I just bought the sonar range-finder for my Heli-bot from Maxbotix.I purchased the most sensitive of their sensors, the EZ0, for the front of my heli-bot, to test out the "autopilot" PICAXE control. This looks to be an awesome sensor, with a 1-inch resolution out to 6.5 meters! It offers either continuous or polled mode, and the sensor output is RS232, 0-Vcc or Pulse-width, all in a package smaller than a cubic inch. Full datasheet is available here. (pdf)
By the time the exchange rate and postage was taken into account, it came to about $90 AUD.
I will be giving this sensor a thorough workout when it is attached to the robot, probably less than 20mm from the front rotor's drive motor, so we can see how it behaves in an electrically and acoustically noisy environment.
