Adafruit Continuous Rotation Servo - FeeTech FS5103R
This servo rotates fully forward or backwards instead of moving to a position. You can use any servo code, hardware or library to control these servos. Good for making simple moving robots. Comes with four different horns, as shown.
To control with an Arduino, we suggest connecting the control wire to pin 9 or 10 and using the Servo library included with the Arduino IDE (see here for an example sketch). Position "90" (1.5ms pulse) is stop, "180" (2ms pulse) is full speed forward, "0" (1ms pulse) is full speed backwards. They may require some simple calibration, simply tell the servo to 'stop' and then gently adjust the potentiometer in the recessed hole with a small screwdriver until the servo stops moving.
Note: This product no longer includes the hole to adjust the Zero point.