SERVO POINT MOTOR
Point Motors can be expensive. You can save over 75% by making your own using cheap RC Servos.
All servos come with a variety of attachments for the output shaft. These are called “Servo Horns” or “Servo Arms” and are “single leg horn, (or servo arm), double servo horn, circular horn (wheel) and others.
They convert circular motion into straight-line motion with the aid of a push-rod.
That’s exactly what we want, to move the track-rails. Any of the horns can be used for this project as you only need a very short travel. The push-red needs to be spring-steel and you can unwind a small spring to get this item.
Servos have 3 leads. Positive, Negative and Signal.
The Signal wire is connected to a PC board containing a chip that detects pulses to activate the motor. We do not need this feature. The PC board needs to be removed. Open the servo and remove the PC board and signal wire. The pot can be left in position but the wires need to be removed. The two remaining leads are connected directly to the motor.
Our circuit drives the motor and gearbox with a short pulse of energy to provide clockwise or anticlockwise movement.
No limit switches are needed because the railway track provides the limits-of-travel and the motor effectively stalls when the end-of-travel is reached. The gearing produces adequate torque (or effort) to move the rails and a current of about 50mA is sufficient to operate the motor to provide this effort.