The presented circuit was developed to control a common remote-control servo. Its operation is simple to understand. When control 1 and 2 are open (dry) the servo remains in the center. When control 1 is at logic level 1 (closed), the motor turns to the left. When control 2 goes to the high level (one), the motor turns to the right. The following table illustrates this operation:
Control 1 Control 2 Direction
0 0 center
1 0 Left
0 1 Right
The circuit was used to drive a satellite dish servo, but other types of servo can be controlled. The power transistors for driving the circuit can be BD135 or equivalent. The adjustment must be made so that the pulses generated have the duration that takes the servo to the desired position when the controls are activated.
