Servo dead zone?

[jeffrey morris]

Joysticks usually have dead zone when the stick is at center position. It's hard for me to center a servo because there is no dead zone. If I use Arduino IDE to center the servo, the servo won't stop moving when the position is at 90 degrees. I'm using BETU DS3225MG 25Kg digital servos. How can I fix the problem?

[Ray Edgley]

All servos do have a dead zone, but the dead zone is a small region either side of the current input signal position, unlike with a joystick where it is always in the middle.

The centre position of the servo will be when the signal being sent to it is at 1500uS

Standard will rotate 90° with a PWM signal of 1000uS - 2000uS

MyRobotLab (MRL) get a full 180° of rotation by sending the signal in the range of 500uS -2500uS

Most servos will have a dead zone of 1 - 2 uS, that is, if you adjust the signal up or down by 1uS it most likely wont move at all.

To make things even more interesting, MRL can adjust the output range limits, this will also move where the servo is considered to be cantered.

Now this is where we need to consider what are you calling 90°?
Is that the cantered position? or is that a position 90° from the centre of the apparent range?

[jeffrey morris]

I found out that the pots that are inside the DS3225MG servos are the wrong kind. The pots don't have stops. I tried a pot that has stops and it worked. Of course, the pot is a regular-size one and not a micro one.