/diy/ - Do It Yourself

>>1277831
This thread's digits brought to you in part by the IRF7831 N-channel power MOSFET.
>dat Rds(on) doe

Should I go for an 888D or a 951? I'm leaning towards the 888D because I'm not sure if I'll feel the benefit of the 951, especially not for more than double the price of the 888D.

>>1277876
you should go for a chink knockoff of one of them for half the price

>>1277878
I've a knockoff 936 and it's done the job for a while but I need better. Thermal capacity etc is so poor and everything just feels nasty.

>>1277882
What brand is your knockoff, out of curiosity? My Yihua feels pretty solid.

>>1277882
nahhh
just get an 862d+ clone soldering station w/ hot air for like $45
https://www.ebay.com/itm/2in1-SMD-Soldering-Rework-Station-Iron-W-4Nozzle-ESD-Design-LED-Display-862D/371820747844

>>1277883
It's a Yihua, I guess some are just better than others and I managed to get a crusty one. Takes an age to get to temperature.

>>1277887
My 862d+ takes 2 seconds roughly

>>1277887
I just retired my old, decrepit, little blue Xytronics 168 in favor of an Aoyue 888A from SRA and I am extremely pleased with my purchase. The 60W handle comes up to temp from cold in about 15-20 seconds. The hot air works wonderfully and has an auto-cooldown cycle. It's sold with a dozen tips for $73 with free shipping in the continental US.

Is it really not worth it to salvage ceramic components like capacitors, and SMD stuff such as resistors or LEDs? I just saw some videos and soldering SMDs doesn't seem that hard, provided I can get myself the hot air station and a microscope.
I'm asking this because I could probably salvage something besides cables from a few older video game console controllers but I'm not quite sure if it's worth the effort.

>>1277922
Consider how you would organize them after you have pulled them. I wouldn't think it worth it except for ICs or inductors or maybe larger transistors and MOSFETs with some unambiguous marking other than just "TK1" or whatever.
SMD ceramic caps are especially worthless. They aren't usually marked and they almost never indicate their working voltage limit. SMD electrolytics don't take too kindly to all that reheating and cooling and will have diminished life.

>>1277927
So most of the good stuff will mostly be THT and [T]QFPs/QFNs, along with maybe SMD LEDs and the other components you mentioned?
One of my current projects uses THT so SMDs are kinda useless to me for now but I was just wondering about it.

I order a lot of components through AliExpress, and a good 90% of the time they come in sicstock.com packaging. I tried going to the website to check it out, and I keep getting a connection refused page. Anyone else having that problem? Is it because I'm an amerifag?

>>1277936
Basically correct. If you've got the microscope you could look at the smaller devices like SOT23 and SC70 and try to look them up, and possibly but unlikely you'll find a PIC10F20x, a micro-ADC, or something similarly hi-spec that way. It's a safe bet that SOT23-(5|6) devices will be voltage regulators of some flavor, maybe 74*1G logic.
BGAs could also be worth the effort, but you'd need the appropriate stuff to reball them.

I bought this transformer for a few dollars and it's pretty ancient looking. It's 250V in, and has two pairs of 0-6-9V outputs, which I plan on putting in series and rectifying to get a ~25VDC power supply. Any idea how much power I can draw through a transformer of this size without overheating it? 50W? I might buy a thermistor to be safe, but knowing what similar-sized transformers can do would be a help.

I'll probably hook up some array of switches so I can have a DC power supply with a ground of various amplitudes.

>>1277922
REHEAT AND SHAKE ALL THE PARTS OFF, SORT THEM LATER

>>1277944
Okay, thanks for the help. I should really get me some sectioned jewel boxes to sort all kinds of shit I might use later, but at least I'm off to a good start.
Also, how do you salvage coils? The moment you apply some pressure to them, they get squished and it's hard if not impossible to get them back to their original state
>>1277946
Sadly I have no hot air station yet and I would have to be incredibly stupid to shove a PCB in the microwave as that's the only thing I have to heat stuff other than the stove.

>>1277948
No oven? I bet you could whip something up with nichrome/propane and an electric motor to whack the side of the PCB every couple of seconds, that might be interesting. Now I've got another shitty project idea, hehe...

>>1277937
Curiously, I've never once seen that, after buying hundreds of dollars in components through aliexpress. It could be that I'm buying in smaller lots. Same/different vendors?

>>1277948
>sectioned jewel boxes
Probably a good idea, but you may find that simply buying sample packs of SMD components would be a better investment of resources.
>how do you salvage coils
Unless you have an LRC meter, I wouldn't. They're literally just wire.

>>1277951
Enjoy your delicious chemicals next time you want to bake something.

>>1277953
>They're literally just wire.
>someone who's never had to wind a 30mH inductor

>>1277951
Yeah... To be quite honest I wouldn't feel any comfortable putting a PCB in the oven, then baking some potatoes or cookies in it.
>>1277953
Yeah, exactly what I thought, but I might someday get lucky and find some of those slightly expensive components, such as low wattage potentiometers or the like.
Thanks for all the pointers

>>1277945
look at the wire gauge on the output to get a hint.

also, do you get 18VAC across the 9s?

>>1277954
>30mH
>air core
mmmmyep

>>1277945
and one more thing, how many ohms from 6 to 9, and from 0 to 6?

>>1277953
I've bought components from different vendors, and they come like that (mostly caps and resistors). I'm starting to think that there's really only a few vendors and they all have 20-30 stores, hence the very similar prices and sometimes the very same pictures/descriptions. Either that or they all are middle-middle men, all drop shipping with the same place. I've gotten some really good deals only to find the item not available anymore a few weeks later when I want to get more, only to find a cloned listing from another vendor at the exact same price.

>>1277963
The wire is 0.5mm wide or so, which corresponds to 24 gauge, or 3.5A ampacity at 60°C or so, but that assumes open air not all coiled up.

>>1277966
The primary is 160Ω, and isolated from the outputs as expected. The two sets of (0, 6, 9) are isolated from one another. The resistance between 0V and 6V appears to be around 0.4Ω with a rudimentary correction for lead resistance, but that is with a shitty multimeter. The resistance from 6V to 9V is around 0.1Ω, and these measurements are similar on both sides. I'd trust them to within 0.4Ω or so since the value does hop around a little.

What's the chances that there's a thermal fuse in here? Before you ask yes I already looked for a datasheet and there isn't one, but here's the box if anyone else feels the need to look for one. The code is "R133" or "TR133" (first is on the transformer and the second is on the box), so that might be a more generic identifier.

>>1277977
That's probably about right, or there are just a shit-ton of resellers reselling what's locally available, chopping up reels, etc. I found a vendor that split up my order of like 8 items into like 5 packages, so I may be about to experience that pleasure myself. (Joke's on them, I paid a total of $2 shipping for that order)
I generally order components in pretty small lots (like 100-200 pieces per type), mostly semiconductors or basic component assortments, and usually they just come in cheap poly bags on cut tape.

>>1278063
OK, so it looks like your 6Vs are taps, which limits your total power out if you wanted to use both 6 and 9. But yeah, the 9s will stack, and you'll get a little less out than 18*1.4=25.2 after you've factored in diode drops and how much ripple you want to smooth out for the load you're expecting.

you can plan to dump some heat where the transformer mounts to a case. kinda doubt a thermal fuse, but who nose.

So father has this old foken power supply to charge car batteries. Has this switch to 6-12-24V.
Says it stopped working.
K, checked diodes, one contact was disconnected. Solder it on. Turn power supply, turn switch to 12V, check output voltage says 6V dc. Turn it to 24V ,multimeter says about 12V dc output.
So I switch my multimeter to ac, swith supply to 12V and multimeter shows 14V ac.
WTF?
Is something wrong with my multimeter?
Checked all diodes, ~+0.500.

Gonna disassemble that 6-12-24V switch and check it.
But, Where is AC coming from?

>>1278103
Probably either a blown cap, or another loose connection somewhere. Draw a schematic, measure voltages, plot on schematic (both ac and dc in this case), and something should jump out at you.

>>1277831
The symbol on the right side of that image doesn't really exist in electronics. I don't understand why it's listed under "basic electronics symbols"

I'm excited, I just got this Onkyo TX-SR707 running brain-free. This series is really simple to analogue convert, you basically just need to bridge out the relays on the amp board and inject a signal into the shielded cables leading to the power amp, and you're done. It even has an analogue protection circuit for you to use, no processor required.

Oh yes.

>>1278103
>>1278107
Those chargers often simply don't even have an output filter cap. Hook it up to a battery and see if you get a current reading on your multimeter. There's a decent chance he's just cooked his battery because those "transformer and diode" chargers are trash.

>>1278148
Yep, this charger is very old, it's just simple transformer with diodes. Dates back to soviet russia and I bet it's older than me.
I looked up internets and yeah, my miltimeter shows what it shouldn't supposed to show.
Simple test: turn multimeter to dc, shows 12V on battery, then turn on ac and it shows 26.4V on battery. Internets say multimeter multiplies dc by 2.2 and shows it as ac.
Anyway, everything is kinda ok now, but I have very big voltage drop. When I measure voltage after diodes I get what it suppose to be. But when I connect on board ammeter and voltage meter back, I get huge 45-50% voltage drop.
There is even some kind of copper plate for ammeter. Probably shunt.
I'm gonna revive this old motherfucker.

I am still having problems with powering my motor with +-3V.
I've got an incoming signal of +-3V (from an Op-Amp) that does not have enough current to power the motor, so I rebuild this H-Bridge, but I didn't know how to connect the four inputs of the bridge, so I tried something out and ended up with two inverted inputs and two normal inputs.
But the motor only turns in one direction, depending on how I hook it up.
I already measured the outcoming voltages (arround 4-5 volts, positive and negative) and have no idea, why the motor does not turn.

>>1278182
So I left only ammeter connected and everything is fine.
But once I connect 1 an 2 contacts on pic related I get huge voltage drop.
What is wrong with that device?

Missed the new bread.
Ive got a question. Will pic related detect zero in 230AC home voltage? if yes how will the voltage betewen A and B look? Is it going to be spike to certain value when zero crossing and then back to zero or is it going to be @ certain value untill zero crossing and sharp drop to 0V followed by come back to certain value?

Anyone in this thread can help?
>>1278173

Reposting from last thread.

>>1277834
I was thinking something more along the line of a CD drive spindle or a laptop hard disk, but they spin at very high PRMs and I'm not sure the speed of the cassette deck would generate a current.
>>1277844
Oh geez, I knew they slipped but I didn't think a small dynamo would generate enough resistance.
I could add a connector to charge the cassettes and have 2 or 3 and have it charge over a cigarrette lighter connector or something. But that sorta beats the purpouse of the project

>tfw don't have a pickit3

>>1277831

I'm trying to make two 12V PC fans run as long as possible to run a bucket and ice portable AC. I have 4 6v batteries two sets in series and then the two sets in parallel. I'm just trying to double check my work, and I'm willing to accept any suggestions to simplify things.

>>1278202
Short 5V pulse every 10 ms (at 50Hz mains frequency)

>>1278217
thanks

>>1278214
looks good

>>1278103
>Where is AC coming from?
You're measuring the ripple in the unfiltered output.
The switch selects a different tap on the secondary of the transformer.
Transformer/Diode/Meter battery chargers don't filter the output.

>>1278188
what kind of motor do you use? is it intended to run in both directions?

I am trying out kicad for a new project, I am looking for a specific part that I need is there any website where you can search for parts and get a library with these parts for kicad. I am looking for a HCF4094BEY

>>1278248
It's a XDrive 2025-22.
In my prior tests it did run in both directions, with basically the same signal. After attaching the wheel to the motor I needed more current, so I built the H bridge.
I assume I made an error while reproducing the H bridge?

So i have tried to use a lower resistance MOSFET (TSM4435) in here >>1274462 but it still gets super hot. Around 80C even with fat pcb traces connected to the pins. I dont think this is normal.

The load is pulling 7A, Vgs is 11,2V the internal resistance should be some 21mOhms, 7^2*0.02 = 0.98W, it shouldn't get this hot.

What seems to be the problem?

>>1278266
You need to learn to add new components at some point in any case. Better sooner than later.

>>1278269
So, basically, you are telling me to make one myself

>>1278268
One watt to an SO-8 is quite a lot. You'll need decent heatsinking (PCB with lots of copper) and it will still run hot.

>>1278270
Yeah.

>>1278272
Theres two 20mm long, 5mm wide copper trace on drain and source, it has enough cooling, more than through the package.

got my hands on a UCC28C40 and want to experiment a bit with it. first time dealing with this kind of IC

i would like to use it in voltage control mode for now. the datasheet suggests pic related for that, saying it would give me a sawtooth on CS pin by dividing down the sawtooth on RT/CT pin and removing DC bias with the cap

i don't really trust this suggestion though. how is this supposed to work? the sawtooth on RT/CT pin looks fine, the one on CS doesn't look like a sawtooth at all. but to be honest i wouldn't expect a sawtooth from this circuit

am i misunderstanding something here?

>>1278277
That's not very much. The usual test patterns have one square inch of copper, or over 3 times more than you used. Pic related.
And even with that much copper it would still run hot.

>>1278282
Right, ill expand it, but im not too confident this heating is normal.

With Junction to Foot (Drain) Thermal Resistance: 22 and Junction to Ambient Thermal Resistance (PCB mounted): 50 it shouldnt raise its temperature by 60C

>>1278279
>i would like to use it in voltage control mode for now. the datasheet suggests pic related for that, saying it would give me a sawtooth on CS pin

perhaps that can be done; I'm not familiar with this chip but am interested now that you've shown it to me. pic related may or may not help, but it seems to say it is an INPUT pin in voltage control mode.

>>1278284
>but im not too confident this heating is normal.

1 watt is about the limit for so-8. they are small, and can only move so much energy out no matter how large the traces are.

>>1278274
ok I'll try that

>>1278198
internal voltmeter may be shorted

>>1278267
Got pics of the circuit you built?

There are some issues with the circuit as drawn there, you can't leave the + input of the opamp floating, connect it to ground. +3V out of the logic isn't enough to turn on your high side MOSFETs, you'll need more like +6.

>>1278219
If you want to get rid of the pulse, stick a capacitor between A and B.

>>1278287
>A voltage ramp can be applied to this pin to run the device with a voltage mode control configuration
this is what i am trying to achieve, but without using an external ramp. the idea is to use the already existing sawtooth on pin RT/CT

>>1278302
Sorry about the floating input, the program just assumes, that it's connected to ground, so I didn't bother.
And the circuit is for a project at my university, so I don't think that I'm allowed to post it online (although I doubt that anyone would check /ohm/).
I gotta test some more tomorrow.
Do you mean by logic the gate input or the Vref I am using.
Thanks for your help!

>>1278279
So long as the cap is sufficiently large it should give a sawtooth, the transistor forms a voltage follower, the cap+resistors form a high pass, which should have a corner frequency well below your desired switching frequency.

Current mode control is generally easier with those chips than voltage mode.

>>1278308
Your +3/presumably -3 input on the left won't turn on your top pair of MOSFETs, the gate has to be a few volts above the source pin which you want to be sitting at 3V, so you'd need a +6 or higher supply for both the opamp and whatever's creating the +3/-3 input. To get around this, can use a P channel MOSFET on the high side instead of an N channel, that way you can use your -3V to turn it on.

>>1278310
>Current mode control is generally easier with those chips than voltage mode.
yes i read about that, but i'd like to experiment with both modes

>So long as the cap is sufficiently large it should give a sawtooth
i thought about that aswell, but wouldn't it eventually turn into something like i posted?

>>1278314
May need a resistor on the emitter to ground to make sure it stays in voltage follower mode. The ESD diode on CS should provide clamping to set the negative limit on the sawtooth, should look something like this. Not starting from zero will limit your minimum usable duty cycle, if you want better, make a nicer sawtooth gen possibly with opamp, or just use current mode.

>>1277831
I need a circuit that takes in 3(or less)-40 volts, and puts out 12v at a max current of 550 ma.

What is the cheapest circuit that can do this reliably?
I started with the LT8302 chip to make a fly back, but found its Nps with my voltage range value only allowed me a 1:1 transformer, which I'm thinking is pointless.
I then used TI webench to make circuit in pic related.
Anyone have any better ideas?


ALSO
How do I prototype and build with surface mount chips? Do I need to special order a board with pre printed leads from a software like Eagle?

>>1278367
Firstly, why do you need such a low input voltage? That'll be your limiting factor for most topologies.

Something like this may work http://www.ti.com/lit/ds/symlink/lm5118.pdf as your controller, allows a pretty wide input range.

For relatively large surface mount stuff down to SOIC packages, 0805/0603 passives, using a veroboard + get creative with your knife can be good enough, for smaller packages you really want a custom printed board. If you're not in a hurry can get decent quality double sided boards from china for around $15 shipped for 10x10cm through PCBWay.

>>1278379
I'm building a charging circuit for a 12v battery, which powers a device that runs at 12v 550ma Max. The power is coming from a 2000:5 current transformer that ranges from 69k-500kv at 100-1000A. becasue of this I have to choose the lowest possible burden resistance(which looks to be 13 ohms) to minimize the power rating of that resistor.
That then goes through a full bridge and a smoothing cap into the converter.

The project needs to be build pretty soon, its due by may, but I want to have it build and tested way before then so I have time to put together my reports on the design and process taken to make it.

>>1278387
I should have read that over before sending.
The CT is clipped onto a High voltage power line with those voltage and current ranges.

I may just connect straight to the devise if I can get this all to work consistently enough.

>>1278367
Things like Pic related work for some cases. I probably wouldn't try to use one for a switching power supply because they really need short, fat traces to work well.

>>1278387
>minimize the power rating of that resistor
y tho? It appears that power is free in this application.
How about building a dynamic shunt-type regulator with a hefty MOSFET and a voltage divider on the gate?

>>1278217

wrong. it'll be at 5V throughout most of the AC cycle, and go to 0V briefly once every 10ms.

>>1278198

probably your onboard voltmeter is really an ammeter. or you removed the series current limiting resistor, which is what makes a voltmeter a voltmeter.

>>1278214

no good. generally speaking, batteries should not be connected in parallel coz they can have different potencies, and then power is wasted flowing from the stronger to the weaker. to fix, run 1 fan from 2 series batteries, and the other fan from 2 other batteries. adding 2 diodes would also do the job, but it also wastes some power.

>>1278198

probably your onboard voltmeter is really an ammeter. or you removed the series current limiting resistor, which is what makes a voltmeter a voltmeter.

>>1278214

no good. generally speaking, batteries should not be connected in parallel coz they can have different potencies, and then power is wasted flowing from the stronger to the weaker. to fix, run 1 fan from 2 series batteries, and the other fan from 2 other batteries. adding 2 diodes would also do the job, but it also wastes some power.

>>1278202
>>1278217
Well actually A is at 5V always except when the 10ms peaks come through, since it's tied to 5V whenever the phototransistor isn't on. B is always 0V because it's grounded, obviously.

>>1278410

nope. when the AC waveform is near zero, the LEDs go off and the transistor goes off, producing a 5V pulse on A. for most of the cycle, the transistor is on so output is around 0V.

I wired a case fan to a wall wart so I could make a laptop fan.

However, it runs like shit. When I first plug it in, all the fan does is buzz, it won't spin until I start spinning it and even then it spins slowly in a jittery manner.

the wall wart is DC, outputs 12 volts and has sufficient amperage, so I don't think that's it

have I somehow burnt out the motor in the fan?

also if I wanted to insert a switch into the mix, is there some sort of voltage limitation to switches that I should know about, or should it be fine since it's outputting only 12 volts?

>>1278387
That's a much more interesting problem then. First thing to consider is your assumption that current transformer output across a resistor makes a voltage source won't really be valid unless your resistor power is much larger than load power.

Treating your input as current source gives more interesting options since you can effectively control your input voltage to be whatever you need. Battery as output also makes things easier as you've effectively got a voltage sink/source.

I'd do a boost converter, or if you need isolation for measurement, flyback.

>>1278418

your wallwart isnt happy driving an inductive load. try a different one, preferably an old heavy non-switching one.

just about any switch will handle 12V at 500mA unless it's a really tiny pushbutton one. anyway, they often have their ratings written on them.

>>1278418
>is there some sort of voltage limitation to switches
yes but a fan doesn't pull much current so anything bigger than a tiny microswitch should be fine

>>1278424
It's an ancient wall wart from the late 90's. I'll just have to dig through my box of bullshit and find another one then

>>1278430
Hmm, dried-up caps maybe.

>>1278401
The burden resistor has to have a Watt rating 2 times higher than expected. So with a 2000:5 Current Transformer the output current range is .25 to 2.5.
The Max power through a 15 ohm burden is ~90W, so I need a burden at 200W rated.
If the Burden was only 10 ohms I wouldn't need such a high rated resistor.
However, I cannot find a converter, of any type, that has a range which is lower that 3 volts.

I could design the burden to spit out any value voltage. But, because of the current being 100-1000A the output voltage is going to be huge. Always having a Vmax that is 10x the vin. So, 3-30, 3.5-35, 4-40.

Really, I'm running out of ideas.
Our range is huge.
I wish I could just buy a 4-50 volt buck boost that was reliable. Everything I see is Chinese garbage that is way overrated for what it actually can do

>>1278412
I'm not too sure how optocouplers react. I assumed that only near the peak they'd be producing enough light to be picked up by the phototransistor, but I guess you'd get a very distorted sinusoid as the output, with the phototransistor acting in the linear region for some part of it.

>>1278418
Use a capacitor to either smooth out the switching or change the power factor. If you've got a 2-channel oscilloscope it should be a piece of cake.

>>1278421
Well we only need 7W out at max, and with a 2000:5 CT and an Rburden of 13, I get a min power output across the burden of ~9W. So I'm good there.
As I said in here >>1278435, the range is always (x to 10*x).

>>1278418
>don't
There's voltage and amperage limits on all switches.

Maybe your wire connection sucks. Did you solder or use a wire connector? Or did you just twist it together

Are you sure its a dc case fan? It should be written on the fan too

>>1278441
I miscalculated that.
Its ZERO point 9 Watts. not 9 watts.

Which makes this even harder.

>>1278435
Okay, how about something like this? R2 is a static load resistor. Q2, a small-signal NMOS, switches on Q1, a power PMOS, when the input voltage is too high according to R3, R6, and Q2's Vgs rating. Q1 shunts current through a secondary load resistor R5. R4 provides hysteresis to keep Q2 out of the linear region. That should get your input range down to a more manageable factor of 3, anyway. Add a resistor and/or zener on Q2's drain and/or gate if exceeding Vgs(max) due to spikes etc. is a risk.

>>1278435
>>1278447
(whoops forgot rectifier on CT)

is super glue electrically conductive?
I was doing maintenance on my laptop and as I was screwing it back up, the speaker cable got caught between a case screw and the case so when I screwed the screw in it pierced the cable clading and shorted through the screw

I used cyanoacrylate to patch the little cut/hole in the wire, but I want to make sure it's not going to spontaneously ignite or just short through it

>>1278441
0.25A into 13 ohm parallel with your load gives a maximum power into load of 0.2W. To get any decent power you need to be in series (or series-parallel hybrid) with your power resistor, not in parallel. Or a much higher value resistor.

>>1278465
also, at max power you're only getting 1.625V at the input.

>>1278447
I like this circuit. R2 is still way too low if they want 6.6W into load at 0.25A in, for that it'd need to be at least 422 ohm.

>>1278447
Wow, I obviously have along way to go in electronics. Even as a Senior in a decent university I only vaguely understand what you just described. I know what each of those components are, but am clueless on how they interact.

Since you posted this I've been souring my textbooks looking for what hysteresis is, and what the linear region is.
I get that R2 is the burden, but at a certian voltage the Q2 is turned on(regulated by the voltage division between r3 and r6?), this then shorts out R2 and runs the voltage through R5, making that the new burden resistor.

>>1278472
Like what is said here, the R2 value would have to be pretty high to get the power we need out at the low end.
I could use a 3000:5 or 1000:5 CT so it doesn't necessarily need to be 400, but it would be high.
I have Pspice at school, I'll play around with it on there tomorrow.

How do I go about choosing real life Mosfets to use in the circuit? I'd assume Q1 would have to have a high power rating.

What software did you use to model this?
How did you learn how to do this?

>>1278464
No, but smudging shit with CA glue does not really insulate it either, as the coating is typically thin and brittle.

>>1278472
Right, just an illustration based on original anon's numbers.

>>1278553
Almost. R2 remains in circuit. Q1 just adds R5+Rds(on)(Q1) in parallel once Q2 turns on. (remember Kirchhoff's current law?) R4 pulls the control voltage a little higher when Q1 is on, and a little lower when Q1 is off, in order to keep the circuit from oscillating or chattering. You'll need to choose your own values for all the Rs, of course.
Select Q1 for a low Rds(on), a Vgs(threshold) somewhat less than the lowest acceptable out voltage. If Vgs(max)(Q1) is less than 150% of max output, you should probably add a resistor in series with Q2's drain to avoid overstress. Q1 probably won't need massive power handling capabilities, as R5 should dissipate the vast majority of the power, but select for a high enough drain current to handle the minimum load condition.
Q2 is less critical, but I'd personally select for a Vgs(th) around 2-2.5V so that R6 can be fairly large and R4+R6 won't affect the load significantly.

I'm the guy who bought a handful of electret mics a while ago to mess with their electrets and never got around to it. Just soldering them to a TRRS cable now, and i've noticed they're much quieter than my TRRS earphones' mic is even when the earphone mic is three times further away than this one. The audio quality is also worse when I amplify it, but that's just due to noise. Is this because I have an inadequate bias voltage? I'll be building a rig to mess about with audio and electret microphones soon so that's something I'll test, probably with a standard adjustable voltage regulator or opamp.

Anyone know how good sound quality picked up from a small 8Ω speaker is if amplified?

I'll be pulling 20W away from a TO-220 MOSFET into a 2.5W/C heat sink, and the transistor shouldn't be allowed to get above 60C. Should I have to use a fan?

>>1278606
Depends on your ambient temperature, of course, and whether the heatsink is in free air or is otherwise constricted.
>2.5W/C
You sure? Heatsinks are usually rated in degrees/watt. Assuming you mean 2.5 degreesC/W, yes, you probably will need a fan to keep below 60degC. Assuming you mean 0.4 degreesC/W, it's conceivable you might need a fan on a hot day.

>>1278615
Shit, yeah 2.5 C/W, it will be in open air indoors. Thanks for the input.

>>1278621
Fortunately, you really don't need much airflow to keep that thing cool. A very slow fan would easily be enough.

>>1278606
you'll have another ~2C/W of thermal resistance in the fet and the interface between the drain tab and the heatsink. it depends on the part and the compound/thermal pad/torque used but you won't get much lower than that. so (2.5C/W+2C/W)*20W+30C = 120C at the junction. that's okay for a 175C rated fet. if the airflow gets it down to 1C/W you'd still be looking at 90C junction which is a fine margin unless you have some special reliability concerns. did you mean the temperature at the tab?

Well, I have a few troubles.

I hav some bad SRAM memories, but I need to test them first to know how many purchase, but well, I have no idea how this memories (and every memory, I suck with digital stuff) works. I tried to make a code in arduino, and well, it does not work.

Somebody give me light to this please, or only explain how this memory works, in teach-to-a-dumbass mode. The model of the memories are TC5546P-25.

Yeah, my english sucks too

>>1278700
>The model of the memories are TC5546P-25.

do you have a datasheet showing the pinout and timing diagrams? all I can find online are TC55416P-25 which could be different.

>>1278742
Shit, I failed.
TC55465P-25

>>1278747
>TC55465P-25

If your arduino has 23 GPIO pins you should be able to do this.

>>1278700
You sure it isn't TC55465, which looks like a rather normal 64k x 4 fast SRAM?
Considering they're in sockets, I'd check the sockets first. They're much less reliable than the memories.

Async ram works usually like this:
Write: pull OE, WE and CE high. Enter address, enter data, pull CE low, pulse WE low, return CE high.
Read: pull OE, WE and CE high. Enter address, pull CE low, pull OE low, read data, return OE and CE high.

Will this work for driving a dc motor rated 3V 1A?

>>1278752

and here's the timing for the write that you describe, which should also work with an arduino that has 5 volt GPIO pins.

>>1278755
Kinda badly. You should drive the transistor harder (with 1k or so resistor) and even then you can expect the transistor to waste quarter of your supply voltage.

>>1278750
>>1278752
I have an Arduino Mega.

I'll try to write something knowing that.

The entire board looks pretty well, and sockets too, but I'll clean all of them.

If anyone has curiosity, it is from an old Video Analyzer. A Tektronix VM-700A.

>>1278766
>I have an Arduino Mega.

And you don't have to use all 16 address lines unless you want to do a thorough test; you could tie as many as you like high or low or manually do that. Once you can read and write one memory location you have proved that the chip is not totally dead. If you cannot do that then that chip needs no further testing.

>>1278769
As a first test would be good, but I need to test it entirely. I don't know how this old analyzer would run with a few bad words on the RAM.

Then, I have another problem. In the board, with the SRAMs, are other ICs, with serial number MB81C75-25P. I don't know what they are, because i don't find any datasheet.

>>1278755
You would need at least 4 mA base current. TIP120 is not optimal for your application, there are better solutions.

>>1278779
>, but I need to test it entirely.

so if you have 23 GPIO that will be easy. If you don't have that many then manually set one or more address lines and run your diagnostic as many times as needed to check the entire address space.


> MB81C75-25P

that number shows up but I can't find any information.

>>1278312
I've tried your solution, but it did not work.
Same goes for a higher input, but the highest I could get was ~5V, so that might be the problem.
But thanks anyway!
I think I'll leave it as it is (just turning in one way), which solves the problem, but not as nicely.

>>1278779
How have you deduced there's something wrong with the RAM chips?
It is also highly unlikely to have just few bad locations.

>MB81C75-25P
That's a 16k x 4 fast SRAM, very similar to the other chip. Cypress' 7C166-25 is equivalent.

>>1278832
The analyzer gives a RAM error when starts, and when it is running a minute more or less, it restarts itself. This SRAM is from an extra module, so it isn't absolutely necesary to the analyzer.

Also, thanks a lot for the equivalent. Now that I know it is a RAM too, and with the pinout, i'll try to test it too.

>>1278805
>it did not work
It cannot, the circuit is self-defeating.

Hi, so I'm trying this lamp proyect, and I got this set of old led lights and I grabbed 25 of them, then I'm attach it directly to the electricity wire... I just want to know if there's anything missing between the lights and the electricity cord. I watched a few vids of people setting up led lights and they used some "diodes", but I'm really not wisey on the matter.

I also noticed, there are different type of led light wires. The lights on the picture use a "thicker" wire (8 copper thin wires) and there are cheaper onces (they use around 4 copper thin wires).

I mention this cus I tried the cheaper and had a hard time with the bulbs, they burned every 10 secs. And I would like to avoid that happening with the ones I'm going to use.

I will deeply appreciate your advise.

>>1278759
>>1278759
I tried to make a program, but it does something strange. I'm not a lot into programming, so this code could be a piece of shit.

So, when I read the output of the pin, it is always high, even if I remove the pins, which is something absurd.

This is the .ino
https://mega.nz/#!J6BEWK6Y!rT_Ow6z3PvTe-CKMiA8H9I3-JPWKw7QBI07nl3p5rJs

Maybe wrong place, but how do I make this Chinese spinning light silent? I'd happily just have it spin at 1% it's speed

>>1278878
cut either the long red or black wire in the middle, strip each end, connect a resistor in between
make it a potentiometer instead if you want to have a way to change the speed

>>1278861

what is a rar file. can you put the text file on pastebin?

>>1278884
>what is a rar file
>on 4chan
>in /ohm/
are you real?

>>1278891
>are you real?

nah, I just don't want to download unrar to read a text file.

>>1278883
Good call anon! Let's hope I don't cause a housefire

>>1278845
Well, it turns out that I somehow messed up the wiring and connected the -3V supply to the output.
I kinda feel ashamed.

>>1278845
Good to know, thanks!

>>1278900
>linear potentiometer
Man those things are cool.

Okay wondering if one of you dudes can help me out.

I'm trying to develop a method re-using waste heat from a CPU (using a thermoelectric generator), to power the cooling mechanism such as a thermoelectric cooler or a standard fan.

My initial problem is testing typical CPU power consumption at various heats (creating a temperature vs watts), to either confirm or deny the idea that CPU's get less efficient (use more energy) when they are heated above around the 70'C mark.

How would I go about getting a precise reading for the CPU power consumption?

>>1278912
I butchered a pair of old busted headphones for them, I kinda regret it but I got 4 potentiometers

>>1278884
https://pastebin.com/KcLFk8ta
I say. I don't know how to write a program. This is a copy from a other project with a lot of modifications.
The idea is: I generate a binary number, that in each loop increase by 1, so I'm testing each address, but well, as I said, I'm not a lot into digital stuff. It's only a hobby.

>>1278934

awesome. unfortunately I have to go offline now. If no one replies we can look at this tomorrow.

thanks for the pastebin.

>>1278934
I don't know anything about arduino but this code is wrong because it's going out of bounds
for ( i = 29; i < 45; i++) pinMode(Address[i], OUTPUT);

you probably want this instead based upon the array at the top
for ( i = 30; i < 46; i++) pinMode(i, OUTPUT);

>>1278919
The problem is that by putting a peltier generator between the CPU and its heat sink you're essentially putting a thermal resistor in the way of the CPU's heat, so you won't be able to run it as fast without it overheating. To use the same power for heating will almost certainly be less efficient, though with a fan I'm not quite so sure.

Anyway, provided your thermoelectric generator can be used as a cooler as well, just put it between the heat sink and the CPU with its cold side against the CPU, and power it with different voltages, starting at the maximum. If you don't have a thermometer you'll need to get one, preferably not an IR/laser one because they can jump around a little. Though if you know your shit you can probably just get the temperature reading from the CPU itself. Set up some default task and wait for the CPU to reach thermal equilibrium, and note the temperature and performance by TFLOPS or whatever. Then change the voltage and repeat. Using different resistors in series with the TEG/TEC works instead of different voltages, but they might get a little hot. You should get a nice graph of some kind, but as far as I know the CPU only slows down at higher temperatures because it needs to, as a way to avoid the increasing propagation delays giving false logical results, rather than doing so naturally. This means you'll probably just get two straight lines on the graph, one flat and the other a steady decline as temperature increases.

>>1278959
Thanks man, yeah I get that completely about the thermal resistance. I need to model the relationship between temperature and increase in power consumption, then relate that to the potential power gain of a TEG from that deltaT.

It's for a dissertation so if I can get a good relationship modeled then work on ways of effectively implementing this TEG/TEC I hope that could give some useful results.

>>1278971
Also in general I kinda like (in theory) the idea of the TEG/TEC combo, you've essentially got a greater cooling power available as the temperature rises. If optimised this could be a self regulating cooling mechanism, ideally self sufficient but so far I doubt it as the potential power gain for this delta T is only a few mW

>>1278973
Well you could use a BJT to amplify the current from the TEG to power a TEC or two, not like power usage is an issue. But a TEG+TEC couple but itself is just going to make more heat.

>>1278973
Nice perpetual motion machine you got there.

>>1279018
Well you're getting the energy from the heat of the CPU vs the surroundings, and using this energy to cool the CPU

I don't really understand how it would produce more heat >>1279016

>>1279019
It's the thermodynamic principle of a heat engine/refrigerator. Have a look at this page:
https://en.wikipedia.org/wiki/Thermal_efficiency
A thermoelectric cooler is a heat pump that moves heat from one side of it to the other, and is at best 15% efficient. Meaning for every 1W of heat moved to its hot side, you're also pumping 6.7W of electrical heat into the hot side. As you might imagine, 7.7W will be harder for the heat sink to dissipate than the 1W that the CPU is making. Unless you have enough heat sink power capacity to spare, thermoelectric coolers aren't worth it. The way to increase the heat sink power capacity of course is with forced convection, i.e. a bunch of fans. But all in all using the TEG will stifle the flow of heat much more than the gains you'd get out of the extra cooling, so I'd just stick to the TEC and some fans, unless you can manage to get a TEG-powered fan to be more thermally efficient.

Some eyecandy for y'all.

>>1279098

i see your 2n3053, and raise you some 50-yo geraniums, still in working order.

>>1279108
That's damn old, in contrast I bought the 2N3053s new. No idea why they keep them in stock, but I figure there's nothing wrong with a few more obscure packages. I had a need for a linear regulator that runs at either Vcc or 12V, whichever is lower, and I'm not too sure if normal linear regulators can do that well, so I'll just use this and a 12V zener.

>>1279119
>I'm not too sure if normal linear regulators can do that well
You'll be losing one Vbe with the usual emitter-output design, at least.
There are low-dropout (often less than one Vbe) linear regulators. ON's KA278R12 came up in a ddg search.

>>1279129
I know about low dropout regulators, I'm just not sure what a 12V regulator will output if you give it 12VDC, or even 8VDC input. I guess I could test that.

>>1278576
If you are still around I've gotten a lot of progress and wanted to run it by you.
I set R2 at 120 ohms, which puts the minimum power outup ( @ 0.25A from CT) at 7.5W.
I then found that when R2 is operating at 50W the current out of the CT is 0.65A.
I then Assume R6 at 100 times larger that R2, making it 12k, which makes R3 360k in order to produce a 2.5V drop across R6 that would satisfy Q2's threshold voltage.

I then assume the Rds value of Q2 is essentially so low it acts like a wire grounding the gate of Q1.
From what I've real, grounding the gate of a PMOS is what allows source to drain flow. Correct me if I;m wrong.
So R1 is just a pull up resistor. I should set that to 10k? That's what I've always used for pull up resistors.

I Then found a Mosfet with a -2 to -4 Vgs(th) value and a Rds(on) value of 0.117.
I then chose R5 to be 20 ohms, which when added to 0.117 ohms and then in parallel with R2 gives and equivalent resistance of 17 ohms, which gives ~7W with an T on 0.65, and 107W at our max current of 2.5A.

I have no idea what value to give R4. And when I try to actually model this on Pspice it doesn't want to run it.
check out?

is this solder flux what I should be buying? if not what should I be using instead?

https://www.aliexpress.com/item/MECHANIC-Reparing-Solder-Soldering-Paste-XG-50/32574193508.html

I usually just use flux core solder but everyone else seems to dip all their things in actual goop first in addition to that

>>1279171
>everyone else seems to dip all their things in actual goop

not everyone! the only time i've seen something like that is when hand-soldering SMD chips using a dragging motion and a big-ass tip.

>is this solder flux what I should be buying?

that's solder paste, i.e. liquid. solder. search aliexpress for ''Soldering Rosin Flux Pen'' if you like pens, or bottles if that's your pleasure. personally, i wouldnt buy something critical like that unless it had a brand name, like Kester. who knows what the chinese stuff is made from; could be crushed cockroach shells.

>>1279133
Typically, they'll output Vin - Vdropout.

>>1279146
Is your PMOS backwards or just a drafting error?
>R1
I get good results with 100k. Its main concern is pulling charge back off of Q2's gate fairly quickly.
>R4
Q1's drain will be at 0V when Q1 is off and close to the rail voltage when Q1 is on. You want (R6||R4) / ((R6||R4)+R3) to be slightly more than Q2 threshold when Q1 is off at max tolerable output voltage and R6 / (R6+(R3||R4)) to be slightly less than Q2 threshold when Q1 is on at min tolerable output voltage. You may need to adjust R6 and/or R3 to achieve that. See Pic related, voltage source is a triangle 0-100V, to sort of approximate your CT. Left scope is Q2 gate, middle is Q1 gate, right is output.
The turn-on and turn-off aren't as sharp as I expected. You can add a series-cap-and-resistor in parallel with R4 to sharpen the switching action. I used C=3n3 and R=220k and still got a reasonable simulation. You may wish to play with these values when breadboarding, or if your simulator can generate current waveforms.
The circuit can have trouble converging because simulators don't handle positive feedback perfectly well. Try establishing an initial state of off, with the node on the gate of Q1 set to the initial level of Vin. And/or decrease your time step.
Remember, the goal of this circuit is just to reduce input variation to something a higher-quality post-regulator can handle. With values in pic I get something like a 33V max before the second shunt activates.

>>1279184
Mechanic is a brand name, and apparently a fairly reputable one in the east. Who knows whether your Kester is actually Kester, gnomesayin?

>>1279184
I heard that pens aren't that good. Personally I just have a tub full of semi-solid (jelly-like and melts at like 80°C) rosin flux and apply it with whatever trimmed component lead I have lying about, but it's a bit like painting a model plane with a paint roller. Something like a flux pen might actually be what I need, but I'm kind of wanting to use no-clean flux instead since rosin leaves a sticky mess.

>>1279190
Pens are god-tier.

>>1278755
why do they still teach people still use darlingtons for hard switching

>>1279195
Those things are no-clean? I need one.

>>1279203
I didn't mention, but this pen is refillable
The thing about no-clean is that it's not the most active flux. It's nice when you have fresh, clean components and boards. Otherwise, you might want something a bit more active which you could just clean off with alcohol and a totohbrush.

>>1279204
I do find the solder flows really beautifully when I slather the board in flux, but I haven't found the ideal cleaner yet. That canned stuff evaporates too quickly. A bottle of isopropyl alcohol is probably what I should be going for, maybe with a spray attachment.

>>1279224
The pro thing to do is to give it an ultrasonic bath, shit's cash.

>>1279240
They're a little expensive looking. Could you make your own with a handful of transducers and a bucket?

>>1278942
I get what you say. Anyway, I'll try some programs to only read the output without the array, and try to fix the problem of reading HIGH. Really, it has me worried. The arduino is a chinese one, so I don't trust a lot in it. I'll test it in some arduino UNO.

Really, thank you for your help.

Hello
I have this usb stick that fell of my pocket a couple times and this component broke from the pcb. I can solder it but i cannot find the component online and i do not know if there is any polarity that i should be aware of.
Can anyone help?
The component reads kts12.0A2J

>>1279224
>evaporates too quickly
The runoff is supposed to carry the dirt with it.
Also, toothbrushes.

>>1279266
It's a crystal. Nonpolarized. It's possible it might have broken in the fall and needs to be replaced, but it's an easy part to find.

>>1279272
>It's a crystal
Tnx anon.
I found some traces in the old solder that were in the one side and not on the other. I did the soldering and it werks.

My laptop charger cable was very frayed near the plug that goes into the laptop, so I cut it shorter and resoldered the inside and outside of the coax onto the plug. I had to remove the ferrite choke because it was very close to the frayed part.

The charger seems to work fine now, but the transformer makes a buzzing sound like the noise from a computer working on something whenever I move the mouse or do anything else on the laptop. Should I be worried about this or is it some harmless feedback?

>>1279280
>I had to remove the ferrite choke
>>1279280
>now, but the transformer makes a buzzing sound
gee, I wonder if those could be related...

>>1279294
Literally not what I was asking about. I'd like to know if I can keep using this thing.

>>1279299
It's harmless feedback.

>>1279244

first of all, things like IO1 are set to permanent values, 46 in the case of IO1, which presumably is the pin number you are using for IO1.

your digital read looks wrong:

digitalRead(IO1); this will read the pin and do nothing with what was read


val1 = digitalRead(IO1); this stores the state of the pin in "val1".

I have no idea what this does:

if((IO1, LOW) & (IO2, LOW) & (IO3, LOW) & (IO4, LOW))

C++ is not what I'm familiar with, but you should be able to do something like this:

If ((val1 == LOW) && (val2 == LOW) && (val3 == LOW) && (val4 == LOW)) {

then they are all low and it's good.

} else {

something is not correct

}

also it would be better to use variables for the four data bits that you write to the sram.

out1 = 1; (or 0)
out2, 3, 4 set to whatever

then after you read, compare to that: if (val1 == out1) etc.

this way you can easily write 0000 or 1111 or 0101 or whatever you like. some ram tests write all kinds of combinations, but for starters I'd just use 0000 and 1111 to confirm that every cell can hold high and low values.

>>1279332
Great. I made it work.
I were all day testing other programs, and I finally find the error in de if with the == and &&. I put the "val" and "out" variables that you mencioned and it is plenty functional, coulding change the data without effort.

Now, it only left make it smart, and make it tell me what address is wrong, but as a start, it's very good.

Thanks a lot mate.

>>1279332
This is the code.
https://pastebin.com/BgWhi0zi

I'll make a post in some forum, and upload it when it is finnished.

>>1279424
>>1279427

Excellent!

I have a power supply that needs its capacitors 820μF 25V replaced.
The capacitors are barrels with a + on top.
I have several others laying around, e.g. some 2200μF 16V with a k on the top and I was wondering if I could replace them with those.
The psu is from a display, so it reaches 50w at most.

>>1279430
>if I could replace them with those
Of course you could if you want to experience a nice explosion..
820uF/25V is available and 1000uF/25V would do as well.
>The psu is from a display, so it reaches 50w at most.
Why would that matter?

>>1279146
I would keep is simple and robust.

The fancy switching action only shifts the problems to the output section and will need a lot of experimentation because of the poorly defined Vth (tolerances) of the MOSFETs.

A 30V shunt regulator is as simple as a 30V to 12V step-down converter. At the low end (0.25A) the shunt regulator barely loads the CT at all and at the high end (2.5A) it has to dissipate about 75W which is no problem for a few 3055s on a heat sink with some simple circuitry around.

The choice of 30V is just a quick guess from the power balance with 0,55A out from 0.25A in. In practice you will adjust this voltage according to the efficiency of the step-down converter. For 88% it would be 30V/75W and for 75% it would be 35V/88W max shunt power, but only at (and during) 1kA.

The optional crow bar serves as life insurance...

so what exactly does the maximum current specification on a charger (e.g. phone, laptop) mean?

a) when delivering more current, the desired output voltage can't be guaranteed
b) voltage can be supplied, but components might take damage
c) possibly both

>>1279481
Normally it means the maximum load current at the specified output voltage. With no load the output voltage stays almost the same. A good PSU has overload and short circuit protection which means the voltage decreases to safe values.

The situation is a bit different with super-cheap phone chargers, here it may mean output voltage at specified current. I had such a thing that said 5V at 500mA. Without load it showed 9V and 4.5V on a 10Ω load.

>>1279187
What is the purpose od the new 50k ohm resistor(R7)?
If R1 is a pull up resistor, why would that be needed.
Doesnt grounding the gate of the Pmos turn it on?
Or should I meet the threshold voltage using those two as a voltage divider.

I'm having a lot of issue with pspice.
Im going to look into a different program.

I'm using a DC sweep from a current source, it's giving linear outputs lol
Not quite right.

>>1279492
I think load switching is a faulty concept. What can you simulate when the threshold voltage is specified as 2V..4V, a tolerance of 100%? Read >>1279480 for an alternative solution.

can someone identify this broken part on my board? It needs to be replaced but I have no idea what it is or how to do it

>>1279508
It is a diode. I can read 942, so it could be this:

http://pdf1.alldatasheet.es/datasheet-pdf/view/76168/MICROSEMI/1N942.html

Chek if you can read better the model, and search it on google.

A relay is rated for 2A 220VAC, can i put 10A 12V through it?

>>1279515
never tried it, but i doubt it

>>1279520
I think so too. This is from a different relay, around the same rating.

>>1279508
Probably a 1N942 12V zener diode, but it might have a letter after the 2 like an A or B. If you can desolder it and read off all characters on it that would help. If that broke while the thing was running, which is likely, then you might well have some other broken components on the board, namely the ICs (maybe relays?) since the lack of the zener will push the supply voltage up at least a couple of volts.

On the assumption that the zener is being used as a voltage regulator for the power supply, you might want to consider bodging a 3-terminal linear voltage regulator in there instead, but it would require a bit of reverse engineering and probably isn't necessary.

Also that's a nice capacitor there.

>>1279480
I'd be worried about a a crowbar or fuse on the cut it with the extremely high possible voltage across the CT when the line is at 500kv.

Would the shunt be able to deliver a constant power that is at least 7W?

Does 30v mean it outputs a constant 30, or if that is a rated max

>>1279534
That's why the crowbar and not a fuse. In case of malfunction all you can do is shortcircuit it all. The shunt regulator is a dynamic load that maintains 30V no matter what input current. It acts like a giant Z-diode but much more precise and easily adjustable. Didn't I outline my calculation? Just check it on your own. Don't forget that simulators are GIGO machines, garbage in - garbage out, but to two decimals.

>>1279534
>high possible voltage across the CT when the line is at 500kv
Wow. A current transformer doesn't care about voltage, only current. But without load the voltage can get very high and possibly destroy the transformer. It is still isolated from the HV side. Do you know how a clamp meter works? That's a current transformer.

>>1279513
>>1279523
Sorry to ruin it, but it almost certainly isn't 1N942. Those are pretty rare, expensive and come in a glass package.
It could be a bi-directional TVS.

>>1279508
Like the other anon said, try to read the remaining text on it.

>>1278292
>>1278284
>>1278282
Found a relay that burns only 0.5W, 40mA, and the LM311 can source 50mA. Gonna try that instead.

>>1279564
Oh yeah, DO-35s. Still, a similar 12V Zener near a bridge rectifier and big filter cap with a resistor next to it isn't unlikely. Not that I've bothered to look up the datasheets to the ICs or consider why there's an inductor there.

whats a good brand for solar panels ? i need to setup a little solar backup system 1kw maybe as a demo for a bigger project, money is not a problem

>>1279567
>why there's an inductor there
because of the 34063 next to it.

>>1279568
wut

>>1279187
>>1279146
>>1278576
>>1278553
>>1278447
>>1278435

OK,
All of this is OK, but it needs to be dumbed down.
High voltage and solid state circuits don't mix.
What you want is a two winding 5 to 30 volt type transformer.
Connected to the CT you will operate it in saturation zone.
Then just buck the voltage down to 13.8v and that will change the battery.

I believe the buck will cut off once the battery reaches that level, so you might not need over charging protection.

Put a MOS in parallel with the buck that cuts out voltage spikes.

>>1279575
photovoltaic cells, arrays, panels or whatever you call it, should i just buy amazon best rated ones ? or look for a specific manufacturer?

>>1279492
>"R7"
MOSFET gates fail destructively under too much voltage. R7 keeps the gate voltage of Q1 within its rated Vgs(max).
>dynamic load
If you want to go this route, simply move R4 from the drain of Q1 to the drain of Q2, thus establishing negative feedback instead of positive feedback. You'll need a bigger Q1, possibly several.

Any audio electronic anons in these threads?

>>1279606
A few.

>>1279610
I’m looking at getting into designing my own audio stuff. I’ve made a few kits and I’m reading some electronics books, but I’m trying to find some projects that go into detail or break down the circuits showing what the components of each part of the circuit do. I’m thinking maybe something like a low pass filter or oscillator...anything really that will help me learn.

>>1279668

good luck with that. you'll have to figure it out yourself like the rest of us did from reading and experimentation. you'll find that just doing a voltage-vs-current graph on individual components and simple circuits will reveal many of the the secrets that men (there's no women in electronics coz you cant apply the results to your face) have discovered in the last century.

>>1279668

good luck with that. you'll have to figure it out yourself like the rest of us did from reading and experimentation. you'll find that just doing a voltage-vs-current graph on individual components and simple circuits will reveal many of the the secrets that men (there's no women in electronics coz you cant apply the results to your face) have discovered in the last century.

>>1279668
I'll be messing around with some audio stuff too, in particular seeing what happens when you put an analogue signal into digital components. Namely flip-flops to half their frequency, and a schmitt-trigger feeding a differentiator, maybe some other ideas. Mainly to mess around with using sounds from all around me to make surreal music.

>>1279668
"Audio electronics" is stuck in a low-knowledge, cargo cult mindset. You need straight electronics/circuits knowledge, up through some basic frequency response analysis.

What are your current resources?

>>1279721
>(there's no women in electronics

>>1279877
That girl only talks about the new products on their website or puts some prebuild neopixel scripts together

>>1279880

>>1279721
>ohshitnigga.jpg

>>1279881
When you pose for shutterstock

>>1279883

she is an engineer.

>>1279721
>good luck with that. you'll have to figure it out yourself like the rest of us did from reading and experimentation.

So no man had any guidance in electronics, it was all self discovery...is it ok to read books or should I only read manufacturers data sheets?

>you'll find that just doing a voltage-vs-current graph on individual components and simple circuits will reveal many of the the secrets that men have discovered in the last century.

Thanks I feel this might be helpful even though I’m guesssing you are trying not to be.

>>1279772
>I'll be messing around with some audio stuff too, in particular seeing what happens when you put an analogue signal into digital components. Namely flip-flops to half their frequency, and a schmitt-trigger feeding a differentiator, maybe some other ideas. Mainly to mess around with using sounds from all around me to make surreal music.
This sounds interesting. I’d be interested in results even if it’s was just hearing the audio.

>"Audio electronics" is stuck in a low-knowledge, cargo cult mindset. You need straight electronics/circuits knowledge, up through some basic frequency response analysis.
Ok I was hoping I could find some really basic audio circuits to get me going. I don’t really plan on skipping the whole learning/circuits thing was just wanting to learn some basics of how electronics work in audio. I’m interested in audio so thought audio electronics would keep me interested and get me experimenting a bit more. You know simple circuit designs or ic’s that a beginner could understand and build experiment with.

>What are your current resources?
Currently reading the forest mims-getting started in electronics, Make:analog synthesisers and lessons in electronics along with these threads and various other bits from the internet.
I have quite a varied set of electronic components, soldering iron etc now from building guitar pedals and synth modules.
I don’t own a scope yet

>>1279949
>I don’t own a scope yet

I'm sure you know it already, but you pretty much cannot do analog electronics without a scope.

I finally upgraded to the Rigol ds1054z at about $400 and I love it. 4 channels used to seem overkill, but I don't think that anymore.

My only complaint is this: Does anyone know how to save Rigol images without all that menu crap on the sides, or how to hide all that crap when using the scope so it's closer to full-screen?

>>1279950
>I'm sure you know it already, but you pretty much cannot do analog electronics without a scope.
I didn’t know that, desu other than testing circuits some how that is all I know about scopes. What frequency would I need for my application would the ds1054z be ok? I nearly bought that model yesterday but couldn’t work out if it would be ok...kinda guessed £370 worth of scope should probably be fine for what I want, but I’d be gutted if I needed a function for audio circuit testing that it was no good for!
I finally upgraded to the Rigol ds1054z at about $400 and I love it. 4 channels used to seem overkill, but I don't think that anymore.

>My only complaint is this: Does anyone know how to save Rigol images without all that menu crap on the sides, or how to hide all that crap when using the scope so it's closer to full-screen?

I think I read somewhere while reading reviews that unfortunately the menus on the side can’t be hidden...I think it was one of the cons of this scope

>>1279950
Oh I also noticed a lot of places had stopped stocking the ds1054z and was wondering if Rigol were about to release a new scope to replace it?

>>1279953
>What frequency would I need for my application

I haven't been following but if you are doing audio any scope in the world will work. The ds1054z comes standard as 50 Mhz and there used to be a hack where you could unlock twice the ram, 100 Mhz, and some other extra-cost features, but I'm happy with mine as is so I haven't risked it.

>>1279954
>was wondering if Rigol were about to release a new scope to replace it?

I don't know, but someone else probably will.

>>1279955
>I haven't been following but if you are doing audio any scope in the world will work.
Do you mean any scope will work for audio waves analysis through the scope? If so then I understand this or do you mean any scope in the world will be fine to test audio circuits and their components? I’m guessing the former.

>>1279955
>any scope

and by that I mean any serious scope. I think they sell some jokes that only have about 5 khz bandwidth.

>>1279958
>r audio waves analysis

lol I was already clarifying because what I said isn't really accurate. I don't know what you mean by analysis, but audio is pretty much limited to 20 khz so if your scope has 100 khz bandwidth you should be able to do any audio work. But then I'm not an audio expert, or an expert of any type, so maybe someone with more experience will chime in here.

>>1279962
>lol I was already clarifying because what I said isn't really accurate. I don't know what you mean by analysis, but audio is pretty much limited to 20 khz so if your scope has 100 khz bandwidth you should be able to do any audio work. But then I'm not an audio expert, or an expert of any type, so maybe someone with more experience will chime in here.
What I mean by audio analysis (probably not the correct term) is analysis of audio waves so showing audio waveforms on a scope as opposed to analysis of audio circuits and components (electronics).
So just to clarify I’m NOT looking for a scope to view or analise audio waveforms. I’m looking for a scope to test, analise , troubleshoot electronic circuits and components that make up circuits that produce audio. Eg the circuits inside a synth oscillator (pic related)

>>1279969

If it has digital components like DACs and whatnot, you should go ahead and get a "real" scope, which to me means at least 50 Mhz. A year or two from now you might be interested in something that involves higher frequencies.

But as far as I know, you can design and troubleshoot audio circuitry with a 100 khz scope, if they actually make such a thing. I'd avoid low frequency scopes unless they have great reviews because they are mostly toys and not intended for serious work. Lots of 20 Mhz used scopes can be found, and they'd be fine.

However, dealing with transients is way easier with a storage scope, which some analog scopes are, but all digital scopes are inherently capable of capturing a signal and allowing you to zoom in or whatever.

>>1279976
>But as far as I know, you can design and troubleshoot audio circuitry with a 100 khz scope, if they actually make such a thing. I'd avoid low frequency scopes unless they have great reviews because they are mostly toys and not intended for serious work. Lots of 20 Mhz used scopes can be found, and they'd be fine.
Thank you this is helpful

>>1279949
>I’d be interested in results even if it’s was just hearing the audio.
I plan on putting it on youtube as background music, so if anything I create does sound good it should be there. I think my first order of business is to make an "electric guitar" with an old bike gear cable and a diy magnetic pickup, since getting a clear tone that isn't mains hum will be tough without something like this.

>>1279949
>Currently reading the forest mims-getting started in electronics, Make:analog synthesisers and lessons in electronics along with these threads and various other bits from the internet.

That's cool. As long as you are ambitious, you will keep expanding your horizons and pick stuff up organically. At the same time, having a formal framework for knowledge can be very useful, say if you want to analyze VCOs. So I would suggest following along with some college course materials at some point.

>>1280116
>So I would suggest following along with some college course materials at some point.
This is kinda what I was asking for. Rather than just trying to self learn and keep interested from books. I thought maybe some basic practical stuff involving audio generators/filters/lfo’s etc might be good, but obviously knowing very little I’ve come here for advice.

>>1280086
Keep us posted anon

Remind me how to tell what resistor I need for a given LED for a power source of two AAA batteries
I'm building a head tracker.

>>1280140
I meant AA, fucking phone

>>1280140
http://ledcalculator.net/
An AA battery is usually 1.5 volt allthough it might be save to use 1.6 in the calculation to make sure you don't break the led with new batteries. Also 2 AA batteries in series or parallel

>>1280148
Standard battery holders are generally series, so series.

>>1280151
Probably, if you calculate parallel and they are actually in series your led breaks if it is the other way around, the led will just not be as bright and in this case it probably wouldn't even turn on at all

>>1280151
Single AA and garden light circuit lasts much longer. 3V is too close to LED voltage unless dark red or infra red.

>>1280209
Huh, cute, and only ten cents each.
>100uH
The datasheet's typical application circuits show two LEDs in parallel. 35mA might be too much for a single LED. Maybe 220uH or so for one?

>>1280214
QX5252 Inductor Output Current (BAT=1.3V)
L 330uH 270uH 220uH 150uH 100uH 82uH 56uH 47uH 33uH
I 11mA 14.5mA 15.5mA 25mA 34.5mA 38mA 50mA 75mA 110mA

>>1279949
>So no man had any guidance in electronics, it was all self discovery...is it ok to read books or should I only read manufacturers data sheets?

the point i was making is that the kind of help you want does not currently exist in an organized fashion. no one is gonna hold your hand and teach you stuff unless you're paying them or blowing them. the only approximate such resource that will take you step-by-step through electronics training are uni-level online courses, but they will drive you mad with excess math, and even madder solving theoretical never-actually-seen-in-the-real-world problems. coz they're not actually about teaching you practical stuff, but making sure you're clever enough that your diploma isnt an embarrassment to the school.

>>1280227
>coz they're not actually about teaching you practical stuff
Disagree. Those contrived, convoluted resistor networks are, like most algebra classes, about teaching you that everything can be solved by methodical application of simple rules, should you need to. It makes practice seem relatively easy.

>>1280232
people are quick to cite near-intangibles like this in defense of academia but the fact of the matter is that a curriculum of more practice and less theory would produce far better engineers.

>>1280238
>a curriculum of more practice and less theory would produce far better _____
applies to just about everything

>>1280227
>the point i was making is that the kind of help you want does not currently exist in an organized fashion. no one is gonna hold your hand and teach you stuff unless you're paying them or blowing them
...but anon I wasn’t asking for hand holding I was asking for people with more experience and knowledge if they could point me in the direction of some projects that were audio based that I could learn some basics from and experiment with?
I gave the example of filters and ossilators as I thought a basic oscillator going through a simple filter might be ideal to learn from, a bit more fun and a bit more relevant than experimenting with say getting a LED to flash at different rates like what I’m reading about now.
I recently built a module that had a filter built into it made from only a couple of components but it wasn’t explained what it was doing or how to modify it which is a shame as I’m interested in that. Kinda thought maybe someone here might know of some resources as so far I’m not finding much online for that kinda thing.
I guess I’ll just keep reading up on electronics until I have enough knowledge to apply those things to audio circuits

>>1280254
I made this:
https://makezine.com/projects/weekend-project-sample-weird-sounds-electromagnetic-fields/
Pretty entry-tier, but fun to listen to. Also replace the caps with the biggest non-polarised ones you can find and increase the gain a bunch. Put dual-gang pots for both volume and gain, an A50k and a B50k should suit that purpose nicely, but I'd mess around with resistors before deciding that.

>>1280256
>I made this:
Thanks anon
This looks simple enough and the description is pretty good telling me what the different parts do in the circuit (capacitors work as a filter). Unfortunately I don’t have any inductors but I’ll order some. I’ve recently ordered some hydrophones so this kinda thing is ideal.

>>1280232
As awful as these comics can be, this always makes me laugh.

Ordered a pair of these old tanker nightvision goggles for fun.

Looking for advise on a easy way to rig a battery pack to it that would be safe to keep in my pocket.

Apparently they aren't picky and run off 12volts. Seen some people even get them working just holding a 9V battery to the right terminals.

>>1280285
3 cell lipo, can get one with the right capacity once you figure out that things current draw

Oh, no!!!! The old TV fell and kinda fell apart!!! What a shame.. it's ok, it was all broken and stuff. Apart from being fully functional and stuff, it was busted. I'll just take some stuff from it, hun.

>>1280374
Is that a VHS tape

Anyone know where I can find a low volt (~3-8v) input, (~20-40v) output transformer thats rated for at least 5 A?
This specific range has alluded all search efforts.

>>1280374
>all those jumper wires
cringe

>>1280438
Input or output at 5A?
Frequency?
There's probably a better way to do whatever it is you're trying to do. Tell us more about it.

>>1280438
I smell a rat called misconception.

>>1280232
Yeah, the first time and maybe the second time if you're kinda slow, but the time spent on drilling that shit far exceeded the amount required to demonstrate that point.
And even with all that practice the commonly taught methods weren't sufficient for real world circuits.

>>1280232
What does this circuit do?

>>1280491
Offers several sensible chuckles, if correctly assembled.

>>1280494
>sensible chuckles
plus nerd sniping.
It makes you think about the topological aspects of the electrodynamic properties of a knot as to the replacement of a common mode ferrite choke..

>>1280518
>now wants a GHz scope and probes just for this
Nerd-sniping me just before bed, you faggot.

Is there a place to search for an whether a component for a circuit board exists?

>>1280552
In what sense? You have a mystery component and you want to know what it is? Just google the markings, one line at a time. Any extra info helps, of course.

>>1278235
FULL BRIDGE RECTIFIER

>>1280442
I'm curious about this circuit idea.

given an input range of 0.25 to 5A AC from a current transformer, how whould one select a transformer to operate in the saturation region like said here.
I think you would want a low input voltage like idea Anon, that would keep the power rating of the transformer lower.
When I look on places like digikey, there are no 5 to 30V transformers at 25VA rating.

I really like the idea of using the second transformer saturation characteristics.
>>1279580

>>1280649
How did you calculate the 5:30 ratio and the 25VA?

How do I figure out the gauge of copper wire I need to safely carry my current?
it needs to carry up to 125A in short bursts and as much as 85A constantly

my issue is that the wire is soldered to a pad that runs through a current sensor, so if the wire gets too hot the solder will melt

>>1280715

you look it up on google. there's plenty of tables available for constant current loads, but not for bursts, since no-one knows what your bursts look like. if they're fast bursts, you can average them.

Is he /ourguy/, /ohm/?

>>1280739
This guy really aggravates me for some reason desu senpai. He's good at what he does but his personality and presentation just sucks imo.

What is the highest possible speed I can run a NE555 at. I don't care about the fact that the output isn't really a square anymore and breadboard capacitance and resistance is also not a factor. The main question in the end is how small a capacitor I could possibly use because I am making a capacitive touch sensor where speed is really important. I am also connecting the resistor and capacitor directly to the output so I have a 50% duty cycle.

>>1280556

No I have an idea for something if it doesn't exist already, but I want to find out if it exists before I put time into it.

>>1280769
He is a bit autistic I guess. But he is really good and explains everything he does so yeah. He can be pretty funny too

>>1280774
If you are asking 4chan. that probably means that it already exists but I guess there is this patent search feature in google.

Does anyone know where I can get this Chroma/QAM demodulator/decoder chip or a cohesive schematic for one I can make.

>>1280773
>so I have a 50% duty cycle
You will not because the output has a source-sink difference but there are ways to get exactly 50%. What is your detection principle and why don't you RTFD?

>>1280705
5A max in, 5 volt inpur

>>1280797
I don't really care as long as it roughly 50% I am just using a low pass filter and a comparator for detection.

>>1280812
That's no meaningful calculation. What motivates the 5V:30V and what makes you think a transformer saturates at its rated power?

>>1280816
Garden-variety 555s don't seem to be recommended for more than 100kHz, according to the nomographs in the datasheets. You shouldn't need much if any more than that for touch detection, and that's getting close to what an LM393-class comparator will reasonably compare.
Is this for an exercise, or can you not get TTP223 chips?

>>1280816

dont do it, dude. i found a container with 25 pieces of the QT110 Atmel Capacitive Touch Sensors for 50 cents. these chips work like magic compared to touch switches i've built before using general purpose components. (these particular chips are now obsolete but various replacements, under a dollar, can be found at digikey, etc)

>>1279884
Why didn't you post this much cuter girl?

>>1281042
she's just barely office cute

>>1281044
The other one looks like a SJW though.

>>1281033
#include <zozzle/filename.h>
Also consider TTP224 4-channel or TTP229 8/16-channel touch sensors, which are available for under USD0.08 from aliexpress

>>1281033
#include <zozzle/filename.h>
Besides TTP223 (8 burgercents), also consider TTP224 4-channel (32 burgercents), TTP226 8-channel (73 burgercents), or TTP229 8/16-channel (80 burgercents), all available from our good friend ali in convenient 10 packs or more, all apparently still active and quite available.

>>1281046
Also, Limor don't make homemade MOSFETs.

>>1281042
that picture is what, 10 years old?
she's a pudgy middle aged lady now

>>1281092
Yepp, that number is about right and it got me interested to find out more. So here is a recent one from twitter.

I would require extensive nude testing to verify that pudginess.

i've never used a cpld before. i'm researching how i might use it to glue an adc, a dram buffer, and a uc together. how good are they at generating flexible waveforms like fig1 in pic related? i'm imagining them in terms of discrete logic where a circuit like fig2 would seemingly tie up a lot of resources in latches for counters and registers. i assume i have some misconceptions since this is specifically what they're for.

/b/ raid or homegrown empty children?

>>1281106
the only thing worse than a shitpost is a shitpost that thinks it's better than the other shitposts

>>1281105
Except for the 128MHz clock, which some slower devices might not like, this is an ideal small-to-medium CPLD project. You should download one of the vendor design suites (they're mostly the same), lern2verilog, write some timing constraints, and try to fit it to real chips.

>>1280792
Is RGB out instead of YPbPr okay? If so, there were lots of decoder chips intended for CRT TVs that you could use, although none AFAIK still available from regular distributors like digikey. Philips TDA3566 for example.

>>1281097
>recent
not recent enough, bub

>>1281124
>americans

>>1280792
MC1496 is an option, it's basically a Gilbert cell in a DIP package. You'd have to generate and sync the 3.58MHz clock to the color burst for yourself.

https://www.ebay.com/itm/LED-Chip-Driver-Power-Supply-Driver-Transformer-AC-85-265V-3W-100W-No-waterproof-/132149697819?var=&hash=item1ec4bc5d1b

using a 20 watt power supply like this for an LED
it's only feeding about 16 watts to my LED and only at 27 volts (my led is 32-34 volts) the brightness is gimped because of this

is there something I can do to up the voltage?

>>1281121
Well that's actually even better. Thanks anon, I even found the schematics for the 3566 so I can build it with any subcarrier frequency. I also want to use something like this with a Sony Umatic tape deck and the dub connector. It's essentially s video but the it uses a non standard but higher subcarrier frequency, resulting in better picture quality for better archive quality, I just can't remember what the frequency was for the dub signal. Thanks anon.

>>1281128
I can always get an lm1881n to seperate the sync. Thx anon.

>>1281185
attach a boost converter in between to step up the voltage from 27v to 32v
something like this
https://www.ebay.com/i/201947726698

>>1281215
The whole point of an LED driver is to control current. Adding a converter in between defeats the purpose.

>>1281185
If there are no trimmers to adjust, then probably not, you should look for a better converter.

>>1281026
>>1281033
The whole point is that I wan't to make this with only basic components and that I wan't to design it myself. And the frequency does kinda matter because I wan't to create a multiplexed capacitive touch piano without any microcontrollers. I am currently running my 555 at 100kHz which should be just good enough for this purpose. But the thing is that the capacitor I am using is still relatively big and I would like to have a smaller one to make the difference more significant but I am Already using a really big resistance. So I'd like to know how much I can decrease my capacitor while not getting into megaohm range resistors because the 555 can't handle the speed.

>>1281225
Ah, ok. See Pic related from the datasheet. Frequency increases as resistor and capacitor decrease. From the figure, C=~2nF and R(disvcc)+2R(disthr) = 10k should get you the 100kHz you need.

>>1281209
1881 only gets you vertical and composite sync, getting a good chroma carrier lock is quite a bit harder.

>>1281228
Oh shit I'm sorry, I read >>1281128 answer wrong, I thought it said to generate sync. So do I have to get a 3.58MHz oscillator and put it in phase with the chroma's 3.58MHz?

>>1281232
Yes, but I think it's a 6.88MHz signal you need to lock to for demodulating the dub chroma, isn't it?

>>1281248
Yes, I that was the frequency I couldn't think of. I just need to find a 6.88 oscillator, or make one.

>>1279882
waifu material

>>1281225

the 555 can do a lot better than 100Khz. the old TTL version is rated around 500kHz (but i've pushed it close to 1Mhz) and the CMOS version is good for 2Mhz.

>>1281257
I was just accidentally running one at 950kHz but it went from capacitive to resistive touch. I am currently running it at 200k with a 12k resistor and a capacitor that I can't identify. can I just use R*C time as rice time and calculate a ballpark figure.

So I have this PID temperature controller.
To connect it it's like eating snacks.
The setup - oh boy here we go.
I set most of my measurements. I need help now with termocouple.
They send me PID with K type termocouple, setting table says I need to set value to 0, so I did, but sensor shows me 100+ Celsius, wtf, it's cold here in the basement.
So I noticed table ends with 7 then continues with 20 and 21.
Where the hell I get other 8-19 value table. Because on package of termocouple it says K type 0-400 celsius.
I attach table.
Tried some of those hidden values, no luck.
Do I need to calibrate it or something?

>>1281257
>CMOS version is good for 2Mhz
or even typ. 3MHz for the LMC555. I rarely use the bipolar version because of its hefty supply current spikes during output transitions (pic). For the C version 100n decoupling is always enough. It also has a much lower supply current, a higher output voltage swing and it runs at 1.5V. My choice is the TLC555.

How does combining filters work exactly? Say I got two filters or more filters. How would I go on about connecting them so that they would be perceived as one filter by whatever signal comes in?

>>1280374
alot of goodies there

>>1281281
fixed
it works

>>1281297
You chain them.

>>1281310
Thanks

>>1281117
>can't download quartus because the altera login page is a 404
i fucking hate hardware company websites

>>1279108
>>1279098
Can I play this game too? Got some old stuff

>>1281215
yea that won't work, which is why I came here to ask...
>>1281218
yea I wanted an adjustable current one with a potentiometer or whatever but I saw none that go directly into AC outlet.. I like these cuz they're only 3CM big about and can just go direct to AC

they're ok just slightly under powered my leds are 700mA at 32-34volts so I'd like 650mA or so at 31-32

>>1281426
Stomptronics loves Germanium & old JFETs

>>1281452

so your requirements are:
- super cheap
- super small
- super effective

this is not super reasonable.

>>1281501
if you're on this board you should at least be able to read
the word cheap isn't anywhere

would injecting 10/20MHz OOKs on a ~100ft dc power line be a particularly bad idea from an emissions perspective?

Is there a DIY multimeter or FPGA based universal programmer?

>>1281559
depends on whose "emissions perspective". want to broadcast?

>>1281542
>if you're on this board you should at least be able to read the word cheap isn't anywhere

you bought a 99-cent board from China instead of a $15 board from the west; so ''cheap'' is very very much implied.

>>1281542
>if you're on this board you should at least be able to read the word cheap isn't anywhere

you bought a 99-cent board from China instead of a $15 board from, say, Philips; so ''cheap'' is very much implied.

>>1277831
i want to control several very small motors that will draw 100mA with an arduino. For a current gain i need transistors right? i do not need quick response or accuracy so will any standard mosfet work? only needs to be on/off.
If i want to control 48 motors but the micro controller only has like 10 output pins how would that be accomplished. multiplexer or a shift register?

>>1281564
Bus pirate might be related to what you want

>>1281648
Mosfets or bjts can work.

48 all at the same time, or some, then others?

>>1281648
Do you need the motors to spin in one direction, or both?

If one direction, the simple option is a high current open drain shift register such as a TPIC6B595

Question... I'd like to build a circuit so I can measure resistance of something that I choose to plug into it. I'd like to measure resistance between 10Ohm to 1KOhm.

Does anyone have any ideas how to implement this? Do I need some specialized IC?

Thanks!

>>1281424
Gotta love that weekend maintenance.

>>1281708
Literally just put a known current, say 1mA, through the resistive device and measure the voltage across it. Current sources are like three resistors and two transistors.

shit, anyone got a good pic for new bread?

>>1281748
>>1281748
>>1281748

>>1281645
if you're on this board, you should at least be able to see correct prices for units on ebay