3. Two modified R/C Servomotors. Two identical model servos are required so that the motors run at the same speed. Servo modifications are described in section 13.3. Any servo should work. The following servos have been tested: Tower Hobbies TS53J, Futaba S148 and S3003, and HS 300. Some manufacturers’ servos appear to run in the reverse direction. This is easily fixed in the hardware design since the motor controller is implemented on the UP3 board. Several robot parts vendor sell modified servos for a slightly higher cost. Ball bearing servos are worth the extra cost, if you intend to run the robot constantly for several months. A third unmodified servo will be needed if you want a rotating sensor turret as shown on the example FPGA-bot photo.