Technical Tips - Modify Servo to Continuous Rotation
Servo motors are used in RC models for position control of mechanical devices such as steering, throttle, rudder, etc. Most servos can also be modified for continuous rotation, for wheel driving, turret rotation, etc. This example shows how to modify a Futaba S3001 servo to continuous rotation. The technique can be applied to other servos as well. The modified servo can be connected to the ROT port of MTC-1 mini tank controller for turret rotation.
Remove screws at bottom. Open top cover.
Remove the output shaft. There is an end stop limiting the angle of rotation. Remove the end stop carefully by a cutter.
Remove two screws securing the motor. Remove the motor and the PCB. There is an potentiometer for position feedback. Remove the potentiometer carefully by a soldering iron. Take care not to damage the PCB.
Replace the potentiometer with a 5K ohm trimmer. Solder the trimmer carefully on the bottom side of PCB.
Make an opening at bottom. Reassemble the servo. The modification is completed. To calibrate, connect the servo to a RC receiver. With the control stick at middle position, rotate the trimmer slowly until the output shaft stops rotate. Move control stick slowly to control the speed and direction of rotation. For most servos, however, top speed is reached when control stick moves one third of its range.