Reddit:Electronics

For years, devices like the RbPi have been described as “credit-card sized”.

And of course the message is rather the footprint, but at some point I became obsessed with taking that idea one step further:

What would it take to build something that is literally sized like a credit card?

I've got a slight feeling that you really don't seem to like questions here, but I hope this rhetorical one is okay :P

That question slowly escalated into months of experiments to find solutions for things where default methods won't work. I can't use large, rigid components, connectors, and find a way to make my own custom flexPCB.

And after months of tinkering, I made the first prototype. Fragile, but it works within the goal of not exceeding 1 millimeter. Somehow, news pages have picked this up and described it as "revolutionary" which is a bit far fetched, but I feel flattered 🤭

To be fair, 'computer' might be a little overstatement, but it's technically perfectly within the definition of one. If you should have suitable words for it that sounds cool, feel free to suggest ^^

The prototype includes:

• ESP32-C3FH4 w/ WiFi & BLE
• NFC read/write
• 1.54" 200*200 E-Paper display
• ultra-thin LiPo battery including charging circuit and power path management
• accelerometer

Finding small/thin enough components wasn't really the main challenge, mechanical stability was. Solder and general material fatigue, pressure distribution (particularly focused pressure) and other strain related issues were the real problem.

This doesn't even include battery protection and some other things to solve.

At this scale, the project turned into a weird mix of electrical, mechanical and chemical engineering.

A few things that became clear over time:

• preventing strain is much easier than surviving strain
• tiny real-world tolerances start dominating the entire design near the physical limit
• many “thin enough” components stop being thin enough once assembly is considered
• FPC connectors are basically obsolete, forcing me to get creative and solder each single wire for each 0.5mm pitch pad one by one.

The prototype is fully self-powered and running from its internal battery.

I documented a large part of the engineering process, including the process of etching my own flexPCB, on my GitHub repo.

And yes, it's not like this thickness is a necessity, going just 0.5mm thicker would probably have saved me months of engineering. This entire project was probably motivated way too much by the 'disbelief' factor 😄

I am curious on your thoughts on this! :)

Finally got a working prototype for my cars instrument panel project. Just running a test script for now to make sure everything works at the same time.

We've got the gauges, warning lights, and LCDs to display the milage.

More updates will come as hardware is added and the actual code is written. GitHub link for anyone interested

Started designing a few joystick cap styles for KY-023/Arduino joystick modules and thought they turned out pretty nice.
Made a classic version, textured grip version, tall, wide, and short variants.

if you wan the model:
https://makerworld.com/en/models/2792322-arduino-joystick-cap-pack-5-variants#profileId-3105095

This is a HUD75 LED panel that is being driven by an ESP32-S3! I am using this library as a driver and this library for the animation.

I have a custom animation that I loaded up and I plan to make more animations from here and turn it into a pet game!

I'm looking for cute names though!

After some hardware fixes as usual, some glorious resoldering and a few lines of 1's and 0's later...I have data! With my DAC working, both receive antennas are working and able to read the I/Q outputs!

Very pleased and now to turn this into something more understandable!

I'm slightly lazy; if I need to do repeated work I'd rather spend my time on building something that will do that job for me. (It's not always never faster but certainly more fun).

In the last few months I went completely overboard and built something that connects to, well, pretty much everything in my workshop that communicates. I can now control my power supply, read data from a power meter, read temperatures etc, all in a single tool. It can even control my 6-axis robot arm and watch and analyse my security camera's.

Using javascript, I can now run automated tests or whatever.

And of course, since it is 2026, I added AI which is pretty awesome. Combined with voice recognition and text-to-speech, I can now say " Set the power supply to 15V, 100 mA, turn the output on" while holding two probes. And it actually works. (Though first attempt it mishard it as 100 mA as 100 million 💀 So I built in a confirmation step). But AI can also write scripts for you and help to write the drivers to your equipment.

The camera and AI can also be used inside a script; imagine you have an old analog voltmeter and want to use the value to do something in your script: just point the camera at it and do something like

So I hope there are more fools like me who would love to play with something like this; if you want to give it a try, it's free! Though very much in Beta so I'm sure you'll find stuff I need to fix. Or stuff I need to explain better...

It should be able to connect to any scpi device over serial/usb or tcp/ip.
muxit.io has all the information and docs.muxit.io has even more.

You'll need to run your own local llm (like ollama or lm studio) to get the AI to work for now. I used lm studio with Qwen3.5 9b, which worked perfectly for recognizing images.
There will be versions in the future that have more advanced, integrated AI like claude and chatgpt but since that will cost me money I need to figure out how to get that implemented. The free version should be able to do all the cool stuff.

Let me know if you have any questions!

I thought this recent project of mine could inspire people on how to reuse the spindle motor on obsolete or crashed hard drives.

After all, it's a shame how these state-of-the-art motors often end up in the bin despite being in full working condition.

I built a so-called "ringing table" for microscopy by creating a drop-in replacement for the original disk controller on a twenty year old WD drive.

My board has a PIC processor, a three-phase spindle motor driver and a simple button-and-led user interface right where the SATA and Power connectors used to be.

It actually worked pretty well. There must be other things one can build from this basic concept! More technical details about the project are laid out on my personal blog.

https://espenandersen.no/ringing-table-from-a-dead-hard-drive/

I built a GPS and temperature data logger equipped with an alarm buzzer and an EEPROM for offline data backup and ESP32S3. I made a mistake with one net name but I was able to solve it.

Pd: How is the market in EE ? Is any opportunity for the new one?

Man the difference between linear and logarithmic pots and faders for volume is pretty interesting.

This is my third TX-6 style mixer that I had time to finally finish. The first used linear faders and pots, and the second had faders that were too high value resistance so it was more on the quiet side.

maybe it's time to start using PCBs

For more detail: https://blog.mehmetasaf.me/how-to-build-a-uart-to-half-duplex-converter-for-your-servo-projects/

Tomorrow, I will build this schematic on a breadboard. I might add some pictures later. Thanks for reading.

I have designed and built a test jig that will automatically test a small USB output for bench power supplies adapter called USBpwrME. The USBpwrME allows users to connect USB powered electronics to a power supply during test, evaluation troubleshooting etc.

Test jig in action

The test jig is built around the PIC18F27K22. This is my goto chip at the moment. It has a lot of configurable peripherals, ADC with really high resolution and a huge amount of memory for being a small MCU. And wide supply voltage range!

Test sequence will cover all the functions of the USB adapter with as few operator interactions as possible. One "funny" mistake i made during the design was not noticing that the relays i use has actually polarized coil so the pos/neg has to be connected in correct way to make the relay click. I missed this so i needed to hand modify all three relays.

Second mistake i made was actually a bit harder to foresee. One test that is performed is to invert the the input polarity to the USBpwrME to see that the polarity protection works. Well the design mistake was that the GND between the jig and the adapter is connected together thru the GND shield of the USB cables. So when the polarity switches the test jig short-circuits itself and restarts.

I solved this by adding in the test sequence when to actually connect the USB cables and performing the polarity test just before.

Even my eight year old son can operate it :) :)

Quite happy although with the result

Of course, the process was not completely smooth. I wanted to add reverse polarity protection to V1, which the prototype did not have. In the first design, I built and tested a reverse polarity protection circuit with a single P-Channel MOSFET. However, I had missed one scenario: although a single P-Channel MOSFET can be enough in some cases, it could not block reverse current coming from inside the device. Even when the IRFP260N MOSFETs were off, reverse current could pass through the body diodes and put the connected power supply into a short-circuit condition. To solve this problem, I reworked the PCB to convert the power input block to a back-to-back P-Channel MOSFET structure. I used the banana sockets on the front panel as the protected input, designed to support an 8-30V range. The XT60 connector on the right works as the unprotected input and supports a 0-30V input range. After the rework, the protected power input caused significant heating at 8V and below because it left the protection MOSFETs partially on. For the next PCB revision, I plan to redesign the power input block using an ideal diode controller and two low-RDS(on) N-Channel MOSFETs in a back-to-back structure. Also, because of the two P-Channel back-to-back MOSFETs, the protection MOSFETs heated to unsafe levels at my target 200W test power. For safe operation, I limited the device to 150W. The device can support voltage and current values up to 30V and 10A within this limit. On the software side, with AI assistance, I developed control, protection and monitoring functions such as toggling load draw with the RST button, overcurrent warning, reverse polarity notification, temperature tracking and fan control. For the V2 revision, I aim to improve the device with more functional features and design a structure with higher power capacity. Overall, this project was a very educational and experience-building work for me in power electronics, measurement, PCB design, mechanical design, rework and fault analysis.

https://omerikinci.github.io/projects/electronic-dummy-load.html

Kept redoing the same impedance calculations during SI work, so I built this into a proper tool.

It covers: Microstrip, Stripline, Coaxial, CPW, GCPW, Differential Pair — gives you Z₀, εeff, propagation delay, loss, VSWR, Smith Chart, dispersion analysis, and parametric heatmaps.

Runs in browser, no login, no account.

Link: tools.vyomex.in/Impedance_calculator

Happy to hear if anything is off or if there are topologies you'd want added.

VSDSquadron FPGA Trainer Kit for High School Chip Design is now ready to ship — a complete hands-on platform to learn RISC-V, FPGA, and real chip design from school level.

Man one month of waiting for the pcb only for me to fuck up the footprint, what a jolly...

Bought a 24GHz radar module to tinker with and, after a few tests and experiments, ended up designing this board to make further testing a bit easier with the eventual aim of designing my own radar system or close!

Has been a really enjoyable learning experience so far. Time to start writing some 1’s and 0’s now!