Problem connecting electret preamp to Prop

lardom

I want to build a circuit with two electret mics so I could experiment with finding the direction of a sound source. I learned that I couldn't match the built-in mic on the 'Demo board' so it seems the solution is to use breakout boards. My question is do I connect the breakout boards to an adc chip first? I've already destroyed a Prop pin because I connected it to an amplified mic output.

average joe

There's a couple ways of doing this, but I would recommend using the on-board Sigma-Delta ADC. Check out this application note, should help you get started. Page 9, figure 9 is the circuit I recommend.
http://www.parallaxsemiconductor.com/sites/default/files/appnotes/AN008-SigmaDeltaADC-v1.0_0.pdf

Phil Pilgrim (PhiPi)

The S2 Robot uses a microphone pre-amp, since the mic and Prop are on different PCBs. You can download the S2 schematic here:

http://www.parallax.com/Portals/0/Downloads/docs/prod/robo/scribbler2/S2Schematic.zip

From the pre-amp, the ADC is done via the sigma-delta technique.

-Phil

lardom

Phil, studying the S2 schematic should answer the question of how to connect a preamp to the Prop pin. I was unable to contruct a satisfactory voltage divider which is why I'm going to try it with a separate pcb. After frying a pin I decided I'd better ask the pro's.