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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?

A comprehensive mapping of old subreddits to new communities.

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.

I recently bought a thinkpad T470 for a good deal, and it turns out that it was a good deal because the BIOS is locked with an admin password so I can't install an OS, or change any BIOS settings.

I also recently came across a paper that describes a "security flaw" in most thinkpads where you can bypass, then reset the admin password by shorting the SDA and SCL pins on the BIOS chip.

Does anyone know where this chip is located on the MOBO? I would be hugely appreciative if you would be so kind as to point me in the right direction. Thanks in advance!

Hello,

No formal training, but do like to repair devices at home (and keep vintage electronics and computers going).

Yet another alkaline battery has leaked prodigiously into a device (after only a few months). A wall-mounted thermostat.

Is the sort of clip pictured, which contacts an AA battery negative terminal at one end, and seemed to just clamp onto a conductive trace at the edge of PCB at the other, an easy-to-find standard form (for replacement) or a custom piece?

It is quite corroded and even peeling, and suspect replacing the clip would be better than devising a work-around.

Visually searching through product photos on supplier websites (like Digi--- and Mous-- here in the US) has not been effective.

Thanks for any comment.

I'm currently looking into various DC DC converters and was confused that the Meanwell DDR-60 series only shows a typical rating but says nothing about the efficiency at idle. From AC/DC converters I'm used to have a curve that starts at idle and maybe 70% and goes to 100% load, having the peak at ninetee something.

(Edit: link goes directly to the PDF)

I got it with https://sabrent.com/collections/hard-drive-accessories/products/ec-ch2b. But since I bought it in EU, it has that charger. Is there no alternative other than buying a whole new charger?

i can’t find ANYWHERE this ic chip, not even in chinese online stores. code is FMM862, laptop model is a Gateway GWTN141-10. it can also be another one that works. thanks in advance.

Hi all! I recently purchased some push-lights for my kitchen from my hardware store, and I stupidly didn't read the package that said that they shut off after 30 mins. This is super inconvenient in my dark kitchen, and I can't return them. I figured I might as well tinker with them, and any help would be greatly appreciated. The first picture is the small, round push-light (it was in a 3 pack, so I've got room for error with these), and the second picture was the even bigger disappointment because it's a larger strip light.

I found them online for reference here and here. It doesn't say they shut off in the description of these, but it says it in the user manual under "product guides and documents" for the rectangle light.

TL;DR: Help me bypass the "power saving" mode that shuts these off after 30 mins please!

Hello! Someone suggested this "If the MOSFET is put into diode connection mode (connect the gate to the drain), you can force a small current (I recommend 1 uA–10 uA; 1 mA would probably be OK; 100 mA would result in significant power dissipation and could influence the results) and record Vds (which is equal to Vgs in this configuration).” There are just some questions i had in mind. *Is it possible to connect the gate and drain on a breadboard to put the MOSFET into diode connection mode? *How to force a small current in the drain. Is voltage divider will be enough? *Is it still possible to apply voltage source after putting it into a diode connection? Also, what is the expected measurement at the Vds terminal. If there will be no voltage source, will it be in the range of 0.1 to 1 V increase? *Why should the MOSFET be connected into a diode?

*Can a MOSFET handle low dosage for example, Cs-137 (666 keV)