u/adeptyism

Shout-out for u/bellabebop for their nice-and-clean looking perfboard layouts.

I built an Arduino-based oscilloscope following this project at the end of February. I was happy with it, but it had some issues: it was slow, kept freezing, and had a very sloppy input attenuation stage. (last photo)

I had a ESP32C3 that was lying idle, so I decided to a) port a scope from breadboard to perfboard and b) port the code to the ESP32, with a little extra features.

All changes are described at the README.md file in the repo, but in short: I made a precise attenuation stage that reduces the 24Vpp signal to 2.6Vpp, which allows the incoming voltage to be accurately displayed on the screen and replaced meaningless original voltage ranges with 3v3, 5v, ±5v ±12V and auto-mode. Also ESP32C3 ADC is 12bit vs Arduino Nano 10bit ADC, which is good too, e.g. for measuring precise (edit: like 0.0833V for 1V/oct) voltage (I didn't implemented that though)

Also there's a non-correctly working spectrum analyzer: there's problem with the math somewhere and I can't find it yet.

>!AI was involved only once with the question "what is 'volatile' variables?".!< Most of the comments were in the original code.

Code, GitHub repo: link

YouTube little demo: link

As you pull away the sound of a 1 bar loop slowly fades in... the 303 filter starts to open up... you notice all the doors are locked.

First occasion of this happened in January, 2025. After that there was zero to one of those screens in a month. At first, the screen simply freezes, then the sound starts to loop for the last 0.8-1 second. After that, artifacts appear. Until the artifacts disappear, I can adjust the keyboard backlight brightness; when the artifacts disappear, the sound starts to jam even faster, and I can no longer change the keyboard brightness (I suppose that's important detail). After reboot everything works normal (in 9 of 10 cases).

This mainly happens when laptop is overheated (no correlation honestly, CPU could be 47 °C and I can get artefacts or it could be 94 °C and I can get nothing), or something hit the laptop lightly (e.g. putting it on the table).

I suspected the memory, SSD and integral GPU, but RAM fully passed multiple memtests, and I switched my SSD in June 2025. EDIT: the artifacts happens with either games or heavy VST plugins (virtual synthesizers) opened, so I'm suspicious about VRAM now.

- Laptop model: MSI Modern 14 B4MW-021 (bought it in 2021)

- CPU: AMD Ryzen 5 4500U with Radeon Vega 6 graphics

- RAM: (i don't know what was originally in it) -> Kingston Fury Impact 16×2GB SO-DIMM

- SSD: some of the SK Hynix -> Kingston Fury 1TB (it's definitely not overheating — 46°C peak)

- OS is Arch Linux, I got kernel panic screen during these artifacts once. Never happened to me again.

Also I noticed that there is a wear on the cable leading to the screen near the hinges. There's no broken isolation, taped it with dielectric tape and everything seems normal.

The laptop was bended slightly over the years, but after visual inspection of the motherboard I think there's barely even 0.1° bend of it and it's mostly affected the case (and possibly the lid with the screen!).

Should I be VERY worried (i.e. it's doomed and I need new laptop) or just normal worried and be even more gentle with it?

That's my implementation of Totoro Synth by syntherjack, which is kind of a "beginner synth," based solely on the MCP6004 op-amp. The general idea behind my remake was to gift it to my friends (and they seem to love it). The PCB is the size of a bank card, an outcome of taking inspiration from the benjiamodular SynthCard project(although I noticed later that Benji used a business card format and not a credit card one).

Totoro features two oscillators: one is a square wave with three "gates," and the second is square/saw in OSC mode and saw/triangle in LFO mode. Totoro has a two-pole low-pass twin-T filter onboard with two resonance settings and modulation possibilities. For a more detailed study, visit the original article (link at the beginning of the post).

I made some modifications to the original schematic, such as:

1. USB-C power — the synth is way lighter and compact that way, and I won't need to switch batteries from time to time;

2. Polarity switch for the saw (something like /|/|/| => |\\|\\\\|\\|\\\\);

3. Adjusted capacitor values;

4. Added OSC2/LFO rate indicator;

5. Safer stereo output for using for Eurorack and other safety features (e.g. overvoltage protection)

YouTube demo: https://youtu.be/jdFurPZiaJQ

I don't feel comfortable uploading my schematics to GitHub, since my KiCad project is broken because of changing references and not synchronizing the schematic and PCB after it, but I hope I'll get my hands around it in the autumn.

I received PCBs for my synthesizers today. In concept, there are three keyboard switches acting like buttons. However, the switches I ordered (outemu low-profile) have a centered second pin, while on the promo card they showed a misaligned one, just like on Cherry MX switches. Since I saw the misaligned pin on the promo card, I used the standard Cherry MX switch footprint and called it a day.

My question is: how would you fix that mistake? I have some ideas, which I don't like, because I'll need to repeat them 36 times:

1. Bending the second pin and soldering thin wire, like transformer wire, to it, then soldering the wire to the hole.
2. Soldering wire directly to the metal plate inside the switch via an extra drilled hole in the switch, which will be directly over the hole.
3. Bending the second pin in such a way that it touches a hole, and soldering it while praying for a good connection.

The boards will not be in extreme conditions or under high stress.

In the first picture, I drew lines to make it clearer that the pin is offset from the center.

This screen is supposed to display the next metro stations, but it displays internal information for metro workers - the position of switches, the occupancy of sections, the operation of ventilation and pumps, etc.