Today
After finding that the power throughput from the pull-string generator is too low to really fire up an arduino board, I had the choice of trying to get down to barebones with an ATMega with various low-power mode 'fuses' set, or dispensing with it altogether. I think I'll end up using the LDRs as a voltage divider, and then have a comparator switching the buzzer (and maybe an LED if the pull is hard enough).
Earlier in the day, Dave was very sensibly trying to reason with me to buy a comparator on an IC, rather than trying to engineer one myself, but I spent so long wandering around The Range that I missed Maplin closing time. Cue an hour of trying to understand circuits like these so I could make one up from the bits I had in the Mobile Lab.
Tomorrow
I'll be going to Maplin to buy one of these.
Worth updating the partslist significantly as I think it's just about to simplify massively.
Follow developments in real time through the enigmaker twitter feed