We don't need no stinking 555 timers! We have an AVR in the same form-factor!
The goal of this project is to design an electronic domino using a small AVR chip and minimal components, but at the same time provide a huge amount of flexibility and capability. Here's the 555 version:
And here's the current design:
1. After reviewing the CR2032 spec, looks like it's not sufficient to drive 60 ma - the maximum current required with 3 LEDs on. Fallback is to use 3xAAA batteries, but that's bigger than the device itself! There must be a better solution for powering it.
2. For the initial version, was not able to incorporate the switch (too expensive for switch and PCB space). Need to come up with a suitable H/W and S/W solution. Springy wire? Using ATTiny44A provided a complete SPI interface and one extra unused pin!
3. Update schematic. The LEDs used for sensing the light input are upside down!