hi David:
I think it is really unlikely that the boards are losing their program (edit: if the fuses are right). That just doesn't happen much. I've never heard it reliably reported as a problem in this forum, and on top of that I've taught about a hundred students to use it, with no spontaneous reprogramming issues. Which is not to say it isn't happening, it's just really unlikely.
A few thoughts:
- If you programmed the Atmega bootloader chips yourself, there is the strong possibility that the fuses aren't right.
- What does the power supply line look like ( on your scope) when that inductive sensor is running? Have you added significant filter caps in the appropriate places?
D
PS: yes that second line wasn't there at first; I am a terrible typist and I often revise my errors... and add things as I go. 