Servo works connected directly but not through a Motor Sheild.

Projects General Guidance
1

Hi, I am building an arm on top of a tracked vehicle. I am using the motor shield to drive the tracked vehicle motors and have servo's attached to Arduino. Due to the power requirements of the servo's they have a seperate positive but common ground with the Arduino board. Attached directly to the Arduino, the servo's work perfectly and follow a test sequence I have configured.

However when I attach the motor shield, the servo attached to pin 10 moves erratically as though it's getting chatter from the board rather than following the test sequence. As far as I can see the motor shield simply passes pin 10.

Any thoughts would be most appreciated.

2

Which motor shield?

Pin 10 may be used by the shield or perhaps it's picking up interference from one nearby that is. I'd try a different one to start with.

3

"Any thoughts would be most appreciated."

Maybe remove the motor board and see if the servo problem stops. As suggested, maybe try another unused pin for that servo and see if the issue continues.