Reddit:Electronics

So i used HEF4094BP, i did the same circuit in this video 4094 shift register long time ago, then in 2022 i bought raspberry pi pico, and in this year i write a long code with MicroPython to count from 1 to 9 and repeat the loop, but i need to optimise it next time.

Over the last few weeks I’ve worked on an Arduino board connected through an ADC converter into 3 magnetometers. They are set orthogonally to one another (around the clear box) so that the magnetic field strength and direction at a given point can be found. The whole lot gets power through a USB cable that allows you to model the direction and strength in python. It’s been an absolute blast building it :)

Left: 1974 (Matsushita Electric)

Right: 2021 (Rubycon)

Both 16V 1,000μF.

Same voltage rating and capacitance, but shrunk this much in about 50 years.

For a biochemical project of mine I needed a very precise scale. The ones I bought were underwhelming, so I decided to just solder one myself.

The sensitivity is kind of ridiculous. Sitting near the scale, I can see my heartbeat in the signal when streamed to a PC. Someone walking on a different floor makes the reading jump — and I live in a concrete building. The coil can lift about 20 g. With different coils, you could trade off dynamic range vs. precision. For my purposes, the precision is already overkill.

Components were about $100 total. The most expensive part was the neodymium magnet.

The principle is electromagnetic force restoration. A 110 Ω coil suspended on a lever lever sits above a neodymium ring magnet. The lever height is held constant by a feedback loop that uses an IR photointerrupter. The current required to hold the weight is directly proportional to the mass.

For current sensing I used a 10 Ω shunt resistor (RJ711, 5 ppm/°C TCR) and a 24-bit ADC (ADS1232). The signal is read by an Arduino Nano and displayed on a small LCD (SLC0801B).

The photointerrupter is built from a generic IR LED and IR photodiode. The LED is driven with a constant current source (using a 2N7000 MOSFET), while the photodiode is reverse-biased for fast response.

The circuit runs from a low-drift 2.0 V reference (REF5020), which provides a stable reference for the ADC. After dividing it to 0.5 V, it also biases the photodiode stage and provides the ADC’s negative input.

The coil current is controlled with an N-channel power MOSFET (IRF540N) acting as a low-side driver, operated in its ohmic region. Its gate is driven by the photointerrupter circuit.

Zero-drift op-amps (OPA187) buffer the reference voltages, drive the photointerrupter, and control the coil current.

I also added a capacitive touch button for tare, so you don’t have to touch the scale directly — that’s surprisingly important at this sensitivity.

The schematic looks a bit op-amp heavy, but it’s actually pretty straightforward.

Challenges and possible improvements - The lever tends to oscillate, so the feedback loop has to be very fast. A lighter lever with a higher resonant frequency would help, and might require a lower-gate-capacitance MOSFET. - All components in the feedback path need low temperature coefficients to minimize drift. - To fully eliminate drift, one would need to monitor and compensate for coil temperature, photointerrupter temperature, as well as ambient air temperature, humidity, and pressure (for buoyancy effects). - A parallel guide system will eventually be needed so measurements are independent of where the weight is placed on the lever.

This build definitely requires some electronics background, so it’s not a first-project type of thing. But if you’re comfortable with soldering and op-amps, it’s very doable.

Hope you like it 🙂

This was a brain fart moment upon finding out they were .25 watt, we needed 9 watt capable. This is a lovely bundle of 36 that has next to no resistance now 🤦 .... 20ohm

Miss the old micro SD upgrade days

I've had an obsession with rockets/flight controllers and decided to make an open source flight controller from scratch (nicknamed Athena). I've added the Github repo/design files if anyone wants to take a closer look.

👉Github repo / Design files

• Triple MCU: STM32H753VIT6 (MPU), STM32H743VIT6 (TPU), STM32G474RET6 (SPU)
• 6 Pyro Channels: Direct 12V battery connection with fuse protection
• 6 PWM Channels: 2 for TVC (Thrust Vector Control), 4 for fin control
• Sensors: Triple ICM-45686 IMUs, LIS2MDLTR magnetometer, ICP-20100 & BMP388 barometers
• GNSS & Communication: NEO-M8U-06B GPS, LoRa RA-02 telemetry, Bluetooth DA14531MOD
• Storage: SD Card + Winbond W25Q256JV flash memory
• Power Management: 7.4-12V LiPo battery with BQ25703ARSNR charger, USB-C PD support
• 6-Layer PCB: Signal/GND/Power/Signal/GND/Signal

The plan was to make 32 bit Countdown timer using ESP 01, which has only 4 pins.

After lurking here forever, I finally get to share something I’m genuinely proud of. This is my power schematic made using KiCad 9

LT8641 buck + MIC5234 LDO chain (my 5 V → 3.3 V power path)

Blown thyristors, hopefully that's all it is. Waiting for the modules before attempting any repair. Circuit board looks okay, so does the power supply and some thick gloves just in case.

I will be plugging this in outside on an extension lead far away from me when turning on.

Hey folks, I’ve been tinkering with an ESP32-based clone of the Motogadget M-Unit Blue and finally decided to throw it out into the wild as open source:

👉 GitHub repo

It’s not a polished product (yet) — more like a prototype playground.
If you’re into DIY electronics/motorcycles:

• Try to boot it up,
• Hack it, improve it, break it,
• Build a prototype,
• Let me know how it goes.

Think of it as: “Motogadget is $$$, but what if… we open-source it?” 😅
Any feedback, PRs, or pics of your builds are super welcome. Let’s see where the community can take this! 🏍️⚡

Hi everyone, I’ve been lurking here for a while now and loved seeing your projects. Now it’s my turn to contribute — an electroencephalogram (EEG) I built from scratch.

It’s open source, and I’d be thrilled if some of you guys try it out, give feedback, or even improve on it! Repo (with gerber files) + demo video are in the comments.

Hey everyone!

I’ve been tinkering away on a little evening project for a while now and wanted to share it here. The Quansheng UV-K5 handheld radio is fun to hack on, but its original MCU only had 64 kB of flash memory. Not enough to run all the cool community-made features at once.

So, I designed a tiny flex PCB “implant” that lets me replace the stock chip with an STM32G0C1CET (512 kB flash, 144 kB RAM). It involved a lot of signal remapping, flex board experiments, and of course plenty of solder fumes....but in the end it worked!

A client approached me because their system suddenly stopped working.The system was designed by someone else and had been working fine for years.

After carefully studying the schematics, checking power supply, and measuring continuity with a multimeter, I spent hours debugging the issue.
After hours of thorough debugging, I found the root cause:
* 1 resistor was open
* 1 capacitor had wrong polarity

Replaced both. System came back to life. Minimal cost. Maximum satisfaction. 😊

https://www.linkedin.com/posts/pournima-choulwar-5a1b98220_embeddedsystems-iot-hardwaredebugging-activity-7373192591435087872-h5kj?utm_source=share&utm_medium=member_desktop&rcm=ACoAADe0VkkBj8YEaQG6Xut_N5ndwX9H6ADxDb8

Pulled apart an old valve amp and was struck by how good the color-coded caps and resistors looked. Modern SMD boards just feel boring in comparison. Anyone else miss this aesthetic?

Only two components, a esp32 board & 0.96 inch oled screen, blue is the 0.96 inch oled screen & black is the esp32 with USB-C