Reddit:Electronics

A few months back I shared a board I designed here. I loved the support from the community so I will be open sourcing the design for everyone to enjoy this.

Open source link - https://github.com/NoamanKhalil/Keyboard-pico

Thyratron inside a Varian EDGE (linear accelerator).

Not exactly a keyboard, but the plan is to hook this up to a Pi pico whenever it arrives and use it as the F1 - F24 keys for a CCTV project I'm working on as a "Camera Control Panel"

With all the IO ports on a pico I'm pretty sure I could have gave each switch it's own dedicated IO, but this felt more fun lol

Continuing from the idea published a couple of days before - Building a programmable DC-DC Power Supply with I2C Interface (I2C-PPS). Part 1 - Idea.

I decided to get some intuition about overall device structure before gathering its schematics. As I sketched it in the picture the buck-boost converter can be seen as the set of several blocks - a power stage, input and output filters with respective current sensors, a set of programming resistors, a digital I/O plus indication circuit, and a master switch. The power stage consist of 4 power MOSFETs and the inductor. The input and output filters are sets of capacitors mixed with current sensing resistors. The converter's operation mode and HW limits on voltage and current are set by programming resistors. And digital I/O with indication circuit provides interface for RPI and some leds for us - humans. The master switch makes it possible to start or shutdown the thing as it needed independently by RPI as it's needed. Normally, it should stay off and should go off if RPI goes down turning the converter off when input voltage is here without running RPI.

For the switcher TI provides a design calculator in form of an excel spreadsheet and schematic design checklist which allow to select values for main components with desired input and output specs in mind. As for now I decided to go with 4-6V input window but it really should stay at 5V and set HW input and output current limits at 5A. With 250kHz switching frequency many 10uH inductors with Isat > 7A and DCR in recommended range should work along with set of recommended power MOSFETs. More details you can find in the project repo - github.com/condevtion/i2c-pps.

Looks like it's time to pull KiCAD into the project.

Didnt think it was a thing! Would have expected some mandatory SMT ICs

I also wrote about it here https://boxart.lt/en/blog/diy_digital_clock

I was lurking through DigiKey catalog and found a TI buck-boost controller with I²C interface - BQ25758S. The controller allows to create a programmable power supply with quite impressive output specs - voltage 3.3-26V and current up to 20A. Decided to give it a try and create a compact board for my RPI Zero. I don't think I'll go above 3A input (which means only 500mA@26V give or take some efficiency) and it's a bit of a shame that the controller doesn't go below 3.3V (much better would be at least 1.8V). For starter created an umbrella repository - github.com/condevtion/i2c-pps. Any "well, actually" are very welcome!

I really like motorcycles, specially old sports bikes, but, they do come with a terrible thing, they don't have any safety electronics at all, ABS, TCS, nothing, completely barebones, and I consider myself a pretty new rider, so I'm starting a project where I'm gonna make my own traction control, using hall effect sensors and laser cut tone wheels for sensing both of the wheels rotation, so the ESP32 inside the main PCB can do the math, alongside the MPU6050 GY-512, so it correct the "slipage rate" as the bike inclines from side to side into turns in the twisties, it's definitely not gonna be perfect from the get go, but I'm really hopeful that this thing can work properly.

If you're wondering, they don't act directly on the brakes, but rather using the relay to shut off the ignition coil for a few microseconds as the bikes takes grip again, hopefully this will be able to help both me and several other riders ride their dream bikes more safely!

Everything is at a very starting phase, but I did already order all the PCBs from JLCPCB and the components I bought locally, so excited to see how it turns out!

I’d like to share my experience building a "rough gauge" for my LiFePO4 battery pack. Instead of using an off-the-shelf Smart BMS, I chose the DIY route to better understand the underlying physics and processes.

Stock INA226 modules come with a 100 mΩ shunt resistor, which limits the current measurement to a measly 800 mA. This is far too low for a power battery.

• Shunt Replacement: I replaced the stock resistor with a custom 5 mΩ constantan wire shunt. This should theoretically expand the measurement range to 16 A.
• Reinforcement: Since handling 16 A+ is serious business, I added copper shims (8x0.15 mm) and performed heavy tinning to ensure the high current doesn't rely solely on the thin PCB copper foil.
• Hardware: The system is powered by an ESP32 (Cheap Yellow Display - CYD).

To find the exact resistance value, I ran a series of tests and compared the readings with a UNI-T UT61 multi meter. The calculated precision value is 4.392 mΩ.

• Comparison with UT61: https://youtu.be/3OMUGPUffBk
• Accuracy: The deviation from the UT61 is only 30–40 mA at a 10 A load.

The biggest challenge is heat. At currents above 10 A, the shunt begins to warm up noticeably. This creates Therm-EMF (the Seebeck effect), which causes "phantom" readings of about 50 mA on the screen for several minutes after the load is disconnected, until the node cools down.

More details here: https://en.neonhero.dev/2026/02/modifying-ina226-from-08a-to-high-power.html

A long anticipated update for "Silly power supply for a lone lamp" post :)

The original post showed a simple set of low power batteries connected in parallel supplying a 12V/50mA lamp. The schematic featured a diode per battery to prevent them from feeding each other.

Here, I decided to check experimentally if the diodes indeed work as expected. I used an STM32F103 module as multichannel ADC, a set of resistors to scale down from 0-18V to 0-3V and a RPi Zero 2W as a 5V power supply and to collect data. Potentiometers were set to 20k creating 6 100k/20k voltage dividers (pic 3).

First, measured lamp and batteries voltages with a fresh set batteries. They held around 3 hours 45 minutes. The set had voltage around 12.6V fresh without load. Upon switching on the load they immediately dropped to 12V and then spent most of the time going from 10.5 to 8.5V as the pic 4 shows. The diodes took about 350mV so lamp's voltage went clearly below batteries.

Then I mixed 3 fresh and 3 used batteries and actually was really surprised with how clearly it showed when used batteries kicked in. The last pic shows voltage drop across diodes and comparing with the previous one you can see that the diodes for used batteries open as voltage reaches around 200mV. Which is a great real-world demo of how low is cut-in (or knee) voltage for a Schottky diode can be (here SD103A used).

Here’s a decoder I made in my class! It takes the binary inputs from the four switches and uses a seven-segment display to turn them into decimal numbers. Made with a 7447 CMOS IC.

I know it’s very disorganized and I could certainly get better at saving space. I’m still new to building circuits, but I still think it’s really cool!

Thinking of using it for either an induction heater or a dual resonant solid state tesla coil, but next up will be having to deal with annoying gate drive stuff first.

it's displaying GHIJKL on the display. The display is a Maxwell MAX7219 7 segment display run from an ESP8266 generic. I had to write my own driver so I could show what I wanted via the letter and not binary literal. Am I a look

Came across this capacitor bank inside of this giant battery charger just figured I'd share, LOL. It has (3) 29k microfarad 200vdc, and (1) 13k microfarad 200vdc capacitors. Gives me the heebie-jeebies just looking at it... It has a built-in capacitor discharge button but still...

Wanted to share a picture of our progress on our open access health tracker.

We hand assembled our first prototype (left) in 2025. Around 140 components with the smallest being 01005. Our learning: DON'T use 01005/0204 if you hand assemble. It was not a lot of fun, but we got our first prototype to work.

We redesigned and improved. This time using a 4 layer flexible PCB + stiffener. AND we learned, ordering the prototypes mostly pre-assembled. However, we ran into the problem that we forgot to thermally shield our temperature related sensors (any suggestions on this very much welcome). We also ran into the issue that our 2.4GHz antenna didn't work anymore, most likely due to the PCB change, but a small cable will do the job.

Now we are working on our third prototype. Integrating more sensors, compacting and fixing mistakes we made.

For a long time wanted myself Poe capable switch but didn't wanted to pay like 3x or just subconsciously wanted to die in house fire one day, it's not important. Basic 8 port 100m switch with all pairs available on connector(Wich is unsurprisingly rare). Ptc fuses rated 0.5a with 1A trip point. Power for switch is made from led driver scalvaged from cheap bulb. It is slightly modified to work from polarity agnostic 48v and provides about 4v isolated which is enough to power small switch. It is second attempt, first switch was fried because there 2 annoying standards with + and - inverted requiring a lot of diodes to ensure not frying anything which I skipped thinking working with a known Poe source I am safe and having non isolated step down converter is fine. Wrong assumptions indeed. Now everything works relatively safe, in final version before assembling I added isolator between fuses and transformer legs. No fire yet.

Designd my own PCB and got it from JLCPCB. Nice gift fir valentines. I am using NE555 to make the LEDs flash if you want to see how it works comment I'll post a video.