/diy/ - Do It Yourself

Is there any harm in powering a motor that was designed for 7.2V with a power supply that delivers 12V or higher as in pic related (where resistor=motor). The clock generator will be an attiny that converts a voltage from a pot to a duty cycle. I could maximise the duty cycle to something sensible in software.

Would I need the cap?

What are the chances that I will succeed in repairing a piece of electronics by replacing the most expensive-looking part, without doing any tests beforehand?

>>1825835
Divide 1 by the number of parts on the board, that's your chance.

Noob here. I'm making a smart phone charger module that turns off when the battery reaches 100%. I'm using a -5A - 5A current sensor. Should I place proper caps to decouple each IC or are C1 and C2 enough?

How do you get over the existential crisis 2 hours in to a project that you could have just bought a purpose built thing for what you're trying to do for $5? Maybe I'm too much of a square for DIY

>>1825835
Nil

>>1825844
Good idea to multiply by 100 for the real result or???

>>1825904
If you like percentages.

>>1825859
C1 and C2 will almost always be enough, but 100nF caps are free and debugging is hard so just add them anyway.

>>1825859
<200nF smd caps are really cheap like 5 cents each may as well use them

I'm planing to use this linear travel sensor and I am not sure what wiper load is in this care. The way it's written in this table I assume it's the minimum resistance, from sensor output to ground, to achieve a correct measurement.

>>1825971
it's the lowest permissible resistance, yes. this looks like it might be a potentiometer internally in which case you really want infinite DC input impedance on whatever's reading from it, the wiper load figure is just a cute number they've come up with to make you feel good about your circuit. post pics of the product if you want to be sure.

also when the fuck did they add facebook reverse searching?

if I cant find a certain cap uF value is +/- 10% okay?

I need (2) 30uF 175V and (1) 20uf 25V for a multisection cap but all i can find is 33uf and 22uf

>>1826324
uh, what's it for exactly? a 4th order butter worth filter, or just like a bypass cap?

>>1826334
its for a 60's tube shortwave radio. right now its a paper cap so I want to replace it with a modern electrolytic

>>1826338
The 20µF is a DC-blocking cap making up part of a tube biasing circuit, so a 22µF should be fine. The 30µF caps are part of a π filter, which could be a red flag if they were on the signal's path, but the filter is just there for noise suppression after the mains transformer, so again 33µF will work fine.

>electrolytics
I'd probably agree, but they're not as noiseless as film caps.

I have mixed feelings about them using a single diode rectifier as a part of the power supply. That diode might be so ancient that its specs make it objectively worse than a modern diode, or even be worn over the decades, so you may want to consider replacing it too. There's nothing else silicon on the entire circuit anyhow.
Does it have a part number?

>>1826344
I could use a film cap but how do deal with polarity then?
This was one of those "build it yourself" kits where you get all the parts and wires and solder it together.

CR-1 is listed as a selenium rectifier 50ma

>>1826347
>>1826344
I also started looking up 50mA selenium diodes and saw a link to this
http://www.w3hwj.com/index_files/RBSelenium2.pdf

guy recommends a 1A 1000V silcone diode and as well as a 200ohm 5w resistor (for a 50mA diode) on a terminal strip. if you agree as well i can go ahead and get those.

>>1826347
>I could use a film cap but how do deal with polarity then
It doesn't matter at all, they can go either way. Pretty sure paper-in-oil caps are non-polar too.
But I'm not actually sure if it will make an appreciable difference, since the caps are only dealing with low frequencies. If the cap was before the detector I'd definitely recommend a low-ESR dielectric, but modern electrolytics are probably fine for this.

>>1826355
>selenium rectifier
Wew, that's some old tech. It says that they don't have good lifespans, so I'd definitely consider replacing it. I suppose the power resistor is a good idea to keep the voltage lower as described in that article, though it will cause worse ripple in your power supply.

Keep the selenium rectifier though, those things are real neat artefacts of the early-days of semiconductor research. Even though they're probably 50c on ebay.

>>1825788
I printed a case, used some scrap wire I found and put a 9v and 2 AAs in series to make the dumbest 12v battery on the planet.

Fear how little I value my time.

>>1826394
Very cool, would not have even known that’s what this was otherwise. I’ll definitety hold on to it

>>1826394
>>1826347
here's the final order before i hit send

>>1826394
>Keep the selenium rectifier though, those things are real neat artefacts of the early-days of semiconductor research. Even though they're probably 50c on ebay.

The stacks look really space-agey. I hate them because they fail and when they do, holy shit, but they have a unique aesthetic.

How do I test to see if pic related is working correctly?

>>1826538
in circuit, or on its own?

>>1826611
Well I just took it out, so on its own.

>>1826612
the first thing i'd check is whether any of the phase legs are shorted to the positive or negative rail(s). if you want to get more in depth then the pinout isn't breadboard friendly so you'll have to solder a few bodge wires to the pins. power the entire module off a 14-19v laptop or bench supply. a 12v may work if that's what you've got, but it's right on the UVLO threshold.
>tie VDD and the top of the phase legs to your supply's positive rail (through a series 1R or something so you don't let the smoke loose if the module's fried or you short the phase legs)
>tie ITRIP and the bottom of the phase legs to GND
>leave the bootstrap pins floating, which might work at these low voltages depending on the internal topology, if not then things get more complicated as you need to add caps and switch at a minimum frequency
>tie the gate driver inputs to GND
>tie one driver input at a time to VDD and measure the phase leg output to verify the operation of each switch

if you're trying to fix your dryer then this is a weird choice of part to test. if you want to repurpose this for /diy/ fuckery then i think you're in over your head if you have to ask how to use it.

>talking to my new uni's head of the EE/CE department
>doesn't know what an optocoupler is
uh oh

>>1826640
>career academic is retarded
say it ain't so

>>1825792
why not just add in a resistor to drop it to closer to 7.2V?

also would recommend using 555 with trimpot instead of the attiny unless youre looking to do some other IO stuff on the controller as well

>>1825792
also by mF did you mean millifarad or mircofarad ? millifarad is pretty big. you probably don't need it and depending on the freq of your duty cycle it could interact with the circuit, i would just take it out or at least demo the circuit with and without it to see if it needs it. were you adding it to try and smooth the movement of the motor?

>>1826662
A resistor would burn a lot of power, the motor needs up to 3A.
I have a bunch of attiny's I don't have a use for, I don't have any 555's.
>>1826663
1000uF, just to get a smooth voltage. I was basically asking (anyone who understands motors well) if the smoother voltage is preferred over the 12V spikes.

>>1826630
Fug I'm just trying to fix my AC.
I don't even have a spare power supply.

>>1826683
not gonna make it bro. what made you want to desolder this part in the first place? most failures are mechanical, even when the issue is with a circuitboard. last time my AC died i spend eons poking around with a multimeter and it turned out some retarded drain tube had backed up and flipped a float switch.

>>1826685
AC has weird failure where it would stop with an overcurrent error after a few minutes. Error signal comes from this part, so I wanted to check it.
It would be funny if it turned out to be something stupid like refrigerant leak.

>>1826689
>overcurrent error
overcurrent can come from excess motor load as well. causes that come to mind are gunked up motor bearings or obstructed intakes, but i'm HVAC-illiterate so take it with a grain of salt

>>1826668
Use something like this to get a high effective capacitance from a small value capacitor. Using the two transistors in pic related with the capacitor in pic related the effective capacitance will be somewhere between 1000uF and 9000uF with the exact value depending on the beta of the transistors. For your case since your current is high you should swap the small signal PNP transistor for a power transistor and also heatsink it. Keep the NPN a small signal type though. Your overall beta will be lower because power transistors usually have low beta, less than 50. That means you should increase the capacitor somewhat.

>>1826690
Well I wouldn't know how to diagnose a compressor.
The part I took out drives the compressor.

Where can i get those long heat sinks that are common in commercial power supplies and electronic loads?
I wanna connect a series of transistors to it (just like in commercial units) to streamline my cooling a bit

>>1826668
show us what you mean by 12V spikes
the motor is an inductive load and will create spikes in the voltage and this is normal
You should probably have a freewheeling diode or RC snubber in parallel with your motor though so when you turn off the power the inductive spikes don't fuck your power supply or other sensitive components in the circuit like the mosfet

>>1826899
Here's my original question: >>1825792

The question is whether I can power a motor with a higher voltage than what it is designed for if the duty cycle is lower than 100%. Or will it still die?

Not talking about inductive spikes in this case. The diode is already there.

>>1826996
The only things limiting a motor's maximum voltage are the wire insulation (probably good up to 300V easily), the heat output (not an issue if it's pulsed at a low enough duty-cycle) and the commutator if it's a brushed motor (probably not a big issue if you're below twice the rated voltage).

As for those spikes, by smoothing them out you're just powering the motor directly off 12VDC, which defeats the entire purpose of PWM in the first place. If you actually wanted to smooth it out you'd put the capacitor across the transistor instead, using the motor itself as the inductor of a low-pass filter.
But inductive loads like motors are perfectly fine with PWM so long as it's fast enough not to match up with the commutations/rotations or cause perceptible vibration/jittering.

>>1826996
>The question is whether I can power a motor with a higher voltage than what it is designed for if the duty cycle is lower than 100%
Look at the motor's spec sheet then?
Unless you know what sort of motor it is. Can't really say much without knowing more
I'm guessing you can't though.

>>1827021
It's butchered from a really old handdrill, so no.
>>1827020
That's about all I need, thanks.

>>1827029
There must be a part number or something written on it
Or maybe you can look at the circuit board to figure it out. That's all i got

Hi, I need to make a z-wave capable motion detector to control lights for just one mode, but I need something that can be listened to by a server constantly. The detector is like a switch, so I need to terminate it probably to neutral but needs a smart wireless sensor module, right?

>>1827021
>>1827033
It's a brushed DC motor, you can infer their specs pretty easily. If he's putting less than twice the recommended voltage through it, he's obviously not going to exceed any sort of breakdown voltage. So long as he keeps the duty-cycle limited for thermal reasons, there's basically no reason to believe that 12V PWM will damage the motor.
Heck, I bet it will probably run just fine when overvolted, though the higher speeds will wear the commutator bars and brushes quicker.

>>1827079
>it's a brushed DC motor
Thats my assumption but i am confused with his PWM business

>>1827085
It's from an old cordless drill, one that runs off ~7V (so probably NiMH or NiCd), it certainly won't be brushless. The only reason he's using PWM is to lower the effective voltage to it, hence the question. PWM is used on brushed DC motors all the time, just search for "DC speed controller module" on amazon or alibay, you'll see plenty of devices made exactly for that purpose.

Just made a breadboard mockup of this bicycle sequential turn signal circuit I designed. Works very well. Anything I could improve about it?

has corona brought the retail prices down on digi etc?

>>1827178
No of course not. There's more demand for components for use in medial equipment and not a lot of supply since many of the Chinese factories supplying electronics aren't open or are still at partial capacity. In addition to that don't forget to pay the import tariff that totally just fucks over you and not China in any way! If anything it's more expensive now than ever.

Was wondering if anyone could break down this circuit for me. The circuit can generate up to 400v I just can't explain why.

>>1827275
It's a very shitty boost converter. If you want to understand the basic operating principle just google boost converter for a simplified explanation of how the general circuit topology works.

>>1827278
I'm just curious what makes it a shitty boost converter?

The relay won't fit into the PCB!
What should I do? I bought 1050 relays to make electromechanical computing components (gates, latches, shift registers, adders, demultiplexers...) and am looking for an easy way to make circuits from them.
I was hoping these universal PCBs would do the job but they don't.

The relay won't fit into the PCB!
What should I do? I bought 1050 relays to make electromechanical computing components (gates, latches, shift registers, adders, demultiplexers...) and am looking for an easy way to make circuits from them.
I was hoping these universal PCBs would do the job but they don't.

>>1827307
i like how close it is to fitting. it's like it's saying "fuck you". you'll have to use jumper wires or design your own pcb. i'd suggest the latter because it's a good skill and custom pcbs are dirt cheap.

>>1827159
>Anything I could improve about it?

there was a kid in the neighborhood with something like this on his bike and it ruined his reputation forever coz all the other kids assumed he was a gay faggit. i have to admit that, i too, find bike turn signals both gay and faggit.

>>1827307
Can't you just bend the legs a bit so it goes into the holes? It won't sit perfectly on the board, yes, but it won't be a problem either.

>>1827307

10 seconds with a dremel: expand existing holes and maybe drill 1 or 2 new ones.

>>1827307

10 seconds with a dremel: expand existing holes and maybe drill 1 or 2 new ones.
if you make a steel template, you can cut that down to 7 seconds.

>>1827352
....you don't know much about PCBs, do you

>>1827354

what the noob calls a ''universal PCB'' is obviously perfboard. very soft. super easy to drill. you can snap with your fingers.

>>1827352
>>1827357
Thank you, I'll buy a milling machine and mill it

>>1827091
You've explained my question better than I could myself, thanks. And thanks for reassuring.

>>1827275
Using a 555 timer as a controller is more of a hack and not a good feedback controller. There are purpose-designed ICs that do the same thing at the same or cheaper price and do it better.

>>1827275
don't listen to them anon. i cannot explain well how it works but it is fun to try to figure it out yourself. the point is to have fun and not make a "better" controller since thats not your goal. if it was you could have just bought one but whats the point of a hobby then.

>>1827307
>1050 relays
holy shit, why do you need so many??

>>1827567
that's reasonable but he should know not to use it to power anything expensive. feedback is important, as are all of the extra protection circuits in switcher ics.

Im trying to find a RF mixer with an integrated LO. The mixer needs to work up 6GHz and minimum 1GHZ.
The only thing I am able to find is RFFC5062 is anyone aware of anything else?

I want to keep track long term, the overall time a machine tool has been on and I need to have a reset able time counter (like a trip meter in a car).

Is there like a small timer thing I can just stick in near the power switch so it counts when its on, and stops counting when it turns off?

>>1827883
www.mcmaster.com/electronic-counters/

ctrlf "hour meters", looks like there are a few resettable options but not many.

>>1827625
Not that he really could power much of anything with that. That crap boost converter can probably only source a few mA at 400V. No way it can handle more than 5W if even. Ultimately it's not too useful since most loads will require at least a little more current than that can source. Even the plate current for a simple small signal common cathode tube amplifier would probably load that down too much.

Can anyone recommend me a decent, non-chinkshit multimeter for hobby use?
Pic related has served me well but it's started going bad lately. Resistance measurement gets offset by 0-300ohm every time you turn it on and the whole thing started going haywire yesterday and displaying random shit on the screen.
I'm not autistic about accuracy, I just want something reliable without paying fluke prices.

>>1827625
oh i totally agree, i am assuming this kind of a project is for learning only.

>>1827997
i thought tube people would have a fit if you told them to use any kind of a converter. it's supposed to be a linear power supply with a bulky transformer and saggy rectifying tubes for warmth :D

Can I use one or multiple capacitors with a total of ~12-14V and a farad rating of whatever the highest I have are to function as a motorcycle battery?
>maybe
But where do I best put it, as before the regulator seems like it would smooth power delivery out way more than after the regulator, but then you have spikes way higher than 12V from the stator, I assume. Both before and after is also possible.
Thing is, I'd like to have lights when it's off and to not have strobelight LEDs at low rpm.

>>1828006
Get the 8008 or the 8009, they're good enough and even if you had to replace them every so often it would still be cheaper than a fluke or whatever.

>>1828033
theoretically yes. in practice definitely not. the energy density of capacitors is far far below that of lead acid batteries, and even supercapacitors fall short. you'd need way too many capacitors.

>>1828102
>the energy density of capacitors is far far below that of lead acid batteries

dont think that's a concern given that bikes dont use a starter motor. you basically just want the batteries to keep a few lights burning while you're stopped at a light. anyway, youtube has videos where people have tried this, so better to learn from experience.

>>1828058
Alright I'll probably just do this.
I had a look around but it seems like the market is completely infested with chinkshit anyway. I'd rather just knowingly buy chinkshit that end up buying marked-up rebranded chinkshit.

I need help with op amps.
On input I have AC signal in range -100mV to 100mV. How do I offset that to a 0.5V - 2.5 but using single supply op amp? Rest of the circuit is supplied by 3V so op amp would also be supplied by 3V. Signal frequency is under 1KHz.

Input comes from piezo sensor, for vibration sensing so it has to be non-inverting op-amp because in datasheet it said the sensor prefers 1MOhm+ impedance on input.

All tutorials and schematics I've found are doing it easily but with +5V -5V supply, which I don't have in this circuit.
Or they have single supply op amp config but their input signal is also offseted.

>>1828194
Well I was going to post this solution but it won't work because the bias network compromises the high input impedance of the non-inverting amplifier. Input impedance is about 50k in the pic. There's no way you can do this single supply then. You HAVE to buffer that input signal before you put it into any kind of amplifier and you need dual supplies to do that, any biasing will load down your piezo sensor. In theory you could just use really large bias resistors until you achieve a high enough resistance where the bias network doesn't load down your sensor but it's generally a bad idea in practice. Large resistors means more Nyquist noise. Maybe it isn't a problem for your application but I don't know, try it out. Actual circuit though, not a simulator.

>>1828194
A solution like this might work. Keeps your stable bias point and requires only one large resistor, 1M rather than 2x 2M resistors to achieve the same bias point. Should be a bit less noisy. That's the only other reasonably simple way I can think of without a buffer and dual supplies. If you wanted dual supplies you could make a rail splitter with an uncommitted op-amp and get +/-1.5V rails.

>>1828244
hmm this is really interesting, I actually have tried almost the same circuit (different values) in the simulator (falstad) but it didn't work. Op amps I have offered in simulator's menu: LM324 and LM741
I understand the theory in this circuit but it seems I need to find suitable real-life op amp model. What values should I look into when I read datasheets of op amps for this application?

Also why are you using polarized capacitor as C1? It can get damaged because of AC signal, am I right?

>>1828244
>>1828286
upper one on picture is using LM324.

I'm thinking about scrapping the idea of piezo and go straight with accelerometer with analog output, it seems they could do the job of vibration measurement

>>1828286
The LM324 and LM741 are not rail-to-rail op-amps and cannot swing all the way to the power rails. They will usually only get to within 2V of the positive and negative supply and when you're running off a 3V supply that is just not enough headroom. Also falstad is kind of a crude simulator. It doesn't really model many parameters of a device so it's not ideal for anything outside of some basic passive circuits.

C1 forms a high pass filter with the bias network. The larger the value of C1 the lower the cutoff frequency is and the less of an impact it will have on your signal frequency. Honestly 10uF is probably a bit overkill, the cutoff is in the ballpark of 15mHz and you could change that to 0.1uF without any major degradation in performance. To answer the original question no, AC does not hurt polarized caps. High value electrolytics are frequently used for coupling low frequency AC signals, typically audio. Reverse DC is bad but AC is fine. In your case feel free to change C1 to a 0.1uF ceramic or film though, it shouldn't matter. For C2 keep it at 10uF electrolytic or raise it even. The point of it is to block DC but be a dead short at your signal frequency. If it's too low it will have some impedance and will reduce the gain at your signal frequency.

>>1828302
C2 should read C3. The C2 I originally had in circuit was deleted when I realized you didn't appear to want your output AC coupled.

>>1828302
>>1828304
thanks a lot man! this cleared up so much for me.
what simulator would you suggest for newbie like me, a simple one that isn't too much of a complication to learn and use?

>>1828316
Multisim essentially designed for students. Has a good library of models and is fairly intuitive and easy to use. orCAD Pspice is probably the industry standard and is very powerful but it's got a bit of a learning curve. LTspice is free and some people will swear by it but I've always found it to be clunky and hard to use. The fact that your component choice is restricted to Linear Technology products sucks (you can import your own spice models though). I'd really just recommend pirating multisim or getting a student edition through school or something.

I can't find anywhere any information on what kind of power connector this is. It looks like a ATX P4 connector but much smaller

how fucked am I

>>1828006
>>1828058
>>1828162
You can get the eevblog one
>inb4 shill
but seriously, its the first big boy-ish meter I had. before that i was using uni-T trash
I don't remmeber who manufactures their latest one, but there was another that was basically a slightly modified and reskinned brymen 235 which is the one i have and that one's pretty nice for hobby use
I am eyeing a 5.5 or 6.5 digit bench top meter but thats mostly the consumer in me since there are few cases i can foresee needing either

>>1828343
Look through Molex's connectors.

>>1828376
read the book, sit in front of the lecture hall, and go do office hours. IF the professor asks a question, answer it so we all don't sit there in awkward silence. Befriend your peers and do homework together.

>>1828376
>7:30AM-8:20AM
haha good fucking luck with that shit

>>1828389
This, but also put your hand up and ask questions often, even if just to clarify things. It disrupts the class somewhat, but if you're here you're probably autistic enough not to care about that.

I'm building an A/V switch and I want to be able to route the audio to a headphone jack sometimes, so for that I would need volume control.
I hooked up the rca audio inputs through an MCP4631 digital potentiometer and into my headphones, and at full volume it sounds great (and loud) but anything lower makes it a crackly mess. So I tried adding some series capacitors just in case I was getting some kind of DC issues or something, and that made the mess sound better at very low volumes, but I still get a lot of crackle at the mid-range. What's causing this problem, and how do I avoid it?

Can I just use pliers for these?
https://www.aliexpress.com/item/32960322306.html

>>1825904
>Not using normalised ranges

I'm making an LED matrix. I don't want to solder a resistor for every LED, because it would be like 80 parts. So, I was thinking to do something like this: Vcc to a resistor, and then 5 leds in parallel to ground. Is this a good way? Constant current should make the brightness the same across the LEDs, but I don't know if that will cause any problems with the voltage being too low once I split it 5 ways parallel. Do I only need to worry about making sure there is 3V on the . Is there a rule of thumb for this sort of thing?

>>1828617
In case not obvious, I would have several columns of this in parallel.

>>1828617
The purpose of the resistor is to limit the current to the LED. If you're using constant current LED drivers, there is no reason to add series resistors to any LEDs.

>>1828640
I'm not using a constant current driver, I'm gating the anode of all of the LEDs with a mosfet so I can dim them with PWM. I already have the mosfet which is why I don't want to buy the driver, and would rather just find a resistor config that works well. I mainly just want them all to be about the same brightness

>>1828617
>LED matrix
Are you wanting to control the LEDs independently? Or not at all, like an LED panel? An LED matrix usually refers to a dynamically controlled array of LEDs. If it's just a panel for light output you want, shouldn't you just go for a smaller amount of more powerful LEDs? If it's a static image, then I can see where you're coming from, but multicolored LEDs will have different voltage drops so even in this case you'll need a resistor for each one.
How many LEDs are you using?

And yeah one resistor can limit current for multiple LEDs. There's some calculating you can do as to how many LEDs you can run on it before thermal runaway becomes an issue again, but I imagine the thermal limitations of the resistor will kick in long before that. A 1/4W resistor can only run 6x parallel 3V 20mA LEDs off a 5V supply, which is almost certainly safe.

>>1828643
they're all one color, and I want to light them all at the same time. But, I have one LED for each feature (they're getting nested in a 3D print) so I can't reduce the amount of LEDs by getting stronger ones.

Im looking to build an FM transmitter that isn't utter shit and has a stable frequency. So ive been looking into pll chips to stabilise the frequency.
Anyone recommend any pll chips that will do 80-110 mhz or where I can find them?

>>1828642
well now that I know that I've misread your question, I have no useful answer for you. This is the kind of thing I would just shrug and then breadboard test. Good luck.

>>1828656
PLL ICs are basically nonexistent past the CD4046 and similar ones, which only go up to a few MHz. Plus the only "PLL FM modulator" I've seen just uses the VCO by itself, outside of the loop, hence not having any frequency stability. I think you could technically get around this by adding a divider stage to both the clock-source and the VCO outputs (frequency lock must be maintained) and maybe adding a more sluggish low-pass-filter to the phase comparator output (then feeding both your signal and the filter output into the VCO with a resistor in series with each), but I've never tried it. Should bust out that one CD4046 I bought and give it a try I guess, but I'm pretty sure that the clock division ratio must be at least equal the ratio between the minimum transmission frequency (~20Hz) and the transmission frequency (~100MHz), which is a pretty big number, in the realm of what a 4.194MHz crystal RTC would use. Plus or minus a factor of two.

I'd instead recommend buying a digital frequency synthesiser IC of some sort, there's one that's rather popular for hams to use though it does output a square wave that you'd have to filter into shape. A more full-featured DDS would certainly be able to output a proper sine. You'd have to have the audio signal fed into it by an MCU, of course.

Alternatively, you might find some specialty FM modulating ICs (perhaps found in automotive audio senders) that happen to take analog inputs. If you do, that would be pretty neat.

>>1828655
Ah, interesting situation. Are they 3mm or 5mm LEDs or something like that? Have you considered a few series strings fed by a boost converter? You'd need a lot less resistors and wires. I'd also consider using an LM317-based or TL431-based or some other sort of current regulator circuit.

I think it might be possible to buy LED pigtails (i.e. with wires already soldered to them and heatshrink over the joints) with built-in resistors, so long as you look in the right location.

>>1828681
yea, just 3mm white leds. it's just for a prop for a friend so not really worth designing a whole circuit for, imo. but I'll read up on the boost converter and maybe that'll make it into my next project

>>1828689
The boost converter would just be a $1.50 prebuilt module bought from alibay or whatever. Or you could make your own if you happen to have an inductor and comparator/555 lying about.

>>1828681
Informative post anon.
I've purchased a frequency synthesizer module that outputs a square wave as you said. I've seen a lot of hams use it for their boomer morse code transmitters or AM transmitters but i have yet to see anyone frequency modulate it.
One way I thought is to feed the audio signal through a varicap somewhere in the module but how would you go about using a microcontroller to do it?

>>1828776
>how would you go about using a microcontroller to do it
Physically programming the frequency to be different for each audio sample. MCUs should be able to run fast enough for this to work. But whether the I2C/whatever protocol or the DDS can do so fast enough is another matter entirely.

>feed the audio signal through a varicap somewhere
Basically, a voltage controlled oscillator/VCO. The frequency modulation has to be done at the frequency generation stage.
Now that I think of it, you could probably use an MCU as a frequency counter and have it physically bias the audio-signal/VCO-input one way or the other (probably with a DAC) in order to prevent frequency drift. Like a digital form of frequency feedback that avoids the issues of having to have a phase comparator in a PLL. You could then use the MCU for tuning also, with a few buttons or a rotary encoder. Whether the audio signal is coming out of that DAC (from an SD card perhaps?) would be up to you. Of course, you'd probably need a large frequency divider, which at 100MHz might not be the cheapest thing to find. It might also give you a little latency in your feedback, but I don't think it will be a big issue.
But VCO circuits are a bit of a pain, especially if you're after a 100MHz sinusoid.

Now I'm wondering if you can use a feedback loop where you have an op-amp sending a signal to a VCO, the output of which goes into an FM demodulating IC, the output signal from which goes into one of the op-amp inputs. Then you put the actual audio signal into the other op-amp input. I think it would be prone to drift though, especially with the small bit of mod-demod latency, unless you also had carrier-frequency feedback somehow.

>>1828776
>frequency synthesizer module
I think the si5351B has a dedicated VCO port.
You may also be able to use a varicap with the crystal. Maybe you can modulate it from software too, with the I2C, idk

>>1828791
>But VCO circuits are a bit of a pain, especially if you're after a 100MHz sinusoid.
Thoughts on the Vackar oscillator?
Here's one I had lying around that should cover this guy's >>1828776
range

>>1828591
yes, thats what i've done. not the best way but it works. it is just tedious and sometimes there is a occasional loose wire that pops out and needs to be fixed which is annoying.

>>1828810
>Thoughts on the Vackar oscillator?
I started off this project trying out all these analogue circuits but I found they are very unstable by themselves which is why I turned to adding a pll to stabilise it. Truth be it when I started, I wanted this project to be mainly analogue and component level like pic related to learn and adjust and tweak the circuit.

>>1828791
>But whether the I2C/whatever protocol or the DDS can do so fast enough is another matter entirely.
Interesting, I would've assumed that doing it like that would not be fast enough or maybe loose too much resolution but interesting concept nonetheless and many other thought provoking ideas which sound a bit out of my league of actually implementing.

>>1828801
>You may also be able to use a varicap with the crystal.
I like this the most and I'm going to try it as soon as I get my board.

>Maybe you can modulate it from software too, with the I2C, idk
I've done a lot of software projects in the past but this one particular one where I wanted to limit the software.

>I think the si5351B has a dedicated VCO port.
In the end I might just fall back on one of these desu.

>>1828642
do you have a 10W resistor? is it cheaper than 80 x 1/4w ones?

>>1828868
>are very unstable by themselves
Really? from what I've read vackar was a bit of an autist about instability.
http://www.f6evt.fr/f6evt_fr/vackar_wholepaper.pdf
Were you seeing jitter instability, mechanical instability, or temperature instability?

>>1828234
What software is that simulation? Sorry for the stupid question.

>>1828906
You shouldn't wire LEDs in parallel off a single resistor like that. There's a slight variation in the forward voltage of LEDs. In parallel most of the current will go through the one with the lowest drop rather than being split evenly. If you're lucky the variation will be small enough that doesn't happen but it's not guaranteed.

>>1825788
I finished soldering an Arduino Punk Console but I’m only getting clicking sounds. Changing the potentiometers doesn’t change anything. My soldering joints seem fine, but something is obviously wrong. Any ideas on things to check? I did have to solder the 556 directly to the board.

>>1829195
Do you mean Atari punk console or is this something else? If it's not Atari punk we can't help without more information about it.

>>1829203
Yes, Atari. My mistake.

>>1829206
Is the speaker connected to the same ground as the circuit?

If this is your first electronics project you might have got chip pin numbers wrong.

Did you accidentally make connections you shouldn't have? In the Atari punk there are two chip pins that shouldn't connect to anything.

Double check you didn't use the wrong resistor and capacitor values.

Did you use linear potentiometers or logarithmic potentiometers?

>>1829209
Specifically I’m using this kit: http://jimmieprodgers.com/kits/apc/

I haven’t put it in an enclosure yet so it’s not grounding against something. One problem was that my speaker had four pads instead of two. I soldered the leads to the two outside pads.

I’m certain that I put the capacitors and resistors in right.

Got a bass amp for cheap recently but the sound was fading in and out. I was told this is because of ageing signal caps that I need to replace, as well as the supply filter caps. I haven't worked with electronics much besides from basic soldering. Are the capacitors circled in the pics the ones I'm supposed to change? And how do I know which ones to get? I read that you have to discharge them and this video makes it seem easy https://youtu.be/OTMUDOEt1N4 but is it as safe as he makes it seem? The amp has been unplugged for almost 3 months now if that helps.

Bridge rectifier anyone?

>>1829425
Ok now what the fuck am i going to do with this thing? Best idea I can think of is ditching the diodes and clamping power resistors to the heat-sink for a variable load, but I'm not sure how the diodes are bonded to the heat-sink. For now, it's just going to be a weight to lock my bike to.

>>1829326
shouldn't be any need to discharge those caps, they should self-discharge in a matter of days. The circled ones are the most likely caps to have aged badly, but if you've got the time and/or the equipment, I'd test them in a simple RC filter at different frequencies after desoldering to see if any are actually bad. This testing could be as advanced as running a frequency sweep on your function gen and feeding that to your oscope in X-Y mode, or as basic as just using an arduino or whatever as a programmable function generator and a DMM to measure the rectified output level.
I've never actually used the frequency sweep on my function generator, but now I know what to use it for.

Bad supply filter caps will only really cause 60/120Hz noise, not distortion and probably not fading. If you haven't heard such a buzz, the large caps are probably fine. The series high-pass / DC-blocking capacitors are definitely what you want to replace though, and it's quite possible that these aren't electrolytic but something like tantalum or film. Tantalums can definitely go bad.

As for replacing them, cross that bridge when you come to it.

>>1829425
>>1829434
Ok I'm using it as a weight to padlock my bicycle to so nobody steals it.

Guys, redpill me on reverse polarity protection and over voltage protection, specifically for electronic loads
I think i'm just going to make a simpleish DC one for now
I only just learned JLCPCB has board assembly service and not just maufacturing boards with no components. I'm slow no buly

>>1829515

dont be fooled. there's a huge conspiracy by Big Semiconductors. you dont need no stinkin' protection circuits.

>>1829515

dont be fooled. there's a huge conspiracy by Big Semiconductors. you dont need no stinkin' protection circuits on electronics ever.

>>1829515
just put a zener across + and - :)

>>1829515
You should reference this for reverse polarity protection schemes:
https://sound-au.com/appnotes/an013.htm
and he even has one for input overvoltage protection
https://sound-au.com/appnotes/an015.htm

For power rail overvoltage protection you could use similar techniques to those in the above article. Zener and TVS diodes will work. A better albiet more complex method would be a crowbar circuit. What protection scheme you should use ultimately depends on what you're designing, how likely it is to take an overvoltage, and how expensive the product is (or how much you value your design I guess for the case of a hobbyist).

Why the fuck do I do this shit? I should be working on my radio or some shit.

This is the most /ohm/ guy ever!

https://www3.nhk.or.jp/nhkworld/en/ondemand/video/4003123/

He has 95% fix rate!

Another, I'm in the mood to fuck up ads if anyone requests.

>>1828578
Sounds like you are overloading the source with too low an impedance. Try a voltage-follower circuit with an opamp to act as a buffer.

>>1825788
This might be a stupid question, but for tag strips, is it bad practice to attach parts to the lower part, where the eyelet is riveted to the board? I circled the part that I'm talking about in pic related. I'm working on an old amplifier and the person who worked on it beforehand crammed a bunch of wires and leads into one eyelet where it would be more convenient to solder it into where it is riveted in place. I just noticed that a lot of times people tend not to use that part.

would this work?
i think the lowest output voltage would be the left diode's drop so maybe i should add a voltage divider there

could i make a similar thing but a boost converter instead? tried thinking about it but cant find a way

>buy cheap chinese W5100 Arduino ethernet shield
>doesn't work
REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
Btw I saw in many places you could make it work if you solder 100Ohm resistors between the RJ45 pins, but I only have 220Ohm resistors. Will it work with them?

>>1829963
>but I only have 220Ohm resistors. Will it work with them?
Why not put them in parallel so you have a few 110 ohm resistors, which would probably be close enough?

>>1829980
>>1829980
that could work I guess since people have done it with other resistances as well (seen it done with 47Ohms)
Space might be a bit of an issue though, since the ethernet shield goes above the arduino and these resistances go on the downside of the ethernet shield so there might be shortcircuits and other undesirable shit.
Will probably just buy 100Ohms and be done with it.

>>1829217
chrome says that site has malware

>>1829945
It will just act in the linear region; the MOSFET will drop a certain voltage across it such that the op-amp/comparator's inputs are equal. You need positive feedback / hysteresis / a schmitt trigger on the feedback line. The result of such a circuit is the "self-oscillating buck converter", because it doesn't have any dedicated oscillator. They're real nice and simple for

As for references, I'd use a TL431 as a fixed 2.5V reference. Go as low as a single diode drop will likely be outside of the op-amp's input voltage range. If you want to get as low as a diode drop, use an NPN transistor in your feedback loop. If you want to get lower, I think you'd have to use a flyback transformer instead of your inductor.

best books for electricity and magnetism? pref rigor, but intro

>>1829943
>This might be a stupid question

yes.

>is it bad practice to attach parts to the lower part

super-obviously not.

>>1829943
>This might be a stupid question

yes.

>is it bad practice to attach parts to the lower part

super-obviously not.

>crammed a bunch of wires and leads into one eyelet

they stick in all the leads at once, so that way they have to apply solder only once.

>>1829943
Well, it's FR-2, which has a nominal max-temp somewhere between 100C and 200C IIRC. Because that's colder than your iron will be, it's obvious that any prolonged exposure to heat will weaken it. For the pads on dot-board where there's nothing but the adhesive of the lamination process holding them to the FR-2, trying to solder a couple of heavy-duty wires to the same pad would be a near-assured delamination. But in this case the tags are crimped in place. So I'd wager that unless it's hot enough for the adjacent tag to start reflowing, you won't decrimp any tags. But you will weaken it slightly, so if you're doing a lot of rework or resoldering for testing, I'd definitely lean towards using the intended holes.

Reasons to want to do so though are hard to see. The ends of the tag strips have a hole in them that's about the same size as the crimping hole, and there's enough meat around the holes to form a solder fillet that's plenty strong even without the extra depth of the crimping holes. When you consider that that extra depth will just be more mass to have to heat up with your iron, you'll be able to get your iron in and out quicker with the intended holes. The intended holes are also easier to get an iron in from almost any direction, as there's less FR-2 in the way.
And if you need more than 2 or 3 wires connected to the same node, there are commoning tag strips specifically for this. I usually only see them for ground/power connections, but there's nothing stopping you from putting a signal on one if it makes assembly easier.

>>1830195
sci recommends griffiths - introduction to electrodynamics

But for magnetism, for homework I'd just say design a helmholtz coil that can produce a 1-3Telsa field. That should teach you all you need to know.

I'm planing to make an extremely fast blast beat drum machine, as in a machine that actually plays drums. A was going to use motors for the drumsticks but then i though about using something simmilar to solenoid valves. I don't have any real experince with electromagnetic parts like that (except changeing a valve in a dishwasher) but the thought of having springs returning the drumsticks seemed like fun, and more simple in a way. It doesnt seem like it would be very hard to build but i haven't used electromagnets in this way so i'm not sure what type of voltages and magnetic material and such i would need in order to pull down a drumstick with enough force. Does anybody have any input our thoughts?

>>1829764
Cool video

What is the best place to source parts (small amounts) for guitar pedal building?

Also, would you guys recommend some of those component kits on amazon for things like resistors?

Also have some questions about a specific circuit if anyone can help.

>>1830477
>What is the best place to source parts (small amounts) for guitar pedal building?

first post answers that

>Also, would you guys recommend some of those component kits on amazon for things like resistors?

silly question. if you can get a billion resistors for 99 cents, why would you pay $1 for a pack of 5?

>Also have some questions about a specific circuit if anyone can help

google has all the answers.
nobody here cares.

>>1830477
there are some mid-tier suppliers that sell hobbiest tier stuff (in the OP). Professional sites are a PITA because they're impossible to browse and everything's obsolete. I personally use tayda, they're decent but sometimes a bit lacking. Arrow electronics, a few other seem also worth looking into
>component kits
if you're an absolute beginner, sure. If not, and price is an issue, just take the time and order what you want/need from digikey or mouser or newark (really, whoever has the cheapest shipping). elegoo's the only company I'd trust on amazon, I've gotten chink'd on amazon way more than on ebay

>circuit
post it

>>1830523
With regards to the kits, I just want to have some common resistor/cap values on hand. I'm not sure about buying chinkshit cap kits, but I don't see an issue with resistors, assuming the tolerances aren't a complete lie. Thanks for the recs though. Any particular brands I should avoid?
Im not super familiar with reading eagle schematics, but I noticed that the caps have slightly different symbols (comparing the 47uF to the smaller valued caps). I assume those smaller caps are those non-polarity sensitive ones; or if it even matters. Other than that I think its pretty straightforward. I was planning on breadboarding it first; after that I was thinking of using a veroboard; unless you know a better way of doing it. Thanks.

How is "Introduction to Logic Design" by Alan Marcovitz? I'll be studying this book for the summer and is wondering if there are better alternatives.

>>1830568

this is completely worthless in the age of the Arduino and the Raspi. Karnaugh maps in 2020? you might as well be learning vaccuum tubes.

>>1830535
>Any particular brands I should avoid?
uxcell and sodial

>>1830578
retard. Hardware and software are the same thing.

>>1830582

great, i'll be downloading a new GeForce RTX 2080 video card then.

>>1830535
If you get any cheap bulk packs of resistors from China just be aware that you should take the accuracy rating with a grain of salt. Most of them will be advertised 1% and a lot of them will meet that spec. But some will fall within 2% or even 5%, the tolerances are very loose. I've never found any worse then 5% in any packs I've ordered. Another thing to note is a lot of resistor will be advertised as or implied to be metal film. If you got a $10 pack of 1,000 resistors there's no way in hell you got metal film. You got carbon composition. Remember if it sounds too good to be true it is too good to be true. Even with all the faults the deal isn't terrible. These resistors will generally be okay for prototyping unless you need some kind of exotic low ppm resistor or something. I wouldn't use them in actual projects though. Buy the parts for your final design from a reputable vendor but for prototyping Chinese is alright most of the time. Same for caps too. Using Chinese brand caps will usually get you through your prototyping phase just fine. Don't use them in the final design. When you're buying parts for your actual design remember to always buy extras and eventually you'll have loads of spares of everything you could possibly need on hand and won't need to buy Chinese resistors and capacitors anymore.

>>1830578
Damn, is there any alternative textbooks I can learn roughly the same material from but more updated?

>>1830589
>If you got a $10 pack of 1,000 resistors there's no way in hell you got metal film.
You can unironically get 1000 brand name metal films off digikey for ~$7 if you're willing to deal with their shit search engine

>Mims III, Getting Started in Electronics
>Geier, How to Diagnose & Fix Everything Electronic
>Kybett & Boysen, All New Electronics Self-Teaching Guide
>Scherz & Monk, Practical Electronics for Inventors
>Horowitz and Hill, The Art of Electronics
I'm told that if I'm completely new to electrical circuits, I start with Practical Electronics for Inventors, is this actually the case? Because I see Mims 'Getting Started in Electronics' and I'm not sure which one to choose.

>>1830591

all you need to know about digital logic can fit in one 20-minute youtube video.
- gates: NOT, AND, OR, exclusive OR
- flip-flops: T, D and RS (JK if you're an eager beaver)
- using resistors and caps to make a differentiator and an integrator
- the Schmitt trigger, and oscilators made from same
- the crystal oscillator
- the counter
- gate speeds (propagation) and voltages of the diff families (ttl, cmos, etc)

>>1830622
Oh shit lmao. Do you have a video/link/book name to those then? Even if you don't, thank you regardless!

>>1830581
Thanks
>>1830589
Yeah I figured as much; I'll sweep em' with a meter to make sure. Good point at the end though. Thanks!

>>1830619
Get both. There is no one single starting point that's perfectly suited to you, and even if there was, we wouldn't know it. Just pick one.

>>1830619
I've read Mims, I tried Horowitz and Hill, and now I switched to Scherz and Monk. I'd say read Mims, it's short and fun and if you're completely devoid of any notion of physics and math it will be a soft start of sort; then read Practical Electronics for Inventors: it's a great book, has everything you need to know and some more, the math is extremely well explained, and the authors know it can be skipped altogether, but it's there in case you want to read it. Obviously you'll need a bare minimum of calculus if you want to understand the math. I'd say avoid th Art of Electronics: it was a well written book until it started explaining transistors and everything went to shit: I'm very disappointed; instead Practical Electronics feel much better for now.

>>1830667
I disagree. I think the Art of Electronics covers transistors, and most everything really, much better than Practical Electronics for Inventors. Practical Electronics for Inventors seems like it tried to be something in between a more conventional text book like Electronic Devices by Floyd and The Art of Electronics. In my opinion it fails at being either. It's not as detail heavy as the Art of Electronics and while it explains basic stuff like biasing calculations alright at best it's comparable to one of many other electronics textbooks out there. I don't really think it does anything particularly well. I think a lot of people don't like Art of Electronics because it cuts out a lot of explanation on basic fundamental math of biasing circuits in favor of a lot more theory and explanation of good and bad design practice. There's a lot more information on stuff like the Miller Effect, the Early effect, the small signal model, and more. Stuff that's very important to understand however is probably not the first thing you need to know. It's a very good supplement to a conventional electronics textbook however it is not a substitute for it.

>>1830617
Uh, no. Assuming you don't just buy one value and instead round out your parts drawer by buying each E24 value between 1 ohm and 10 Mohm (7 decades) that means you need 168 different resistor values. Let's say you get 10 of each for that price break discount which is actually 1680 resistors instead of 1,000 but whatever, price break. 33k 1/4W THT metal film resistor RNMF14FTC33K0, is priced $0.07200 per unit in 10 qty. Now of course not all resistors will be priced equally but we'll assume in that ball park. Hell, I'll even be generous and knock the price down by half $0.03600 which is already unrealistic but hey we're buying more resistors than planned so it's fair. 1680*0.03600 is a grand total of $60.48. You were only off by an order of magnitude.

>>1830681
>>1830617
Now to be fair, below 100 ohm and above 1 Mohm you could make a fair argument that you don't need EVERY resistor in the E24 series and you could quite reasonably cut back to the E6 or E12 series instead and save yourself some money. There isn't any sense in having ten of each 1, 1.1, 1.2, 1.3, 1.5 etc. ohm resistors in your parts drawer when the values are so close together. So you can save yourself some money but you even accounting for that there's no way you're getting the price under $30.

>>1830675
I talk as a complete novice in electronics (but not in studying engineering): while reading the Art I had serious difficulties understanding the explaination given, and after a bit of thinking I realized the authors just gave for granted some basic concepts; the wording too seemed a bit difficult for me, as a non-native speaker, and math-wise it tried to simplify things too much jumping from one concept or notation to the other with a bit too much ease for my taste. On the other hand, for now, Practical Electronics puts a lot of effort into being very accessible to everyone, so it has yet to take for granted anything.

>>1830694
>I realized the authors just gave for granted some basic concepts
Yeah, I'd agree with that. Even before transistors in chapter one a lot of basics like Thevenin's theorem and network analysis are glossed over very quickly. You are right that it's not the ideal book to start with for a beginner. Practical Electronics for Inventors or [Circuits/Electronics textbook of choice] is better for teaching the fundamentals if you are starting from nothing. I'd call The Art of Electronics kind of an intermediate level book. It expands on basic basic principles and dives into more nuances of practical circuit design.

>>1830688
>there's no way you're getting the price under $30.
metal film resistors are like ~$0.001 apiece and works in the megahurtz, wtf u talkin about

>>1830667
So do you feel that Mims book is necessary? Or could I jump straight into Practical? Yeah, I looked at the Art one and I honestly got lost almost immediately lol.

>>1830702
>metal film resistors are like ~$0.001 apiece
No they're not. What the fuck are you talking about? And nobody said anything about what frequency they work at, what the fuck.

>>1830710
>paying 10 cents for resistors
what the actual shit lmao

>>1830699
>I'd call The Art of Electronics kind of an intermediate level book. It expands on basic basic principles and dives into more nuances of practical circuit design.
Yes, I'll probably read it after Practical if I'll ever need some extra knowledge, but for now, and for anon, I think the best thing is Practical Electronics.

Also, one thing that I hated with a passion in the Art was the excessive use of footnotes, and how in those footnotes the author pitched in the X chapters book: it broke the explanation, it created confusion, it robbed space to the page, and it tried to sell a book within a book, which is really despicable. Moreover all the drawings were a page after where the text talking about them was located: forcing the reader to detach from the explaination to flip a page and look to the picture should be considered a crime.

>>1830709
It's not necessary, since Practical Electronics will teach you the same things a bit more in depth, but it's a really fun read.

>>1830711
There's the proof that when you buy a 1,000 or 2,000 resistor pack of "1% THT metal film" resistors from China that you are definitely not getting actual metal film resistors. There's no way they can sell them that cheap. They are actually carbon composition.

I found this on my disk but I can't remember what I was doing. This is supposed to be a constant current load but without the usual feedback loop to an opamp that feeds the fet. Here it is sort of a manual mode, I think? This seems to be working in simulation, but I am not sure about the definition, I forgot everything since then. i.e. what makes the circuit a constant current load? Is it supposed to keep the current constant regardless of the load R4? Or the voltage V1? In that case this schematic is not a constant current load, until something sense the voltage on R3 and varies the PWM dute cycle on V2, right? So technically that could be done with an ADC connected to a micro. So in theory this could still work without an op amp in the feedback loop? Also what is the purpose of R8 C2?

>>1830568
Personally I studied under Digital Fundamentals, I think I've still got the textbook somewhere but I never bothered looking at it. Got A+ anyway because the paper was simple and I'd had prior experience.

>>1830578
>Arduino and Raspi
lmao entry-level pleb detected
>vacuum tubes
Are still used in 2020 for real high-voltage and/or high-current circuits. The sort found in substations.

>>1830588
His point is that even if knowing boolean algebra and karnaugh maps to implement in hardware is near-useless, such boolean expressions are still used in MCU programming quite frequently. Even more so if you're programming FPGAs or CPLDs.

>>1830622
JK FFs are more relevant than RS and T FFs these days.
I'd also add to that:
>different types of ADCs and DACs
>sample rates, nyquist, etc.
>aliasing
>shift registers
>DSP algorithms?
>digital communication protocols?
>basic computer architecture
While not a part of digital logic, interfacing with serial or parallel data is important enough that I'd recommend learning of DSP and ADCs and DACs.
Ben Eater makes some good videos on communication protocols, error correction (real fun those ones), and basic computer architecture. Because otherwise you won't know what to do with those tristate outputs, I guess.

>>1830903
Banks of thyratron tubes are used in HVDC transmission. They handle higher voltage and higher power better than conventional silicon thyristors.
Klystron tubes are still in large radio transmitters. 1kW+
I think there are several different types of tubes that are still used for microwave oscillators, not just the magnetron in your microwave but there's backward-wave oscillators and TWT tubes and stuff.
All super niche uses for vacuum tubes, they are definitely obsolete in consumer electronics for sure outside of audiophiles and hobbyists that just happen to fancy them. But in some high power or mm-wave applications sometimes silicon just cannot beat tubes.

>>1830908
>thyratron
Those are what I was referring to, yes.
>klystron tubes
I had a feeling tubes were used in radio transmitters, but I hadn't heard of that name. Something to look into.
>magnetron
I guess those are vacuum tubes too.
Other tubes of note will be geiger tubes and scintillator tubes, which are both definitely still used. Not sure if they still make radios and the like with VFDs, probably not as they require a HV PSU board. I'd consider laser tubes (particularly CO2) to be vacuum tubes, and those are still quite widely used, as the power density of a lot of gas is hard to beat with a tiny piece of silicon. I suppose fluorescent lamps and incandescent lamps and maybe also neon signs and laser tubes are also vacuum tubes, not that they should probably be counted. Barometers and thermometers should definitely not count.

I find it really interesting how there's a silicon analog for basically every possible thing a vacuum tube can do, albeit with different limiting design factors that make one or the other more practical. With the exception of TV tubes and CRT tubes, I think the scanning of an electron beam in 3D space to make/use an analog TV signal isn't something that silicon can imitate. Scintillator tubes also fall into this category I think, but I don't understand the mechanism behind photomultiplication. Magnetrons and their electron cavities are also something I suspect is tube-only, though I suspect there's room here for some sort of MEMS micro-size vacuum pocket.

>>1830710
Quit being a chungus and buy 200

>>1830710
what in the goddamn fuck are you smoking
$0.0056 apiece

>>1830995

you probably have to buy 1K or 10K (of the same value) to get those prices.

>>1830995

you probably have to buy 10K or 100K (of the same value) to get those prices.

>>1830995
>minimum quantity 1,000

Are you going to order 1,000 of each E24 resistor value between 1 ohm and 1 Mohm? No. That would be ridiculous. They only cost half a cent a piece when you order 1,000 at a time. Whose the real retard here?

rewiring the basement in a 63-year-old cottage.

how often should #14 building wire be lubricated?

>>1830995
>>1831071
btw, that's $5.53 to get 1,000 of ONE VALUE of resistor at $0.00553/unit. Now multiply that by the 168 E24 values from 1Ω to 10MΩ and that's a grand total $929.04 to fully stock your parts drawer.

How I measure the current my remote control uses?
I tried sticking probes in the battery terminal but it reads zero.

>>1831124
Current measurements are made in series. You'll have to disconnect the battery at one end and put the meter between the battery and control.

>>1831124
it probably only draws a few uAmps. hard to measure with a generic MM.

>>1831128
Thanks. It draws -0.02mA. -1.3mA during startup.

>>1829434
Only use I can think of is for solar power really

Holy FUCK I have something that runs off 8V DC and adapters are impossible to find.
Do I just fix the brick? I really don't feel like fixing more shit.
What the fuck were they thinking why even 8V.

>>1831175
get a wart off aliexpress. $20 says a common 9V brick will work fine.

>>1831201
It's for a 15 years old Korean karaoke mic.
I'm not quite sure. I think I have a 9V brick though, might test with that.

>>1831175
>>1831207
Don't turn it on, take it apaaart.
See if there's anything in there that can't handle 9V, like maybe a tantalum cap or whatever. Again there probably isn't, but it's worth looking at just for the intrigue. Looking at the circuit of the BM800 microphone, I discovered that it really doesn't need a 24/48V phantom power supply at all, and using 12V will work perfectly fine, since it just runs it into a 9V zener diode anyhow.

I'd suggest that 8V was more common in the day of transformer-based wall-warts, and that it was a voltage somewhat commonly used in larger circuits that run off multiple transformer taps like audio amps. That's 5.7V unfiltered.

Solder in an LDO if you're concerned, it will drop the noise down anyhow.

>>1831017
>>1830710
>>1830702
>$0.1? oy vey, who can afford to spare $1 in these times? how can they get away with charging a whole $10? how will we afford our family vacation in the maldives when a single resistor costs $100?

I need to replace a dual output power supply (+30V and +60V outputs), but a direct replacement costs something like $3.5k, and replacing it with two independent power supplies would be much cheaper. Is there any situation where that wouldn't work? I can't think of any reason the dual output psu was used in the first place beyond convenience.

>>1831225
>a direct replacement costs something like $3.5k
this sounds like something you don't want to fuck up. post details. what's it powering and what's the current draw?

>>1825788
Is there an app for phone or computer that lets me experiment with circuits and trouble shoot? Something along those lines

>>1831245
falstad is the most accessible. i'd recommend you pirate multisim because i like it the most, but i can't defend that preference. be warned that all of these simulators will break frequently and give you terrible advice as to why they've broken. generally it's because the simulations are highly idealized and the sim doesn't like it when your model does unrealistic things like instantaneous voltage or current changes because you're missing parasitic passive components.

>>1831238
Yeah, context is good isn't it? It powers the printheads in a big ol' UV-cure ink large format printer; specifically the firing voltage and heating element for each head (21 of them in this case). The output channels are rated 30v @ 20A and 60v @ 10A. The machine is 12-13 years old at this point, and been on its last legs for several of those years, but need to keep it going another 3-4 months preferably.

>>1831251
>falstad is the most accessible
It's also the most useless.
>all of these simulators will break frequently and give you terrible advice as to why they've broken
True. I find multisim really struggles with switching power supplies. Almost always convergence errors. Sometimes I can resolve it. Sometimes I can't. Sometimes it's fine unloaded but when I attach a load everything gets fucked up. It's bad.

Amplifiers, filters, and other small signal analog stuff it tends to handle just fine though.

Is there any way to discover the output of a transformer if the primary coil is shot and it has no markings identifying it?

>>1825792
I'd probably just use an adjustable buck converter

>>1826643
yeah genuinely. I went through university for a MEng in Electronics, literally the one decent lecturer has joined academia after years in industry.

>>1831327
what do you mean by output? parameters of the secondary, how many windings? what is your end goal?

>>1831337
Voltage and amps, it's from an old radio and i want to replace it. Couldn't find the circuit on the internet.

>>1831339
But if the primary is shot, you'd need to repair it by unwinding the secondary first, and then maybe also the primary so you could find out whats wrong with it. In that case just count the turns and figure out the ratio. Or are they wound next to each other not one over the other? As for the max current, you can estimate it by checking the wire gauge of the secondary. Also if you unwind it and find out where it is damaged, you won't need to buy a new one you can just repair it. I've done this before and it is not that hard.

>>1831345
They're wound next to each other, i could count the windings but there's a lot of them so i would rather avoid that if i can. I believe the wire on the primary burnt at some point after the radio was plugged on a 220v socket instead of 110v. If i solder that wire would that make it work again?

>>1831327
Unwinding it or finding a service manual or schematic for the product it was in (may not give turns ratio but would at least show the winding configuration, any taps, and hopefully would show the output voltage.)

>>1831360
Yes you can solder it, it is very easy to do once you found the spot. Just strip and tin the two ends and solder them. You wouldn't need to count anything, as long as you unwind it rewind it back carefully. Since they are next to each, you'd only need to rewind the primary. The only complication is it could be soaked in that sticky varnish crap. that could make it hard to unwind it without damaging the wire. But hey you don't have much to lose. That still sounds easier than trying to guess the parameters by measuring resistance/estimating the length/ampacity etc.

>>1831381
i'll try doing that when i have the time, thanks a lot.

>>1831385
Sure, if you are stuck for whatever reason, post pictures, we might help.

>>1831388
i want to solder qfps with ilya!

>>1831217
It's a integrated mic that also acts as a karaoke machine, it has a lot of components inside.
The brick is also a smps I think.

>>1831541
Oh also transistor biasing might be a bit off when running it off 9V, probably not enough to cause anything to sound off, but it might get clipping distortion a little more readily. Maybe.

Hi, I'm trying to design a switched-mode power supply (SMPS) which consists of a full bridge converter with two MOSFETs as synchronous rectification (the circuit in the image). The four mosfet of the full bridge are driven in phase shifted in order to achive a zero voltage switch (ZVS). Should I add a circuit snubber protection for the mosfets or the zero voltage switch acts as snubber protection? In case I need a snubber, which type of snubber i can use without create problem with the zero voltage swich?

>>1831579
Fuck me it says right on the label DC 8-9V

>>1831604
It also runs off 2 AAs so I wonder why they even need 8V.

>>1831602
What, something like a zener diode or more precise shunt-regulator? Anything with a reasonable capacitance I'd be wary of putting before the rectification stage since it could cause ringing. So long as you clip any voltage spikes and take care of problems arising from the FETs not switching on in time, you should be fine.

Interesting circuit though, I'm interested in three things:
A: Why use a full-bridge to drive the primary coil when it only serves to double your voltage swing over a half-bridge+caps, something which could be accommodated by doubling the number of primary turns.
B: How do you plan on driving the rectifying FETs while keeping them properly floating? Have another winding or two powering a couple of op-amps?
C: Isn't that basically a bridge rectifier, but with two diodes replaced with inductors? It's something I haven't seen before, are there upsides of such a topology, aside from having to bother with two more ideal rectifier circuits?

>>1831632
Thank you for the reply, but the clamping snubber doesn't effect the ZVS condition?

A: I use a full bridge becouse the power is high and in order to keep the core size small

B: Yes the microcontroller is powered with another circuit that is floating

C: With a diode rectifier i have an horrible power lost

I am building a CNC controller box.
It has a few power supplies, microstepper drivers, a coupler break out boards, and a VFD in it.
Im reading this is susceptible to EMI and needs shielding.

I bought shielded twisted pair wires for the control wires, and the VFD to motor cable is also shielded.
Its an MDF box, one guy online went as far as using aluminum duct tape on the box for shielding.

Will putting aluminum duct tape onto an MDF box help shield from interference?
Should it be put on the outside? On the inside?
Looks kinda tacky, but if itll make a difference ill do it.

>>1831651
Why not just use a metal box?

>>1831653
It needed to be bigger than a standard computer case, and I had MDF laying around so I built it all from scrap for free. I looked around and didnt really see a suitable metal enclosure, and the few I did find were expensive.

If red is positive, black is ground and grey & green are data, then which is the negative? Is it the naked wire?

None of them is blower up?

>>1831676

the most negative wire is called ground here. so there is no ''negative wire''.
the nudist wire is the shield, which may or may not be joined to ground inside the equipment.
the nudist wire is almost always connected to the metal parts of the connectors at both ends.

>>1831676

the most negative wire is called ground here. so there is no ''negative wire''.
the nudist wire is the shield, which may or may not be joined to ground inside the equipment.
the nudist wire is almost always connected to the metal parts of the connectors at both ends.

>>1831690

they all look delicious. not a blowered one in the bunch.

>>1831758
>the most negative wire is called ground here. so there is no ''negative wire''.
Ground isn't the most negative - no single wire is "negative".
Ground is the "zero" of your circuit that you measure all voltages against.

>>1831758
I'm searching if the power board is dead but I cannot find any capacitor dead

>>1831776
There's not much to go wrong on that board by the look of it. Check the bottom for solder issues if you know the problem is there but otherwise check elsewhere.

>>1831764
> no single wire is "negative".

when every voltage present is positive w.r.t. ground, then ground is BY DEFINITION the most negative.

>>1831783
And when every voltage present is negative in respect to ground it's by definition the most positive.
What's your point?

>>1831781
I'm searching online if anyone have the same problem with the same model of TV
Many people fix it with a heat gun on the cip

But I don't have a damn heat gun for test

>>1831783
Technically true in the case where all voltages with respect to ground are positive but a lot of devices have negative rails referenced to ground and some devices have two or more grounds. You see it a lot with 4-20mA outputs. All the circuity driving the output VCCS are referenced to one ground and the other ground the the return for the loop and there's usually somewhere between 100mV and 2V across the sense resistor.

Either way considering ground to be the "most negative" point is rigid inflexible thinking that will create confusion and is generally bad practice. Don't do it.

>>1831785
>What's your point?

my point is the dumbass who corrected me is wrong. and i'm helpfully improving his mind.

>>1831795
>point is rigid inflexible thinking

it wasnt a generalization, but a specific observation about a specific event. LRN 2 REED!

>>1831789
Hate to be that guy, but buy a cheap adjustable heat gun. You'll be glad you have it. Boards like that are largely 'black box' without very specific information and/or knowledge. Best you can do is test the voltages vs what they should be at the connectors if you think the board you showed before is the problem.

>>1831809
Just did

Only one is reaching the 3,3v instead 3,5v
Everything else seems fine

>>1831758
>>1831764
>>1831783
>>1831785
>>1831795
>>1831803

All I wanted to know is which wire to connect to the negative pole of a led.

Dummy here, I have a project I would like help getting references to.

Primary goal: I want to set up this battery to power this air pump with on/off switch.
Secondary Goal: I want to manually control the amount of power that goes into the pump to dictate the flow of air, more or less air as needed.

My first impression is to simply strip the wires, and solder the ends to a switch to complete the circuit. But I'm a brainlet, and I want safety to be first and formost before anything as this is going to be portable and used for 8+ hours continuously. .

Anyone able to identify these caps?
They are on a cdi for a boat motor ignition system.
Early 1980's mercury 2 cyl.
The cdi has two seperate outputs for each coil. Only one cdi output will fire.
I can move the working cdi output and fire each coil individually.
If i series the coils both will spark.
If i switch the caps inside the cdi from one side to the other the spark moves sides.
This makes me think the one cap is not good.
Help a bro... i just want to go fishing.

>>1831830
>All I wanted to know is which wire to connect to the negative pole of a led.

ask a simple question, get a simple answer: the black wire.

>>1831830
>All I wanted to know is which wire to connect to the negative pole of a led.

when you ask a simple question, you get a simple answer: the black wire.

>>1831838
>This makes me think the one cap is not good.

pretty obvious conclusion.
but replace both coz they're probably both aged the same, so it may be approaching its life expectancy.

>>1831836
>My first impression is to simply strip the wires, and solder the ends to a switch to complete the circuit.

that's fine, but you only cut and strip ONE WIRE. then introduce the switch as shown, in series. i've seen noobs wire all three parts in parallel.

for speed control, you'd probably wanna buy a PWM circuit from Ebay (china)

>>1831640
>ZVS condition
That should remain unchanged so long as the sense voltage required for the MOSFET active rectifier occurs, which is should. However, this voltage drop will of course mean that it will dissipate heat when it's used. You'll need to do the calculations to figure out if this will be a feasible amount of (instantaneous?) heat to deal with. A more traditional RC or RCD snubber could be better in this respect, but could still have thermal issues if the transients are long enough.
Have you done any simulations to see what sort of transients you get?

>With a diode rectifier i have an horrible power lost
No I meant why not use 4 MOSFET active rectifiers instead of two and two inductors? Pretty sure it would save on space.

>>1831838
>Help a bro... i just want to go fishing.
Right in the feels. You ideally need a capacitance tester, the value is critical and if wrong can destroy the primary and thyristor. Best bet find someone to test the good one and replace both but be careful as they are usually 600 volt parts if not more. A schematic would be a godsend but from my experience in the motorcycle industry nothing but a hope and a dream.

>>1831838
I'll bet you can find the right part or even just a new CDI box if you search the year and HP of the motor. There is no way to identify the capacitance and voltage rating of the part from those part numbers if a google search turns up nothing.

>>1831838
Measure the capacitance of the one good cap? Reverse engineering the circuit might help.

So I checked the in and output of the PSU and seem fine

The red light work but every time i try to turn it on the light blinks and go's black,

Any place where I can get a motherboard for a LG 42 lb5500in Europe?

Apologies for the amatuerish question. My project runs on 12V DC. There are two circuits (12V and 5V) linked through a voltage regulator. My MCU toggles relays on and off which control two 12V devices. Whenever the relay toggles the relays toggle on/ off, the LCD screen loses/ gains brightness. Any ideas why this might be happening and how to solve it? Many thanks in advance.

>>1831913
insufficient current. What's your power supply rated at, and how much current do the devices require? What's the regulator rated at?

>>1831916
the power supply outputs 12V 1.25 amps.

the devices are two solenoid valves that (from what I'm reading from the datasheet) require 320mA each. The regulator is a through hole L7805CV. The datasheet (https://www.st.com/resource/en/datasheet/cd00000444.pdf)) says its current output is internally limited, but I'm not sure at what value.

>>1831814
>Only one is reaching the 3,3v instead 3,5v
Some load is probably pulling it low. Might be a short somewhere.

>>1831905
Same anon,

Is bake the motherboard legit?

>>1831923

first off, dont ever trust the current ratings on power bricks unless you've personally measured the DC voltage under full load AND watched how clean it is on an oscilloscope. if it says X amps, assume X/2 is the real value.

secondly, solenoids are just coils, and like all coils, they take an inrush current which can be several times larger than the steady-state rating of 320mA. the relays also do the same thing but less pronounced.

use a 4A supply and see all your problems resolved.

>>1831934
>Is bake the motherboard legit?

you're a noob. any baking you do will just make things worse.

secondly, 93% of the time the problem you're experiencing will be on the power board not the TV board. let me see what my crystal ball says................................ it says that the backlight is taking too much current so the power supply is shutting everything down and signalling an error using the power LED.

dont waste money on buying parts, buy (or steal) a new TV. if you were in Minnesota, this would be real easy right now.

>>1831950
thanks boss, appreciate it

I'm going through all the guitar pedals I made to convert them from copper stripboard to etched SMD PCB. I have a distortion pedal that sounds like the end of this song but shouldn't:

https://youtu.be/5Zdg4Sbefg4?t=536

It's falls into that farty/splatty bit-crusher sound at the end of any sustained note. I've done all the usual continuity checks, wiggled wires to pots, etc. but I can't pin down the problem. Has anyone dealt with this before?

>>1831950
Yeah the backlight are probably the problem, I will not give up yet

>>1831846

It worked. Thanks.

>>1831957

an op op-amp running at very low voltage can make sounds like that. however, this is just one of a thousand possibilities. start by measuring DC voltages on all 8 pins. 1,2,3,5,6 and 7 should all be around 4.5V. next step, unfortunately, needs a scope so maybe you can look at making a software scope. needs interface hardware and some software download.

>>1831971
Unfortunately, I already did that, as well as outright replace the op-amp. I am using a OP275 instead of the 4558, so I'll look into that. Thanks

>>1831971
Actually, now that I retest it, pin 4 is acting wonky. Like a loose connection alternating between 3V and GND. I'll test some more

>>1831957
>>1831971
Well I feel like a retard. The opamp was mirrored in the software I was using, so pin 1 and 8 were swapped, etc. For some reason the software kept the pins the same whether the chip is on the front or back of the board. Sometimes you just have to take a break for a minute, I appreciate it.

>>1831981
Wow, surprised it sounded like anything at all. Do you have a name for this new guitar effect you've discovered?

also kicad doesn't have that problem

>>1832136
I just made my own six-knob distortion pedal like two years ago. If the effect was intentional, it would be a bit-crusher. The pinout of the op-amp makes me surprised it worked at all, too.

>he doesn't bend the legs of his op-amp to slot upside-down in the IC socket

>>1831950
I checked the voltage without the light attached and measure 100v exactly
But attached it measures 105v
How does it work exactly?

Thinking of doing a power supply design for my bench as I currently have none. Proposed specs: 0-18V, 0-3A, three channels. Selectable manual 10-turn pot control or microcontroller control of voltage/current limits. I think it would also be nice to have a UART interface to control the system, USB interface, SD card reader/logger with RTC to replay or record voltage/current limits.

I've watched a bunch of videos on rolling your own benchtop supply. I'm thinking of basing it off of Dave's microsupply he did in 2011 but without the microcurrent capabilities, and using LT3083 instead of LT3080.

So far, so good. The only part that I'm not good on would be getting the required input voltage to the system from line power. Would I be best to get a fixed meanwell supply that could handle the required wattage of all outputs on at max at the same time?

>>1832385
>Would I be best to get a fixed meanwell supply that could handle the required wattage of all outputs on at max at the same time?

best? no. coz (1) they're switchers and so come with noise as a free add-on. pure supplies are linear from start to finish. and (2) it destroys the ability to have truly independant supplies, when one is shorted, they're all shorted. also you cant wire them in series, or wire them bipolarly.

>>1832385
>Would I be best to get a fixed meanwell supply that could handle the required wattage of all outputs on at max at the same time?

best? no. coz (1) they're switchers and so come with noise as a free add-on. pure supplies are linear from start to finish. and (2) it destroys the ability to have truly independant supplies, when one is shorted, they're all shorted. also you cant wire them in series, or wire them bipolarly. (which is the same thing)

>>1832385
Ideally you want a switching pre-regulator and then linear regulate that. It solves the problem of either dissipating a shit ton of power in your linear regulator and having horrible efficiency or needing a large complex expensive transformer with multiple secondary taps to achieve good efficiency.

>>1832596
I've been digging around in some of the older supplies that are out there such as the HP 6236B, it seems that they opt for the latter with multiple secondary taps.
( http://reza.net/files/hp-6236B.pdf see page 34)
So I guess I will either find a suitable transformer on Digikey--looks like that may be roughly $15-25 not including any pre-linear stage filtering caps, or go for something like this https://www.digikey.com/product-detail/en/mean-well-usa-inc/LRS-200-24/1866-3332-ND/7705026
The attractive thing about a transformer is that it makes doing a negative supply very easy, but I guess that could always be done by simply using one of the regulated voltages as ground in whatever circuit is being powered instead.

Sounds like I should do some more research on what is done in modern benchtop supplies. I wonder if companies are still publishing schematics with lab equipment manuals, I kinda doubt it though

>>1832164
>his components has pins
grandpa....

>>1831836
>>1831850
Regarding PWM, I understand how it works, and how safe it is compared to a potentiometer. However, all the products I've come across has the knob that adjusts the power on the circuit itself. I've draw up a shitty design of what I'm looking to do. I want the means to adjust the air flow on a part of my body I can easily reach.

>>1832636
I'm assuming you plan on buying an existing PWM circuit? It will have an input +/- pair of pins, and an output +/- pair of pins. Both those negatives may be connected, for what it's worth, and it's possible that your PWM circuit will just have 3 terminals, an IN+, OUT+, and GND, or maybe even the opposite IN-, OUT-, and VCC. You can just desolder the potentiometer and solder long wires between it ant the PWM circuit. It may use just two of the three wires, or all three, but I'd stick with three just to be safe. Note that desoldering the potentiometer may overheat the pot itself, as it's a bunch of metal parts held together with plastic, with some spring-loading between them. So you may want to buy a replacement potentiometer

Pic related

>>1832652
>So you may want to buy a replacement potentiometer
Would this be a one time purchase, or will overheating be an issue?

>>1832636
>all the products I've come across has the knob that adjusts the power on the circuit itself.

not all of them.
the wires for the pot can be extended a meter or two.

>>1832676
ooo, yeah, this looks promising. thank you, again, dummy here.

hello im here from /pol/ with what might be a dumb question: is it possible to build a resistance to electricity (like you can with snake poison)? the goal would ultimately be to be able to resist taser shocks. any information would be appreciated thanks.

>>1832733
Nope, sorry! You're going to have to take the taz just like the rest of us when you go on your false flag adventure my stormfront friend.

>>1832739
then how come electricians sometimes get shocked and survive? i thought it was built up resistance, or maybe some device like the ohm stuff that coudl draw away some of the current? i dont really understand a lot about this which is why im here.

>>1832748
ac mains only hurts if it goes through the right side of your body :)

>>1832748
Go back to your containment board.

>>1832754
ac mains = electricity? how do i direct it to the safe area of my body?

>>1832755
the faster you educate me the faster i can leave fren.

this is the ohm device thing i remember from physics class btw, not sure of its name but i remember it converts the electricity to heat instead.

>>1832758
Don't listen to those other losers man, they're just trying to fuck with you. Those are called resistors, as you probably remember from your class, they resist electricity. You could theoretically cover yourself in resistors to resist the taser shock, and I bet it would draw most of the current away from yourself. I think the only reason no one has made a resistor suit yet is the cost. Resistors are the most expensive electrical component you can get. You're looking at a thousand dollar suit, and that's just with shitty metal film resistors. If you can save up around ten grand, you'll be able to afford a suit of carbon resistors that will make sure NO electricity gets through. You won't even feel a shock. Hope this helps man.

My project, forgotten, butchered, all because of a white fuck boy. Fuck this country.

>>1832671
>will overheating be an issue
No, no appreciable power goes through the potentiometer. Another reason to replace the initial one is because some of them have poor build quality and a loose-fitting/no knob. The very job of desoldering a rigid component with 3 leads is often destructive, unless you can somehow reflow all three joints at once.

>>1832676
or yeah buy one of these

>>1832768
Inductors resist AC better than resistors do. He wants an inductor suit. Unfortunately it'll be about 10 times the cost. Don't bother with the small signal inductors. They'll fry with high voltages. You need heavy duty toroidal inductors with large windings that can sustain many amps of power. You also need a lot of them, basically a chainmail suit of toroidal inductors.

>>1832830
>basically a chainmail suit of toroidal inductors
The legendary Tesla Suit? I'd instead recommend a suit made from diodes, pointing away from the person. Diodes are one-way valves, so they'll ensure no electricity goes into the person, only out of the person. This way you'll be able to store this taser charge until someone touches you, upon which they'll get shocked instead. If you don't want to risk shocking your fellow revolutionaries, just go with the inductor suit.

>>1832837
The diode suit is pretty good but you need to be careful as a lot of diodes have kinda low reverse voltage ratings. A 1N4001 is only 100V and won't even protect you from mains let alone a taser. A 1N4007 isn't good enough for a taser either. You need high voltage diodes specifically in order to ensure protection.
Once concept I've read about but never seen implemented is a MOV suit. MOVs work well for transient HV pulses but I'm not sure if a MOV suit would work on sustained HV. Some testing needs to be done.

>>1832768
thanks man, that name is super stupid which is probably why i couldn't remember it (sounds so much like resistance). i don't know if i can drop ten thousand dollars on carbon resistors, is there something inbetween that's not as shity as metals but not as expensive as carbons? and where can i find directions or a guide to make something like this if they're rare?

>>1832830
>>1832837
>>1832839
what are inductors and diodes and what are the pros of using this over the resistors? as you've probably already understood i don't really understand electricity so you might as well be speaking chinese.

>>1832849
>where can i find directions or a guide to make something like this
You probably won't find any, this is the sort of thing that industrial corporations make to sell to contractors working on high-voltage lines. Hence, the designs and service manuals will only be circulated inside the corporation itself, with the contractors getting something like a user manual. That's the way a lot of expensive equipment goes, no need to provide any information to lowly individual consumers. I think I saw a glove of such a suit in a junk shop a few months ago though.

Diodes are like resistors but they only resist electricity in one direction. They can be cheaper than good resistors, but more expensive than bad resistors, all depending on what sort of diode or resistor you're talking about. Personally I quite like the look of Selenium diodes, but they're not even made any more.

Inductors are like resistors that start off really strong and get weaker over time, according to an exponential decay. For the short pulses of a taser, this would make them really good. They're more expensive than diodes or resistors, but unlike those you can make your own by winding lots of wire around something that conducts magnetism, like iron, or even better, a magnet. I've seen them made with over a thousand turns to them, but that's really slow by hand so I often see people doing it with a power drill or some other electric motor. They have to use really small wire. And here's a handy tip, you can bend/fold the length of wire in half and wind it starting from the bend, you'll get twice the number of turns this way, saving lots of time.

Well, technically you can also make your own diode with a cat's whisker (other mammals probably work), but a full suit would mean a lot of cats.

>>1832859
he's probably going to drown/skin cats now.

>>1832676
> Seller: happy_guys
>est date jun 11-jul 6
why do i feel I'm not going to be a happy guy

What manufacturing logo is this M?

Is it a older micron or marvell or microchip logo?

>>1832983
Micron. It's not like their logo has changed all that much.

Retard here, can I replace some rare thin capacitors with bigger ones by just connecting them to the pcb with some wires and having them hanging somewhere else

>>1832985
Yes, so long as the capacitances are sufficiently matched and the voltage rating is sufficient. And also so long as the caps you're replacing don't need to be particularly low ESL/ESR. Long wires means more delay/more inductance, so if they're bypass caps on ICs or noise suppression caps on noisy loads, it's best not to have them hanging on wires. Caps in high-frequency harmonic networks (filters, crystals, LC oscillators, etc.) or otherwise in high-impedance circuits are also cases where I'd want to keep the caps as close to the board as possible, as you'll end up with extra stray capacitance both between your capacitor's leads, and from them.
Also ensure that the wire connections aren't prone to work-hardening from vibration or wiggling. Do this by adding silastic/equivalent, using some sort of crimp connector to hold on to the wire's insulation, or fixing both the PCB and the capacitor such that there's very little slack in the wire. Though if the whole thing is properly enclosed this isn't a huge issue.

What's a good resource on reading up on transformers and basic design choices like cores, total sum of windings, distances, etc.?

Every site I found is kinda useless. For example I'm confused where the inefficiencies from air core transformers come from but everything I read just goes on about how they don't have core losses (duh).

>>1832998
Download an EE book from libgen.
Aircore is inefficient because the EM field is leaking all over the place so the flux is low as not a lot of juice is transferred from the primary to the secondary. Obviously any kind of a metal core is more efficient but it does have losses such as hysteresis losses and eddy current losses, and a tiny bit of the EM field is leaking too. But those losses are negligible compared to the overall advantage over the aircore. Seems pretty straightforward to me.

Under what circumstances would I use an RL filter over an RC?

>>1833095
practically speaking never. RCs are used because Ls are expensive and not ideal. if you need more complicated filtering then you're either working with RF or you'll use active/digital filters.

>>1832984
Thanks mate.

>>1833095
When you want a comparatively lossless filter, in other words, in power applications. If you have a class-D amplifier that's basically outputting high-frequency (MHz) PWM, you want to filter out the high frequencies to average the voltage to a proper audio signal. Using RC filters here would mean losing half your power inside the resistors. Basically the same reasons we use inductors instead of resistors in buck converters, I guess because a class-D basically is a buck converter. Class-D amps are perfectly valid choices to use as variable benchtop power supplies, and don't let anyone tell you otherwise.
Other power applications that LC filters are used in include speaker crossovers, AC line filters, and impedance matching networks. Sometimes you'll find a PI or T filter after a SMPS for extra ripple rejection. Strict matching networks are rare outside of RF cases though.

LC filters are also used when you want a high-Q passive band-pass filter, like in a simple radio tuner. For audio frequency stuff, you can make high-Q multipole filters (with highly customisable frequency/phase response) with enough op-amps, basically using active RC circuits as virtual inductors, but this isn't as much of an option at high frequencies. There are also active filter designs based on single transistors that you may see occasionally, the simplest being the capacitance multiplier.

As the other guy said, there's also the option of using digital signal processing, which can have even more extreme or diverse phase and frequency responses than active filters. But these are limited by quantisation error and sample rate, so these also aren't usable at higher frequencies. DSP is actually pretty interesting and has its own equivalent of the fourier transform, with simple algorithms describing the relationship between the input and output. Makes me want to buy a USB programmable DSP dev-board of some kind.

>AP6476
Here's an interesting IC/board, it's got BT, WiFi, FM receiving, and GPS receiving. Not sure how I feel about the UART though, but it should't matter with a GPS tuned XO.

Need a 10k digipot but don't wanna wait for ordered parts and can make do with min/middle/max for now. Submitting circuit for peer review.

>>1833535

how is that a variable resistance? it puts out a variable voltage instead of a variable impedance. try the 4016 or 4066 or 4051 instead.

>>1833552
Oh right, I should have given context. The wiper goes to an analog input of an MCU. As far as I can tell the original pot was set up as simple voltage divider.

Hey all, i'm replacing a bunch of crusty old Rifa X capacitors with modern equivalents and am wondering which brand to get - Vishay, Kemet or Epcos/TDK? Currently leaning on TDK...

>>1833535

there exist ''digipot emulators'' (see A) but if you dont have any, they can be salvaged from the hundreds of discarded toys in your closet. (see B).

>>1833535
You could make a 2-stage R2R ladder instead.
Also with your current circuit you should put 100k+ resistors across the optos, because when neither opto is on the output is High-Z. Unless you wanted that.

What could be the purpose of this circuit?

Noob here, am I missing something really obvious or is this 555 monostable circuit constantly going to be wasting current? Won't current constantly be flowing to ground through the discharge pin?
Wouldn't it make much more sense to use the output pin to charge the capacitor so that current is only flowing in that part of the circuit when the timer is actually activated?

>>1833802
Ok so I put a transistor between Vcc and R with the base connected to the output.
Idle current usage goes from 2.6mA to 1.9mA and the circuit still works, however the output time is like 50% longer. Is that just because the transistor is lowering the voltage across the capacitor?

My idea is this - A device between the power and a smart device (like alexa). The device automatically cuts power to the alexa after a configured amount of time. The device can be 'awoken' with a whistle/voice/snap/button and then send power to the alexa again.

This seems simple, a timer, input trigger, and relay. Where do I begin? I know nothing.

>>1833802
I mean sure but who cares? 555 was designed before battery powered electronics were really a thing. If you increase R and decrease C you can reduce the current until performance becomes too atrocious for your use case.

>>1833844
there is a low power version of 555

>>1833811
Just use a 100kΩ resistor and be done with it.
The quiescent current of a 555 on 5V is 333µA anyhow, they're pretty shitty to be using in 2020. Not to mention the output voltage never getting properly pulled up to 5V, the horrendous pinout, and the slight suboptimality of making a PWM circuit that does FM at the same time.

A SR latch with schmitt inputs and totem-pole outputs would actually be more useful, and could fit into a package with less pins. Also nicely sized diodes on the inputs so you could just put a cap in series with an input to use it as an edge-triggered input without having to worry about any voltages popping over the rails.

Can I drive a 12V 300mA 2-pin PC fan with 24V using 50% PWM?
Or am I better off using a linear regulator instead even though it pisses away half the power?

This seemed like the most appropriate place to post.
I was approached via LinkedIn for a job that pays twice what I make now.
I have every other skill they want, but I haven't soldered since middle school, 17 years ago.
They know that and said they'd teach me, but I'd like to be able to say 'hey, I wanted to show my interest by brushing up so I'm at least semi-competent.'
Are those Learn To Solder kits floating around online any help? By like Elenco or whoever.

Is the phase inversion on a TL072 or similar bad for the device? I'm about to make a FET tester that pulls down to Vss when unplugged, so would the time between tests burn out the amp?

>>1834066
>Are those Learn To Solder kits floating around online any help?

wouldnt recommend it. learning to solder is like learning to sex: hands on experience will only confuse you - better stick to reading and watching videos.

i want to replace a jack on my headphones, so i snipped the jack off and there are 4 wires, red, green, copper and white (white is probably microphone)
i tried to use a multimeter to find out which is which but i am getting strange results. I am assuming the bare copper wire is the ground, resistance between the copper and green is 500ohms, between copper and red 500ohms and between red and green 1000 ohms (makes sense since the path goes red wire -> L speaker -> ground wire -> R speaker -> green wire, so 500 + 500ohms)
I googled headphone impedance and it says it should be around 10 - 50 omhs,so my readings are way too high
Any idea why?

Been forever ago and i forgot what direction the + and - go on. Just to the left of the led on the top. There's 2 little holes for a female micro usb port. Somehow someone managed to mangle the port but everything else was fine. Now i cant figure out what way to put the new female port on.

Pic 1/2

>>1834052
>Can I drive a 12V 300mA 2-pin PC fan with 24V using 50% PWM?
no. it's a brushless motor with an internal controller that may fry if it sees 24V for even a microsecond. a linear regulator will waste 7.2W here worst case so heat sinking it will be annoying. get a buck converter module.

I want to make a cheap USB battery pack run at 3.7 volts instead of 5 volts. The little charge controllers on the things typically have a basic buck/boost converter to drive the things at 5 volts.

Would it be possible to change the oscillator components (probably the capacitor) so that it runs at 3.7 volts instead? I'm afraid this will goof the microcontroller and make it explode the battery or something

>>1834417
This?

I'm pretty intensely dissatisfied with my job (software, nuff said). I'm looking at becoming an electrician by trade and eventually just doing on demand work. Anyone here do that? Curious as to what Id be getting into

>>1834066
Don't bother with "learn to solder" kits, just buy generic simple kits. Like the standard chinky LM317 power supply kit that people use to test their soldering speed. One kit I had was that DSO138 or whatever single channel oscilloscope. Pretty shitty scope, but good enough for troubleshooting audio shit. Get 2 or 3 of these kits, taking plenty of time to examine your soldering joints (possibly asking feedback here). Then buy an SMD soldering test kit, because they almost certainly use SMD assembly at this new workplace.

But I'd say what equipment you have access to is just as important as what your technique is. A temp-controlled iron/station, flux, wick/sucker, copper wool, IPA, and good flush-cutters and small needle-nose pliers are what I'd recommend. But having a solid vice to clamp a PCB in and a couple of helping hands really help too. When you don't have to worry about your board shifting one way or the other even under moderate pressure from your iron, only then can you show your soldering potential. But that isn't to say I don't usually solder without that support. I have one of those twin-arm swivel helping hand things that's meant to hold a PCB. They hold up to no more than light pressure, they're useless for most work. So definitely use a vice. The helping hands can hold a component in place on your PCB, giving you both your hands to heat up and apply solder to the joint.

>>1829442
Late but thanks anon. What are the caps I need to replace then? I don't think I heard noise when I tried it so yeah I'll leave the large ones alone. I also don't have any tools for electronics other than a basic soldering iron

>>1834502
You don't have a scope, but you can still use software like audacity to analyse the signal, be it through a preamp and speaker and microphone, cheap usb sound card, analog optoisolated circuit, or just a careful direct connection to your computer with safety diodes.
Pic related should cover all your bases, though it won't measure DC at all. Even a cheap $5 DMM would let you measure that. Oh and maybe a potentiometer should be used to tune the gain of the buffer. The final resistor should have a resistance significantly higher than that of the potentiometer, and the impedance of the series pass capacitors need to be negligable compared to the other impedances near them.
A DMM would also be essential in ensuring there's no AC or DC voltage between the 0V of your amp and the GND of your computer. Using a laptop or phone running on battery power would avoid this question.

You could then use an audio output from your computer (or phone) hooked up to the aux input in order to probe it.

>>1834241
anyone?

Stupid question here:
https://aliexpi.com/mdzQ
Is there a legit difference between the metallic and golden looking connectors or is it just the look? Price is the same.

>>1834547
better conductivity but the difference is so minuscule it doesn't matter

>>1834552
Alright, thanks. Which one has the better conductivity even though it doesn't matter?

>>1834556
you think chinks would be coating contacts in gold to make them conduct worse?

>>1834241
The wires have a thin enamel insulation on them which you'll need to somehow strip off. Something like acetone should do the job pretty well. You should expect GND-L and GND-R to be about 32Ω, while GND-Mic will be non-ohmic (the mic circuit goes through an internal JFET amp/buffer). It's slightly possible that the impedances really are 500Ω, it would mean less than a 10th of the maximum power, but for IEMs this can be a good thing anyhow. I'd drive the speakers with a 0.1-1V function generator (or you know, wires soldered to a TRRS jack) such that you can ensure that the connections are made properly.

I imagine your guess as to the colors to be correct, but you should be able to strip the other end off the jack and measure continuity from there to the TRRS jack itself to be more certain.

>>1834282
Solder small wires off the 5V and 0V pins and send them to a USB socket off-board. Thankfully it looks as if the data pins are unused, except for one which may or may not be tied to a rail (probably the ID pin). Look at a pinout diagram to see which is which.

>>1834417
Should work fine so long as nothing on the PCB runs off the 5V output. But actually editing the circuit to output a different voltage sounds somewhat difficult, especially if it's a fixed-output converter with internal voltage sensing.
>capacitor
Changing the timing capacitor won't make a shred of difference to the output voltage, it will just change the frequency at which it switches. You'd need to change the voltage feedback or voltage reference side of the circuit. Read the relevant datasheet/appnote for the relevant IC.

>>1834622
>>1834622
>>1834622
>>1834622
>>1834622
>>1834622

>>1834467
>>1834216
Thank you both!