Microphone

Progress on the microphone as a digital input:
We now have a circuit that takes the two mic leads and outputs a digital signal that can be interpreted as "whether someone is/was recently screaming into the mic.

Here is the signal processing/circuit overview

1. Input signal is the microphone input which I assume to basically be a sin wave centered at ground
2. run through an inverting amplifier (gain of 22), this gives a bigger amplitude and saturates all voltages below gnd.
3. the output of that is run through a diode to charge a RC circuit (R = 1M C = 10uF tau = 0.1 sec)
4. This is run through a buffer
5. and into a standard comparator with hysteresis circuit for a clean digital input.

It's pretty nice in that complicated words usually come out as just being one digital signal for the length of the word.

Also the zigbees are soldered. yaay!