Reddit:Electronics

Every time i want to do an experiment in the lab and use USB power to my DUT i need to find a cabler with correct connector and thick wires enough for the purpose and then cut it :(:( to be able to connect it to my bench power supply.

So finally i decided to solve this reoccurring issue with a universal adaptor that will solve all my challenges and stopping me cutting cable after cable.

This led up to designing the small adaptor that fits most power boxes since it has moveable banana binding posts. I have added polarity protection and over voltage protection that can be disabled to make it flexible and pass thru voltages from 3-20V out to the USB-A and USB-C connector.

I have also added charging negotiation circuits for both USB-A (up to 10W @ 5V) and USB-C (up to 15W@ 5V).

The adaptor can handle up to 6A so it will work for most application!! I have worked a lot with heat managment and tried to keep low resistance in the current paths. When loading max the hottest component reaches around 85 degrees C in room temp

I’m attempting to make an LED scoreboard for my cricket team using large 7‑segment LED displays. I want it to be battery powered, so I’m trying to reduce the power needed to run 6+ digits at once by using multiplexing. Each segment is connected to a high‑side switch, and the digits to the low‑side. That way I can turn on each digit by pulling it low, and only the segments held high will activate.

The code I’m using runs on an Arduino, which talks to a cheap PCA8695 PWM board. That board connects to a custom MOSFET driver board that handles the high‑ and low‑side switching.

Running code that worked fine in my prototype setup just gave me an epileptic strobing effect on all segments, which completely threw me. I spent hours probing with a multimeter, using the oscilloscope at work, and eventually started cutting “non‑essential” components off the board. Instead of getting an inverted 12 V PWM signal like I expected, I was constantly getting a square wave oscillating between 12 V and 11.5 V no matter what I did.

I was about to post on r/AskElectronics for help, but I wanted to be 110% sure I wasn’t missing something obvious. So I went to falstad.com and built the circuit in the simulator. Sure enough, it behaved exactly how I expected. Then I noticed a little checkbox for “Swap D/S,” and out of curiosity I clicked it… bingo.

For testing, I’m going to desolder the PFETs I’ve got and jankily wire them in upside‑down just to confirm that’s the issue before ordering new ones.

Moral of the story: make sure you’re using the right datasheet for your parts, because manufacturers love reusing part numbers even when the pinouts are completely different.

(p.s. pls don't be too mean about diagram conventions, signal noise, etc. cos this is a self-taught learning exercise and I'm trying my best)

I've been experimenting with using a fiber laser to fabricate prototype PCBs.

Current workflow:

- design PCB

- laser isolate traces

- drill vias

- clean

- solder

Total time from design to board is about 30 minutes.

Trace pitch so far is around ___ mil and I've been able to do reliable double-sided boards.

I made a video showing the full process and the relaxation oscillator circuit I designed for it:

www.youtube.com/@Electronics_with_Joe

The goal was to find where to buy electronics that i need(STM32F103C8T6 and STM32F401RET6), but figured it will be cool if i put all that in one post. Maybe someone finds it interesting.

I designed the case myself. Use esp32-c3 with WifiManager library. The time updates automatically:)

Yes, I will try to build a precise voltage/current measurment equipment from scratch just for fun. Wish me luck.

One step at a time: - 5-digit multiplexed display with the К176ИД2 driver - MC34063 negative rail DC-DC converter - 555 timer 120kHz click source - REF3333 precise voltage reference

There are a lot of "AI generates hardware" claims floating around, and most of them produce garbage. I've been working on a tool called boardsmith that I think does something actually useful, and I want to show what it really outputs rather than making abstract claims.

Here's what happens when you run boardsmith build -p "ESP32 with BME280 temperature sensor, SSD1306 OLED, and DRV8833 motor driver" --no-llm:

You get a KiCad 8 schematic with actual nets wired between component pins. The I2C bus has computed pull-up resistors (value based on bus capacitance with all connected devices factored in). Each IC has decoupling caps with values per the datasheet recommendations. The power section has a voltage regulator sized for the total current budget. I2C addresses are assigned to avoid conflicts. The schematic passes KiCad's ERC clean.

You also get a BOM with JLCPCB part numbers (191 LCSC mappings), Gerber files ready for fab upload, and firmware that compiles for the target MCU.

The ERCAgent automatically repairs ERC violations after generation. boardsmith modify lets you patch existing schematics ("add battery management") without rebuilding. And boardsmith verify runs 6 semantic verification tools against the design intent (connectivity, bootability, power, components, BOM, PCB).

The tool has a --no-llm mode that's fully deterministic — no AI, no API key, no network. The synthesis pipeline has 9 stages and 11 constraint checks. It's computing the design, not asking a language model to guess at it.

Where it falls short: 212 components in the knowledge base (covers common embedded parts, but you'll hit limits). No high-speed digital design — no impedance matching, no differential pairs. No analog circuits — no op-amp topologies, no filter design. Auto-placed PCB layout is a starting point, not a finished board. It's fundamentally a tool for the "boring" part of embedded design — the standard sensor-to-MCU wiring that experienced engineers can do in their sleep but still takes 30 minutes.

Open source (AGPL-3.0), built by a small team at ForestHub.ai. I'd love feedback from people who actually design circuits — is this solving a real annoyance, or am I in a bubble?

I posted this a bit ago for the keyboard diode matrix I made. Please ignore the shoddy soldering on the prototype board lol.

But this project has been my first dive into microcontrollers, and after watching some videos on how easy circuit python KMK firmware ( https://github.com/KMKfw/kmk\_firmware ) was to install and configure I just knew I had to do it. In essence this thing is just a clunky big macro board that I made as a proof of concept before I make a nicer one.

The software it's intended to be used with is a bit of python that I used gemini / chatgpt to make ( https://github.com/IvoryToothpaste/rtsp-viewer ) that maps all the camera feeds to a specific hotkey via the config file.

This thing was a lot of fun to make, and I'm excited to post the final version of everything :)

Finally got my phase control circuit off the breadboard and soldered together. Adjusting the potentiometer changes where in the ac waveform the scr fires, thereby allowing for more or less average power delivered to the load. It is the same idea as a triac based lamp dimmer circuit, but using back to back scrs allows for higher power handling capability, and is more suited for inductive loads. This one will be used to adjust the speed of an angle grinder for use as an asynchronous rotary spark gap for my Tesla coil.

I'm playing with it for now. I'll see what the measurements show and what the difference is between a wall adapter and a linear power supply.

But a quick measurement showed it was pretty good.

Plc 20 Max = 5.0008206V Min = 5.0008197V Std = 0.2 ppmV

Also I need to make a box for it.

These photos were taken under a microscope, the mouse was gaming and I found the shape of the sensor interesting since it was mounted on a flexible board and had a lens on it.

Make sure the package markings are clear in your picture. I used grok. It will even find parts if it doesn't have the part number on the part, just a marking code.

I started this a few months ago. No university, no engineering background, just a goal: 4 input switches, 10 LEDs, light up N LEDs when the inputs sum to N. I figured out the logic, built it in simulation, got told I was wrong by experienced people, proved them right, and then discovered what I built has a name in a field I'd never heard of.

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**The Core Idea: Non-Binary Weighting**

Most 4-bit decoders assign binary weights: 1, 2, 4, 8. I didn't do that. I assigned decimal additive weights:

- SW-A = 1

- SW-B = 2

- SW-C = 3

- SW-D = 4

Maximum sum = exactly 10. Every integer from 0 to 10 is reachable. The 16 physical switch combinations collapse into 11 unique output states. Five of those states are reachable by two different switch combinations (e.g. A+D = 5 and B+C = 5). The circuit correctly treats these as identical — it decodes *value*, not *pattern*.

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**Logic: Series NPN AND Gates**

Each output channel is a chain of NPN transistors in series. All transistors in the chain must be ON for collector current to flow — logical AND. Chain depth varies per output:

- 1 NPN: single input conditions

- 2 NPNs in series: two-input conditions

- 3 NPNs in series: three-input conditions

- 4 NPNs in series: sum = 10 only

The Vbe stacking problem is real — 4 transistors in series drops ~2.8V. I solved it by using a 9V supply and adding a booster NPN after each AND gate to restore a clean full-swing signal before hitting the LED stage.

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**Output Stage**

Each booster drives an LED via a 330 ohm resistor to VCC:

R = (9V - 2V) / 20mA = 350 ohms → 330 ohm standard value, ~21mA per LED

This fully isolates logic voltage from LED forward voltage. Without this separation the LED acts as a voltage divider and corrupts the logic states — I learned that the hard way in the simulation.

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**The Part That Surprised Me**

After I finished, someone pointed out that this circuit structure is identical to a single hardware neuron:

- Weighted inputs → synaptic weights

- Arithmetic sum → dendritic summation

- AND gate threshold → activation function

- Thermometer output → step activation

I had never heard of neuromorphic computing when I designed this. I just landed there by solving the problem from first principles. Apparently there's a billion dollars of research built on the same idea.

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**Simulation Results (all confirmed working):**

- A → 1 LED ✓

- B → 2 LEDs ✓

- C → 3 LEDs ✓

- A+B → 3 LEDs ✓

- A+D → 5 LEDs ✓

- B+C → 5 LEDs ✓

- B+D → 6 LEDs ✓

- A+B+C+D → 10 LEDs ✓

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**Detailed document**
https://docs.google.com/document/d/18wD1k79H8T8Y3WScr6QKEXsPy5rKq8as/edit?usp=drive_link&ouid=102019556573904444870&rtpof=true&sd=true
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Happy to share full schematics and simulation screenshots. Thanks for reading.