/diy/ - Do It Yourself

this thread's digits brought to you by the TEA1755 combination PFC/flyback controller, a slightly clever example of high integration

>>1621755
The fuck is this Lego pic?

>>1621755
>terminal blocks as mechanical connectors
clebber :DD

What's the go-to way to interact with the GPIOs on a raspberry pi?
the RPi.GPIO python library seems very limited.
All I need is the shiftOut function from the arduiono library or equivalent.

>>1621755
highly impressed at the accuracy of such a commonly available, relatively low-cost sensor as the BME280. in the temperature data I can see the 0.2°C rise from myself sitting down at my bench half a meter away

>>1621777
>go-to
depends on what language you're programming in, if any. you can actually configure and control GPIOs from shell script in a pinch, by manipulating /sys/class/gpio files
>limited
how so? GPIO doesn't imply any capabilities beyond setting direction, reading/writing value, and optionally turning on pullups/pulldowns. there is a library called libbcm1 or something, containing an extended API for the Broadcom-proprietary features of the GPIOs (timed sequence generation etc.) which might be useful to you

>>1621809
Perhaps he wants to do I2C or other serial communications protocols?

>>1621777
>shiftOut
that's like a 25 sloc function. should take you 15 minutes while crunk and watching porn at the same time. fine, use mine, no warranties
also consider the following https://pythonhosted.org/RPIO/

>>1621820
many of which have specific hardware and specific drivers to handle them. frequently, there are also command line utils and various bindings for popular languages. faster, more efficient, less fiddly etc. if you have the right pins available
in particular there's an spidev library for python that does just the sort of shifting that other poster wanted, once you turn on the SPI device tree overlay in the boot configs

The output current of 74xx 40xx IC should be limit with resistor or it's not necessary?

>>1621837
нeт блинчики

>>1621837
Are you driving LEDs or BJTs with them? If so, yes. Though some ICs (possibly some 7400s and probably some 4000s) have current-limiting drivers inside them, especially 7-segment ICs (drivers, decoders, decimal counters, etc.). To find some just go onto the wikipedia page for "list of 7400 ICs" and search for "decoder/driver".

If you want to drive a load like an LED, it may be worth checking the output sink and source currents, as some may have pullups that are too high-value for more than a few mA.

>>1621777
>What's the go-to way to interact with the GPIOs on a raspberry pi?
directly accessing mapped memory, like a man

>>1621840
I want to cut some rising edge a few usec
and DSP output current should not exceed 20mA, should i put a resistor before 7414 input??

>>1621845
Don't need anything before inputs, no resistor will be fastest. Inputs can handle any voltage within the rails, and are high-impedance so draw very little current.
>DSP
>schmitt inverters
Now I'm curious, what circuit is this?

>tfw just blew a FET
>soldered the flyback diode input to wrong source instead of drain
https://youtu.be/lT3vGaOLWqE?t=509

>>1621845
Modify the RC time constant.
Also, symbol of 4049 is wrong.

>>1621172
60Hz still visible in Italy.

I want to make a tiny coil gun for fun, but the problem is that if you power the coil the metal you stick inside will just bounce back and forward because magnets. So i need some way to detect the projectile at a certain position and shut the power off.
I wonder what kind of cheapo sensor would be fast enough? Something like arduino is just way too slow.

>>1621854
It just a buffer+deadtime and isolation between dsp and power stage

>>1621871
optical
many instructions

>>1621871
most such projects use an optical means to detect the projectile
>shut the power off
lots of traps for young players here, see existing projects for deeper discussion of the fun

>>1621879
>traps
pretty sure a flyback diode is all you need

>>1621865
I guess that 60Hz is from the US? Looks like I won't have to worry about that considering the S:N relative to that 60Hz peak and that I'm further from a 60Hz country than Italy. Judging by that 50Hz peak, I'll probably want a notch filter with a FWHM of 4Hz or so, probably something like picrel.
Actually looking at some simulations, I can probably plug one of these active filters right into mains without anything more than a few zeners and maybe standard rectifiers, which will make for an interesting experiment. Though I imagine I'll get a bunch of noise from switched-mode PSUs backfeeding noise into the grid.
If I wanted to design a circuit for listening to anything over a few hundred kHz I'd probably want to steer away from conventional op-amps and hit up some RF transistors. Feeding such a circuit into an upconverter and into an SDR might be a nice project.
For audio-frequency stuff I'd probably want to have some sort of custom filter where I can specify the pass and stopband(s) live, which sounds like a right pain for both software and hardware implementations.

I have this outlet switch and it has 3 contacts. The two brown wires just close or open the circuit for the live wire when you flip the switch, nothing strange going on there.

But what is the third contact for? The one that has the blue neutral wire connected to it? No matter in which position the switch is, on or off, the third contact never connects in any way to the other two contacts. So what is it for?

>>1621871
Photodiode. Or you can just use a fixed-width pulse which you manually adjust to maximise speed.

>>1621880
A flyback diode will maintain the current, not shut it off. You need to dump the coil energy into a capacitor; the higher the voltage, the faster it will shut off.

>>1621905
That's most likely an SPDT switch, meaning in position A it connects pins 1 and 2 together, and in position B it connects pins 2 and 3 together. Often for an on-off use, the output comes into pin 2, with the other pins tied to neutral and live respectively. This ensures that the device is grounded when turned off. Other times pins 2 and 3 are commoned to either the output or input, with the opposite sitting on pin 1, which has the same effect as just leaving pin 3 disconnected, though often it's soldered redundantly like this when on a PCB for added mechanical stability.

>>1621906
>You need to dump the coil energy into a capacitor
Capacitor and diode, right? Otherwise the power will just oscillate back and forth. Could a spark-gap work instead if you're feeling like a shitlord?

>>1621910
Like i said, regardless of the switch position, the third pin is not connected to the other two pins in any way

>>1621912
Oh, oops, in that case, I suspect it's just an SPST switch with a third pin for mechanical purposes, and so they can use many of the same processes/parts for their SPDT switches from the same factory. It could also be an LED or neon that you can't measure the continuity of because it has a higher resistance. In the case of a neon, the resistance would probably show as open circuit. Considering the switch has a clear top, it's somewhat likely. Can you scrounge up a datasheet for it?

>>1621915
Oh shit that makes perfect sense actually. I didn't even realize that. The switch has a light in it when you turn it on, so of course it needs to have a neutral wire connection for the light to work, so when you turn it on it connects pins 1 and 3 except there is a led with a resistor and a diode (or something like that) between them so they don't beep on the multimeter.
It's so obvious now, i can't believe it didn't click in my coconut.

>>1621765
wire wrap mother board

>>1621912
>the third pin is not connected to the other two pins in any way

yes it is, only you're not detecting it. it's near certain that it has a resistor in the 100-500K range in series with a neon bulb. the bulb looks like an open-circuit to a multi-meter. it only conducts at 70+ volts or so.

>>1621777
Use the bcm2835 library, its all you need.

>>1621898
>60Hz is from the US?
Mostly I guess.

>end up searching some symbol that contains a p mosfet on google for my library for 20 minutes
>none of the poos know in which direction the mosfet arrows and the diodes are pointing

>>1622001
If it looks like PNP it's N-channel
and the diode points to D
If it looks like NPN it's P-channel
and the diode points to S

I need some help with a VFD display driver.
It is the 10967P-50. It uses synchronous serial data. I'm using Arduino, and tried to use SPI, but i have several issues.

My code looks like this:

#include <SPI.h>

void setup() {

SPI.begin();
SPI.beginTransaction (SPISettings (64000, LSBFIRST, SPI_MODE1));
}

void loop() {
SPI.transfer(0x00);
SPI.transfer(0x01);
SPI.transfer(0x02);
SPI.transfer(0x03);
}

It should display @ABC, but it displays @DBF, looks like it is sendind one 0 at the end it mustn't. (in the datasheet, A corresponds to 00000001, but it displays D, which corresponds to 00000010).

It just don't work the way it should, and i don't know how to manage that.
I read SPI.transfer waits to receive data, and then it sends to the slave, I don't know if it may be the problem.

I tried using shiftout, but I have nothing in the display. I think clockspeed is out of limit with this IC, which supports 66kHz or something, and i can't manage to change the shiftout baudrate.

The next thing I'll try to do is just set the data pin and the clock pin "manually" in code to try sending data, so please stop me before I do it, because it wil be a pain in the ass.

Some advices? Excuse my english anyway, talking from Spain.

>>1622028
It displays BDF, and B corresponds to 00000010.

>>1622028
>mode 1
modes 1 and 2 are kind of unusual. try the other modes?
>SPI.transfer waits to receive data
SPI is a full-duplex protocol. the master always transmits and always receives, simultaneously. either end pays attention only when the exchange calls for it to pay attention

>>1622033
Mode 1 and 2 are the only ones that make something.

> the master always transmits and always receives, simultaneously

If it does simultaneously, it should not matter then.
I just finnished the charachters matrix. Im gonna play with the code.

>>1622049
I wonder if this is one of those weird chips that treats the active edge of ~CS as a bit clock, or maybe if your SCK state is wrong when ~CS goes active

>>1621910
>Capacitor and diode, right? Otherwise the power will just oscillate back and forth. Could a spark-gap work instead if you're feeling like a shitlord?
Resistor. Very large magnetic stuff have quench resistors that are put as load if something goes wrong.

When designing a pcb with mulitple voltages, is it better to make the majority of the power plane the highest voltage, the most used or...?

>>1622091

in order of preference
1 - the one that carries the most current (the lush)
2 - the one that goes more places (the gregarious one)
3 - the one with fewest power spikes (the quiet one)

>>1622091
most-consumed current. if that power plane is doing double duty as a reference plane for transmission lines, you might need to consider the prevailing I/O level(s) in your system

I'm a bit confused with handling impedances~
I need to find the capacitor's value so that the power factor is 1. Now, correct me if i'm wrong, but if it the circuit was in serie i would just need to put a -16j capacitor, but i guess that my question is how to find the value of the resistence in parallel.

>>1622139
I've tried using reciprocal but got a funny result so am confused more than anything

>>1622139
>I'm a bit confused
>100v @ 60Hz
>+ and - signs
I'm confused too.

>>1622139
Zcap = -j/(2πfC)
Zparallel = Z1*Z2/(Z1+Z2)
You evaluate the parallel impedances equation, multiply it by the complex conjugate, then since you know that the imaginary component is zero, you can fairly easily figure out the answer.

>>1621755
Noob question here. I had ground connected in my circuit, and the switch to +24V power was open. I wanted to make sure that the circuit was wired up properly, so I "shorted" the open power switch with my Ohmmeter to make sure that I would get infinite resistance. To my surprise, this closed the circuit (the motor driver LED turned on). Is this normal behavior for an Ohmmeter, or is mine broken?

How realistic is it to take out the CPU, flash drive, motherboard... basically the whole "computer" (System on a Chip aka SoC) on a mobile phone and replace it with another SoC?

>>1622225
Did the ohm meter survive the noob attack?

>>1622249
Yeah, I think so

>>1622256
Then it is normal behaviour.

>>1622269
Okay, thanks

>>1621879
hey dave didnt know you browsed this site

>>1622286
big gay clive is the only youtuber itt

>>1622287
the guy who disassembles $1 junk all the time?

>>1622143
1/(12+16j) = (12-16j) / (12+16j)(12-16j)
= (12-16j) / (12^2-(16j)^2)
= (12-16j) / (144-(-256))
= (12-16j) / 400
= (3-4j) / 100
= 3/100 - (1/25)j
To cancel it, the capacitor needs to have 1/Z=(1/25)j => Z=-25j, which works out to 106uF @ 60 Hz.

FWIW, the "resistor" is 12Ω in series with 42.4mH.

>>1622286
wish someone could have put him through the snapchat genderswap filter

>>1622272
yeah just don't put ohmmeters into live circuits

>>1621871
>Something like arduino is just way too slow.
You have a lot to learn newfriend.
First, find out which controller your arduino is using. Then read about analog comparator and interrupt in the reference manual.
And then you can determine if your (probably) 16 MHz system with the propagation delay of the analog comparator and the interrupt delay and whatever is fast enough for you.

>>1622399
did you just assume my onboard comparator

>>1622028
Kek, I wrote wrongly the part number. Its 10937p-50.
http://pdf.datasheetcatalog.com/datasheets/400/27307_DS.pdf

>>1622411
neat. looks like the only way to realign the byte frame is with the POR input, are you asserting that after you set up the SPI?

>>1622418
I'm attaching the POR pin into the RESET Arduino ICSP header pin. It looks like it resets the display just cool. I saw in the datasheet you just need to pull down that pin first and then you send the data.

Anyway, I discovered OKIC1937 is an equivalent, and I see some codes using it as https://www.mikrocontroller.net/attachment/298717/vfd.ino, https://forum.arduino.cc/index.php?topic=513312.0, https://www.mikrocontroller.net/topic/332928#new, so this afternoon I'm gonna have some fun.
I think the board where the chip is installed is doing some stuff with the digital levels, as it powers the 15V with 5V. Maybe some of the references need a look, but anyway, no big problem to fixing that I think.

>>1622421
ah cool, was thinking you should bring it under software control so you can make sure there aren't any uncontrolled clock-high situations being created causing frame skew

>>1622290
Is that the one who can use his tap water for etching?

wow ir leds are thirsty little shits, normal leds i use at 1.5V slurp like 30ma, and the ir led at 1.5V chugs 150ma like nothing

>>1622492

this. I have a lite bulb that scarfs 200 mA.

yay my mini radar microwave sensors are here from china
too bad i have no idea what to do with them
fuck i really have to stop impulse buying shit i see in youtube videos nearly every day

>>1621755
how difficult is this project: make a custom phone from scratch. get all parts (case, camera, radio equipment, SoC, touch screen display, speaker, microphone) and write all the firmware for it. then put grub + android on it.

>>1622558
hard. if you have to ask, it's too hard for you

>>1622558
>then put grub + android on it.

nice touch.

>>1622553
Power them all up and wait for the FCC.

>>1622577
writing a functional kernel is a bit too much work (read: a fuckton of work that was done better by someone else)

>open collector output have large undershoot
pull up resistor too low???

retard here
so i have this saturation graph for the 2n2222a tranny
if i understand it correctly, if i want up to .5A to flow through the collector -> emittor
And i have 5V power source connected to the base of the tranny, i need a resistor that drops 4.2V, to get 0.8V at the base. But to calculate the resistor value i also need to know current since R = V/I
But how do i find out what sort of current do i need to go through the base?

>>1622630
Ib ≥ Ic / beta, which varies wildly between individual devices
if you want a more precise current regulating/limiting action, you would need to build that separately

>>1622632
I don't want to limit the collector > emittor current at all, i just want to fully saturate the gate for up to .5A without wasting like 200ma going through the gate, when i only need say 5ma to fully saturate it enough to allow up to .5A currents

>>1622643
find the minimum current gain for your transistor (sometimes they are binned by it) and divide maximum expected Ic by it, then put that much current through the base. round up

>>1622653
I see, so at .5a it's 40x gain, so i need 12.5ma through the base which means
R = 4.2 / ((500/40)/1000)
R = 384 ohm

Does that make sense?

>>1622658
sounds good. that's a non-trivial amount of current, make sure you consider any voltage drop at your driver outputs in the base resistor selection. or just fuck it and use a MOSFET lel

>>1622658
>R = 384 ohm
No, 336Ω.

>>1622672
I rounded it up

>>1622630
>if i want up to .5A to flow through the collector -> emittor

if you actually do this you'll be discovering the difference between data-sheet max values and real-world max values. scorched fingers will help you remember the lesson.

>>1622028
Well, a few hours and it's doing pretty stuff. I added the moving effect so it doesn't looks that slow. Im driving via terminal, and the arduino lasts 1,1 seconds to display anything.
Well, I think I have another display like this somewhere. I'll test it and I'll see what can I do whit those.
Thanks guys

is cpu design gonna get more replies here or on sci?
anyhow im wondering what sorts of operations i want to have in the alu
so far ive got sum,xor,leftshift,and
im wondering if thats good enough to be turing complete because having more than 4 will fucktouple the amount of wiring i have to do
i know every operation can be done with nand/nor so is leftshift/rightshift/nand good enough?

if you guys have better ideas on which ones to choose please enlighten me

>>1622800
Here is much better. /sci/ is slower and not as many EE people.

How many bits are you playing with?

Technically as long as you can add bits (SUM) you can do anything. Maybe just do basic logic gate functions like AND, OR, NOR, ect...

At the end of the day it really comes down to what your function will be. Are you just making a bare-bones CPU for shits and giggles or are you making something that can really do some hardcore calculations?

>>1622809
8 bit, for shits and giggles
so shifts arent needed to be turing complete?

Hello, I only have access to sheet aluminum and copper plated is too expensive for this. I need to build metal bawkses to isolate circuits from their RF and external stuff. How would I weld them to Al boxes? Normal solder doesn't work for shit..

>>1622813
Olive oil as flux if you want to solder on aluminium.

>comparator hysteresis circuit works on falstad but not on spice
Why is that?
I used these calculations for my resistors on page 7
http://www.ti.com/lit/ug/tidu020a/tidu020a.pdf
My Vh is 3.6V and my Vl is 3.4V
At 3.5V the LED is supposed to be off (no current going through R3) according to the pdf
I have no suitable comparator right now and I'm left wondering why the spice schematic isn't working

>>1622815
Am I being memed?

>>1622843
It won't act as a flux.
It just suppresses immediate oxidation.

>>1622843
>>1622849
Just tried it. It didn't seem to work. Maybe it works on foil, but not on the sheets.

>>1622553
To be honest I find the PIR technology much more interesting.

>>1622751
>not 4channel
Nice work tho anon

>>1622851
Perhaps the sheets are sinking too much heat?

>>1622854
>sinking heat
Yeah I think that's it. I'll try pre-heating or soldering on top of a clothes iron

>>1622856
Reflow it in an oven?

>>1622851
You're being baited.
You need special solder and flux to do a satisfactory job of soldering aluminum.

If you're working only with aluminum, many hardware stores sell packs of aluminum 'brazing' rods.
They're great for 'welding' seams or attaching two aluminum parts together.
They're tricky to use but once you figure out all the necessary steps it's pretty easy.

>>1622907
I just wanted to join the copper ground with the Al casing. I guess a good old screw will have to do...

>>1622912
>join the copper ground with the Al casing.
This is the case where the 'soldering' kit is useful.
It's a soft solder like normal lead/tin but a different alloy.
The kit includes the solder and special flux just for aluminum.

>>1622811
What I meant is that cpu's literally do nothing but add 1's and 0's, really damn fast. You can do any operation as long as you know HOW to add those 1's and 0's.
Adding in commands that do it for you take a lot of work out of coding programs for it.

Shifting would def. be a plus, both left and right of course. I really couldn't suggest what commands to build into it, maybe check out an 8-bit RISC cpu and pick from those. Off the top of my head, I would say that bcf(Bit Clear F), bsf(Bit Set F), btfsc(Bit Test F Skip if Clear), and btfss(Bit Test F Skip if Set) would be kinda critical for decision making.

Some commands like multiply and divide would just be overkill.

>>1622912
>>1622914
how about copper electroplating?

>>1622959
>ow about copper electroplating?
not easy to do on aluminum (at home)

>>1622800
> im wondering if thats good enough to be turing complete
Turing-complete isn't good enough for a CPU. A CPU with no arithmetic operations but increment and decrement is Turing-complete; you can calculate x+y with
> while (y>0) { x++; y--; }
but that's going to be slow for large y.

At a minimum, you need to be able to test bits (AND) and set bits (OR, or AND+XOR). Left-shift one place is just x+x, but if you don't have a right-shift then you'd have to iterate over the bits, setting y[i]=x[i+1].

> because having more than 4 will fucktouple the amount of wiring i have to do
Deal with it.

> i know every operation can be done with nand/nor so is leftshift/rightshift/nand good enough?
No. A CPU which doesn't at least have addition is a joke. Being able to implement every operation in software isn't enough; the speed of the most common operations matters. There's a reason no-one ever built physical Turing machines.

>>1622800
I love cpu design. what are you making?
consider not just the ALU but what you're going to use to feed it. if you have a way to generate +1, -1, and 0 constant operands to replace one of the inputs, you can do a lot more. e.g. 0 - x = two's complement negation, -1 - x = one's complement negation, 1 + x = increment, -1 + x = decrement, x - 0 = test for zero/negative
in general, it might help you if you sketched out the structure of the rest of the processor (microcoded or hard logic? discrete logic or FPGA?) and programmer model (what address width? what registers/condition codes and how do you get at them?) along with the instruction set, all of which feed back into one another

>>1622811
a + a = a << 1. maybe make that an arithmetic right shift instead, or add a barrel shifter to one of your ALU inputs and replace the shift insn with something else (subtract/compare, the only diff being compare doesn't write back the result to a register)
btw an excellent and well-studied minimal CPU is the PDP-5, might look it up and crib some ideas from it

>>1622831
hey dummy, why you keep putting your loads on the emitter

I'm making a temperature control circuit using a variety materials to serve as the heating element. The idea is to read the resistance and correlate this against known temperature to resistance values.

The issue I'm running into is the method to sample and provide power at a high enough speed to keep the temperature with 1-2 degrees.

I have 2 PWM outputs with a 25MHz max stable frequency. One will be part of a mosfet driving circuit, the other a sampling circuit.

I think I could get around the capacitance of the coil by discharging it before it's sampled.

My idea is to run a short duty cycle for the sample, then this signal to ADC, and then the signal to the mosfet circuit, and have a digital pot to get me in the approximate range.

Is the digital pot going to be losing steps? I could reset it(calibrate) every few seconds since the application only requires it to be heated for about that time.

Is there anything generally wrong with this concept? I was considering doing a PID as this is the most accurate algorithm, but if it's overkill, I'd like any suggestions.

As far as software goes, I'd like to take 5-10 samples and lose 1-2 outliers, then average and use this value for the next possible cycle given software lag (this would be a problem since it's a SBC running some linux, probably debian).

>>1623096
>keep the temperature within
that is all physical-layer stuff that you need to build and try. it depends on how much heat the sample is absorbing and how much heat you can deliver to it
>digital pot
wat
>software lag (this would be a problem since it's a SBC running some linux
that's why many people use 8-bit microcontrollers to do the lo-math hi-precision scut work and just accept/return cooked values via some serial link

>>1623100
>digipot
digital potentiometer

I'm thinking of hacking at some risc os build to handle it at a lower level, seems like too much work for one person.

Another mc seems like a pretty good solution, thanks

>>1622660
>use a MOSFET
I love fets and i would like to replace my bjts with them since so far in 100% of cases i only used trannys to turn stuff on or off.
The problem is that BJTs come in this cute little 4mm diameter ball casing with 3 legs and fit nicely everywhere, while all logic level mosfets i found on ali are either in that huge case with the metal back and the hole on top for big currents or some tiny smd shits that are like barely a planck length across and you need the antman suit to solder them.

>>1623100
>>1623105
What specs should I be looking for when it comes to the mc? I'm thinking an integrated ADC would be nice, but what about flash and ram?

I've also come to the conclusion that if I do use a secondary mc it would also need to run the PWM so there is no latency between it, the SPI and the software on the SBC, am I wrong?

Anyone know any cool projects you can do with just two op-amps?
I got my hands on a pair of K2-W tubes and I'm trying to think of something other than a headphone amp.

I might just reverse engineer them and make a few more so I can do something more interesting, like a simple VCO.

>>1622831
>At 3.5V the LED is supposed to be off
No, it is supposed to stay at the state is was before. Transitions only happen at 3.4V and 3.6V.

>>1623109
Personally I'd have the speedy MCU doing everything except the data storage, and even that you could outsource to an EEPROM or flash IC, or even a micro-SD socket. Any reason you're using an SBC running linux in the first place?
Pretty sure STM32s have both an ADC and DAC, so you could ditch the digital pot, but I'm unsure how high-level they are for avoiding that latency you were talking about. You're sampling the resistance with a current shunt, right?

>>1623112
>VCO
That would be nice, or perhaps something else you'd want to use a transconductance amplifier for. Frequency mixing perhaps.

>>1623105
>>1623109
an STM32F030 would be plenty for this application. internal 8MHz oscillator + up to 48MHz PLL, lots of timers with PWM and more. 12-bit ADC, 4kB of RAM and 16kB of flash. TSSOP-20 package though, but maybe its rather elaborate hardware timer suite and lazy-mode Cube config tool would still prove helpful
the STM32F103 is all that + 72MHz core + a real 2-channel DAC + you can get them on 0.100" large-print module boards for grandpas cheap as chips
>wrong
wouldn't need to, you could just monitor the pi's PWM and step in when it steps out, but it would make life quicker and safer to centralize the entire control loop onto the MCU

>>1623108
is SOT-223 too small for you? Pic related, 12 cents each at LCSC

>>1623123
>SOT-223
i already have some sot23 fets and those fucks are tiny as hell, i could maybe solder them if i tried really hard, but the main problem is that i need the fets to be THT

>>1623126
Being real, I don't think you'll need any higher a PWM frequency than 10kHz considering you're dealing with something with as much hysteresis as a heating element.

>>1623127
it's not about that, i make my projects on perfboards and use wire wrapping heavily

>>1623133
So PWM frequency/gate capacitance isn't a limiting factor for choosing a FET?

>>1623136
Well in most cases i use the fet as a simply on or off switch to for example turn a pc fan on or off.

But in few rare cases, for example when modulating IR led signal i need to switch the gate on and off at 38KHz but i assumed that most fets can handle that with a big enough pull down on their gate

>>1623139
>pull down
No, you want a totem-pole or asymmetric variant of such when it comes to high enough frequencies. Though if your pulldown results in minimal switching losses in the FET and doesn't sink a significant amount of heat to ground via the resistor I guess it doesn't matter, which is likely the case at these frequencies and modern MOSFETs.

>>1623126
>need THT
SOT-223 are very close to 0.100" spacing, you should be able to work with them just fine on a perfboard if its holes are plated-through (which the cheap chink greenies are)

>>1623126
Just filter MOSFETs for TO-92 package.

Here's the cheapest one on LCSC - 20 for 50 cents:
https://lcsc.com/product-detail/MOSFET_Changjiang-Electronics-Tech-CJ-2N7000_C9114.html

>>1623149
That one likes great, it's smol, only 3v vgs and cheap as dirt.
i will tried to order a lot from ali and see, thanks

>>1621845

What program are you using to make the schematics?

>>1621905
If its a light up switch, this is the wiring diagram. Just bought one for a project and was wondering the same thing.

Do switching PSUs have interference with small electronics?
Like these:
https://www.ebay.com/itm/5V-12V-24V-DC-AC-1A-10A-30A-50A-70A-Switching-Power-Supply-Adapter-For-LED-Strip/361924688555
I have a grbl micro controller that will be running 4 steppers on a CNC I'm making and my box has all the shit next to each other (pic related)
Should I separate them into different boxes? or will it be able to control steppers fine?
I saw mixed things, I've never had any issues but idk if in the long term it'll cause issues.
THanks

>>1623161
Also the reason I ask here is because there's too much mixed answers everywhere else.. Hoping someone has real info about it

>>1623153
its Rds(on) isn't gonna be pleasant for a 500mA load and it will die quickly without a heat sink (maybe even with). I think you want this one instead
https://lcsc.com/product-detail/MOSFET_Wuxi-NCE-Power-Semiconductor-NCE0106Z_C191374.html

>>1623161
>Do switching PSUs have interference with small electronics?
yes
>do stepper drivers/motors have interference with small electronics?
yes
>is it enough to matter?
unless you're trying to receive radio signals bounced off the moon, probably not

>>1623165
>unless you're trying to receive radio signals bounced off the moon, probably not
lmao ok thanks
I'm going to use cat6 STP (not UTP) to transfer signal for the steppers just to maintain good signal

>>1623166
>not hand-braiding your cables out of strands
>2019
y u no
>signal
I really, really hope you don't mean "power" here. any but the smallest steppers are going to lose drive in that thin cable. the ohms/ft column at https://www.powerstream.com/Wire_Size.htm is educational
I'd consider using microphone cable or something similar. it's usually thiccer and super flexible, which might be a benefit in your machine

>>1623165
>I think you want this one instead
Looks better, but nobody on ali except one shady seller with no sales offers it.
What parameters do you use to search for them? the to92 package, and then some sort of rds value? I am struggling to select a filter that is something like "with 3V at the gate you get up to 1A at the drain-emitter"

>>1623174
Why not just order from LCSC?
They're pretty good and cheap.

You just need to find some more shit you need to save yourself the handling fee.

>>1623169
I know how to check wire gauge & amps, thanks.

>>1623174
Rds(on) at load rating vs. case size. P = I^2*R, so you want an Rds(on) low enough to not dissipate too much power in the MOSFET for its case size and generate too much heat. a TO-92 case has a thermal resistance to ambient of 350°C/W which means it gets 350°C hotter for every watt dissipated (extrapolated)
assuming 0.2 ohm Rds(on), 0.5*0.5*0.2 = 50mW lost in the MOSFET at 500mA, that's a 17.5°C rise, warm to the touch
now, assume 2 ohm Rds(on), same load current, 0.5 * 0.5 * 2 = 500mW lost in the MOSFET to heat, that's a 175°C rise, will burn your finger if the MOSFET doesn't die first

>>1623119
>it is supposed to stay at the state is was before
according to spice the LED was off at >3.6V so it shouldn't turn on
I've been trying to figure this out for hours but I just can't fathom it because spice seems to contradict the pdf where it says: Vin < 3.4 causes Vout to transition to 5V

>>1623248
>trying to figure this out for hours

5 minutes with a breadboard will give you the definitive answer. low-tech is sometimes better than those time-saving simulators coz reality is bug-free.

>>1623283
>coz reality is bug-free.
The term "bug" came from literal bugs shorting out shit.

There's much more shit that can interfere in the real world than in a simulation.

>>1623248
show stimulus

>>1623248
I would use a tringle-shape voltage to test the transitions at 3.4 and 3.6 V.

Suppose I want to make a device which is going to be programmable. It's a development board, for kids, so that they can use motors, sensors, etc. Nothing really new right there.

What would be the best approach to make the process of writing code, compiling and uploading as easy and fast as possible?

A) Using eLua or microPython
B) Using a cloud compilation service and uploading the code to the board via a bluetooth serial IC

In both cases the kid wouldn't write code on their own, just draw a routine in a visual programming language like scratch or some unknown flowchart, which would generate correct code. I think for a MVP the first approach sould suffice, but if I have the venture capital money to do it, alternative B would be better.

>>1623292
I'd go with an interpreter and a serial shell so the kid can quickly try out stuff.

>>1623122
The user peripherals and IoT stuff pretty much. I refuse to do this shit myself when I already have ti for 5 dollars.

How the fuck are they selling these things for a buck fifty. This replaces like 4 individual different circuits I would otherwise have to make.

>>1623123
No 2 channel DAC...?

>>1623283
I will see if I have a suitable comparator somewhere

>>1623287
What's that?

>>1623291
I tried a DC sweep from 4V to 3.2V but the transition was instantanious. I'm not at home right now but I will try and see if the triangle shape voltage will make a difference

>>1623302
fugg, you are correct

this might be retarded but would it work? adcs are SPI, low-res, v cheap and fast. to multiplex big led array to display moving pictures n shiet.

do the pros do it differently? i dont want to buy a 10 dollar driver ic. cheers.

I need something that is a linear pot but I need it to be loose, like I need it to be so loose that if it's tipped vertical it would fall down under gravity. It's for an autofocus for a CNC laser, I've tried just springloading a regular pot but even with the minimum force required to bring the pot down there's still too much pressure exerted on the workpiece if I'm using lighter materials, it moves the piece around

>>1623345
>do the pros do it differently
usually a dedicated LED driver IC like Pic related, or maybe one that has PWM built-in, driven by an FPGA board that speaks HDMI on one side and many shift registers on the other

Is 10e-6 sample time too much for 200MHz MCU???

>>1623364
>a linear pot but I need it to be loose,

pots need friction. if you want frictionless, that means using a rotary encoder. for example, a mouse wheel with the notch spring removed.

>>1623396

completely depends on the MCU. it's a simple matter of figuring out the instructions needed to do one sample, including loop overhead, then research how many microseconds per instruction, then add them up. if you get 6uS, you're good, if it's 15uS you SOL.

LC oscillator guy here. So the wobbler gives out a clean 50Mhz wave with 0.8Vpp. I need to decouple and amplify it, is there a way to make an AGC for a common emitter amplifier so the wave is always at the same level?

>>1623396
no

>>1623364
if you don't need absolute position at startup, linear encoder?
if you do, maybe a capacitive or optical sensor based on Gray code, see https://www.tinaja.com/glib/h_hack_me/hhack_9_85.pdf

>>1623435
>>1623364
good input, I'm building it around a microcontroller so I can take a reference starting position, I'll try an encoder approach

>>1623441
Work in progress.. The loop gain of the ECO is set by its emitter current which can be used to stabilise the amplitude below the clipping level. Look at the circuit for a while..

>>1623485
It'll take a while for me to understand that. Analog is hard.. thanks my man

>>1623495
>>1623485
I'm thinking with my almonds here, but if I rectify the oscilator output, I could feed that to an opamp and use it to control a cascode amplifier right? Even thought the signal is 50Mhz the opamp wouldn't care because it'd be comparing DC-ish signals.

>>1623519
Yes, that should be possible.

>>1623345
I'd agree with using a driver IC, you should be able to get five for a dollar or so from the usual scumbags.

Also if you do want to go ahead with your circuit, I'd definitely replace the first transistors with PNP transistors (in common emitter configuration), the LEDs will hardly light up the way you've drawn (common collector configuration). The same applies to MOSFETs. You'll likely want base resistors on all your BJTs, and I don't think you'll need those pulldown resistors since LEDs will act as their own pulldowns.
But since you may have more than one LED from the same row on at the same time (I'm assuming you won't be strobing the LEDs one at a time) you probably can't use the BJTs for current limiting, and will have to have a current-limiting resistor for each LED. Probably. That puts you at 8 transistors and 24 resistors, which should work fine, but a dedicated LED driver would probably be more elegant. If you want to strobe the inputs then you could get away with 8 resistors. With MOSFETs you could get away with 4.
So the question comes down to, what sort of digital outputs are those? Just parallel ADC outputs like I'm assuming? Because that would be highly unusual in this decade.

>>1623580
I meant DAC sorry!

>>1623584
that's even worse tho

I'm looking for an IC that can detect an arbitrary change in signal voltage. For example, if the input changes from 4V to 1V across a few seconds, the IC would output 3V. Then later if it dropped from 5V to 1V, it'd give me 4V out. I'm trying to avoid a microcontroller here.

>>1623591
you have to define either a sampling interval or a continuous bandwidth. you can use a differential amplifier for both cases, preceded by a sample-and-hold circuit in the former case.

>>1623595
>sample-and-hold circuit
Perfect, that's what I was looking for.

>>1623602
bear in mind that sample and hold circuits will drift, and that gets hard to manage if you want to hold the value at a decent resolution for longer than a few seconds. if you need a long sampling interval then an adc is still your best bet.

Can anyone help me. How do i calculate the capacitor frequency response in the circuit in the pic

>>1623607
C1 100nF
R1 240k
R2 25k
R3 690k
R4 165k
R5 17k
R6 475k

>>1623607
Draw a diagram with the op-amps replaced with virtual grounds, then figure out the transfer function with Millman's theorem and Kirchoff's laws, then plug in the values.
Or just google "bandpass filter transfer function", click on a useful looking article that shows the correct topology (IGMF), and read the article.
I'd check out:
http://www.ece.tamu.edu/~kentesar/ELEN457/ELEN457_4.pdf
pic related
Just multiply the transfer function of the first filter (C1, R1, R2, R3) by that of the second filter (C1, R4, R5, R6).
Depending on the values you may have a particular shape to your transfer function (like a Chebyshev or Butterworth, or in this case possibly a Bessel going by your image title), in which case you could use a lookup table that will specify your central frequency and Q values, among other things.

>>1623625
wrong pic, oops

I'd like to record sound to my computer via multiple small piezo-electric microphones/transducers. I'm interested in audible frequencies. Questions:
a) I can't find any piezo summers or the like that reaches below 1.4 KHz. Is that... unusual? Or do they just require really high impedance?
b) what's the easiest way to amplify the signal and carry it into the computer in a way it understands?

cheers

>>1623345
>adc
>analog to digital converter driving npn transistors
adc's sample a signal and output on a digital bus.
I'm going to assume you meant a DAC or digital to analog converter but that is still bad since you don't need a continuous non-periodic waveform output such as audio just an on-off signal to control the leds.
What the "pro's" do is a shift register or just plain old gpio's to the transistor bases and multiplex over time to get a picture with a specific refresh rate

>>1623607
there's the EE student way and derive the transfer function from theory.
There's also the EE professional way and just use a simulator such as LTSpice.

>>1623519
>if I rectify the oscilator output, I could feed that to an opamp and use it to control a cascode amplifier right?

the classic method is to use a JFET in linear mode as a variable resistance that's controlled by the rectified AC signal. alternately you can use an LED-photoresistor combination (a vactrol) in the same way. i remember building a JFET version a long time ago, where i needed to try 10-20 different FETs to find one that was free of distortion.

of course, the best AGC is no AGC at all. there should be no reason for an oscillator to be varying its levels unless it's sick.

>>1623641
>what's the easiest way to amplify the signal and carry it into the computer in a way it understands?

google knows the answer, and he's feeling hurt you didnt ask him first.

>>1623641
piezos typically have a pretty high resonance frequency. If you thing about the sound vibrating back and forth across the panel, the resonant wavelength will be twice the diameter, and the speed of sound will be pretty high (up to 6000m/s), so getting a low resonance frequency would require a large piezo element. However, to use a piezo as a microphone, you don't have to be near the resonance frequency at all. You should be able to find piezo microphone datasheets that show a response curve that's somewhat linear below the resonant frequency.

To convert this signal into something usable, I'd throw it through a jfet op-amp non-inverting amplifier topology, perhaps with filter elements, probably with a gain knob. Then I'd feed this through a DC-blocking capacitor and into your microphone/trrs socket. The capacitor is to avoid feeding the microphone socket's phantom power back into your circuit. You could either use USB to power this, or an external battery like a 9V. If using USB, you could buy a cheapy USB-soundcard and use this as both your power source and audio input, such that you only need one plug into your computer.

Pic related, using the second op-amp to buffer the ground rail. The 1kΩ resistor is there to limit the maximum gain so you don't make a naughty when you accidentally bump the knob up to maximum.

>>1623649
>DC bias
>to a piezo
Lmao, though the protection diodes could be a good idea I guess.

>>1623652
>>DC bias
>>to a piezo

the bias is for the op-amp, coz it's using a single rail (battery) . serves same purpose as your artificial ground.

>>1623654
Yeah but it has a small effect on the frequency response, doesn't it? Since the piezo is mostly capacitive.

>>1623652
this is amazing, much appreciated.
>to use a piezo as a microphone, you don't have to be near the resonance frequency at all.
that's exactly what I needed to hear. now I can actually go with the piezo elements I had in mind. the ones I've looked are indeed very linear in the relevant ranges. thank you so much.

>>1623644
Better yet, just used the pre-formulated equations.
Quicker than mucking about in a simulator, and less work than deriving the equation yourself.

https://www.analog.com/media/en/training-seminars/tutorials/MT-218.pdf

>>1623674
Actually now that I test it with a scope and a couple of piezos from buzzers, it's not very linear at all. Plus it's picking up a bunch of 50Hz noise, so you'd better shield that thing. Though if your elements are linear where you care about then go for it.
But what I did find interesting is that they're quite sensitive to me blowing on them even from quite a distance away. So perhaps they might make a good pressure sensor for another project of mine, considering I just want to detect a pressure difference of 10 or so Pa.

>>1621767
Oh shit that's what they are?
https://www.youtube.com/watch?v=VfiuIlEdE2c

>>1622751
I don't know if it's nostalgia/old school vibes or what but I looove me some VFDs. What kind of board is that (chinesium?) and i guess it has the drive cktry already?

Is there an easy way to transmit at data rates approaching 500 megabits per second over a tiny distance? Building a 3D POV display and I need a way to transfer data to the rotor without a slip ring. I've looked into using an LED and phototransistor but most phototransistors have too long of a rise fall time. Could I DIY up a radio solution with a low signal to noise ratio? (I know nothing about RF design)

>>1623712
>a radio solution with a low signal to noise ratio?
most definitely

>>1623674
>>1623695
oh and the voltage will definitely get pretty high if you knock it, so be sure to include diodes like in >>1623649. Though I'm unsure what happens with that on an SMPS, so back-to-back zeners might work better. Or just a few standard diodes in series at that point.

>>1623715
yeah I was easily getting 20V or so

>>1623717
Not him or into electronics that much, but aren't small microphones like that often coupled with preamps because the signal is so weak? Why amplify it if you get those voltages?

>>1623720
Audio signals will be pretty weak, but a sharp knock to the case will couple energy much more efficiently, assuming the sensor isn't suspended by elastic, which it often is for large microphones. The audio signals I was getting were particularly weak, so much so that I was battling with the S:N ratio of my scope, hence why I recommended using a nice high-impedance jfet op-amp to process the signal.

>>1623712
Fast photodiodes exist, but if you're considering slip-rings you're probably doing something wrong in the design from the get-go. Does the part really need to handle a continuous rotation?

>>1623178
Thanks i understand now, I always only looked at the vgs th, but now i realize that the vgsth only give the fet a semi-chub and to get it erect enough for your purposes you have to look at that rdson curve thing and find out if say with 3V at the gate the d-e resistance and resulting voltage drop will be low enough for your load purposes

>>1623485
FET version of the diff amp oscillator, gain adjusted by R2.
>>1623646
50MHz is not audio.

>>1623738
Slip ring is only for power and gets smoothed, simpler than induction. Whole device needs to spin at 60rps, can't be avoide

>>1623760
>Whole device needs to spin at 60rps
Could you explain this in detail? What is spinning and why?

Don't know if this is quite the right place, but figured I'd ask anyway just in case - I've been wanting to make something like pic related as a work light but haven't been able to find proper brightness LEDs on Amazon. It seems all I'm finding is kits for backlighting TVs or rooms which have LEDs spaced out 4-5cm or so. I decided to bite the bullet and try one out, but not only is the white not consistent brightness along the strip, it's not even really white (some parts are bluer, some are yellower, some are greener) and way too dim for any sort of real work, even if I quadruple back with the strip (which uses almost all of the 5m with the table size I have). Any suggestion as to a good RGB(W) LED strip that's not stupid amounts of money? Ideally I'd love to have a minimum of setup at the moment, so a plug-and-play with a remote would be fine, but having something that's really long that I can cut to length and use another controller with would be fine, too.

>>1623768
Forgot to mention, I don't need them to be individually addressable, whole strip changing colour would be fine.

>>1623712
Air-core transformer. Two coaxial helical coils, one stationary one rotating. Use 8b/10b encoding to eliminate low-frequency components. No modulation required.

>>1623768
RGB or dimmable white LED strip + piece of aluminium. DIY Perks did a video on it.

>>1623768
You need a 5050 pixel strip

>>1623778
Didn't he say he didn't need an addressable strip?

I love the smell of Pic related in the morning. it's the smell of victory!

>>1623641
please check out these fine MEMS mics with surprisingly good wideband performance e.g. 45-15.7kHz ±3dB, a resonance frequency of 27kHz, and analog or digital sigma-delta modulated output https://www.digikey.com/en/product-highlight/k/knowles/sisonic-mems-microphones

>>1623715
the point of those diodes is not to limit the voltage to some absolute value, but to keep it within the rails so that the op amp's common-mode voltage limits are respected and it doesn't self-destruct

>>1623768
you want a separate white, then, perhaps a CRI-rated one if you're sensitive to that sort of thing
if you check ali, you can find manufacturers flogging high-density strips with CRI-rated LEDs, such as this (not sure whether to believe them) https://www.aliexpress.com/item/FREE-SHIPPING-High-CRI-90-High-Density-300leds-m-SMD2216-LED-Strip-Light-24vdc-5meter-Benis-XDD-1500leds/32997822789.html

>>1623779
Don't know, i have short reading attention span.
In that case he needs a regular 5050 strip with 4 wires (r g b and ground or 5 wires if he also wants separate w)
But rgb wires are deprecated and he would be stupid not to get a pixel instead since i don't cost much more

>>1623790
Every time i solder SMDs they always look like that even before i turn them on

>>1623795
>rgb wires are deprecated
citation needed

>>1623806
Make sure you also run all your wiring with aluminum wires retro hipster fren

>>1623807

will regular solder work

>>1623807
see OP: an art/science of applying principles to requirements. if you need to add glow or low-medium densities of light to something, RGB strips are a cheap and effective way to do it, iff you can keep dimming RFI under control
>hipster
no u

>>1623805
that board saw a lot of rework before that happened
hypothesis: the ease of use and quality of a jellybean-ish chip might be proportional to how many sellers on ali offer it for sale

>>1623809
only if you use organic flux

>>1623790
>the point of those diodes is not to limit the voltage to some absolute value
I was more worried about a 50V spike that's more than the op-amp or power supply can handle. I'd want it to clip down to a much lower level, no more than a diode drop greater than the rails. I guess it would do so just fine with normal reverse diodes like that and a large enough capacitor (read: over 10nF) across the rails, no? But if you're running it off a PC I'm unsure whether any momentary voltage spike above the power supply's rails would be acceptable.
I'll keep this in mind when dealing with that sort of circuit in the future.

>>1623795
RGB LED strips can easily be driven without a microcontroller, addressable LED strips not so much. Though I'd quite like to know if you could use some PISO shift registers to manually bit-bang a simple serial peripheral like that, perhaps with some PROM.

>>1623807
your implications are erroneous

>>1623813
>only if you use organic flux

I have some olive oil i will try that thx

oh no

>>1623820

Is there some advantage of black tips over regular ones?
Also, which tips from 900M series would /ohm/ recommend? I want to get 900M-T-K, 900M-T-2.4D, 900M-T-3.2D and 900M-T-2CM
>https://www.hakko.com/english/tip_selection/series_900m.html

Sup lads, bought that Siemens radio a bunch of years ago and only now really got to it.

For some reason it refuses to find any ultra short wave station
The tiny elta next to it and even old mobile phones have no problem catching them tho
It somewhat manages to find stations on short and medium wave, but it doesn't seem to find the same stations as the elta

Any ideas? P sure it's not just the antenna>>

Bidirectional warning light (5 LED chaser) with dual CD4017 + tri-state buffers:

>>1623709
It is just bakelite I think, and yes, it has all circuitery on board. The only connections are VCC, DATA, CLK, POR and GND.

>>1623909

whats with all the retarded gates? are those pull-up or pull-down resistors? shouldnt stuff like that be obvious.

>>1623941
They are the IEC standard symbols.

>>1623941
>>1623945
I've done some PLC programming before and just find the IEC symbols clearer.

my laptop draws (peak) 26 watts from a ~19 volt charger, which works out to about 1.3 amps but that sounds a bit low to be charging a battery of 6 18650s
am I missing something or is that about right

This is essentially a power bank. How would you make it, /ohm/?

Easy way out (which is OK for prototype) is to use IC from 2 cell powerbank and run the target board at 5.5v. It would work perfectly but I'd like the added functionalities. I'm looking at BMS IC's right now but I'd like /ohm/'s input since some of you might have done this already and gone with a different approach

>>1623941
>pull-up or pull-down
both, push-pull, source-sink

>>1623946
>IEC symbols

those three little words that, ignored, led me to kill five dc-dc converters
moral: read the fucking datasheet

>>1623973
switching dc-dc converters conserve power rather than dissipating it. 26W into a 11.1V battery pack is perfectly reasonable for a 2-hour Li+ charge, plus losses and housekeeping in the laptop

I've heard good things about "High Speed Digital Design" by Johnson and Graham (https://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241).). But, I went to check it out and it was published in 1993, that's nearly 30 years old (you're welcome)

given its age, can anyone here verify if it's still relevant or if it's hopelessly outdated?

What's the smallest common thickness of PCBs?
I got some PCB offcuts with unknown thickness (but it's not going to be something exotic) and want to use it for something high current.

>>1623687
How do I include values that differentiate between capacitors like ESR ESI* (correct me if im talking bullshit this still very confusing to me)

>>1624053
depends on how many layers. it's usually some multiple of prepreg + some multiple of copper. I see 0.8mm thickness around a lot
>high current
oh, copper, you mean. 1 oz is standard, 2 oz is common for high-current projects, I haven't seen much thicker than that but you can if you really want to

>>1624054
>ESR
>ESL
you add the inductors and resistors where they would appear, in parallel or series. Pic related, the model of a real-world capacitor

>>1624059
>oh, copper, you mean. 1 oz is standard, 2 oz is common for high-current projects, I haven't seen much thicker than that but you can if you really want to
No, I'm asking the opposite. Is there something lower than 1oz that is common?

>>1624068
1/2 oz is commonly used for inner layers and you can often get it on the outer layers too. much thinner than that and the plated through-hole process doesn't work

How hard would it be to make this into a proper board with 2 layers. I have 5V and 3.3V and I would like to use a ground layer.
Now I read that ground layers shouldnt be disturbed with any additional traces so I'm essentially left with 1 layer to work with making it an impossible task

Hi guys, it's been a long time. I'm looking for a schematic for a highly efficient (as in efficient to build)12v DC to 220v inverter. I looked around using not-google and all I can find quickly is pozzed nonsense such as pic related. He has to be joking. I need this thing to power a welder and the sauce is a photovoltaic array. I'm using car batteries for the battery bank. I'm not a total newfriend when it comes to this stuff. I was actually one the first anons to use /diy/ after moot made it. I've been gone for a while. Glad to see that the board has evolved beyond dumpster diving, making booze, and container houses. Anyway, if you get a chance pls post a badass inverter schematic. I like OC :^)

>>1624088
>shouldnt
back in the real world, people prefer to get the board routed and just try to disturb the ground plane minimally. you want to minimize a signal's length, which includes its return path, which (given free rein) will be on the ground plane right under the signal or power trace. don't put detours in the way = don't pass any high-speed or high-power traces across the gap and try to keep the plane as wide as you can as much as you can
what's your minimum trace size?

>>1624100
>don't pass any high-speed or high-power traces across the gap
So you mean that high speed or highpower traces on the top lane shouldn't run over the gap in the bottom (ground) plane? Why is that?

>what's your minimum trace size?
I haven't decided yet but it's probably going to be standard 0.035mm

>>1624111
0.3mm or something like that*

>>1624097
ayyyy
holy shit you're gonna need some surge current, which isn't really compatible with easy
if you want easy, there are lots of one-chip mains-output inverters and inverter controllers out there, some of which do true sine wave, which might make that welder happier. you can check their datasheets for a full schematic and BoM. in any case, the hard/not cheap part is to procure the transformer. you might have to spend several tens of bux on a sample batch of custom-wound transformer from a place like Ranlo (search aliexpress)
if you want powerful, I suppose that, if you're clever about it, you can just keep stacking FETs and transformers in-phase in parallel until you get bored or run out of heat sink
perchance can I interest you in some immitation crab meat

>>1624111
the impedance discontinuity causes some of the voltage to reflect back to the transmitter and also creates a small loop antenna (Pic related, red) which can couple remarkably large quantities of power into the air. if you really have to pass a sensitive or edgy signal trace across reference planes, it's recommended to connect the two reference planes with a capacitor. if you have to change layers it's recommended to connect the old and new planes with vias and/or capacitors as appropriate
not that any of that matters below a few tens of MHz (but do mind your harmonics)
>trace size
if you're sending out you can go down to 0.2mm trace/space and still get the cheapest service just about anywhere. most houses will let you do 0.15mm without surcharge. that should be enough to route between some of those connectors, even with the relatively thick annuli

>>1624138
Thanks for the input, crab-bro. But I'm already crabby enough. As for running out of heat-sink, I don't care how big my quasi-African-engineered inverter is. All I care about is efficiency of cost and fabrication. I can get aluminum at the scrap yard for 1.75 a pound. Happy crab-slanging. And thanks for all the fish.

>>1624143
noice
on second thought, you simply ain't gonna find one for welding duty at 12V. that's asking for surge currents on the order of 100 amps, where ten milliohms of cable (or MOSFET or solder) drops an entire volt. you are gonna want to use a slightly higher voltage so that Ohm's Law doesn't bite you in the ass like that. also you might want to use welding cables throughout this thing
anyway, if you can get the +400V (personally, I recommend connecting a lot of batteries in series), Pic related will give you pure sine output from it
no sweat about the crab meat. just trying to sell some of it so I can buy an arduino before it goes had

>>1624088
are you building a digital radio? usb3? motherboard? atomic clock?

chances are you don't need to worry about good practice for high speed and impedance

saying that routing difficult pcbs is part of the fun. just have a go at it see what you can get done on one layer. dont be surprised if you get 80% oif the way through and have to start again because you realize a better way to do it. dont be afraid to move and rotate things.

>>1624138
Ah thanks. So basically I shouldn't run fast signal and power traces over gaps in the ground plane. I have found this picture regarding that.
>reference plane
Hm I thought there's only 1 plane in my example. How exactly would that look like then?
Just randomly place vias at unoccupied space?

>>1624148
>>1624143
note well that there are no transformers in that inverter schematic

>>1624154
much better picture
there is only one plane in yours. just mentioning it
one method is plane-joining vias at least four points around the signal via, at a distance that maintains trace impedance thru the board thickness. looks like Pic related, but Pic related is not an example of this method. anyway this sort of thing isn't really relevant until you start doing 4-layer boards and tens of MHz.

>>1624148
I don't need +400V. All I actually need is 120V as my Harbor Freight TIG/Stick welder can run off of 120 or 220V, and I prefer the latter, obviously. As for welding cables, I have been getting some real nice and purty bright 1/8 inch copper rod/wire that some crackhead lovingly freed from it's pesky insulation-prison with which I intend on creating a new kind of 3-d circuit, but that's another story. Anyway, I reckon that if I twist and weld or melt and form enough of that shit I can get enough valence to push just about anything. Looks like your schematic for the sinusoid inverter is a WinRAR. Chicken dinner for you tonight. May I suggest you use the imitation crab meat as cat-bait? I've figured out a way to control their little kitty minds using a kind of electromagnetic kitty-helmet, thereby turning them into defacto drones that I use for counter-surveillance and various other tasks. With enough imitation crab meat you too could be the proud owner of a vast and invisible kitty-drone army. I even use them as a mobile mesh-net! Unfortunately I can't post the schematic for the kitty-mind control device as the feds are already on my ass. For all I know you might be one of them! I didn't get the design from the aliens. I found it just laying around in some IRC channel.

>>1624150
true, I just try to make it "as good as possible" because it's going to be a part of my bachelor's thesis

>>1624164
Ah okay, it makes sense now. thanks

>>1624167
yep. anyway, for interest, the reason I'm doing it there is more about low inductance and resistance than controlled impedance
don't overbuild for a bachelor's. of no less importance than knowing how to do all that impedance control shit is knowing when to do it, and knowing when to just slap some traces on a board and ship it

>>1624166
that schematic calls for 400V, see there at the top on the right. you need it because 240Vrms = 370Vpeak. wouldn't a big-ass bank of photo flash capacitors be great fun?
anyway, it's a decent chip and available on ali, mounted on a board with MOSFET drivers, for $3 or so. also kits that come with the goofy little status display for under $10. just add MOSFETs, wire (I guess we call it "bar stock" by now), heat sinkage, and a big-ass dc power supply, and you're on the go
apparently I need to get on IRC more. everything I've ever heard suggests that toxoplasmosis works the other way around and creates human armies controlled by cats

>>1624143
>All I care about is efficiency of cost and fabrication

out of curiosity, what voltage does the welder put out? it would be pretty inefficient to go from 12Vdc to 120Vac then back down to 12Vdc.

>>1623712
slip ring noise is common. If you send differential signalling through it it should help reduce most of the noise. There are also "liquid" slip rings that use conductive liquid instead of pins to remove most noise at the start
http://www.mercotac.com/html/technicalinfo.html

>>1624185
>it would be pretty inefficient to go from 12Vdc to 120Vac then back down to 12Vdc.

Yes, it sounds silly, doesn't it. Unfortunately I've not yet gitted gud enough to solve the fundamental stupidities of our civilization. If there is a way to bypass this glaring stupidity I wouldn't mess with it anyway, as I can't afford to mess up my equipment as I am poorfriend.

>>1624174
>apparently I need to get on IRC more

I wouldn't. It's full of idling and if they get a whiff that you're from imageboards it's over for you. IRC is dying and it's truly tragic. The one single aboriginal platform forever free from government and big tech control and kids these days would rather use discord. Brings a tear to my eye. Even freenode is dying. Oh well. Maybe someday when everyone has chips implanted in their brain to keep them from wrongthinking there will be some kind of rebellion formed in the ruins of IRC. But you're right about the cats. I simply decided to stop being a victim and take control.

>>1624097
lmao just make a DC-DC converter, most of what you'll run with it run fine off HVDC anyhow.

>>1624166
>>1624203
Oh it's a welder? Check if it has a SMPS or transformer. If transformer then yes you'll need an inverter.

>>1624203
>>1624203
>lmao just make a DC-DC converter,

Sounds easy in theory, but unfortunately my TIG welder runs off of 120/220V AC and I'm not willing to take it apart as I seriously fucking need that thing.

>>1624205
>I'm not willing to take it apart
Just taking the outer case off won't hurt anyone. If you can't take apart a welder without fucking it up I doubt you have any business making an inverter for it.
>my TIG welder runs off of 120/220V AC
If it has a SMPS those things rectify the power before using them (assuming no phase correction) so all your inverter circuitry would be a waste of time.
Alternatively, look up the welder's specs online, or tell me if you can hear a 60/50Hz humming when it's turned on. I suspect welders are usually made with transformers, but who knows about the new ones.

>>1624207
>I doubt you have any business making an inverter for it.

Look man. Maybe your little snarky comments work on other anons fresh off the boat from Thingaverse, but I'm not the one. I was posting on /diy/ when you were still figuring out how to /diy/ your way into the cookie jar. Furthermore, the welder will not be touched. The welder is sacred, if anything is still sacred to you kids these days. I just came here for a schematic for an inverter that I could nagger rig into not costing more than $30 and fuck the aesthetics. And since you don't know, yes, welders are basically inverters but they're like special inverters that allow us welders to work magic. Heh, maybe you take a word from the /diy/ wise and learns some welding, kid. That is if your soft little hands can handle it. Welding is the basis of all things /diy/ and I'll duel anyone that says different. Need a box? Weld the bitch. Need a crane? A fermenter? Weld the bitch. You see? If you can't weld you can't do shit. I'm literally trying to convert sunlight into DC electrode negative arcs to do work. WORK. Something I suspect you're too fresh like imitation crab meat to be familiar with. PROTIP: imitation crab meat is made from FISH and that's what we call fresh meat in prison. Welcome to the prison of /diy/, bitch.

where can I go to learn about mobile power design?
I want to build 18650 power bank circuits for all of my projects, but I just have 0 knowledge on the subject and don't even know where to begin

>>1624218
more specifically, I don't want to be shown a guide so I can blindly copy what they did

I want to learn the theory, how, and why behind it all so I can design my own arbitrary portable power sources with confidence

Any recommendations for cheap FPGA board for a beginner? I'm interested in sampling linear CCD chip with it.

>>1624219
where are you starting from, skill-wise?
I'd start reading lots of app notes and datasheets of battery chargers, power path managers, etc. they'll usually describe the charge algorithm in detail and other considerations in power system design. TI, Maxim, and LTC all have good reading, and thanks to the mobile revolution, plenty of it
if you want to be confident in your Li+ designs, design safely, using the same level of ordinary care that you would apply to, say, handling volatile solvents. for example, say a charger chip has a safety timeout, don't try to make it feed power through it to a step-up converter in an attempt at a load sharing manager, get a proper one. if a charger chip has a temperature sensor input, get a thermistor and use it. don't skip the protection circuit. spot weld, don't solder. etc.
batteryuniversity dot com is also a fine resource for learning how batteries really work, the failure modes you must be aware of, and the ways to manage them

>>1624220
suggest you design whatever front end you're sampling with, select an ADC and ADC interface to suit your sample rate, and choose an FPGA suite (software, chip, dev board, JTAg pendant, etc.) that can do it

>>1624225
>where are you starting from, skill-wise?
not very much, I'll be honest. I thought narrowing my scope down to something as specific as portable power design would give me a more focused subject to learn about and overall teach me more about electronics but it seems it's still outside of my reach

>>1624245
have a look at the MCP73831 datasheet from Microchip (33pp). it's a simple example of the genre, a 1-cell linear Li+ charger with load sharing (note that I am assuming that the ability to run from battery *and/or* line power, transparently, is important to you). see how much of it makes sense to you

>>1624245#
have a look at the MCP73871 datasheet from Microchip (33pp). it's a simple example of the genre, a 1-cell linear Li+ charger with load sharing (note that I am assuming that the ability to run on battery *and/or* line power, transparently, is important to you). see how much of it makes sense to you or not

>>1624256
>>1624254
It's funny you mention that exact chip, because that's the exact datasheet I have pulled up in my other tab. I was just starting on the Device Overview section when I saw the new post

>>1623776
Did you even read the post before responding?

>>1623778
The one I got was a 5050 but too dim - at the same distance as my lamp, it's about 1/3 the brightness. And it's not a particularly great lamp.

>>1623790
I'll look into CRI ratings, thanks; I'll try to find something that doesn't take a month to get here, though.

>>1623364
Use an RVDT (rotary variable differential transformer) or an LVDT (linear variable differential transformer) depending on your setup. Off -the-shelf is expensive, but they can be constructed from scratch.

A sinusoidal signal is sent through a coil, which is adjacent to two interconnected coils. The configuration depends on whether it is a linear or rotary encoder. For linear encoders, the primary lies between the two secondary coils, all in line with each other. A mobile ferrite core is able to translate between the centers of the coils, yielding secondary voltage based on its position. One side of the encoder is fixed to the coils, and the other is fixed to the core.

For sensing rotational motion, the secondary coils usually rotate relative to the primary. When two coils are orthogonal to each other, very little current is induced in the secondary. The voltage at the secondary is proportional to the angle. Alternatively, one may be able to rotate the core.

Both of these setups are stable, providing the same readout despite power interruption, and are analog systems, so high accuracy can be achieved. They give positive and negative readings, so direction can also be discerned. The primary and secondary, along with the accompanying circuit, can be totally sealed, allowing operation in harsh environments. They can be made with very low friction through bearing use or can be frictionless if there is no contact between the two sides.

Googling "LVDT signal conditioning techniques" will yield a lot of information on the subject.

An in-depth discussion on the operating principles:
http://nliebeaux.free.fr/ressources/signal.pdf

An example of a circuit that can translate secondary voltage into something more usable:
https://www.analog.com/en/design-center/reference-designs/circuit-collections/lvdt-signal-conditioning.html#cc-overview

>>1624338
Of course, if an optical encoder is workable, it is a much simpler approach. The downside to it, however, is that position data is not preserved on power interruption.

>>1624339
This is to mean that optical encoders are solely based on change in position. They have no concept of what the actual angle is. If you care about absolute position, then you need a reference, such as swinging to full range before returning to position after power-on, or having a spring-return to dead center. When power is lost, any change in position screws with your reading, as does any change in your reference.

LVDTs and RVDTs are based on absolute position, not change in position, so this is not a problem.

>>1621755
How difficult would it be to install a cpu socket in an x220

>>1621755
Plans for compact bench top power supply? 0-30V and 0-3A (off 220V mains), 0.1 step resolution. Something with four leads that can put in backpack if necessary.

>>1624385
If you want it to be portable, wouldn't you be better off with a battery-powered supply?
There's lots of project like that, for example Dave's uSupply.

>>1624389
>battery-powered supply?
No need, backpack has built-in mains socket.

hey hey people
https://www.changpuak.ch/electronics/calc_06.php
parallel resistor calculator

>>1624397
I don't think anyone capable of even basic electronics has sufficient trouble solving a pair of fractions to need an online calculator

What's the practical difference between iron and copper soldering tips?

>>1624402
It's not just solving a pair of fractions, it's mainly finding the closest two E12 or E24 standard resistor values.
For example, to get a 50Hz notch filter the calculator (and my spreadsheet of standard capacitances) told me that an 8.2M in parallel with a 39kΩ would give 38.815k, which is 0.007% away from the ideal value of 38.818k (5 orders of magnitude larger than 1/π).

>>1624389
I know where I will need it it will be close to the mains but I just need something thats easy to store, not necessarily portable to the point of being battery powered

>>1624385
>>1624423
Laptop power brick + boost buck module crammed into a small case?

>>1624017
Still highly relevant. Some things don't change that quickly, if at all. The book has a lot of factual things in it like calculations for real components.
Its not a HoW tO dO aN aRdUiNo type book with pointless stuff and opinions.
Its worth the read.

>just want to learn electronics
>textbooks either hide everything behind "Circuit Analysis" where you endlessly apply KCL and KVL and don't actually learn anything practical or pragmatic
>or claim to be suitable for a "beginner" and then go from 0 to supersonic (The Art of Electronics), going nuts deep into unintuitive beginner-complex circuits
I just want to make shit man

Any good and free schematic drawing program
recommend??

>>1624472
>unintuitive beginner-complex circuits
such as?

>>1624479
shit with transistors. Maybe I just don't have much of an intuition yet but trying to imagine what it all does in regards to the entire circuit fucks me up

>>1624472
I think it's easier to make your own projects and learn everything neccessary along the way

>>1624478
easyEDA

>>1624483
>shit with transistors. Maybe I just don't have much of an intuition yet but trying to imagine what it all does in regards to the entire circuit fucks me up

You don't sound very intelligent. Working with electronics is not easy for someone who is not very smart.

>>1624492
you are an asshole

and btw the art of electronics isn't for a complete beginner

>>1624472

>Principles (by increasing skill level):
Mims III, Getting Started in Electronics
Platt, Make: 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

try with the first one, idk what you already know or something like that dude, just keep trying

>>1624498
What's a good book if hypothetically I have a degree in electrical engineering but don't know shit about shit

this is obviously purely hypothetical as nobody would ever find themselves in such a ridiculous position

>>1624479
Gromit studies the free version

Visitor from the guitar general on /mu/. I remember a few scrapings of EE from my youth, and I'm putting together an old guitar, some effects pedals, cables, etc.

Can anyone recommend me a good quality 40W soldering iron available in the UK? And what should I be looking for when purchasing a soldering iron? Thanks.

>>1624527
The go-to recommendation for straightforward soldering is a 936 clone, they're dumb and reliable. Look on ebay for an Atten or Aoyue 936, you should find it.

>>1624533
Thanks a lot, there are a few available now.

>>1624339
but you can absolute optical encoders, see >>1623448

>>1624478
what's wrong with eeschema?

>>1624483
transistor intuition: 1 electron goes from emitter to base = (beta) electrons go from emitter to collector. does that help?

>>1624499
>obviously purely hypothetical
obviously hasn't been to college with brahmins

>>1624527
>what should I be looking for
power and range. you would like to be able to solder components to boards without lifting copper, yet you would also (ideally) like to be able to tack shield braids to pot housings
the 936 clones are pretty good. if yours doesn't come with a tip assortment, get one as well for better range

>>1624599
>soldering iron advice
Thanks. Sounds like I do need range, because I'll be soldering components to boards (effects pedals) as well as getting shield braids onto pot housings and jack plugs.

>>1624599
I understand how all of the components work *individually*
once you put them in a circuit that's when all hell breaks loose for me

>>1624625

yeah, that's a sad situation. it's like knowing all about the physical bits of the reproductive system: it doesnt make you a lover. practice does.

I have a 12v 0.28A fan that I want to run at a slightly reduced speed. I have a 9v 0.2A power adaptor, is it safe to run the fan off it, or do I need to use a adaptor with equal/greater amperage?

>>1624790
the current ratings on those adapters are real and you shouldn't exceed them or you might get some funny voltages on your output when they melt down internally. if you happen to have a multimeter you can measure the current at 9v and see if it's under 0.2A. it probably will be.

if you're just dicking around and don't care about the hardware then go for it.

>>1623871
The black ones look fancy.

K best tip.

>>1624798
oh dat petite SK doe

>>1624811
do not lewd the shota K

I bought a bunch of cheap switch plugs and am going to convert them into smart wifi plugs.

I looked around the market and all smart plugs are overpriced as fuck and force your to use their own shitty cloud based app to control them with no api for shit like iot.

So i am going to make this prototype to see how well it works, it's nice since i can code it up to work with anything i want like google assistant, including without internet with direct p2p connection and it will still cost 1/3 of what the cheapest wifi plug costs here

wish me luck

I want to mount a connector (pic related) to a board.
But I'm worried that solder on the backside alone isn't strong enough, since it takes a bit of force to plug it in and out. What's good way to strengthen it? Just slather some superglue everywhere?

>>1624959
Don't burn your house down.

>>1625002
>What's good way to strengthen it?

by using it properly: attach it to a heavy cable that is long enough for you to hold while plugging it, and strain relief the cable to something that will protect the solder connections on the board. There's no normal circuit board that can handle that sort of connector mounted directly. If you have to have large power connectors on your board, use screw terminals.

>>1625017
This is supposed to replace the screw terminals I'm currently using. I also don't want loose cables.
I've seen boards with connectors that require much more force directly mounted on it. Surely there must be a way.

I would also be okay with a different way to stationary mount it other than a PCB. Just seemed like the most straight-forward way but there's no complex circuitry that would require one.

>Chinese hoverboard battery
>No balancing
>BMS trips it every fucking time

How can I make my own BMS with balancer? Are there any designated ICs, out I have to fuck with TL341 or wherever it is called, the programmable voltage reference?
And how do I overcurrent and overvoltage and undervoltage?
And where can I get decent slow 42vdc 20a fuses?

>>1625002
Superglue nor any other adhesive won't work. They would flex far more than the solder joint and leave all the force on the solder and copper. If it has to be on the PCB, I'd strengthen the whole PCB and the pads with bars of (tin-plated) copper soldered upright in multiple directions from each plug contact. This isn't very practical and isn't terribly common, bodge-wires from a chassis-mount plug/socket are far more normal.

>>1625020
>I've seen boards with connectors that require much more force directly mounted on it. Surely there must be a way.

well, derp, if you've seen how it's done, do it that way, which means buying a power connector designed to be mounted on a circuit board, unlike the ones in your pic (which I love, btw).

>>1625022
Tl431?

>>1625024
I've seen it for XT connectors for example.
But I don't see anything special done or why it would have any better hold than a Deans connector.

Oh and I've even found one that uses the same style of connector:
https://www.amazon.com/gp/product/B00FZX6ZTW

>>1625030

maybe that is a reinforced circuit board? I'm sure they can manufacture one that can handle your connector, but an ordinary board seems like it would flex too much. what if you fabricated some sort of reinforcing plate, that either is part of the solder connection, or glued like your original comment? if you distribute the force over a large enough area it might survive repeated plugging.

>>1625037
I could take a wood board, chisel out a hole for the connector and screw it on top of the pcb.

If I wanted to convert the pwm analog voltage to true analog would an opamp be enough for a really stable voltage or should I just get a buck converter. I need a steady analog voltage of ~2v. Its the reference for an analog device that Im measuring so if its not stable the values read are wrong.

>>1625052
You're probably better off getting an actual voltage reference chip if you need a really stable voltage.

You can filter a PWM signal, but there is a good chance you'll have a lot of ripple unless your PWM frequency is really high.

>>1624220
you can find several cheap boards on ali based on spartan 3 and 6 round to $40, but I don't recommend it because you'll be forced to use the ISE.
try getting an artix 7 board, which is bare minimum and at around $60.
get a xilinx programmer again from ali for about $25
download vivado and you are ready to go.

I have this one, it has a SoC and an fpga next to it.
https://www.aliexpress.com/af/XILINX-ZYNQ%25252d7020.html?ltype=affiliate&d=y&CatId=0&SearchText=XILINX+ZYNQ%252d7020&trafficChannel=af&SortType=price_asc&groupsort=1&page=1
it's more complex to tinker with it.

>>1624959
most of them seem to be ESP8266-based and you should be able to load whatever open internet-of-shit firmware you like
SeeedStudio has a lot of open IoT stuff worth looking into

>>1625020
best bet is to use plated slots for your connector blades. not all board houses do those or may upcharge for the additional manufacturing step

>>1625097
They still cost three times as much and i don't get to pick which exact parts i get to use, not to mention the great feeling of knowing i designed and built the thing myself from the ground up

>>1625022
>>1625025
>Datasheet: Max current of tl431 is 100 ma.
But all circuits use tranny of sort to discharge stuff... Why? Can I simply use tl431 with some resistor to pull 100 mA from battery? Or use multiple tl431s for more current.
Yes, I know that it will balance forever, but I can leave it over night outside inside BBQ thing

why do appliances need to be grounded?
isnt neutral grounded at the transformer?
google tells me its in case of a lightning strike but if that were the case, woudlnt most of it go through the neutral which is pretty much ground instead of the gorillion ohms through the entire building

>>1625180
belt and suspenders
there are occasions where corrosion or other problems with the service input causes the neutral to be 'above ground'
this is usually manifested by a difference in potential between the neutral and earth ground
the difference in potential will increase as the load to/through the fault is increased

>>1625184
>Belt and suspenders is a term used to mean conservatism and safety in lending practices.
the more you know
shouldnt the stuff you touch not be live anyway?
i know it's better for safety but i cant imagine a scenario where you NEED ground separate
apart from the case where you touch both neutral and the metal drainpipe while the wiring's fucked

https://www.instructables.com/id/RoverBot-1/
I want to make a FPV robot, this is a pretty sick idea. Basically takes an IP camera and straps it onto an arduino bluetooth tank.
I have an IP camera and have taken it apart, looks like its just a few wires (like 5-6 for servos for some reason). I’m thinking of attaching the IP camera to the arduino itself so you can combine video/audio output with the control RX in a single bluetooth stream.
Alternatively, I could take the motor shield and IP camera innards and attach them to a raspberry pi, and control it / view the FPV over wifi LAN. Probably the better option.

>>1625190
what happens if, during normal usage, the neutral comes undone, as could happen due to weather, not just poor workmanship? leakage currents flowing from line to neutral will bring the entire device up to line voltage (relative to ground) and possibly create a hazard. a residual-current breaker, as is the new standard, will notice the difference in current between hot and neutral due to that diversion, and will cut power to mitigate the hazard
>cant imagine a scenario where you NEED ground separate
under normal conditions, the ground lead is meant to be a low-impedance voltage source, not to carry current as the neutral does. thus, the ground is not only less hazaradous, but less noisy. sensitive circuitry may choose to use ground as a voltage reference rather than float around on the noise produced by other appliances on the wire
under fault conditions, the ground lead is meant to carry a large current just sufficient to trip/blow the breaker/fuse and protect the wiring

>>1625190
search for it 'problem with neutral above earth ground potential'

https://duckduckgo.com/?q=problem+with+neutral+above+earth+ground+potential&t=ffab&ia=web

>>1624795
Thanks, I went ahead and connected a couple of 12v fans (rated 0.28A and 0.08A, to total 0.36A) in parallel to a 9v 500mA adaptor.

Just to be on the safe side, I took your advice and got the multimeter out, seeing as this needs to run safely 24/7 unattended. I set it to the 10A setting (seeing as the next lowest is 200mA) and took a reading. It showed ~2.5A and the fans stopped spinning while I took the reading. Am I doing something wrong?

>>1625234
No, you just tested whether the 9V adaptor is short circuit proof.

>>1625234
current is through. voltage is across. therefore ammeters go in series with the load you're measuring, not in parallel

>>1625243
>>1625245
Thanks

>>1625180
If you connected the case to neutral, if the neutral connection breaks the case is effectively going to be live (because the components in the device are connected between live and neutral, and typically have a fairly low resistance).

Neutral and ground are usually connected at the main entry point (board fuse, meter), and also to a grounding pole. So the only way for the case to become live would be for both neutral and earth to break away from both the supply neutral and the grounding pole (without any break in the live connection).

Also: any current flowing from live to earth will trip the RCD.

So how can this be right? I can't trust ltspice anymore, falstad seems to get the values right
The base current should be in the microamps region, Uout should be 3V and the hysteresis just isn't working.
Are there alternatives to this?

>>1625314
>The base current should be in the microamps region
why? what's limiting it?

>>1625315
The emitter current I think

>>1625322
the base-emitter junction behaves as a simple diode. BJTs as switches need a base resistor.

>>1625339
I see, that did the trick. Thanks.
Although I wonder why the hysteresis doesn't work.

>>1625346
the b-e diode pulled more current than the opamp delivered (probably internally limited) so the output swing was severely reduced

Will pic related work as battery balancer?
Zener is TL431

>>1624959
>all smart plugs are overpriced as fuck and force your to use their own shitty cloud based app
For plugs that follow the Zigbee Home Automation spec, you can get a USB Xbee radio and control them from your computer. They're still fucking expensive though, like $50 a pop. (But I was feeling too chickenshit to play around with mains voltage, so I bought them anyway)

how bad of an idea is a computer engineering degree for someone who hasn't ever done much programming before

>>1625566
fuck off we're full

>>1625566
Hard to say, but you have to start somewhere. Try learning C++ or some other non-babby language by yourself and see how you like it.

>>1625475
50 is a lot i am making mine for about $9 a pop

>>1625594
and boy will they go pop

How hopeless would it be to first build a working prototype of a board and only then develop most of the software for the mcu? It's been sometime since I started thinking about a little device for hiking, with gps, a little screen and sd card for logging paths, being controlled by a stm32f3 mcu. However, I've been only making a fraction of the software because to actually test it out I'd have to bring the breadboard outside which is kinda cumbersome.
So I'm actually wondering whether you guys think a "build now, program later" kind of approach is bound to fail, or if it could actually be feasible with a good planning beforehand.

>>1623448
"While they did a really great job on this, I'm left with the feeling that so much more could be done so much better by using the latest in integrated circuits, the newest of antenna and battery technology, and the best of inside military information, particularly if aided by someone with some decent aerospace background."

Say I have an analog device that outputs an analog voltage of 2v to 4v. How do I use an adc with a pga to get the maximum resolution of this range.
For differential readings Ive read that Vin=V2-V1. So I was going to make V2=2v and Vref =2v.
But when looking at the datasheet vref by default is 2.5v. Pga:1,2,3,4,5->voltage range of 5,2.5,1.25,...

>>1625645
Low-noise jfet op-amp and/or resistive divider circuit to push 2V to a bit over 0V and 4V to a bit under the reference voltage. Though I think to push the 2V down to 0 you'd need a negative voltage rail, or possibly simulate a negative resistance.
To make the output range (0V-2.5V) larger than the input range (2V-4V) you'll need an amplifier in there somewhere, but picking an external voltage reference could serve to simplify the circuit in one way or another.

>>1625621
>inside military information
First 'Hell' must freeze over, torching 'Paradise' was not enough.

>>1625587
it's not that I haven't learned a language before or don't know the basics, it's just I can never figure out how to bridge the gap between "write fizzbuzz" or "print the fibonacci sequence" to writing useful, usable software

>>1625617
Its a pretty common design style. I typically build hardware first, then software second. Its called a prototype for a reason. More often than not, you'll need working hardware to really flesh out code anyhow. Simulators are great, but they can only do so much.

>>1625696
Then try making a finished project. Like a morse code demodulator or trainer, a waveform editor, a practical calculator full of formulae for all sorts of stuff you're likely to use, or the software end of some arduino serial project. Stumble through stackexchange threads and pajeet tutorials on youtube, mess about with GUI libraries and graphics packages until you have a finished application you can double-click and run without issue.

>>1623909
why use 5 OR gates when you can just use diodes?

>>1625617
very hopeful/10
I mean, you could always bodge a mock NMEA sentence generator in where the GPS would ordinarily be, but you're doing it right either way

>>1625764
premature optimization is the root of all evil

>>1625645
use diff mode, divide both the reference and the measurement voltages by 2, and set PGA to 2 or as needed

>>1625696
as a comp.e, the odds that you'll need to write useful, usable software that directly faces an end-user are low. instead you'll more likely be tasked with writing useful, usable low-level APIs or useful, usable hardware interfaces or useful, usable ABIs, all off which are designed for a more technical user and so are not quite the same kettles of fish. if you have managed to write some non-trivial programs, you will probably have some working appreciation, from the consuming side, of the art that goes into a "good" interface, one that does what you tell it to and otherwise stays out of the way
as with any other practical art, the best way to develop a working feel for it is to consume and critique what others have been doing in past and present eras. if you aren't reading The Mythical Man-Month in the first year, pick up a copy and read it on your own time. while that book chiefly concerns management of software teams and division of labor and is somewhat dated, it is worth reading in light of Conway's Law ("organizations which design systems ... are constrained to produce designs which are copies of the communication structures of these organizations") and some appreciation of the non-technical restrictions that the comp.e will be pressed to deal with, pulled by physics and the arrow of time on the one hand, the needs of other professionals on the other
tldr: make a thing

>>1625617
If breadboard prototype works OK, go ahead with first iteration of hardware.
Usually if I'm going with something untested - I will try to build hardware in a way that would be possible to fix or adjust as needed (like excessive amounts of mlccs, resistors inline, maybe a slightly modular approach)

On a plus side if shit does not work it will be great opportunity to find out and learn from mistakes.

>>1625455
y not use this

so a bjt is a current controlled switch (current flows if there is current flowing from the base to the emitter)
a mosfet is a voltage controlled switch (current flows if there is a significant enough voltage difference between gate and source)

am I getting that right?

>>1625895
basically yes. you can also just think of a mosfet as a voltage controlled resistor if it helps. that's basically true except for the body diode and significant parasitic capacitances.

>>1625895

>>1625902
>German engineering

So basically I have this step/dir stepper motor controller and I have a PIC18 microcontroller. I'm trying to find a way to make a variable frequency (controlled with two buttons, one to increase one to decrease) square wave. I can manage using a timer and a small delay inside it's ISR, but now i'm trying to find a way so it fully works aside from the main things my pic must do. Now i'm reading the datasheet on the PWM to see if I can do something like that with it.

Not really asking for help though, unless it is in the tip of your tongue, but I still have to read a lot, so I don't want to go against the rules, just letting you know about my day.

so, yeah, fun times.

>>1625617
The thing is, you'll have to be prepared to add lots of things that you "might" need to your first prototype in order to prepare yourself and use it for testing. that would be way cheaper than making prototype board 1 through 5. But you'll have to think ahead and prepare for things you are not preparing for, or things you know that might go wrong because you have done them before. You can always try though, sounds like a good learning experience

what are these doodads on this board

>>1625927
2SD882 npn transistors

New to /diy/ but got a quick electronics question.

I'm a Britbong looking to join the army and train as an Electronics Technician. You can graduate with a BSc in Electronics Systems Engineering so it looks like a good option for me.

As someone with beginner experience in electronics, what can I be doing now to get a head start on things? What is electronic engineering like in a military environment?

8s: my linux CAN device according to iproute2
13s: I monitor my CAN bus
18s: I turn on the power to my two CAN slaves
26s: start the daemon
27s: first data back for insertion into InfluxDB
37s: next data

>>1625920
nice blog
anyway, most MCU timer/counters offer a square wave output on a pin, but you are usually (but not always) restricted to integer divisors of the system clock, which may or may not work for you. the bad news that comes with the fractional counters is jitter
if you have time, and that fractional hardware isn't available, you could add your own jitter to the reload counter in the counter overflow IRQ such that the average pulse width is correct (real arithmetic may be required)

>>1626004
>webm related
>doesn't webm related

webm related, the Grafana instance where I view all that and eventually much more, illustrating the fine resolution of the BME280
the blue arrow is >>1623790 kek

experimental setup. USB-CAN F072 at bottom left, two F103 slaves at center and near-right. CAN=yellow+/green-, 12V=red/black. BME280 at near-left, connecting to near-right via yellow-to-grey. red/green/blue/black to ST-Link clone.
>inb4 dupont cuck
these sensors are tricky to solder and kinda expensive, yet I need that accuracy and precision for my application. maybe on the next spin

u like my bodge resistor?

>>1626140
how bout my sneaky bodge capacitor?

>>1625902
Isn't that FET a depletion mode one? Or a PMOS one I guess, it's kinda hard to imagine P/N type for either of those two transistor equivalents.

What is the difference between 7401 and 7403 IC???

>>1626200
read the datasheets

>>1626164
If you want water models get the PEFI book.
>>1626200
You would not believe it.

>>1626233
well that one doesn't work at all. Closing the gate means pulling on that cord which opens the collector, not the other way around. Not to mention that pushing on the emitter would push the collector open by itself.

>>1626234
this is nothing compared to water inductors

>>1626239
Coupled paddles and a flywheel works pretty well, provided you put some sort of rotational high-pass filter between the two.

>>1626242
At this point it will be 5 times harder to explain to a person the water analogy than it would be to just explain the actual electricity

>>1626244
Considering the analogy works well for inductors resistors and capacitors, that's still a large subset of electronics you've got covered, what with pulse responses, filters, and even impedance matching.
The analogy serves to get a qualitative understanding of the fundamental laws regarding current in a circuit, particularly Kirchoff's current law, so I'll still use it for that.

>>1626244
There's something about making up weird mechanisations that simulate components though.

>>1626246
>i want to be electronics engineer
>time to enroll into plumber college

>>1626247
*fun

>>1626248
>first class in plumbing
>alright to explain how piper and water pressure works, we will use electric analogy, imagine the pipe is a wire and the water is current and the water pressure is voltage
honk honk

>>1626234
Maybe this one works better for you.

>>1626248
How would someone without a concept of charge understand the conservation of charge that implies k's current law in the first place? It serves as a stepping stone towards intuitively understanding how simple electrical systems work, and it does so particularly well.

Though the hydraulic analogy does require a few nasty little things around the fluid needing to be incompressible such that you can treat mass and volume interchangeably for impedance calculations with readable units, but that doesn't really matter as you're not supposed to do calculations with the analogy anyway.

>>1626253
It's better, but still a little faulty as the collector can force the lever open if it's already open halfway. I'd just look at a simple air-actuated pneumatic valve.
The FET one was basically perfect though.

>>1626246
>Kirchoff
you again

This one is nice but the top item is the water op amp.

>>1626257
>it's Kirchhoff
a

>>1626258
I like the rubber membrane clamped between two tubes better, as it isolates the force better.
Though imagining hydraulic circuits/tools that run off AC pressure is strange. I wonder if a hydraulic (or pneumatic) synchronous motor can be made more compact than the standard turbine?

>>1626248
>plumber college
Electron plumbers have their laws.

Capacitor question. This DC-DC converter has tiny unlabeled capacitors on the input and the output, parallel to the larger labeled caps. Is it possible to roughly determine their capacitance by their appearance or their function? What is their function anyway, do they filter higher frequency noise that the large (electrolytic?) caps don't?

>>1626328
>filter higher frequency noise
Yes. When you RTFD you find 105 at input and output.

>>1626336
>When you RTFD

do what?

>>1626338
read the effing datasheet

>>1626264
>hydraulic circuits/tools that run off AC pressure is strange
Pic related, boost converter

>>1626328
not reliably, MLCCs aren't labeled
most of these module boards are copied from the main IC manufacturer's datasheet anyway with few or no changes

>>1626328
>do they filter higher frequency noise that the large (electrolytic?) caps don't?
ding ding ding
real caps have some amount of series resistance and series inductance. as the frequency of interest rises, the inductance eventually overtakes the capacitance and it turns into an inductor. (and, conversely, inductors turn capacitive at a high enough frequency, but that's another story). there is also an ohmic resistance of the plates in the capacitor and wires to it. both dissipate power in the conductors as heat. Al-elcaps and some foil caps especially because of their spiral construction
sometimes you have a bulk cap that, due to construction or size or long wires/traces from the load, doesn't have low enough ESL or ESR at the frequencies of your interest. you add a ceramic cap 1-2 orders of magnitude smaller than a bulk cap to counter the bulk cap's series resistance/inductance. or, to put it in time domain terms, to provide a lower impedance reservoir absorbing higher frequency noise, such as the fast changes in current when the boost switch turns on and off. EEVblog did a few episodes on decoupling caps a while back, could be worth an hour of your time