Building Tips – Servo Stretchers

There will be occasions when you want more than the 90° rotation that manufacturers set their servos to. Most of the servos I have come across are capable of more than the 90° rotation that we normally use. In fact, many are capable of as much as 180° rotation.

         One method of getting the extra rotation uses a feature found in some modern radios. You may discover that it has an “end point adjustment” facility. If you only need a little more than 90° rotation this facility may be all you need.

           If you need more than the radio can provide, or your radio does not have the facility, the second method is to connect a “servo stretcher” between your radio and the servo. 

             There are two varieties of servo stretcher, with and without end point adjustment. Some servos cannot rotate the full 180°, and a stretcher without end point adjustment may try to make your servo rotate the full 180° or more. If your servo rotation hits an end stop and cannot get the rotation that the stretcher calls for, then the servo motor stalls, keeps trying to reach the set limit, gets hot, and may burn out. To ensure you don’t face this situation, you have to limit the amount of rotation.

          You may be able to limit the rotation using your radio’s end point adjustment, otherwise a stretcher with the facility is necessary. Robotzone make a stretcher with  adjustable endpoints, currently available from Servocity and Active Robots. Stretchers withoutend point adjustment are available from a number of suppliers.