BASICS / CAMERA CRADLE / 360° SERVO CONVERSIONS

Method 2 - Geared External Pot

Figure 4 Figure 5 The geared external pot works by removing the internal servo pot (see page 1 Fig. 1 ) and replacing it with an external pot of the same resistance value (usually 5K ohms). Gears are attached to the output shaft of the servo and to the shaft of the external pot (Figure 4). The gear ratio that you use will be determined the same way as the ratios in method 1.

The rig will rotate about the red shaft that is also connected to the small gear. If connecting the red shaft, the small gear and the servo output shaft becomes too difficult, try mounting the red shaft separately with a gear the same size as the small gear on the output shaft of the servo.

You can get a small 5k ohm pot from an electronic supply store or a Radio Shack. Get one that has threads and a nut for mounting through a hole. You will have three wires running between the external pot and the inside of the servo. The center connection of the external pot MUST connect to what was the center connection of the pot you removed from the servo. The two outer connections of the external pot can go to either one of the outer connections in the servo. A small hole must be drilled in the servo case for the wires to pass through.

The stop on the servo final gear/output shaft and the two stops inside the top of the servo case must be cut out (Figure 5) to allow the output shaft to rotate 360°.

Advantages-
The control stick can be calibrated so you know the pan angle by looking at the joy stick.
The rig will turn at least 4 times slower than method 1, which will be close to the sevo's normal operating speed.

Disadvantages-
Servo must be open and modified, including some soldering.
Care must be taken when mounting the components so that the gears mesh properly.
Can not use most mini-servos because of partial gears.

NOTE ABOUT OTHER TYPES OF SERVOS

If you wish to use a servo other than the S3003, make sure that the output shaft has enough supporting structure to operate if the "pot" is removed. If the final servo output gear depends on the "pot" for support, then you can possibly leave the "pot" in place and disable the "pot" by carefully removing its insides and making sure the output shaft can freely rotate 360°.