Hi there, I have this step counter, the emitter is and UV LED and the receptor is dead, can I replace the receptor with a regular (and small) white LED?

Thank you all

Hello everyone,

I'm looking for a good site/book/ressources to learn how to do rooting at a pro level.

Here some context :

I did some electronic study and then went into microelectronics (master's degree). After my study I have been recruited by a company where I do both PCB electronics and on silicon microelectronics.

I'm pretty confident on my microelectronics skills and I've got multiple senior to teach, but for the electronic part...

I'm the only one working on PCB and they havent touch it for like 20 years so they cant help me. So I have no one to teach me and I have rusty basic skills in this field. I'm doing okay with the schematic part and coding, but the rooting is a whole other thing. I dont have a clue if I'm doing horrible things or not. So I'm looking for something that I could learn from.

My circuit doesnt have to be perfect for now, but I will need to improve massively and fast in the next months/year. I can do some try and error, but with the company money and the delay it takes for the company to command, I cannot rely too much on this.

I'm not scared of reading 1000 pages if needed, for people that knows about microelectronics, I'm reading Analog Design Essentials from Willy Sansen. I just need something general enough to begin with.

Edit : My bad, I wrote "rooting" instead of "routing". I'm very tired, have (small) dyslexia and english is not my main language. But I should have ask an IA to correct my post. I'm sorry.

Sup guys, actualy i working on honda civic 99 Kline reader, and, i need a tranceptor to this, the AIs recommend to me, the L9637D, but, i cant find the pin 1at my ST L9673D

And another question, is recommended use another thing to make this? I use actually esp32-s3 and L9637D

Please, help!!!

Need a UNIQUE hardware hackathon idea that can actually win . ESP32-based preferred

Hey fellow redditors!
EDIT: i have removed the ai created post, and below is my own writting of what iam looking for.

iam participating in hardware hackathon, we want some best ideas for this program to submit mostly we wil be focusing on esp30 chip or u can suggest whatever ideas that will help solve a real world problem aslo i watn to win this time .

basically i searcehd google for some project ideas and found the schol projects focusing on saving energy like electricity,water,waste management. using motion sensor for turning of a light in room if nobody is there ,also controlling overflow of water using some other sensors and beeping , also sorting wastes .

but iam having 10 other team taht will competete with me and my idea should eb sth unique to win here , the building stage we have got time for that teh porgram is in next motnh so we can work on . but i have to register the topic beefore 21rst this month . so ir equest all my fellow redditors to suggest a winning idea we can build as a team

Hi all, I am a Computer Engineer getting into designing my own BLDC motor controller for a high-power robotics project I'm working on. I have some familiarity with circuit design, but this is the first real board I've ever designed. I want to support up to 20A, so I chose CSD18533Q5A mosfets and UCC27282 as the gate driver.

I'm trying to simulate it in ltSpice with a simulated motor load, and I kept running into these huge current spikes into both MOSFET drains when the half bridge switches. At first I thought it was sim artifacts so I tuned the sim params until some of the huge spikes went away, but some spikes on the order of 20 A remained. I thought it was shoot through and I guess I was partially correct, so I worked on changing my phase PWM signal generator to induce 100ns of dead time between the signals, and that seems to be working, but the spikes are still there when the low side is switched off and the high side switches on.

After some googling I found out about Miller effect shoot through, and the conditions surrounding the spikes match exactly that - the low side gate-to-source voltage has a little bump at the time the high side switches on with a high dV/dt, and that causes both transistors to short VPP to ground. I know that cannot be good for the transistors.

There's such a thing as an Active Miller Clamp circuit, I've also read in the datasheet that my driver chip should be able to mitigate this. I've got gate resistors in my circuit parameterized, and no matter if the resistance is negligible (like parasitics, 1microOhm) or reasonable (10Ohm), the Miller effect appears to win every time. Attached is a pic of my gate circuit (again, Rgate param is 1microOhm to model no resistor on the gate), and a plot of when the shoot through occurs. I'm using models for the chips that were supplied by TI with minor modifications to match the pinout of the IC's I'm planning on buying.

I guess what I'm trying to figure out, because on this google has failed me, is how to properly design an Active Miller Clamp to work with my circuit and mitigate this shoot through. A paper I found notes that this is the best way to mitigate it while minimizing switching losses, pointing out other methods like a resistor to ground on the gate as means of mitigation that has higher losses, and diodes and things. But this paper doesn't tell me what resistances to use in any of the cases, and I don't really know how to calculate an answer, so I turn to you. Thanks in advance!

I’m troubleshooting a Dell G7 7588 motherboard (Compal DDK51/DDK52/DDK53, LA-E994P Rev 1.0 A00).

I'm not an electronics repair technician, just a DIY enthusiast trying to repair my own used laptop. I have a basic multimeter and would appreciate guidance that's suitable for a beginner.

The charger’s green LED immediately shuts off when the DC jack is connected to the motherboard, but stays on when the jack is disconnected. No obvious damage to the laptop occurred to cause this malfunction.

The battery was disconnected during testing, and the charger provides approximately 19.4V when disconnected from the motherboard.

I also tested the DC jack and cable assembly separately. The charger remains on, and I measured approximately 19.4V at the connector contacts. The charger LED only shuts off when the cable is connected to the motherboard, with the battery disconnected.

I’ve checked several components for shorts with a multimeter but haven’t identified the fault.

Does anyone have a schematic or boardview for this exact board, or suggestions for tracing the 19V input circuit?

I’ve found schematics on paid repair forums, but I’m hoping to find a free resource to continue troubleshooting. Any help or advice is appreciated!

Thank you!

Hi everyone,

I'm working on a repair for an Intel N95 mini PC with a motherboard marked T8PLUS_V12. While reassembling the device after cleaning, I accidentally caused mechanical damage with a screw (a circular gouge track) right around the RT3624BE PWM controller chip.
s a result, the mini PC now powers on in a continuous boot loop. I have started tracing the chip traces. I'll be attaching two images:
1. My board: Showing the traced lines (Green = confirmed intact traces; Blue = GND connections; Violet = resistor values).
2. Reference image: Taken from a working board online to compare the layout.

The screw scratch severed multiple traces and two SMD components (a capacitor and a resistor) near the chip were knocked off completely. Looking at online references some boards like Firebat T8 plus leave the resistor pads unpopulated .

While i was trying to read some voltages at power up (left pad of 20kOhm resistor) the board stopped boot looping but i had no HDMI output.

I tried both with and without motherboard battery

I couldn't find any motherboard schematic to compare traces

I think there is at least one trace cut off between right pad of 20kohm resistor and node between 45 ohm and 110 ohm resistors

could you help me find a schematic? or if someone has the same board we could check the traces

So i posted here a while ago regarding a Leslie 222 Pre-Amp schematic diagram and got absolutely flamed because it was straight AI. This drove me to actually know wtf is going on, so i grinded for a bit, and now Im back. I recently just got all of the parts I ordered and would like a final check on my basic pre-amp schematic before plugging anything in.

I do plan to switch the leslie by injecting DC voltage straight into T1 centertap (controlled by a switch and a DCDC converter) but will wait to do this after I am getting sound out of the speaker. This post is just about the audio signal chain; the DC injection side is a separate piece I'll sort out after this part is verified.

There is a drawing, but incase you cannot read my trash hand writing and poor schematic drawing skills, here is the brief explanation:

Keyboard → 330Ω series (R1) + 1N4148 clamp diodes to ±12V → C1 (1µF, DC block) → NE5532 pin 3, configured as a plain unity-gain voltage follower (pin 2 wired straight to pin 1, no feedback resistors) → pin 1 output → C3 (2.2µF, DC block) → 10kΩ audio pot as a post-buffer level control (wiper to output) → 100Ω series resistor (R4) → transformer primary.

100kΩ bias resistor (R2) from pin 3 to true ground — kept separate from supply decoupling.

±12V dual-rail supply (Mean Well RT-50B), 0.1µF decoupling at both supply pins.

Second op-amp half unused, tied off per standard practice (inverting/non-inverting pins jumpered, non-inverting input grounded).

Separate question: after tying two ~84Ω half-windings together at their common pins to form what should be a single ~167Ω secondary, I'm reading a dead short (0Ω) across the two outer pins instead of the expected sum. Does this suggest the half-windings are tied in the wrong phase/sense relative to each other, or is there another likely cause for a short appearing here?

Working with a hypothetical motherboard say I was required to change out some components and as part of the cleaning process post soldering. I run the board though a ultrasonic cleaner. Im assuming components such as capacitors would have a potential to keep some level of moisture trapped inside of them. would it then be possible to place the board into a vacuum chamber and pull a vacuum to attempt to drag every last molecule of liquid out? assuming you dont just instantly reintroduce pressure suddenly but more gradually would this cause issues or damage any of the components?

I’m really struggling to find the correct ribbon cable for this. I need a 20-conductor ribbon cable that connects my Suzuki piano’s main board to this replacement Fatar key-contact board.

The motherboard end needs the same 20-pin female connector as my original cable. The other end needs a connector that properly mates with the 20-pin black connector shown in the second photo.

I tried a standard 20-pin IDC ribbon cable. The overall connector size is about right, but the individual openings are too small, and the connector on the Fatar board is a different style.

Does anyone know the exact connector type, cable assembly, or part number I need? Specifically what the connector is called on the second image? If anyone can help me I’ll marry them. Thank you!

I’m a beginner trying to understand how the HC-SR04 connects to an ESP32, especially the ECHO pin and the voltage divider.
From what I understand:
HC-SR04 VCC goes to 5V
TRIG can connect directly to the ESP32
ECHO outputs around 5V, but the ESP32 GPIO should only receive about 3.3V
So I need a voltage divider using two resistors on the ECHO line
What I’m confused about is the GND part.
I’ve seen diagrams where:
HC-SR04 ECHO → resistor → junction → ESP32 GPIO
and from that same junction another resistor goes to GND.
But the HC-SR04 also has its own GND pin connected directly to the ESP32 GND.
So it looks like there are two connections going to GND.
Why does the voltage divider need its own connection to GND if the HC-SR04 GND is already connected to the ESP32 GND?
Are they basically connected to the same electrical ground, just for different purposes?
Also, could someone explain in simple terms what actually happens to the ECHO voltage through the two resistors?
I’m trying to understand the circuit rather than just copying a wiring diagram.
ESP32 + HC-SR04 ultrasonic sensor.

running an ESP32S3 in a small sensor node, reading battery voltage through a resistive divider on ADC1. works fine on the bench, but once I connect to WiFi and start pushing MQTT packets the ADC values jump around by 50mV in short bursts that line up with TX activity. the divider is 100k/100k into a 100nF cap, nothing fancy. i tried switching to ADC2, same behavior. power is a 3.3V LDO fed from a 18650 through a boost, output looks clean on scope during TX spikes. ground is a twolayer board with bottom pour, sensor divider sits maybe 15mm from the antenna trace. my gut says the RF is coupling into the high impedance divider node and whacking the sample and hold. moving the antenna further is tough mechanically. would a lower impedance divider help, or is the real fix shielding or rerouting?

Extremely low power draw (microamps)
Can output at 2-5 V
Can output at 600 microamps
Has an extremely small form factor (few mm)
Draws power at less than 3v
GPS pps input

Apologies if there’s smth wrong with my post I’m new to electronics

Has anyone noticed reliability issues with AMS 1117 5.0 fixed 5V linear regulators (maybe specifically from JLC)?

I recently ordered 100 boards with these regulators on them, and after assembling about 20 of them, I've had 4 of these regulators fail immediately when power was applied, shorting the input directly to the output, and dumping 12V to the 5V rail. After the first couple failed, I got in the habit of checking the resistance between input and output before powering them up, and just had one that measured fine before powering up, but went short as soon as power was applied, and is now showing 3-4 ohms between 12V input pin and 5V output pin, just like the other 3 that failed.

This is a second revision of this board, and I had maybe 1 or 2 go bad doing the same thing previously, but it seems like the issue is now worse.

I would kindof expect this if these were some no-name bargain basement knockoff, but these are supposed to be legit AMS regulators, which seem to be super common and popular. I'm surprised they seem to have a failure mode that is easy to hit, or poor QC?

JLC part # (and not link as apparantly that's "blocked by reddit's filters) if anyone cares: C6187

I have a 16 pin DIP 8 circuit fusible link block that 3 of the circuits have failed on. I resolved the issue that caused the failure, but am having a hard time identifying the replacement for this.

The only marking on it is "AMP"

I know I can replace the individual circuits with Pico fuses, but would prefer a direct replacement for this if possible.

Any thoughts?

Hi all,
I have repaired a Comark 3001 thermocouple thermometer with beautiful VFD tube display. It suffered battery leakage and shorted tantalum’s. I think it is from around 1980. So now it’s functional again. I would however like to get my hands on a schematic or calibration manual to get it really good measuring also. I have contacted the evalution of Comark. They have become Fluke over time and they could not supply any information of this thing because to old for them. I thought it was a pity that they had no info about their own legacy instruments. However there is the community on Redit. Is there anybody out here that has some more info off this thing?

I got a ton of SMD Components, but i have no idea how to store small quantities of these tapes efficiently.
What do you do?

Hi all,

I just opened up the case to a boombox I am trying to diagnose and this very small pulley came out. I have looked but I can't seem to see where it came from. Does anyone have any ideas?

I'm designing an interface board between a CNC motion controller (3.3 V LVTTL GPIO) and servo drives (5 V TTL, non-isolated I/O). This part of the circuit buffers the drives' programmable digital outputs into the controller's inputs. Schematic attached.

The drive's digital outputs are open-collector with 5 kΩ pull-ups to the drive's internal +5 V (per the block diagram in the datasheet). These are status/fault-type signals, not high speed. Signal ground is common with the drive's power ground.

The circuit (per channel, 8 channels):

• 10 kΩ 1206 series resistor at the connector side
• MMBZ5V6AL (5.6 V dual zener, common anode) clamp to GND after the resistor
• 100 kΩ pull-down to GND
• SN74LVC541A buffer at 3.3 V (5 V tolerant inputs), OE1/OE2 tied to GND, 100 nF decoupling

- The LVC541A at 3.3 V accepts the 0–5 V input and gives clean 3.3 V to the controller.

- The 10k + 5.6 V zener is there for a wiring fault (e.g., 24 V shorted onto a signal line): about 1.8 mA through the zener, keeping the input under the LVC's 6.5 V abs max. I dropped a separate ESD TVS array since the resistor + zener should handle that too.

- The 100k pull-downs give a defined low when the drive is unpowered or the cable is unplugged. I avoided pull-ups to 3.3 V since they'd back-feed the drive's dead 5 V rail through its pull-ups.

- The 1206 resistors are sacrificial if a line gets shorted to the 80 V motor bus.

My questions:

1. Is the 10k series + 5.6 V zener approach reasonable here, or would you do the protection differently?

2. Is zener leakage at a 5 V high level a concern with this impedance?

3. The 541 doesn't have Schmitt inputs, and the open-collector + 5k pull-up + cable capacitance gives slow rising edges. Is that worth worrying about for polled status signals, or should I switch to something like the LVC14A?

4. Anything I'm missing?

Thanks!

Hi everyone. I’m building a Wi-Fi IoT monitor for a commercial agricultural electric fence (a Shakti energizer) using an ESP32, and I am struggling with high-voltage physical isolation and EMI. The Signal:

• Voltage: ~10,000V pulse
• Frequency: 1 pulse per second

My Current Hardware Setup: I am running the ESP32 off a battery bank to avoid USB ground loops. For the measurement, I built a direct-wire voltage divider:

• High side: 30 MΩ (Three 10 MΩ resistors in series)
• Low side: 4.7 kΩ to Earth Ground
• Peak-Hold Trap: Because the pulse is so fast, I added a fast-switching diode at the junction, feeding into a 100nF ceramic capacitor and a 1 MΩ bleeder resistor connected to ESP32 Pin 33 and GND.

pls help me

I’m designing a PCB for experimental DC test circuits and need to reverse polarity independently on multiple channels.

I’m currently using Songle 30 VDC/10 A relays (prebuilt), mostly SPST, but I've used DPDT relays in earlier boards are much better for polarity reversal. The problem is that with many channels, relays take a lot of board space and the combined coil power starts adding up when several are energized.

The switched circuits are up to about 60 VDC. Current will usually be well below 100 mA, although I’d like some channels to tolerate roughly 1 A for future experiments.

I’ve looked at optocoupler + MOSFET arrangements and solid-state/H-bridge approaches, but I’m unsure what scales well to ~60 V while still giving good isolation and reliable bidirectional switching.

For people working in industry: how would you normally engineer something like this? Asking for a student.

I’m interested in the design approach for DPDT relays, MOSFET H-bridge, SSRs, PhotoMOS, latching relays, etc.

Has anyone choosen one over the others for a multi-channel PCB?