[PhilBot]

Originally Posted by surly

DC Motors with encoders can be used in LabVIEW through three VIs on the "NXT Robotics >> TETRIX" palette.
Move a Fixed Distance :
Motor Status:
Reset Encoders:

It's also very easy to use the encoders to regulate the motor speed (vs the motor power)

eg: On the driving portion of the code, on the move motors VI, change the Polymorphic selector (small oprion box under the move motor VI) from Power to Speed.

Assuming you have the encoder and motors wired correctly, this will enable you to get MUCH finer control of the driving. eg: with constant power, it's hard to get a slow move. You always need to have a certain amount of power just to get the motors to overcome friction (eg 20%). However if you use Constant Speed, (with encoders) you can get the speed as low as you want (eg: 5%) and it ALWAYS runs at that speed, regardless of friction. It's great for slow turns etc.

If you try using encoders and you always seem to go at 100% speed, then you have a wiring problem... Could be your encoders and motors are switched, A-B and B-A or mayve your motors are wired in reverse (red -ve, black +ve)