A retrofitted magnet kept falling off the Hall effect sensor inside OrangeTungsten's Citroën door-mounted logo projectors, repeatedly killing the circuit. The fix: remove the sensor, wire in a mechanical button that contacts the door frame directly. Full documentation is on GitHub.
Cracking open the projector revealed something worth noting: an 8-pin microcontroller whose only apparent job is to poll the Hall effect sensor and toggle a transistor to switch an LED. That is the entire function. No fading, no flashing, no complex behavior documented anywhere. A discrete component solution would have cost less and broken less.
The write-up is worth reading in full because OrangeTungsten traces the complete circuit before cutting into it, which is the right way to do this kind of mod and a good template for anyone reverse-engineering a similar aftermarket automotive accessory. The MCU-for-a-transistor design choice is also left open, and that question alone is reason enough to dig into the comments.
[READ ORIGINAL →]