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Hello everyone! I'm designing a PCB and I have some doubts about how to connect the 4 resistors at the top to capacitor C34. They are 4 traces, and all of them terminate at the same pad of the capacitor. As I have currently placed them, are they connected correctly? Or should I connect them in a different way?

My goal is to drive an infrared LED like (this SFH 4727AS) to control IR remote controlled devices (for example a TV).

I can already output the signal on a pin of my microcontroller. The signal has a carrier frequency of 38kHz.

I am however limited to a 5V 1A power supply and would like to drive the LED as close to the 5W psu limit as possible.

I first thought about using a MOSFET like this AO3400A together with a resistor, but decided it was worth using an LED driver, do you agree?

Now I'm looking at this PAM2804 constant current LED driver but I'm not sure if I can just supply my signal to the EN pin. The EN pin is meant for PWM-dimming, so does that mean the output is smoothed to prevent flickering?

I'd love to hear your thoughts about how I should go about this. Thanks

First of all, I apologize for the lack of a "formal" schematic... I tried to draw one out, but got buried in the nuances of it :)

Second, I've done enough research to have some idea of what my problem is: namely, I need a decoupling capacitor in the mix. Problem is, I'm new enough to this that I'm not 100% sure where to put it, nor what capacitance I should use.

So the setup: -I'm using a Wemos(like) D1 Mini to drive 8 relays via an HC595 shift register -The D1 Mini microcontroller, HC595, and relay module are all powered by the same 5V DC and ground -The microcontroller addresses the shift register via 3.3VDC data pins -The relays power a water valve via a separate 24VDC power supply and transformer - plugged into the same AC outlet

And the problem: everything works just fine UNTIL I actually add the 24VDC power load. Once that's done, the results are very erratic... usually turning on the correct valve correctly, but rarely turning it off in the same way. As I mentioned, I intuitively suspect noise in the data caused by the sudden power to the valve... but it doesn't make too much sense since everything is on different power supplies.

Any guesses as to where I need to put some capacitor(s)? Thanks!!

Hi, I found an old cellphone battery (from a Pixel3A phone) and I'd like to reuse it for my robotics experiments. (link to images: https://imgur.com/a/Oj09tai)

2 questions:

1. how can I trasform the output connection to a more "standard" output connection (ideally V+ and V- wires)
2. how could I recharge the battery?

Any safety concerns, other than don't poke it? :D

If I wanted to make a USB desk fan from a spare CPU fan (input: 12V, 0.15A), could I just solder a resistor to the positive lead of the USB wire? I plan on getting an adjustable voltage booster, but I was curious if this was possible. I think I would need a 13 ohm resistor for USB 3.0.

I am looking for a Toggle switch that will allow me to actuate an actuator manually, or otherwise set the actuator to an 'automatic' mode, logic for which which I am coding on an arduino. The switch I want should have momentary On's for manual trimming that will spring back to an Off position, or it can be left in another maintained On position to signify the automatic logic should take over.

I had in mind something like a 2-axis Toggle switch that will have in the X-axis an MomentaryOn-Off-MomentaryOn configuration which will allow me to trim when in manual mode, but there should also be a fourth position (3rd Throw) above or below the 'Off' which would be a maintained On. Hopefully my diagram below explains the kind of switch I'm after too:

       On
       |

(On) - Off - (On)

I have spent about a day searching for something like this, and the only things I have found are a few old Cutler-Hammer aviation switches which seemed to do exactly this (8905K514, 8905K671, and 8905K608), but these are rare and expensive, and I wanted something I could easily get spares for.

I know I could achieve similar using a combination of two or more switches, but I feel it would be more elegant to have one switch that does everything. Does anyone have any suggestions?

Thanks in advance!

I bought a PWM Dimmer based on a 555 from AliExpress to regulate the brightness of a 12V 1A 1 meter LED strip, I already built one myself years ago on a perfboard but this one was the exact dimensions I needed for a project. I built mine from components from AliExpress and components found in old electronics so I thought nothing functionally would change The dimmer is this one https://www.diymore.cc/products/pwm-10a-speed-regulation-led-dimming-ultra-high-linearity-band-switch but I attached a real photo of the one I got from AliExpress My problem is that it isn't doing any regulation while connected to LED strips, I tried with the 1m one and with another light that has three 30cm LED strips in parallel Every other light or motor I connected to it seemed to make it work. I really have no idea what could be causing this, maybe it's sensible to capacitance? LED strips are two long straight parallel contacts but I don't think it's enough to cause anything as displayed here in the video: https://live.staticflickr.com/video/53017878188/54f865d36d/1080p.mp4?s=eyJpIjo1MzAxNzg3ODE4OCwiZSI6MTY4ODMxNzgwMCwicyI6ImI2MjZiMzk3MjExNTQxZWIyOTYwYzAyNTRmZDNhZDZjZTcwOWUxOGYiLCJ2IjoxfQ

Please no prejudice on that oscilloscope, it's good for what its made for, it's "calibrated", it shows a clean square waveform on my simple diy dimmer (photo to let you see what I mean with simple) versus what is shown in the video with the AliExpress one, an hybrid ramp/square. In the first part I show one of those LED strip that doesn't work, in the second part I show one that does work, just like every other light or motor I've tried

I tried adding an AUX jack to a car stereo with an internal CD player and no native support for one.

When I first did tests, simply attaching to one of the amp's input lines while the stereo was at min volume (1, not 0, more on this later) worked wonderfully.

To install the jack itself however, I thought that it may be dangerous to have the stereo send current to the AUX device and vice versa, so I thought about installing a switch to cut the stereo's audio input lines when using the jack and vice versa.

I thought about just muting the stereo, or turning the volume to 0, or using a dummy paused CD, but all of the three activate the mute line on the amp, which isn't a simple binary on/off deal, and activating it would also mute the jack.
Image

This is the original schematic of the amp circuit: Image
I attached to the IN1-4 lines like this: Image

I left the rear channels disconnected because a friend of mine suggested jumping two input lines could cause issues to the amp

However, once all was done, it wasn't working correctly. First of all, when I flip the switch, some signal from the stereo still gets through. It's very faint and you have to turn the volume way up to hear it, but it's there. This concerns me if it may lead to damage to either the plugged in device or the stereo, and if it could be the cause of the following issue.

Second, when a male to male cable is plugged in the other end (without even anything attached to the other end), a high pitched whine starts playing from the speakers. I tried bypassing the jack with alligator clips to the rear terminals, but it still happens, and when this happens I suddenly read a resistance of 7~8MΩ between either of the jack's channels and ground. I haven't tried another cable, but if I test the cable itself when it's unplugged I can't read anything between the rings.

I'm especially puzzled as to why there were no issues when I tried by tapping into the lines, but now that I did it """properly""" (at least in my head) it's problematic.

The full schematic for the stereo can be found by googling "BLAUPUNKT FIAT B-MPV CD-MP3 7645324316 SM"

I have a 12v 6.67A power supply with a male co-axial plug (with centre pin) that's 7.4mm OD and 5.08mm ID. The metal tube is 12.5mm long.

The pin is recessed and about 1mm in diameter - which seems impossibly small for 6.67A.

A chassis mount socket that would take it would come in handy. But I don't seem to be able to find one. Am I just using the wrong search terms?

Any pointers much appreciated.

So I wanted to design a children's toy, where the electronics could last 100 years (ignoring mechanical abuse). I figured some people here might be interested.

I settled on a CR2032-powered night light, using an attiny10 microcontroller, where the flash is rated for 100 years unless you're writing to it (which I am not). I did some pretty heavy power optimization. The firmware is hand-optimized assembly.

When you turn it upside-down, a tilt switch toggles an LED @ 3mA via a pretty intense debouncing routine.

A watchdog timer has it auto power off in 30 minutes.

When off, it consumes less than 1 uA. So it has about 25 years of standby time, although the battery is only rated for 10 years (it is replaceable though).

If a child uses it every day, then the battery should last about 4.5 months.

I made custom boards for it -- I kept is simple with few components as possible (resistor is for scale):

I kept assembly simple. A better design would snap right in to the pins of the CR2032 holder, but that's an addition I'll make another day. I also should have added one more ground pad to solder to, but forgot. Still, an OK result I think.

I used some spay-on lacquer to protect the traces a bit after assembly.

I want to connect five OV2640 cameras via FPC to an ESP32 on a custom PCB. Is this generally possible and does the ESP32 have enough power for this or do I need an ESP32 for each camera? The frames per second are not so important as the cameras will be used as QR code scanners. Which components allow to run so many cameras with one ESP32?

I'm looking for a version of this connector (2x2, 2.54mm):

https://www.adafruit.com/product/4855

with extra long pins, like this: https://www.adafruit.com/product/2223

Any sources for this?

Since I never understood op-amps from reading or practicing problems I wanted to build a circuit to probe around and use different resistor values to set the amplification.

Currently I am attempting to build an LM358 Non-Inverting Op Amp. I am using my power supply for a +/- 12V rail, and my Arduino Uno for my 5V supply at the V+ input pin. I have chosen two 1k resistors to amplify the signal to 10V at the output and put and led as a indication that the circuit is working.

My questions are as follows:

1. Is the ground for the voltage rail and input signal the same?
2. What exactly is wrong with the circuit I built? I want the LED to only turn on when 5V is supplied at the input, right now the LED can turn on if I connect the ground to the voltage rail supply even without an input voltage.
3. I've seen the post on Adafruit with the feedback resistors connected to the same ground as the rail supply, but the circuit diagram does not show where the input voltage ground is? Link: https://blog.adafruit.com/2012/06/13/ask-an-educator-making-a-non-inverting-op-amp-circuit-on-a-breadboard/

Is there a reason why the banner and logo of this community are just the reddit logo?

To be honest that doesn't seem very appropriate, nor is it very pretty.

What I've done is take a large 2n3055 BJT NPN power transistor, and decap it (it is a large metal-can type). Then I carefully removed any coating from the exposed silicon (it typically has a dab of silicone potting compound on it).

Then, I had a weak alpha source at ~5MeV lying around the lab from previous work. This was inserted into the can with the beam facing downward towards the exposed silicon, and the can reattached and made lightproof.

Then I threw together the circuit shown here using the modified transistor (the base is left floating). What I expected to happen was that at TP1 (relative to GND), with my scope AC-coupled, I should see small voltage spikes followed by a decay. This is caused by alpha particles impacting the silicon and knocking loose enough electrons to permit some current flow.

However, I just see... more or less nothing, maybe some electrical noise from fluorescent lamps in the room next door. Certainly not the spike+decay curve I've seen with other detectors.

Did I make a wrong assumption somewhere? It's been a while since I worked with discrete transistors much, and I feel like I am missing something silly.

Or is this more or less right, and I should maybe question whether my alpha source is still good? Or whether the signal strength is in a voltage domain I can even clearly see without amplification? Or maybe I should suspect that a thin passivating glass layer is added to big BJTs these days, enough to block the alpha?

The source is past expiry, but not by that much. I'm mostly interested in characterizing and documenting the detector as an academic exercise.

I've been looking for a simple low-voltage cutoff circuit for a 12v SLA battery, but many of the ones I find have reviews saying that the protection circuit itself drains the battery slowly as well. Is this just inherent in the design, where it has to draw a little to measure the voltage, or are there low-voltage cutoffs that don't draw anything until the battery is recharged?

I've wondered this occasionally over the years, but never got it working.

I tried just putting a dried piece of chicken bone pressed between two plates (mild compressive stress perpendicular to the bone), and using an inverter just like I would use a crystal. It did not work. Maybe I need a really thin segment?

I have no practical application in mind. I might make a CPU from it for Halloween I guess?

I'm not sure if I would classify it as electronics or necromancy, but I thought it was an interesting question to ask here :)

Hello, I have a strange problem with the LM337 regulator. I have built a classic LM317/337 power supply - and it works, giving proper voltage, etc. however when I start it under load (approx. 300mA per regulator) using a switch, the LM337 goes into some sort of protection (audible buzz), but when I start the circuit under load using on/off switch on my laboratory power supply (I think the input voltage is rising then slower) the LM337 works as normal. I heard that when the LM317 is starting as first, then such effect may occur (but I don't know anything about this). What would be your first suggestion in solving this problem?

I bought a random cheap crystal oscillator off AliX. It was advertised as a "constant temperature crystal reference".

I also didn't know what voltage it took. I found a photo of a similar one which apparently needed 12 V. However, smoke started coming out when I tried 12 V.

It seems to oscillate OK on 5 V though. However, it seems to be fluctuating in frequency, and I don't know if this is normal, or whether I have damaged it.

Bought it a long time ago and can't remember. There's a jumper cable and I remembered using it to flash something. I only dabble with Atmega32U4, Atmega328p and stm32 blue pill, so it's probably either of them.

Or maybe my brain short circuited and it's a totally different hardware.

I actually needed an AVR flasher to fix a pro micro with corrupted bootloader that cannot enter dfu mode. So I want to make sure I don't have it before buying a new one.

Thank you!

I'm getting a little bit frustrated with my AliExpress 2.54mm dupont ribbon cables. The female housings get loose after just a few cycles, and the connections start falling apart easily.

I've gotten some Amphenol Mini-PV 47649-000LF, which are amazing and are close-enough to being compatible with a standard dupont housing. But it's a hassle to crimp the wires myself, especially when I just need another female-female 6in wire.

Lots of stuff on the internet, but it's impossible to tell when it's actually good and when they just repackaged AliExpress. Anyone have a vendor they've had good experiences with? Ideally multi-color, but I'm flexible on that.

Hi all

I'm working on a DIY 18650 lithium ion home battery, built out of old laptop/ebike cells that have been tested for performance (capacity, internal resistance and temperature during cycle) and found to be good enough for use.

There are several safety precautions in my setup. Each cell has a 1A current fuse and a 60C thermal fuse attached to it(in series). Should a cell overheat or develop an internal short, the cell gets deactivated easily without fancy electronics. (protip, don't hotglue thermal fuses!) The BMS is a DALY BMS rated for 60A, although I'll probably never use it above 30. Additionally, an Arduino monitors the individual cell voltages as well as overall temperature (secondary BMS that can communicate over serial to a proper webserver.). This Arduino also watches a smoke detector and controls a solenoid killswitch should anything fishy happen, like overvoltage/temperature or the smoke sensor triggering.

This may or may not be a bit overengineered but I want to leave this system running pretty much autonomously with several layers of safety. A Chinese BMS on its own is not good enough and a professional one is outside my budget. Also the learning process is worth the effort.

Should, god forbid, a cell actually catch fire despite all safety measures I want to have the battery in a fire safe container as well. An iron cabinet like the IKEA Lixhult won't melt in case of battery fire but it will vent hot fumes that could set surrounding objects on fire. What would be a good way to engineer that? A metal cabinet with a metal chimney attached to it? So that the hot fumes get directed away from flammable objects? Perhaps something built out of stone where sand bags may be placed above the battery. Fire would cause the sand to drop on the batteries and smother it.

There isn't any way to crosspost on Lemmy right?

Hi everyone, I've just resurrected a broken Weller TCP1 and need a 24v ac supply for it.

I have a 23.5-0-23.5v toroid that I was just going to use half the winding - but it's overkill (8A rating) and going to be very big and heavy.

I've also got a pair of identical transformers with 8-0-8 and a 16-0-16 secondary windings.

I'm thinking of paralleling a 16v winding on each transformer, doing the same with an 8v winding and putting the two in series to give the 24v. However, that leaves two 16v windings and two 8v windings left unused.

Is there any advantage in paralleling those windings also? Any disadvantage? Or just leave them unconnected...Which is what I was about to do..

Sadly I cannot split either winding into two independent ones.

I'm interested in learning how to make a proper PCB rather than perf board with wires all over the place.