Infra-Red Remote Control For Stepper Motors

16 EE INFRA-RED REMOTE CONTROL FOR STEPPER MOTORS Many audio purists balk at the use of an electronic volume con- trol, but would still like to upgrade a home-made preamplifier with remote control. This can be accomplished by using a good- quality potentiometer, a stepper motor, and the simple, yet versatile, infra-red transmitter and receiver described here. One particularly interesting application of the proposed infra-red remote control system is the actuating of the volume po- tentiometer in a high-quality audio pre- amplifier, such as the one described last month. Basically, the potentiometer is operated by a small stepper motor, whose direction of travel is controlled by means of pulses emitted by a hand-held infra-red transmitter. Infra-red transmitter The circuit diagram of this part of the remote control system is shown in Fig. 1. Simple data encoding is used to keep the cost of the circuit as low as possible. The direction of travel of the stepper motor fitted at the rec...