhere already, have you only been doing this for two weeks

>Why don't you have that shit in a drawer somewhere already

10 USB sticks for various editions of windows
+ 3 USB sticks for Live editions of Windows or Linux (coz some will work on some hardware but not others)
+ 1 USB stick for password recovery for XP
+ 1 USB stick for password recovery for Vista
+ 2 USB sticks for antivirus
+ 1 USB stick for HDD regeneration
+ 1 USB stick for file recovery
+ 1 USB stick for incognito anonymous surfing
+ 1 USB stick for Hirens utility disk
+ 1 USB stick for Spinrite
+ 1 USB stick for Ghost
+ etc etc
the cost is nuts.

>>840197

What the fuck, man. Don't put Windows installation on to a USB.

Take the target drive out, and put it in a USB enclosure. Then install onto that from a laptop. Takes a fraction of the time and effort.

>>840175
You just multi-boot one USB stick, Einstein.

There's only six versions of Windows anyway*; that's only 32GB.

* (Vista, 7, 8.1)*(x86,AMD64)

>>840197
I see at least six or seven things you could have crammed on one USB. Anything that doesn't need to be bootable can be crammed, or just left on a machine until needed. Don't you have networked storage or a home server?

>>840288
he probably keeps around the different versions of each for some reason instead of just defaulting to the highest one like most people. Who the fuck ever used home edition anyway?

>>840084
I'm just going to make a bootable USB, or if I would really need an ODD for something in University or some shit, I'd just buy an external one, or a cheap internal one but with not shitty connections, like fucking ribbon cable that doesn't fit anywhere
>>840020
Question still stands

> There's only six versions of Windows anyway

check the pic, I count 23 listed here from Win 10 to Vista. multiply by 2 for 32 and 64-bit versions. and add some more if you have people who need other languages.

if someone has a serial for Win 7 Home Premium, and they dont want a pirated version, then that's the ISO you gotta have to please them. even with multiboots, that's a lot of fucking wasted money if you buy USB sticks. on the other hand, a 50-pack of DVDs should be enough for all your OSes and emergency software. costs roughly the same as one single USB drive.

> but with not shitty connections, like fucking ribbon cable that doesn't fit anywhere

ah, so you care about the internal appearance of your computer. what about the external appearance? did you paint it pink and added bows and My Little Pony stickers?

so I wanna do something extremely basic, wire up two LEDs in series so I can hook them over my Kindle.

The only problem is, I need somewhere to hook up/insert a battery. All of the enclosures I've found online are from bulk distributors where you need to buy ~100+ in order to just get a quote from them.

What would you guys do in this situation? I'm thinking about just dismantling an old remote

What are some ways to keep a component steady and preventing it from falling off all the time

>>840366

dollar store fan. replace motor with lights.

>>840368

- stick it in, bend leads on the bottom side. friction holds it in place.
- tiny bit of blu tack
- a third hand
- alligator clip

>>840368
>>840380
Tacky flux for surface mount components.

>>840379
Great idea, I'll do just this

anybody electric train enthusiasts in here?

I've got this old power control unit that came with a train set my dad passed down to me.

It says on the front that it outputs 12V DC, and when I checked with my multimeter it indeed did.

In normal operation though turning the dial affects the speed of the train, so I'm not sure how it manages to do that. Some kind of potential divider action maybe?

Sadly don't have an oscilloscope to poke its output with and this thing looks a bit tough to open up so I figured I'd ask here first

>>840405
usually these things are current controlled rather than voltage.
if your multimeter isn't drawing much current it will be maxing out the voltage to try and get the current up.
measure the voltage/current when you run a train )or any load) with it.

>>840405
dial is most likely attached to a variable resistor in parallel with the load (trains) which will cause the current to be more or less depending on direction the dial is turned

>>840411
>>840413
ah, that would make sense, cheers guys

I NEED HELP WITH A POWER SUPPLY QUESTION

I need 18v, with higher amps
my 18v power supply aka laptop charger is only output is 3.16amps

Can I hook up my 18v power supply up in parallel with a 12v atx power supply ?

>>840428
>Can I hook up my 18v power supply up in parallel with a 12v atx power supply ?

No.

> I need 18v, with higher amps
What are you powering and exactly how high are its current demands? With certain pieces of equipment you can solve current demand problems with starter capacitors, or reduce the current draw by reducing the voltage.

>>840439
i was thinking starter capacitors also but i dont know how to do that

Its a 18v battery power tool that i need to run without a battery and be able to turn on/off with an I/O. Im thinking it might have a higher load when its cutting things or something i dont know but its gonna need amps probably

>>840453
I see we're on the same boat. I'm trying to DIY a CNC router, but can't find the appropriate supply or tool. If you already have a power supply for the tool, your best bet is to use an opto-isolated solid state relay with the original power source.

fuck your shit this is a spiderman thread.

I have a non-functioning solenoid on an old 1970s VCR i'm trying to fix (thread here >>837154)

when the play button is pressed the pinch roller solenoid should activate pulling the roller tight to the tape, but nothing happens at all
I checked the schematic and using my MM i'm reading 24V like it says so I dont know why its not working

advice?

>>840458
It could be the solenoid itself that's broken down. Does it move properly when you apply 24v from a source you know for sure is good?

> VCR i'm trying to fix
Why?

>>840468
I dont know how to apply 24v to it directly by taking it out of circuit if thats what you mean

>why
personal interest. my dad has about 25 tapes of material he recorded in the 70s on an obsolete format, so I really wanna help him out and get it working again. for the first time in 10 years I actually have been making progress

>>840175
> I got a virus and have to re-install, how do I know my USB isnt infected also.
The format that is performed by your ISO ripper would solve that problem.
> my sister wants to reinstall Windows but now I gotta phone that idiot for 20 minutes just to set the laptop to boot from USB
So, not only do you go onsite unprepared without a laptop and a phone (for tethered internet) you're also too stupid to google "select boot source [machine type]". I think I see a pattern forming here.
> my computer crapped out, so I gotta download the Win7 ISO, then burn the ISO to a USB. how do I do that without a working computer?
You keep a USB stick or external tub with a macrium/ghost snapshot of your current machine build in your desk drawer like I have been doing for years.
> that cute girl wants me to come to her house to fix her Windows, but she doesn't know which version, or which edition of Windows her serial # is good for. so now I gotta spend $120 to buy 10 USB sticks, instead of $5 to get 10 DVDs. or lose face.
Or of course, you just rip an image immediately on the spot with your laptop (which i'm guessing you're too pleb to have, again, why go onsite if you are unprepared for all contingencies?)

I think you need to find a new career dude, you appear patently unprepared to perform onsite support.

>>840197
>>840321
You pair as well. Dump them all on an external drive, rip them as you need you fucking muppets.

>>840326
You are aware that a lot of machines have acrylic panels so you can see the gubbins, right?

It's like the worst of /g/ has come to visit. I hope none of you idiots charge for what you do.

>>840470
>I don't know how to apply 24v to it directly by taking it out of circuit if thats what you mean
So throw a multimeter onto points where the solenoid connects to its controller, and test for your 24v? Also, you should be able to drive it with a 9v battery or 12v power brick. It will have bugger all pull, but any movement will be an indication that the coil is good.

>>840094
its a generator, whatever side you tie to ground is neutral and the other is live. Its like a battery, you can tie the pos side of a 9v battery to ground and get -9v on the other end, but with a generator, you get AC no matter which way you do it, except they will be 180 degrees out of phase, which has no effect on whatever you are doing with it.

man im shitty at soldering

>>840670
It looks like you're using too much solder. Also, push the solder bead towards the leg, not away from it. But hey, it's not a complete disaster either! It took me a while to get nice joints too.

>>840673
thank you! I will try that next time :)

>>840662
It reads 24V in circuit.
Well actually, ALL my voltages are reading 1-1.5v lower than spec, but i think its just my shitty multimeter.

>>840660
> I think you need to find a new career dude

dude, you seriously lack reading comprehension. the argument i was making was for using a cheap pack of DVDs for emergency situations instead of USB sticks because they're cheaper, safer, and more durable. your suggestions to use USB sticks or external HDDs, or even an entire laptop are silly coz all those things...
- are easily writable and can be infected by viruses. and even if the virus did not come from you, the person will be still be suspicious, whereas a manufacturer's ISO that passes the SHA1 checksum is so much more trustworthy.
- can die from being dropped
- are too expensive to leave behind so the user can fix their own problems next time

>>836221
>>836226
>>836275
>>836241
This some real sexiness right here

Does anyone have any recommendations for a small/inexpensive float switch?

I'm going to make a beacon that attaches to a life jacket and activates when the person falls into the water. Really rather not build a switch from scratch.

>>840841
I believe most life jackets use a gas cartridge and a salt valve. The salt dissolves in the water and the cartridge fills the life jacket.
Perhaps you could somehow combine this with a spring-activated switch?

>>840845
im not trying to inflate the thing, I'm just going to make a lifejacket that flashes lights when it goes into water so people can see the person floating in the water better. I want to use a float switch like pictured so it can be reused. Just wondering if anyone has bought one for anything before and how it worked for them.

>>840321
8.0 doesn't count, because Windows Update converts it to 8.1 after you install.

10 doesn't count, because it's not RTM yet.

So that's three, multiply by two for x86-vs-x64, and that's six.

You don't need to account for premium/ultimate/comes-with-happy-ending, because you just delete ei.cfg, and the installer asks you which one you want.

>>840848
Water is conductive. You could use something like pic related with a blink led (one with built-in flasher).
The sensor would be two wires near each other so that water can bridge them.

>>840858
i thought about that, might be an option. I still like the mechanical nature of the float switch though so it can be activated and deactivated quickly plus it won't false trigger when it gets splashed.

I never stoped to think about it and it may seem a dumb question, but I'm building a project that has a big heat sink and the circuit is a little EMI senitive. Should I ground the heat sink? My house is a old house and dont have ground wires. My project uses a center tap tranformer. If I do need to ground the heat sink should I connect it to the center tap?
I have an old computer PSU that I disassembled and the heat sink is connected to the +12Vcc line! I know I have to isolate the ICs from the heat sink, its just the EMI protection that I dont know. Sorry if this question is too dumb.

>>840849
> because you just delete ei.cfg, and the installer asks you which one you want.

monkeying around with a Windows ISO means it wont pass SHA1 verification leaving you open to accusations of using pirated or infected software.

>>840866
I'd avoid a float switch, if only because it's mechanical and if you roll across the deck the right way the beacon will go off.
Maybe a pressure sensor looking for a sudden spike?

>>840873
Has anyone ever actually asked you to validate the checksum of the OS you are going to install? Ever? Seriously?

I do keep a genuine pressed DVD of Windows 7 and 8.1 around but usually it's actually faster to copy the ISO to a flash drive and then install from there than to use the real DVD. DVD transfer speed just sucks.

Also you can combine Linux liveCD, ntpasswd, Memtest, Hirens and pretty much anything else you want on one USB stick if you know how to edit GRUB. I still end up carrying 3 or 4, one with windows 7, one with 8.1, one with Linux and antivirus and stuff, and one just for Macs. Screw Macs though.

> Has anyone ever actually asked you to validate the checksum of the OS you are going to install? Ever? Seriously?

of course not. they get some other guy. he finds an excuse to put the blame on you, such as the SHA1 problem, and you never hear from them again. and your reputation is shot.

''you know, I bet anon gave you that virus so he could install a keylogger to spy on your email. what a creep!"

so, you've gone from a good guy who just wanted to save 50 cents to a scary rape-y creep.

>>840880
Well I'd encapsulate a verticals switch in a tube open at the bottom. I'm curious about the other switch posted where water is used as the conductor. I'm wondering if it will be reliable enough though and how itd really preform. Either way, I'd have the switch in a tube so splashes wouldn't activate it.

I just finished my first year in Computer Science and I'm interested in electronics and I wanna learn more about computer architecture in a practical way.

I found this kit for $109 which is a clone/replica of the computer kits in the 80s and this is a description of it:

>The micro-KIM is a clone of the KIM-1 created by MOS Technology in 1975 as a development board for the 6502 CPU. The micro-KIM uses many of the same components as the KIM-1 to give it that authentic vintage feel. No custom components are used and the micro-KIM is designed with off the shelf parts.

and heres the link

Ihttp://www.brielcomputers.com/wordpress/?cat=24

What's your opinion /ohm/ or any computer engineers around?

Is there a better kit?

> Is there a better kit?

is there a worst kit? do you think a 6502 is gonna come with a TCP stack? wifi drivers? USB interface? no, you'd end up with a completely useless curiosity and the only things you'll learn are irrelevant today.

you need something relevant like a Raspberry Pie or Odroid, where you could be using the hardware hours after you bought the kit.

>>840873
You punch it out by flipping one bit in the UFS directory tree, making the file appear deleted. This means you can punch it right back in again, and Bob's your proverbial.

Bits are like that.

>>840858
Water is hardly conductive. The minerals dissolved in it are. This circuit could be improved with a comparator of some sort, biased so if the 2 probes detect any continuity the LED will go to full brightness, and a pot to adjust that level. Though no telling how much more it will react in sea water compared to fresh water.

>>840967
that's why i like the float switch, much more simple for me to build that as well. I also plan to have an IC blinking an SOS or something with high powered LEDs.

>>840952
If you want to learn more about Computer Architecture, take your $109 and spend it on Hennessey and Patterson [1].

Vintage microcomputers don't have a lot of the stuff that you'd see in an actual CA course: for instance they've no MMU, no DMA, no bus-mastering, no cache hierarchy.

Even in their day, they weren't where the research was: that was going on on mainframes and minicomputers; home computers were just the bare essentials of a computer, built to a price a home user might afford.

If you really, really want to dick about with an old computer, get a PC from the AT or XT era. Get some ISA prototyping boards, and build it some kind of interesting or modern peripheral.

ISA is easy to work with, but at the same time is a real bus. You'll make some real hardware, and write a real driver. You can then sling it in a Pentium era PC, install Windows 95, and learn about modern operating systems by writing a Windows driver.

[1] - http://amzn.com/012383872X

>>840968
Its definitely worth a shot, try hooking that float switch to a 555 and report back to us about it

>>840848
I'm not seeing how a pair of contacts with a soluble substance between them couldn't be reused.

You'd have to replace the substance, but presumably you're not planning on requiring a lifejacket on a regular basis anyway.

A communion wafer would probably work well enough: water makes it squishy, contacts squish it.

Float switches have the disadvantage that if you invert them, they'll think they're floating. Relativity and all.

>>840970
Not him, but thanks for the link. I'd been planning on building my own z80 machine from discreet components for years now, this should come in very handy.

>>840974
i'm thinking about using this for sailboat racing or other boating conditions where you are always wearing a lifejacket. So say you are hit by something and knocked out and fall into the water or it's simply dark/stormy (i race as the sun is setting), your life jacket will automatically flash so your boat can find you easily, even if you are incapacitated.

I need a transformer that would generate about 18kV on a ferrite core
running at about 15kZ

I need to wind it myself, how many turns do I need for the voltage, what kind of insulation do I need and it needs to be wounded to standards because of the high voltage which must NOT punch thru the isolation !

there are definitely some tutorials on winding HV transformers/windings (flybacks) are there ?

>>840899
What would happen if, hypothetically, I was wearing the beacon and performed a somersault?
That's what I'd be worrying about in this case. If it's not going on a sailboat, then NBD, otherwise that's a problem.

>>840970
Hennessy & Patterson may be a bit too heavy to start with, covers mostly processor architecture and it doesn't teach any practical implementation details. Patterson & Hennessy [1] is more appropriate as a beginner text on architecture, and there are some old books (eg. Wilcox [2]) that really go in-depth on how to design and build a computer. They are however pretty difficult to find at a reasonable price. There are some FPGA-oriented books that cover designing processors, but that's not really my area.

[1] - http://amzn.com/0124077269
[2] - http://amzn.com/0138113998

>>840970
Yeah, I already have a 2nd edition of Hennessey and Patterson, I bought it for my computer architecture class. Thanks. man.

>>840985
>covers mostly processor architecture and it doesn't teach any practical implementation details.
68000 Microcomputer Systems it is, then.

I'm still going to clone the TI-84+ with an ez80 instead of the base model shitchip they keep putting in it, even after more than quadrupling the load on the newest model. Runs like molasses.

>>840841
>small/inexpensive float switch?
wooden or plastic clothespin
tiny brads or screws for contacts
coated aspirin for trigger

>>840985
>http://amzn.com/0138113998
Everyone seems to be recommending this 68000 Microcomputer Systems book but I can't find it for a reasonable price anywhere. I just want to tinker with a hobby project but after shipping, tax, duty (I'm not in the USA) the price is ridiculous. I would gladly pay something reasonable for an ebook copy but they don't exist. Nothing on ebay either. Is this thing unobtanium or what?

>>841107
Probably lots sitting on bookshelves and in dumpsters.

Heat is killing me, I want to use a CPU fan to cool myself off. It needs a signal, just giving it the power it needs does nothing.

I don't know shit about electronics, but what's the cheapo way to do PWM? If possible hooked up to potentiometer so I can adjust the fan speed.

I have an arduino that could do it, it seemed way too excessive.

>>841119

all CPU fans i've ever played with, like maybe 20, worked fine with just power on the red and black wires. 12Vdc, red = positive (in case you dunno)
anyway, there's no way a 4W fan is gonna keep you cool. a cold wet towel will work 862 times better.

>>841123
So what's the signal wire for? I put 12V on it and it didn't budge.

>>841126
That's tachometric feedback for fan speed controllers. Pulses appear on that wire that vary proportionally to the fan RPM, allowing a fan controller to monitor and adjust the fan speed by varying voltage on the V+ line. Disregard in this scenario.

>>841129
I'll try it again, I did read 12V and ~200mA on my multimeter.

dunno what you mean by signal wire. there's either 3 or 4 wires. red and black for power, a third for speed sensor output, and sometimes a fourth for PWM control. the speed sensor can be ignored, and the PWM can also be ignored. it should run at max speed without it.

There it goes. I guess I was doing something stupid before. And you're right >>841123, it's weak as shit.

>>841107
It was printed in 1987. I waited at least over six months until a cheap copy popped up (either on Amazon or eBay, can't remember). But I think it's really good. The tech is outdated (pre-CMOS logic, long-obsolete components) but it goes all the way from datasheets to a functioning computer.

This may be of interest to you:
https://en.wikipedia.org/wiki/N8VEM
http://www.s100computers.com/index.html

I'm using a 12V 2A PSU to power a LED strip using a 555 pwm regulator, the problem comes when I lower the brightness, at some point the PSU starts to hiss, I wounder if the PWM has to do something with this (the frequency is around 1kHz). I'm worried it will break if I leave the brighness at it's minimum ignoring the hiss.

hiss is normal in any PWM situation. nothing to worry about.

>>836577
>>840794

Well shit, have another one then. Motherboard from a Commodore 4016 that's about to get some restoration love. I'll prolly need /ohm/'s help on this one, but I'll wait till the next thread.

>>836822
roll

I work as a clerk and a small shop and I'm getting things together to make a diy alarm/front bell. The problem I have with most guides is of the range of the sensor to the alarm.

How could I connect it to a bluetooth speaker about 10-20 m away? So I don't have a wire noticeably running, and I don't have the bell going off by the door where I wouldn't hear it anyway.

>>841508
>bluetooth
Honestly an arduino's gonna be the best way to go about that. But really wireless alarms like that are $20 at home depot, but when in /diy/...

My first Arduino project. It's kind of retarded really.

All the Arduino does is control a relay to switch the spindle of my CNC machine off when the CNC machine's computer tells it to through the USB port.

The way my home CNC is set up right now, the spindle is not controlled by the computer at all, and I'm long overdue for making an emergency stop system.

I'm planning to make this part of an overall CNC machine monitoring system with a webcam and internet connection to my garage so I can watch the machine work from anywhere with my phone and shut it off before it starts a fire or destroys something. This would make me feel safer letting the machine run while I am not at home.

>>841508
I don't think you can DIY this better and cheaper than a home depot model, if you do it for shits and giggles, I'd recommend an arduino.

>>836822
reroll

>>836221
Where is the anime girl

Guys, do not try to use an 1.4A 60W Mean Well driver to power a single 12V PC fan.

Going to buy a 12V adapter and a new fan.

>>841939
You idiot. Those aren't straight DC they're brushless like in RC planes, they have entire ESCs in there. Please don't be dumb with shit you've hooked to mains.

>>841944
But in this video a PC fan works just fine with an adapter?
https://www.youtube.com/watch?v=sIttaw1E2Hc

>>841950
Some. But you still pumped way the fuck too much juice into it.

>>841953
Regulated power supplies don't "pump juice into" anything. They hold the rail at a steady voltage, up to the power draw they're rated to. Above that power draw, the voltage will droop. Below that power draw, absolutely nothing untoward will happen.

This is why you can run a 5w fan inside a PC with a 1000W PSU.

>>841944
Doesn't make a damn bit of difference, so long as you supply it a voltage above its minimum and below its maximum. >>841939 probably hooked it up wrong or backwards. Doing that for even a second can kill a PC fan dead.

> 1.4A 60W Mean Well driver

dunno what that is, but if the word ''driver'' refers to an LED driver, then that could be bad news coz some LED drivers are constant-current types which will put out as much voltage as it can to deliver the set current.

>>841950
Every pre-PWM PC fan works just fine off a regulated voltage and nothing else. This is exactly what happens inside the PC, so why would you expect it not to work outside one?

Three-pin fans came in two voltage ranges: 0-12v and 0-5v; 12v fans can usually start at 5v; 5v fans tend to die above 5v.

Four-pin PWM fans are always 12v: Intel's four-pin fan specification explicitly states 12v +- 10%. Power a four-pin fan correctly, supply no control signal, and it'll run at 100%. Again, this is explicitly stated in the specification.

>>841968

>>841939 is a picture of a constant-voltage supply. If it's not a picture of what >>841939 was using, then >>841939 is indeed a moron.

>>841971

yep, the pic does not match the name, it's just illustrative.

>>841973
That's a strange use of the word "illustrative".

>>841904
Right here
>>839697

illustrative
adjective
serving as an example or explanation

pic shows an example of a power supply, so it's illustrative. nothing strange here, boss.

>>842009
It's illustrative of "a power supply".

It's not illustrative of whatever it is that's being talked about.

The straightforward test is:

- Clarifies issue --> illustrative
- Confuses issue --> not illustrative

pic shows an example of a thing made of matter, so it's illustrative.

>>842009
>>842015
(The correct word for a picture that has nothing to do with the topic at hand, other than adding visual interest, is "decorative").

if you show the real thing, then it's depictive.
if you show a representation of the thing, then it's illuminative, indicative or illustrative.

>>842015

if you show the real thing, then it's depictive.
if you show a representation of the thing, then it's illuminative, indicative or illustrative.

so that pic depicts an elephant but illustrates a mammal.

>>842062
But we were talking about fish.

>>842168
>>842062
>>842018
>>842015
>>842009
>>842001

Hey /ohm/, can I use a polymer universal glue for potting instead of an epoxy one? It says it doesn't glue PP, PE, PTFE.

It only occurred to me until just now, but how do you know what version of SATA the SATA backplanes support?

Is it just some kind of passthrough where the amount of bandwidth per port is only dependent on the controller card on the motherboard?

Or can these backplanes limit the throughput?

Ok so I know with IC interrupts you have a main program running and then an ISR starts when the interrupt is triggered and it runs then the IC goes back to its normal program. But how would you make the IC do nothing UNTIL an external signal is detected? Do you just run an empty loop the majority of the time and have the program you want to run be the ISR? Or is there usually a sleep mode or something used? My end goal is to the have an event trigger a program and then run continuously until the IC is manually reset.

>>836823
what does "military class" entail?

>>836822
rollin

>>842386
Yes there is a sleep instruction that puts the uC into low power mode until an interrupt is triggered. On an AVR waking up from sleep will increase the program counter by one so you'll have to put it into an infinite loop if you want it to go back to low power after the event is logged.

I have a circuit like this, I'm trying to control high power LEDs with an IC to flash a pattern. With the voltage regulator regulating the power to the IC, if I increase the voltage to the circuit, the blinking pattern of my small test LED goes wacky and will just shut off completely if you increase the power to the circuit. I assume the voltage regulator is doing this for whatever reason. When I use my multimeter and read voltage before the regulator on the input pin side, the voltage drops low like the rest of the circuit. Why is it doing this and how do I make it not do that? I need the voltage before the regulator to be higher so I can power my big LEDs on the other side of my relay.

>>842548
Nevermind, I figured it out. You have to actually follow the datasheet and use caps with the regulator like it says, then it works fine. I'm retarded.

>>840970
I've got a joystick that connects via serial and I want to make it work.
I've taken computer architecture and operating systems courses, but I don't know how to make a Windows driver.
Are you familiar with any resources that might help me figure out how to do that?

The controller itself is well documented, it's just that I have to write the interfacing software myself
http://www.bgsystems.com/Software.html

can someone redpill me on the atmega328p's analog reference pin and the Avcc pin?

I am trying to make a simple programming board and I can't figure out what I should do.

I want to convert this circuit to work with a 9V battery, however I lack of knowledge to do this. I've studied OP amps and I know how to use them and their configurations, but I would appreciate some neat links with more advanced and detailed theory to keep expanding my knowledge and be able to modify this circuit.

Just put a voltage divider on your source. Then you don't have to change the circuit at all.

>>842899
just use a voltage regulator

>>842905
>>842946
B-but my goal is to learn, the circuit can wait. I already thought about using a 7805, but that was wat too easy and inefficient.

>>842899

that circuit will operate perfectly well over a large voltage range, up to 30V probably.

the only thing you need to change is the 220-omh resistor. at 5V, the LED takes 15mA, so at 9V you would use 470-ohms.

>>843057
I was suspecting that, but It was just a guess.
Correct me if I'm wrong: The voltage input of the OP amps doesn't matter as long as it is bigger than the voltage designed to work at (5V) since the gain will be always the same, and the final waveform will have the same size (maybe with more offset)

Also, is there any difference between the input impedance of a non inverting amplifier and an inverting? I say this because I have a voltage divider with an insignificant amount of current flowing through (about 2 MOhms total R), the smallest current change could affect the output. And I was wondering about choosing an inverting or a non inverting for the first stage.

>>843071

> The voltage input of the OP amps doesn't matter as long as it is bigger than the voltage designed to work at (5V) since the gain will be always the same, and the final waveform will have the same size (maybe with more offset)

if you change the word ''bigger'' to ''smaller'' that becomes true. well, true-ish, usu. the max it can handle is about 2V lower than the supply. there are specialized op-amps that do better.

>is there any difference between the input impedance of a non inverting amplifier and an inverting?

for inverting, the input impedance is equal to the resistor in the input, typically 10-100K. for non-inverting, it's infinite, meaning 100's of megs. varies with part.

(since you have the 68K in parallel with the + input in that circuit, that becomes the input impedance to that stage)

>>843183
Thank you!