The stock Hitec HS-785HB servos that drive the pan and tilt can rotate several turns in factory form. By coupling the servo to an external gear set, the amount of rotation is decreased by the ratio but the torque and precision is increased by the ratio. In order to tailor your pan and tilt system to the controller you wish to use, we offer a 3.8:1 ratio as well as a 7:1 ratio.
*Figures are calculated by multiplying the PWM range by 1.525 to get the number of degrees the servo will rotate.
Example – I am going to use a servo controller with a 1000-2000usec PWM signal range and a have selected the 7:1 ratio on PT785-S pan and tilt:
2000usec-1000usec = 1000usec
1000 x 1.525 degrees = 1525 degrees. This is the amount of rotation the HS-785HB servo itself will rotate.
1525 / 7:1 ratio = 218 degrees. This is the amount of rotation that each axis on the pan and tilt will rotate given the stated signal range.
The speed, torque and precision of the PT785-S are altered by the external ratio. The 7:1 ratio will yield higher torque and higher precision but will be slower than the 3.8:1 ratio. The 3.8:1 ratio will have more rotation given the same signal but will have less torque and less precision when compared to the 7:1 ratio.