We’ve simplified the Tankbot so much that this has to be one of the simplest and cheapest robots around. Instead of a 5v Arduino, which needs 3.3v to 5v logic level converting, we’re using a 3.3v Arduino Mini Pro. The TX and RX pins can connect directly into the HTC breakout board on the bottom of the Android G1 for serial communication.
The only tricky part was getting a thin 30 gauge wire to run into the back of the phone and wrap around the positive battery terminal. We tried some thicker wire at first but it prevented the phone from maintaining a connection and it would shut off accidentally. The thinner wire sits there nicely and we might try making a permanent connector on the outside of the phone so it can fit back in a pocket without a wire sticking out.
The top picture is a working version with the red 30 gauge wires above is an early test with a thicker green wire that had a flaky connection. You can see that we’re still using the HTC breakout board wiring for TX, RX, and ground, and we’re not yet connecting the fourth wire that you see here. That would be used for charing the phone but doesn’t provide enough power out to run the robot.
This video overview shows you the whole thing moving around to prove it works. No word yet on the effects of doing this on your battery so please do so at your own risk.
If you get something similar working, share it in the Cellbots support & discussion group. Bonus points if you hook your robot up to a wireless charging station!