CMU Cam servo jitter

[adamdb]

When I hooked our CMUCam2 up to my PC for testing, both the pan and tilt servos "jittered" constantly. Kind of like they couldn't decide on what the exact center position was and were constantly switching between two positions.

I am using an external wall-wart type supply that supplies 12V and 500mah. The jumper for "use internal power to servos" is on.

Is anybody else experiencing this? In RC airplanes we will occasionally see jitter like this when using a fully charged 6.0v battery and it will continue until the voltage has dropped off a little, but I am assuming that power for the servos in this case is regulated to 5v, so it should not be an issue.

Thanks,
Adam

[Obi]

Yes, we are experiencing that also. I believe that it is from the servo trying to return to the position you tell it to. How is it mounted to your test robot? We have it on an old robot with tape, and since that isn't as sturdy, it gives a little. Thus, the weight of the camera moves the servo around more than it wants, and it continues to over-correct. We can stop it from jittering by holding it in place.

[Mr. Lim]

Originally Posted by adamdb

When I hooked our CMUCam2 up to my PC for testing, both the pan and tilt servos "jittered" constantly. Kind of like they couldn't decide on what the exact center position was and were constantly switching between two positions.

I am using an external wall-wart type supply that supplies 12V and 500mah. The jumper for "use internal power to servos" is on.

Is anybody else experiencing this? In RC airplanes we will occasionally see jitter like this when using a fully charged 6.0v battery and it will continue until the voltage has dropped off a little, but I am assuming that power for the servos in this case is regulated to 5v, so it should not be an issue.

Thanks,
Adam

We saw this jitter too when we powered it directly from the 12V breakout on the robot, but realized quickly that you're not supposed to do that unless you switch the "Servo Power" jumper to "External" - and then power the servos directly from a 7.2V source.

Chances are you're giving your servos 12V of power, like we were, and it's probably not a good idea to keep doing that. They like 7.2V much better.

I would recommend powering your camera right from a PWM output of the robot controller. Just pick one that isn't going to be used, and steal the power leads from it =).

-SlimBoJones...

[adamdb]

Obi,
The servos aren't even mounted. Just sitting on the desk.

SlimBoJones,
You confirmed that we are seeing the same thing we see in the RC airplane world, servos don't like too much voltage. I will try a 7.2v source as the controller and I are in different locations currently so I can't use a PWM output (although that is what we will do eventually).

Thanks,
Adam