A short aside here to discuss the uProgrammer. In the last post, I kind of brushed over the uProgrammer, although it was an area I was very worried about. If it hadn't worked, the whole project would have been a Fail-of-the-Week! The concept was discussed in the Circuit Board and Programmer Project Log, but now that I know it works, I can talk about the implementation. The idea was to use a spring contactor to provide the connection to the board with the microprocessor on it. A footprint for the contactor contacts to hit was included in the microprocessor board design. As previously mentioned, a frame was 3D printed to provide the spacing between the contactor and the footprint so the contactor could be reused.A small notch in the board mates with a tab on the frame for easy alignment. These pictures should help you to get the idea.

This scheme turned out to work really well! A clothes pin works as a clamp to hold the microprocessor board and the uProgrammer together.

Since this approach allows building very small "Arduinos", it may be the most useful part of this project.