I'll try to do this as I get things done, just in case somebody catches something stupid - here's an "alpha" schematic of the peak detector, if anybody wants to do a bit of peer review. It's meant to sample the signal for passing to the ADC in the microcontroller.
I haven't put it on the schematic yet, but for those of you (heh... as if that leaves anybody) who don't want to do the math for the voltage divider, here it is:
Vthev = 15 * 220/(2k2 + 220) = 1.364
Rthev = (220*2k2)/(220+2k2) = 200
Vout = (Vin - Vthev) * Rthev/(Rin + Rthev) + Vthev
Vin-max = 10V;
Vout-max = (10V - 1.364V) * 200/(1k5+200) + 1.364V = 2.38
Vin-min = -10V;
Vout-min = (-10V - 1.364V) * 200/(1k5+200) + 1.364V = 0.027
Which puts it roughly in the scope of a 2.5V reference. A 10-bit ADC gives a resolution of:
(2.5V / 2^10) / Rthev/(Rin+Rthev) = 0.0208V
Edit: A couple things I've tweaked - but haven't updated the schematic (so don't pick these nits
): 1) Simplified the two-transistor reset circuit for one of the detectors to a single PNP transistor with an inverting input (the MCU will have plenty of extra pins, so no reason I can't use two of them for the reset signal). 2) Somehow I swapped the reset circuits - the max detector should be reset by pulling to ground, and the min detector by pulling to +3.3.