BASICS / CAMERA CRADLE / 360° SEVERO CONVERSIONS

Introduction

Most servos have less than 90° of rotation without being modified. The servo used for panning the rig ideally needs at least 360° of movement to allow the camera to be aimed in any compass direction. A servo used for tilt ideally needs to rotate 90° and the servo used for depressing the trigger only needs 15-20° of rotation. There are at least 5 different methods for modifying a pan servo for 360° movement. Only method one can be performed without opening the servo and modifying inner parts.

Servo Primer - Principles of Servo Operation

Figure 1 Figure 2 Eliminating all the unnecessary technical details we will say that servos work by matching the resistance of potentiometers (sometimes called "pots" for short or variable resistors) connected to the joy sticks of the transmitter with the resistance of a pot in the servo. Moving the joy stick changes the "pot" resistance in the transmitter this causes the motor in the servo to start turning. As the servo motor turns it is connected by gears to a pot in the servo (Figure 1). When the resistance value of the pot in the servo equals the resistance value of the pot in the transmitter the motor stops turning.

The final drive gear that turns the "pot" in the servo also serves as the output shaft for the servo (black gear in Fig 1 & 2). The "pot" shaft fits into a slot in the bottom of the black final drive gear (Figure 2). The "pot" in the servo can not physically turn more than about 200° because of the way it is constructed. The "pot" is further limited in its angle of rotation (180°+) by stop tabs located on the final drive gear and inside the case top of the servo. These stops prevent the servo from accidently turning beyond the range of the "pot" and physically damaging it. The servo is further limited by the fact that the transmitter only turns the "pot" through half of the range between the stops.

We will use this information to show you several methods used to modify servos for 360° operation.

IMPORTANT
You can do 360° conversions on other types of servos as long as all the internal gears are 360°. Most mini-servos have only partial final gears and CAN NOT be converted except using method 1.