Vario version 2
The second iteration in the development cycle of our minimal variometer design differs, hardware-wise, from the first attempt in the following ways:
1) The VTI SCP1000 barometric sensor is replaced by a Bosch BMP085; The decision to use different sensor model was simplified by the fact that the SCP1000, even though adequately sensitive and robust, is no longer manufactured.
2) The clunky "walkie-talkie" hack was abandoned in favour of a regular simplex RF link; That initial transmitter choice was an experiment anyway, and, as it turned out, this was no success. The radio range seemed quite good but the microphone's behaviour was erratic, being much too sensitive to the RF noice generated by onboard electronics. The combination of evident RF frequency emissions from the nearby BEC, and the intermittent chatter and hum (in the aural range) from the servos' action, meant that the beeps could not be discerned reliably most of the time.
Well, it was worth a try...
3) The microcontoller board itself is now an "enhanced" Solarbotics Ardweeny instead of the Sparkfun Pro Mini. There was no particular reason for the change of Arduino board type, other than curiosity!