I am learning what I can from taking apart retired Sonicare electric toothbrushes. After playing with an Sonicare charging base, my attention turned to the old Sonicare HX6530 control board. I had some idea of how a few components might work together, but if I want to follow up my ambition of building my own controller for the salvaged actuator, I need to dig deeper into how such a circuit is built.

A tool I'll need for this job is a circuit diagram a.k.a. electronic schematic. Making notes in the form of word description will only go so far. I can always draw a schematic by hand, and I'll definitely be drawing fragments as I probe the circuit. But to get a good picture after that, I should transfer that knowledge into a piece of software designed for schematics. (Versus general purpose graphical software like Inkscape.)

Around 2019 I dabbled in Digi-Key's online tool Scheme-It but found it limiting. In early 2021 I used the electronics design portion of Autodesk Fusion 360 (derived from Eagle) to draw up reverse-engineered schematics for L298N and DRV8833 motor driver boards I bought off Amazon, as well as a quick stepper motor experiment with ESP32 and TMC2208 drive board. It was serviceable, but then Autodesk yanked on the chain of Fusion 360 subscriptions a little tighter and turned me off on it. I don't like it when my user experience is at the whim of some Autodesk executive's decision to seek more revenue, so I decided against investing any more time or money into learning Fusion 360.

What I think I should do is pick up where I left off in late 2017. That's when I played with KiCad and got as far as getting a board made by OSH Park. I can't remember why I didn't continue building my KiCad skills, and annoyed at myself that I didn't write those reasons down on this blog. (This is my project notebook! This is what it is for!) Since KiCad is free open source software, it wouldn't have been licensing subscription fees like Autodesk Fusion 360. Perhaps I ran into problems with the software itself? Based on KiCad release history, late 2017 was the tail end of KiCad 4. (KiCad 5 would be released in early 2018.)

As of this writing, KiCad is at version 7.0.7. It would have seen significant advancements during my time away, possibly resolving whatever issues that annoyed me in 2017. Maybe it's worth another look. At the moment I'm not interested in building a board, I just want to capture a reverse-engineered schematic. I don't think that necessarily makes things easier as I learn the ropes again, because I remember a very tight coupling between logical schematic symbols (which I care about right now) and physical component footprints (which I don't.) Even then, I hope the immediate goal would help keep me focused. Which naturally meant I was immediate distracted by a spell-checking side quest to the KiCad side quest.