Half of a broken circuit is a joint, not a design.
Three seconds on, three seconds of solder, three seconds off. Get the timing wrong and the joint looks finished and is not.
Making a through-hole joint, and telling a good one from the four kinds that fail.
The other fundamentals track
Electricity
Volts, current, resistance and the mistakes that kill parts. 35 pages, true of every board.
35 articles →The other fundamentals trackPower and protection
Fuses, ideal diodes, TVS and lithium cells — every part that sits between a supply and something you would rather not replace. 11 pages, with part numbers.
11 articles →Next, in the ESP32 bookWires on the board
How two chips agree on what a line means, sorted by what it costs you in pins
9 articles, no board required →Next, in the ESP32 bookMessages on the network
Once there is no wire left to agree about, the question is who talks first
5 articles, no board required →