Got Gyro drift? Try Sensor Fusion !

[Richard100]

Phil - The issue you're describing can be caused by the programming error I identified in post #21 of this thread - if you're using one of the newer IMUs (purchased after last Oct). You can either download the corrected project file, or simply make the change illustrated in the code image attached to that post.

Another cause of deviation between the rate gyro and it's fusion (the grey & red needles, respectively) can be over-ranging the rate gyro by rotating it faster than the range it is set to. You won't damage the sensor but will miss some angular displacement reporting while beyond the set range. This is easy to do when the IMU is off the robot (say, rotating it in your hand).

I suspect that the problem is the the first thing, though, since you describe the grey needles as not moving at all. Both needles should track out of the box, within a tolerance affected by the quality of the calibration process, and assuming the sensors are not over ranged.

If you haven't already, try the code update and let us know if that resolves it. Let us know if the symptom persists and I'll look around for another cause.