r/AskElectronics

I used an inverting topology with positive feedback and R5 and R3 are like DC blocking high pass filters is this good and will this work?its an audio amplifier

i have done most of the stuff . including adding libraries and all. still why cant it run?

I opened my Corsair membrane keyboard to clean it and I washed the membrane layers with alcohol.

After that, I plugged the keyboard in before it was probably fully dry, and now it no longer works.

I noticed some darker areas on the membrane traces and I’m wondering if those traces look burned/damaged to you guys.

I attached close-up pictures of the suspicious areas.

Does this look repairable?

Would conductive ink or trace repair paint help in a case like this?

Thanks.

I'm looking for another set of eyes to see if anyone can spot anything wrong with either of these boards.

The pictured boards are from a Logitech G923 Racing wheel that is well out of warranty. While gaming on it, a thunderstorm started, lightning struck nearby and immediately the wheel stopped working. The wheel was plugged into a Belkin surge protector power strip, but it seems like it didn't fully stop the strike from killing the wheel.

Troubleshooting steps I have tried so far:
- Different (known good) outlet and (known good) USB ports were used
- Power brick outputs 23.75V both when unplugged and plugged into the wheel
- Measured a maximum of 6mA current being drawn for a split second after plugging it in, afterwards, 0mA
- Attempted to power using a different 24V/1.75A power supply with no luck
- I do not smell any "magic smoke", nor have I seen any

Diagnostics I have tried so far:
- Both larger capacitors near the 24V input read at or above whats printed on them
- The R033 and R100 resistors do not read as dead shorts
- Voltage is does make it through from the "main" board to the wheel board, and depending if the USB cable is plugged into a computer (reads 4.5V) or not (reads 0.25V)
- Motors run if powered directly

Details on the boards:
- Board pictured in pictures 1-4 is the "main" board in the body of the wheel
- When looking at first picture of it:
- Top right 2pin connector is input 24V power (+ on left)
- Other two 2pin connectors go directly to the motors (+ on top)
- Bottom left connector is input USB
- Bottom middle connector is H-Shifter input
- Bottom right connector is motor encoder
- Top left connector is steering wheel
- Top middle connector is pedals input
- Board pictured in pictures 5-7 are the wheel board

Was really hoping I'd see a clearly exploded SMD or something on the board when I opened it, but I can't see anything wrong. Any troubleshooting/diagnostic advice is welcome. With the warranty being long gone, I'm willing to try pretty much anything to save buying a new wheel setup.

Hi all,

I teach an introductory analog audio circuits class. Towards the end of the semester, students learn the basics of CircuitLab.com, and use it to create a first draft of schematics for their final project for the class.

Recently, a student handed in the two absolutely bizarre "schematics" above. Any thoughts on what AI or other software could have created these?

I am new, and this is all very messy and hard to work with, is there anyway to this all into a pcb, which I can plug into my raspberry pi, that can function as a motor driver and more like wheel encoders, and a lidar?

My self-design DC7DC synchronous step-down converter is working over hours as expected when switched on for the very first time, however it blows up as soon as I switch it on the second time. What did I do wrong? Where is my design broken?

I designed my own DC/DC synchronous step-down converter from 12.5V-14.5V input to 12.0V at 2A maximum output current based on the TI TPS62136RGXR. I had already asked for feedback on the design and the layout before I have put it into production and had incorporated all the feedback from this sub and other platforms. It is basically based on the TI reference design.

The load is a LED stripe, i.e. the load is constant and does not change after installation. The power is switched on the input side and comes from a battery, hence the input range 14.5V-12.5V.

When I installed my DC/DC converter the very first time and switched on, everything worked as expected. The input voltage from the battery was 13.5V at that time, the output voltage was 11.9V and the monitored currents were as calculated. The DC/DC converter had been running for about 3 hours before I switched it off again. During that time the monitored voltage, current and temperature were more than satisfying. The temperature of the IC and the PCB did not even rise noticeably.

However, when I switched the DC/DC converter on again for the second time the LED stripe stayed dark. The converter only delivered 600mV which (obviously) was too little to drive the LED stripe. I did not notice any other problems.

As I had to order 10 pieces in total from the manufacturer, but only needed six I had some to spare and tried some other specimen. These are the results

Specimen	Result for 1st power-cycle	Result for 2nd power- cycle
1	Worked flawlessly for over 3hrs. All monitored values (current, voltage) in range. No noticeable temperature rise.	Died "silently". Output voltage only 0.6V with load, no other effect.
2	Worked flawlessly for 1.5hrs.	LED striped flashed for a brief moment. Then the DC/DC converter exploded and triggered 20A DC MCB.
3	Dead from the beginning. Not clear whether due to the the same problem or due a faulty production. Output voltage only 0.1V with load, no other effect.	n/a, as 1st power-cycle already failed.
4	Worked flawlessly for over 15min. After that I decided that nothing important would happen anymore and proceeded to step 2.	LED striped flashed for a brief moment, then turned off. The DC/DC converter became really hot and started melting, but did not trigger the MCB as input current was "only" 10A. I switched it off, before worse things could happen.

What is wrong with my design which could explain those observations?

Summary of figures:

1. The schematics
2. Top layer of layout (please not that the silk layer still says 11.0V output voltage)
3. Bottom layer of layout (please not that the current layout has much more thermal vias)
4. BOM
5. Specimen #2 after the 2nd power-cycle
6. Specimen #4 after the 2nd power-cycle

Hi everyone, i'm in the middle of designing my first circuit board and wanted to just get some general advice for pcb design, what the most important things are to look out for and maybe even if someone sees an obvious mistake i made during routing or something.

some context: I'm trying to sample the (differential) signals from 2 underwater microphones at 200 ksps (each) with a 16bit ADC and a teensy 4.1, which will save all the data to a micro sd card. So far the circuit works (on two breadboards) and this is the pcb i designed for everything to go on to.

I have a second one of the bigger panel and searching for component parts leads me to the now defunct Tesla Lanškroun, piece of history or hot garbage?

The board is a dot-matrix control board (7-rowsx10-columns) with can communication interface

it has 3 voltage rails:

1. +24V input goes to a MC34063 buck ic
2. +5V from the buck converter
3. +3.3V from an AMS1117 regulator

in this test setup I'm feeding the board a 3.3V from an stlink just to program the board but I noticed that there is also a voltage appearing on the +5V rail when measuring I get about 2.5V

I disconnected the stlink and measured the resistance between the 5v and 3.3v rail and go about 7kohm resistance

on the board I have:

1. stm32f103c8t6
2. ULN2003 darlington array IC to drive the dot matrix rows
3. MCP2551 ic for CAN communication

I'm suspecting the ULN2003 to be the reason for this because I'm connecting it's Vcc to +5V

what could be the reason for this?
could this create problems down the line??

EDIT: You can find the shematic in the link below

https://imgur.com/a/87KbhPC

I built a bookcase set up that uses 28 of these little 5 W Kapplake USB powered lamps. Everything is hooked up to a few USB hubs and a surge protector that I can switch on and off so all the lights come on simultaneously. Problem is, some of these lights have weird memory issues, they wont stay on and have to be manually switched on by clicking the lamp. I’m handy with micro soldering and board modifications, just never had to learn schematics and could use some advice on how to modify this PCB so that there is no longer any on/off functionality and that power always results in the light being on.

As the title suggests, I’m building a unity gain preamp. Some of you will probably ask “why? Why not passive preamp?”. To that, I would simply answer: “for reasons” ;)

The real reason for this post is to ask for a peer review of the schematic, in order to spot any possible mistakes before moving on to the PCB design stage.

I’m open to any suggestions.

Hi,
First things first, I’m a mechanics guy so sadly (for now) I don’t know much about transistors apart from how they work and the basics, no idea about typical specs.
I’m using this pressure switch on my motorcycle to get rid of the mechanical one for the brake light, the problem is that these are made only NO, while the mechanical switch is NC so I need the same type.
Instead of going through the hassle of fitting a relay, I was thinking to use a transistor to invert the output signal, considering my brake light is led and rated for 3.8W at 12V, so around 0.3A.
Are there any transistors than can handle that current and voltage or is it too much?
Thank you.

Hi everyone,

As part of my coursework, I need to build a Lorenz oscillator as an analog electronic circuit. I have been working from the model described here: http://seti.harvard.edu/unusual_stuff/misc/lorenz.htm

Despite many attempts, my prototype never produces the expected oscillations. I have re-wired the connections multiple times, but nothing seems to change. After some research online, I noticed that many people use Analog Devices components rather than Texas Instruments ones.

So my question is: do you think that replacing the multipliers — and possibly the capacitors as well — with Analog Devices equivalents could finally get the circuit working?

I would also like to ask whether anyone who has already built this circuit would be willing to share a photo of their prototype and their output results.

Thanks in advance!

Super basic question: Why are there two grounds? Are they connected together? Or is one a common and the other v- ?

Many thanks for helping me understand this circuit