At long last, the perfect platform for tabletop autonomous robots!
A small, inexpensive but high-precision Faulhaber gearmotor/encoder combination is available surplus for about $12.00 each. It seems to be ideal for a line maze solver, micromouse, etc. It has an optional right-angle ball bearing drive shaft (3 mm diameter by 7 mm long) which is extremely convenient as it fits the Solarbotics wheels perfectly.
I’ve built a small platform using the circular base and ball caster from Pololu. Gearmotor encoder specs are 5 volts, AB quadrature, 141:1 reduction for wheel motion of 70 rpm, 564 counts/wheel revolution. The motor draws about 30 mA @ 5V no load and seems to have plenty of torque. The encoder output is triggered by an internal magnetic disk with one sector per motor revolution, which even at 10,000 rpm is a light interrupt load (about 6 milliseconds per revolution, 1.5 ms/channel).
To mount a side-by-side pair of motors, I machined a simple bracket out of 3/4 inch aluminum. A 41/64 drill is a very close fit for the motor body and the result can be snugged up with an 8-32 setscrew. See below for photos. At the moment, I have the ball caster at the back due to the uneven weight distribution. The platform moves 22 feet/minute at full speed!
The gearmotors are available at maximumrobotics.com and Electronics Goldmine, among others. You cannot beat this buy. See the instructions posted on the maximumrobotics web site for removing the output pulley from the drive shaft. Also see the extensive info on Richard Greenway’s site http://www.fenchurch.org/cgi-bin/ids/index.cgi?mode=album&album=./Computing/%23001_RobotStuff/Faulhaber_Motor
The controller will be the Orangutan, and I’ll post details later. Some time ago, I posted software for the Orangutan that uses pin change interrupts to decode quadrature encoders, see Quadrature encoder for the O. I used this without modification to track the wheel position and am currently working on PID speed control.