which sensor to use

[DuaneB]

Originally Posted by tilky

we want to measure the absolute angle of the robot itself. so a potentiometer would be good?

The angle of the robot relative to what? The field? I don't know of a way to do this, except maybe to use a potentiometer or the rotary magnetic encoder on a follower wheel - but that will have issues depending on your drivetrain.

What our team usually does is to assume the robot starts aligned with the field at power-up and integrate all the rate-of-change inputs from the gyro over time to get an absolute rotation. Note that the gyro will tend to drift a bit over time, and you'll probably want a driver station button to reset the baseline gyro output (that is, the voltage reading from the gyro which the software interprets as zero rate of change).

[tilky]

we want to be able to read the angle of the robot relative to horizontal so when we go on the bridge, it will balance itself. we got it to work, but we have to reset it before and i didn't know if there was a better way

[DuaneB]

Originally Posted by tilky

we want to be able to read the angle of the robot relative to horizontal so when we go on the bridge, it will balance itself. we got it to work, but we have to reset it before and i didn't know if there was a better way

Ah, you want to measure tilt angle. The accelerometer (on the same board as the gyro, but with a separate digital interface) will work well for that. Keep in mind that the vector magnitude will be higher than 1G while the robot is moving, so you may need to compensate for that.

[tilky]

so there really is no "perfect" sensor to use?

[Alan Anderson]

For measuring tilt? A multi-axis accelerometer is the only reasonable choice. But no single sensor is "perfect". If you want the best possible information about the robot and its environment, you have to use many different sensors and a good algorithm for combining imprecise, noisy, and sometimes contradictory signals.