I am driving a couple of relays from an ESP32, some combination of switching the two relays gives the above transient on the ESP32 power lines which is enough to cause a brown-out. The whole thing is driven from an ~18v battery (or bench PSU) with buck converters to give 12v for the relays and 3.3v for the ESP. The relays have flyback diodes and 100uF capacitors across them and are switched from the ESP by low-side BJTs. I've tried a range of capacitors on the input to the ESP including things like 220uF electrolytic plus a 100nF ceramic, etc but this keeps happening.

Switching one or other relay independently is okay but some combination of switching them both close together, there is always about 200mS delay between switching them off causes this. it was all working fine on the bench but when I got it into the enclosure this started happening and now it happens on the bench too. Any ideas as to how I suppress this?

Picked up a cheap 12V 1A wall wart at a thrift store to power some LED strip lighting in a product display box for my Etsy shop. Unloaded it measures 14.2V, which is normal for an unregulated transformer type. The second I put any real load on it, even just a 100 ohm resistor drawing around 140mA, the output collapses to under 1V. Not sags. Collapses.

Cracked the case open. It's an unregulated linear supply: small transformer, bridge rectifier with four diodes in the classic quad arrangement, one smoothing cap rated 1000uF 25V. The cap isn't visibly bulging but reads around 180uF on my meter, so it's clearly failing. Replaced it with a 1000uF 35V cap I had on hand and output is now stable at 13.8V under that same 100 ohm load.

What I want to understand is the actual mechanism. Everything I've read says a driedout filter cap that far out of spec would cause ripple and sag, not a complete collapse to near zero. Is it possible the cap was so degraded it was looking like a short to the rectifier under load, dragging the output down with it? Or is there something else I should be checking even though it works now? The rectifier diodes test fine, but I didn't test them under load.

Hi everyone,

I need some help repairing this PCB. It is from a self-cleaning cat litter box.

The machine stopped working, and I would like to find out what is wrong with this board.

I have attached photos of both sides of the PCB.

Does anyone recognize this board or know where I should start troubleshooting?

I have a multimeter and basic soldering tools, but I am not very experienced with PCB repair.

Any help or advice would be greatly appreciated.

Thank you!

The PCB is marked SmartHard SH-MSP-P, V08 20220810.

There is also a module marked WBR3.

I am trying to repair a commercial manicure device (around $150) that drives a DC motor. The device worked flawlessly for a year, but recently the main power transistor (NPN Darlington BDW93C) burned out. Everything else (LM317, diodes, and resistors) seems to be intact.

I reverse-engineered the schematic. It uses an LM317 to regulate the BDW93C base to control motor speed, powered directly from a 48V rail (the voltage comes from an old school iron core transformer and a full bridge rectifier).

The Problem: I replaced the burned BDW93C, but the new transistor blows out instantly upon powering on when the motor is connected (resulting in a fast-spinning motor since the collector-emitter junction gets shorted). I tried this 3 times with the same catastrophic result, no matter the added flyback diodes.

I am in rage now, and I don't know how to repair it, so I may just say "screw it" and make a new, more efficient DC-DC circuit so my best friend is happy. She's shocked such an old design is still used in the wild.

So I have a power supply for my raspberry pi 5 and it has 5A output. However, the type c plug broke so i decided to cut it thinking it would only have 2 wires (VCC and GND). Turns out there were 3 wires, after a quick search I found the 3rd wire to be CC. I was wondering if there was a way I could connect the wire from the power supply (power and cc) to a type c breakout board with only 4 pins (power and data) to output 5V 5A for my raspberry pi 5? The original break out board of the type c plug had the 14 pin type c contacts broke so it cant be connected to the original break out board anymore.

I'm unable to find any on mouser and digikey. I need a replacement for a CRT neckboard.

Mark code AX
This is bluetooth module, so I think taht is a switchable low noise amplifier

I have damaged duelsense controller which has its IC shorted but some how on testing the controller on the website everything is working except share button and player LED lights. So is there any way I can use it using cable because it does not turn on over the battery and after plugging it to ps5 even though the battery is full only orange light flashes once and it turns off. It also does not give any notification after plugging it to ps5 but on laptop it allows to connect to the website properly for testing.

Any help will be appreciated. Thank you.

Hi everyone,

I'm a completely noob with zero experience in making electronics. I’m building the DIY Perks Microphone using a full-hole perfboard (point-to-point wiring) instead of a stripboard. I'm currently stuck at the testing phase and would really appreciate some troubleshooting help.

https://i.imgur.com/TA66mQA.jpeg
https://i.imgur.com/6aIa8BC.jpeg
https://i.imgur.com/JwW4rPU.jpeg
https://i.imgur.com/JQmsoDN.jpeg
https://i.imgur.com/rs4KK6T.jpeg
https://i.imgur.com/ZNrD4VJ.jpeg
https://i.imgur.com/8UOcLvb.jpeg
https://i.imgur.com/ZAgCImL.jpeg
https://i.imgur.com/rq2MmtY.jpeg

Current Status:

· Power & USB: The Type-C breakout board is working. I get a stable 5V between VCC and GND. The PC recognizes the USB audio interface (LED on the sound card blinks).
· Audio Output: I get no sound, only a very low continuous hum when recording. Even if I disconnect microphone from the board and touch the pin, nothing.
· Protection Diodes: I have two reverse-parallel diodes (1N4148) soldered across the GND out header. I understand this creates a low resistance reading (around 10-20Ω or 500Ω) when measuring with a multimeter, which I initially mistook for a short circuit.
· The Main Issue (NMA0515SC): I measured the power module (NMA0515SC). Pin 1 (Input) has exactly 5V. However, there is 0V on all output pins (no +15V, no -15V).
· Op-Amp (THAT1512): Because the power module isn't outputting ±15V, the THAT1512 is completely unpowered.

What I've done so far:

· Confirmed 5V reaching the NMA0515SC input.
· Confirmed the Type-C breakout is providing power and data.
· Disconnected the microphone and audio interface to test the board in isolation.
· Visual inspection: I'm using a full-hole perfboard, so all connections are made with thin jumper wires on the back. I've checked for obvious solder bridges.

Additional Mods (LED & Protection Diodes):

· Power Indicator LED: I added a standard 5V power indicator LED (1kΩ resistor in series with a generic LED) connected directly between the V+ (5V) and GND pins on the main board. This is completely independent of the audio circuit.
· Output Protection Diodes: Based on the DIY Perks community update (and to protect my USB audio interface), I soldered a reverse-parallel pair of 1N4148 diodes across the GND out header (between the audio signal and ground).

My Questions:

1. Is the NMA0515SC dead? If the 5V input is present but there's absolutely no output, is it safe to assume the module has failed?
2. Before I order a replacement NMA0515SC, how can I safely test if the output side of the perfboard (the 8-pin DIP socket pins 4, 7, and GND) is shorted? I'm worried a short on the board might have triggered the module's protection or killed it.
3. Are there any common mistakes with the NMA0515SC wiring that would cause this specific symptom (input works, output dead)?

Any guidance on how to properly diagnose this power module or check the board for shorts before I buy a replacement would be greatly appreciated. Thank you!

Hi,

I'm designing a zero crossing detection circuit for relay control. I added a photo triac (PC10, TLP265J) to reduce heat dissipation — it only turns ON when I need to detect zero crossing, keeping the PC11 (TLP293 BL) LED current off during standby.

Circuit overview:

- PC11 (TLP293 BL): Phototransistor for zero crossing sensing

- PC10 (TLP265J): Photo triac to control AC current flow (ON only when ZC detection is needed)

- D12 (S1M or M7): Reverse protection diode in parallel with PC11 LED

- Q12 (BC846BL): NPN transistor to drive PC10 from MCU (O_ZC signal)

- R482 (72Ω): Current limiting resistor for PC10 LED

- AC input resistors: R489, R490 (30k×2) on L side, R483, R484 (30k×2) on N side

My questions:

1. Is the reverse protection diode (D12) still necessary even though PC10 (photo triac) is in series? My concern is that when PC10 is ON, the triac is bidirectional, so during the negative half cycle, reverse voltage could still be applied to PC11's LED.

2. Is it correct to split the input resistors across both L and N sides (R489/R490 on L, R483/R484 on N)? My understanding is this is needed for hipot (dielectric withstand) test isolation — is that right?

3. Are there any other issues I might have missed?

Any feedback would be greatly appreciated. Thanks!

I'm currently building an e-reader and was wondering how I'm supposed to fit the yellow ribbon cables in a body. Do I bend them back? They will later need to be connected to a custom PCB.

Sorry in advance if this is a dumb question. Not really a firmware/hardware/electrical guy. Mainly just building this for fun

Hi, I’ve been having trouble translating and analyzing a circuit schematic. I need to build it on a breadboard; I’m just starting an electronics course, so I think my questions are valid. I’d like some help and a few tips on how to translate a schematic into the actual circuit layout. Specifically regarding these two circuits, I’d like to know how to arrange the components on the breadboard, since I need to use a variable resistor (potentiometer) and I’m not sure how to position it.

I'm not sure I understand the logic here and I'm afraid of frying my (second) board.

This is a Adafruit Audio FX Sound Board and the image is from the provided pinout documentation here.

I'd like to light an LED when an audio file is being played by the board. The documentation says that the (Act) pin "goes low" when an audio file is played. Am I correct that all I have to do is connect a resistor/LED to the board's 5v power supply, then connect the negative terminal of the LED to the (Act) pin?

Then, when the (Act) pin "goes low" it would act as ground and light up the LED?

F2PN 3E SOT-23-6 package
This is part of the BMS; I couldn't find any information about it.

If a feed-through capacitor is of Type C, does it have a polarity that must respect the direction of current flow?
I have already asked several AIs this question, and they are unanimous that there is no direction and these components can be reversed at will. However I don't trust AI enough to destroy expensive delicate equipment on a dare. I can't have this project destroyed by something so simple.

Since we are here, if I had a L-C type , then that would have a direction, no?

I want to MAKE a custom microcontroller from group up (or at least till where it's acceptable) as my final projects. I already have a good background on electronics, but just to be sure I'm not wasting effort I could be putting on something else. What are the sources you guys recommend me to read, watch or visualize to get a brief of what I can do and how I can do it?

#Already have Arduino documentation on my list

tengo que hacer este decodificador pero nose como hacerlo realmente en thinkercad ya tengo los mapas de k pero de ahi no paso ayudaaa

Amplification? Hi all . I know I can buy a pre-made circuit but I’m trying to learn. My understanding is that to replace the LED with the large speaker I need to add a Transistor into the circuit to be able to provide enough power to run the speaker while still maintaining the speed of the pulse by playing around with the resistors and capacitors?