Phototropic BEAM vibrobot
Added a video of the bot in motion.
This is my first vibrobot. I've wanted to create a phototropic BEAM vibrobot for a long time but I was not sure how I was going to steer it to achieve the "phototropic" part. After seeing Evil Mad Scientist's Bristlebot I decided to try out a "catamaran-style" bot, essentially joining to Bristlebot's together and driving each side at different speeds to steer.
To control the bot's direction two LDRs are connected in parallel across the terminals of the motors (see below).
The LDR placed across the motor reduces the speed of the motor by reducing the voltage across it in bright light (more load on the output from the solar engine, the lower the voltage). The diodes allow the two LDR/motor circuits to operate independently. This configuration saves on using a transistor for controlling the motors' speed.
This configuration works quite well and the robot quite happily (erratically) drives toward the sun when left outside. The LDR's are on the same side as their motors so, for instance, bright light on the left side of the robot slows down the left motor, turning the bot to the left.
That's it for now, I will upload a video when I have consistent sunshine and my camera's battery decides to play nice :)