Servo - August 2012

Easy To Build Wireless Servo C ontroller

If you are in need of a simple, inexpensive, and easy to construct wireless remote control that can independently operate up to two servomechanisms, this design may be just the answer for you.

Wireless remote controls for servomechanisms have always been an integral part of R/C projects (including model airplanes and model cars). The numerous available systems can handle many channels and are very elegant, but in general are also quite costly. The total cost of parts for this project is less than $50.

by Robert H. Walker www.servomagazine.com/ index.php?/magazine/article /august2012_Walker

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There are only three key components employed in this design, as shown in the circuit diagram in Figure 1. The first is a 27 MHz or 49 MHz toy car two-channel receiver which has been removed from the car chassis. The second component is a micro-sized gearbox which is linked via shrink sleeving to a potentiometer. The third part is a 555 IC timer based servo controller.

Figure 2 is a top down view of the controller module. Starting with the receiver board at the top, go clockwise around to the gearbox/potentiometer linked pair, and then to the servo controller board. The only other part is the gearbox speed adjustment — a Cermet trimpot. The entire module measures 5” x 3” and could obviously be made a bit smaller, since many toy car receivers are actually much smaller than the one shown.

The gearbox is a Microgear Motor Block ( 45 rpm) available from ServoCity.com. (An alternative is to modify a small servo to operate as a gearbox). The servo controller is available as an easy to assemble kit from

HansenHobbies.com. The only revision necessary is to replace the included board mounted 10K trimpot with an outboard wired 5/8” diameter 10K linear taper potentiometer. The potentiometer has to be mounted with the shaft horizontal and lined up with the output shaft of the gearbox.

The heat-sensitive shrink sleeving is slipped over both shafts and then shrunk down. The sleeving links the gearbox to the 10K pot and will also act as a slip clutch when the pot hits its