Ask Electronics

So far I have been using RCY connectors to connect some low power fans for a custom thingy (fursuit head, this will be relevant later (space limitations)). They have a fairly low power draw, so around 5v 0.1A.

This has worked for around a year, but as there is a lot of movement where I use it, the power leads have ripped right at the connector. It looks like this is caused by the lack of any strain relief as the connector is crimped and does not have the usual stress relief thingies, which are often seen at other stuff like psu cables, usb etc.

So I'm looking to upgrade / replace that with a different connector. I'm looking for one which has:

• stress relief against bending
• is twistable / unidirectional (so something more like a barrel jack / headphone jack)
• is small / slim (I have very limited room that's why I initially used RCY). The size is mostly limited in thickness, not length.
• is able to carry the very low voltage and current of 5v 0.1-0.2A (so basically anything will do that)
• available in germany (most likely most things should be)

Things I have already considered:

• 5.5mm 2.5mm (/2.1mm) barrel type connector --> too thick sadly
• trying to protect the RCY plug with stuff like shrink tubes --> doesn't work, just slips off
• thinner barrel type connectors --> can't find a matching set of cable with plug and cable with receptacle

Rn my best bet seems to be 2.5mm headphone jacks. I do have the feeling that there might be something better out there, so that's why I'm asking here.

Any help would be very appreciated. Thanks in advance!

All the fridge repair videos I have seen demonstrate how a fridge with a damper works -- in which case all the cooling happens in the freezer and a vent with configurable damper diverts some cold air to the fridge. Perhaps that is a US design.

European fridges are apparently different. The fridge and freezer are separate with no interconnecting vent. No fans either. The freezer is surrounded with coils embedded in the surface panels. The fridge has a plate with embedded tube for coolant. I am surprised that a plate the size of a large dinner plate/platter is big enough to cool the whole fridge.

The plate also has a tube in a loop of tubing that is not embedded into the plate but against it. The two ends of the tube join into a molding with 3 wires going to the thermostat (one of which is a ground wire). What is that thing?

There is a separate wire that goes to the thermostat. I think that is the probe that actually reacts to the temp.

I couldn’t easily send pics because the plate does not come off. I can barely pry it to get an eyeball behind it. I think everytime I bend the plate to see behind it I probably bend the tubes carrying coolant (not good).

Hey I'm not sure if this is the right community for this but it seemed applicable, let me know if I need to delete!

I am seeking anyone with a Square brand magstripe reader (not contactless, magstripe specifically) willing to run a quick test for me. It's just:

• Connect Square to computer
• Open any text editor
• run any card's magstripe (except a chipped payment card. Costco, non-chipped card, gas station rewards card, etc will work fine) through
• Does it type out the data from two or three tracks in the text editor, the way traditional USB readers do?

Thank you for your time reading this, and double thanks for anyone willing to test. This is as close as I can get to trying before buying lol.

I am wiring this up, and I would like to limit the current being drawn from 18v DC/DC converter.

What would be the simplest way of doing this?

cross-posted from: https://slrpnk.net/post/26897688

Either the relay is broken or the thermostat. I know this because I could force the fridge to run by hotwiring 220V across the common and run pins then briefly jumping the start pin to the run pin (thus sending 220V through the start winding for a split second).

The thermostat assembly has too many wires to know what to measure resistance on. But I figure that the thermostat can be black-box tested simply by checking whether it sends 220v to the relay switch. There are THREE wires involved (in addition to ground). With the relay removed (thus compressor disconnected), I plugged the fridge into mains. Got these measurements:

common pin to run: 220v
common pin to start pin: 20v

I’m tempted to conclude that the start winding /can/ accept 220v (proven by hotwiring), but 20v is also sufficient to cause enough motor movement to get it started. Does that sound reasonable? Can I conclude that the thermostat works and the relay is toast?

It’s hard to be confident without a service manual, particularly when the relay¹ has continuity. The common pin goes through a cylinder marked “Klixon MRP342LZ-32Q1”, which as 0.5 Ω. The start and run pins go through what seems to be a ceramic disc having 45 Ω. Is that reasonable?

I am ½ tempted to attach the relay, bypass the thermostat, and wire the relay to mains with start-run jumped persistently. Is that crazy? I assume the relay would internally disconnect the start winding. The fridge has no fans AFAICT, so no need for anything else to have power in this test.

¹ The relay I have has part № “A 3B7 8100” printed on it, which I cannot find online. But it looks exactly like this one.

Update

I hot-wired the relay. It was non-trivial because the relay has /3/ inputs. After studying it closely, I realised that one of the inputs (apparently for the start winding) is phony. The spade connector that attaches to it ultimately goes nowhere. When connecting the remaining 2 pins to load and neutral for the house mains, the fridge started and ran just fine.

Thus I have to conclude that the thermostat went bad. And replacements are not sold. However, Amazon has what’s claimed to be a universal fridge thermostat. It’s cheap, but I boycott Amazon. I think I will wait until someone throws out their fridge. Perhaps I can just take any thermostat and make it work.

Hello everyone. totally nob here but very enthusiastic. I'm trying to repair an old SA610 pioneer amp that is shorted. I remove the power transformer and it's ok, generating 64 volts between red and orange as 32 volts between any of these and the white wire.

So, the short lies elsewhere, but I'm having a little trouble trying to find it ou. Can anyone help me?

I have an older electrical device which I would like to switch to charging with a USB C cable and a standard USB power supply. The device's power supply unit supplies 14V and 400 mA, so 5.6 W. The device documentation certifies it for 12V with 2 Ah.

I found a useful answer on stackexchange about the Source Power Rule for USB 3.1. This implies to me that my device is not compatible with 3.1 because at a power draw below 15W, PD 3.1 defaults to 5V.

According to Wikipedia, a USB4 DFP is required to supply at least 7.5W Type-C current, which is above the power requirements for my device.

Based on this, it seems to me that the power supply of my device is too non-standard to be supplied by a standard USB power supply. Have I understood this correctly?

Thank you for your help.

I recently got a bunch of old 80's crts which I cant find any information about online.
I do have the service manual tho link
Looks like standart composite with external Horizontal and Vertical Sync to me but I'm not 100% sure and I dont want to fry anything

Thanks,
Oha

(Electrical Discharge Machining)
In terms of current, voltage, frequency, rise time, etc. What makes this one special for switching topologies?

Got a used business laptop and found a recessed dongle in it. The original owner says they have no clue, that it’s been in there since they got it. There’s no way a dongle is keeping this thing running, is there? I’ve already swapped the OS, if that matters at all

Update: yubikey! Thank you all for the information, I’m definitely still learning

I have a controller for an electric throw blanket that I would like to repair, but I have no experience soldering on boards

You can see at bottom left a yellow box and a resistor. Something has burnt out in this area, and likely both will need to be replaced at a minimum

I would also need help identifying parts. The yellow box is embossed 'Tenta' and has printed on the side 'TC MEX/TENTAMKP 0.1 uf 275VAC' with some other markings obscured or damaged

Is this an achievable project?

So there are tons of 12"x9" magnetic grids out there for dropping screws onto when taking apart electronics, but my projects typically involve integration into other materials.

Having a sewing mat (about 24"x18") with all the metric/imperial grid lines and angle lines, but with a magnetic backing for holding screws in place would be perfect.

Has anyone ever tried to make a DIY magnetic desk pad? And if so, how did it go?

Hi, hope this post is fine in regard of rule 2.

Currently doing some fun stuff with an Arduino and have it hooked up to an 128x160px and communicate with it over SPI. If i color in all 20480 pixels it takes about 2 seconds to be done and i can watch the rows change one after another.

I was wondering if there are some tricks to speed this process up a bit or does it really just come down to minimizing the pixels to be changed?

The module im using is this one: https://www.waveshare.com/wiki/1.8inch_LCD_Module

Here is also my current code if anybody cares to take a look, even though i just rewrote the example code more or less so i would understand it. https://codeberg.org/bvoigtlaender/open-phone/src/branch/main

EDIT: Thanks to jeinzi, nickwitha_k and cmnybo I have managed to bring the rendering time down from 2142ms to 80ms

• write directly to registers keep in mind that the pin is different when using that method 2142ms > 1912ms
• write bigger chunks of data 1912ms > 272ms
• set spi clock 272ms > 80ms

After playing around with some greeting card modules to modulate sound onto a LED i found out that the driver part of said greeting card modules are not audio drivers but PWM drivers (oscilloscope confirmed).

This made me wonder if normal PWM controllers could be used to drive more power full LEDs.

My idea was to just remove the potentiometer and feed in music from Aux at that point.

Is there a chance of this working?

Update: I just tryed if it works and sadly it dosent, LED gets modulated somewhat but there is not audio to recover from it afterward, its only noise.

I tried to start my laptop earlier, only for nothing to happen. It won't start on battery or when plugged in (it can run without a battery when plugged in). The battery does seem to be dead, and so is the 3V CMOS battery.

I opened it up and noticed a circle visable on one of the inductors. Hopefully you can see it in the picture.

Could this be the problem, or is that normal?

Update: I've tested some suggestion and watched some repair videos, but I found nothing. Goodbye old friend 🥲🤚

Thanks for the help guys

I’m trying to fix my daughter’s electric scooter. The company sent me a brand new motor, out of warranty, however the adapter is wrong (see pic). I’m thinking I’m better off swapping the couplings rather than cutting and splicing, but I don’t want to destroy them - what is the best way to remove the wires? There appears to be some sort of yellow wax/paste holding the wires in.

EDIT: Thanks to all who replied; I’m going to try and splice the wires. Solder should be here tomorrow, so hopefully she’ll be up and running in no time!

So i have this sound module "FLR104A-A-V1.4" and it works fine, i can record and play audio with it.

But i am struggling to get the loop function working.

Sadly the Chip dosent have markings on it so i didnt found a datasheet to help.

There is a pad called "Loop" but it dosent seam to do anything, i tryed connecting it to VCC ~~or ground and~~ it dosent make the module loop.

I cant use a NE555 timer to trigger looping via play button because the sounds on it wont be the same runtime every time.

Any ideas?

Update: It may be a ISD1820 style Chip but with 4 min of storage compared to the usual 10-20sec...i cant find anything about it online

Update 2: from the functionality it could be a ISD4003 but it has to few pins for that

Update 3:

After soldering those 2 pins together AND hitting the playbutton it loops. It dosent loop on its own when turned on sadly there is still a initial play button press needed but i think this should be fine for now-

Update 4: Sadly the recording only loops 4 times and then stops again :/

Update 5: Connecting the loop pad to the negative side of the play button seams to send it into a endless loop yay

I messaged the seller asking for the exact name of the connector, but they just reiterated the listing title. I need a two Metri Pack-150 connectors, but I can't find prewired ones and I'd rather not buy a 200USD kit.

Trying to reuse this screen for a project I'm working on (yes I know I can buy another display for cheap, but I hate to waste a perfectly good display that I already have) but I am having difficulty tracking down a datasheet or even just a pin out

The text is "2.4HYDIS171+9325 24PIN", but I've tried searching it 6 ways to Sunday and nothing useful comes up.

I do know that the matching pin out should have the LED anode pin on pin 1, LED K/GND on pin 2 and VCC 3.3v on pin 3. It's also a 2.4" screen and should be a resolution of 240x320

I've probably gone through a million Alibaba listings, and while some get close they just miss the mark

If anyone could help me out that'd be amazing!

Additional pics:

I have a simple circuit where 5V signal is fed into a buffer (Nexperia 74LVC1G07), then from the buffer into another device. The buffer is fed 5V by a switching DC-DC (R-78HB5.0-0.5/W). After it's been off for a while, the buffer works, the signal is recognized by the receiver. This continues for some time, minutes, to tens of minutes. Then the buffer stops working. The DC-DC still works as well as the source. If I unplug it and let it sit for an hour, it resets back to working for a while until it stops.

Context:

The setup runs on an ebike 36V battery. Theres a hub motor connected to the same battery (via power controller). The signal source is a torque sensor. The destination is a bike computer.

Any idea what could be causing this? I don't know much about electronics. I learn specific bits to do something but I'm ignorant otherwise. E.g. I know what a buffer does, I understand how it works on high level but I have no clue for example how it could be affected by the rest of the system electrically through noise, EMI, etc. My physics intuition here makes me think there must be some charge buildup happening which dissipates with time when turned off. I've no idea if this is remotely valid, or if it is how to fix it. Any ideas are appreciated!

I just found out I can buy a decent 400W solar panel in the local hardware store for around 90€ these days.

Are there people around with experience in off-grid solar? There is quite some supply in cheap MPTT charge controllers on the internet. And I can't afford a 700€ power station. But I would be able to buy a few power tool batteries or one of the lead-acid batteries people put in their caravan. Are there projects building a power station myself? Is this even worth it?

Maybe someone alredy wrote a blog post with recommendations or findings and failures along the way. Or has something similar running at home?

(Thanks to the mods for steering me towards the correct community.)

Hi all. Does anyone have experience with the BMSs from Daly? I'm looking to get a 16s BMS for a DIY li ion battery pack. I have a large box full of li ion 18650 cells and want to make an emergency battery system for home use.

That power outage in Spain motivated me to finish this project.

I'm using an Arduino and through a library working with an IC (MCP2515, a CAN controller) over SPI. The IC indicates interrupts by causing a falling edge on an interrupt pin.

Components are connected using jumper wires on a breadboard.

• When a logic analyzer is not attached, the IRQ gets called a few hundred times. It should only be called once. I thought it must be noise on the external interrupt pin but a pull-up doesn't help. I've tried the internal pullup and an external one.
• Trying to see if there is a ton of interrupts from the IC, or an error internal to the Arduino, I attach my logic analyzer. Now it works perfect.

Any idea what might cause such a weird issue? Looking around I haven't found anything.

EDIT: I found a Reddit post for a different circuit where a user suggested placing a small capacitor to make the edges of a signal rise slower. This has fixed my problem.

Since I've already created a post: does anyone know why I was getting an unending number of interrupts? Why would the edges of the interrupt signal changing too fast cause something like this?

It's the trace going towards the mode button, so I'm pretty sure resistance won't exactly be critical over a ~3mm gap, as long as it recognizes when the plunger button is pressed down.

Not sure if this is a dumb question but this has me quite puzzled.

The legs on TO220 packages are very small. How is it that there are e.g MOSFETS rated as being able to continuously conduct ~100A? e.g IRF1404Z

From what I understand such large currents need busbars on PCBs and these appear a lot larger than the legs on these components.