Hi there,

Very new to MindStorms, tho I've coded up AVRs and microcontrollers...
Question- For the NXT servo motors, can I read the current position? To clarify, there could be an obstruction that makes the motor move less than it's been told. My goal is to use it to aid in detecting whether an object is gripped.

I read that the NXT servos have tachometers built in.

Hi cyman,

You read correctly. You can easily read the current tacho count with:

You can reset the count simply by assigning 0 to nMotorEncoder, like this:

- Xander

You're hilarious, Xander

Thanks! Also, one big issue is setting the motor to an absolute position. Can i do that?
For example, I have a hand that i want to open and close, but i need the motors to be in the right initial position for it to work. in practice, when i start my robot, the motored hand is typically semi open or semi closed, forcing me to physically calibrate it.. A big pain.

Ive used servo controllers like the ssc32 that will let you set an absolute position. Wondering if thats possible.

Nope, you 'll need some other way to calibrate the starting position. Perhaps something like a button that's pressed when the hand is at the the limit of it's movement. For absolute position, you need something like a potentiometer.

ok thanks!

A button could work, but that would cost you a sensor port; you could also do something like this
That would make it go backwards until it's detected that it has hit something and can't move any further. That would only work if, again, the motor can't physically move past one point like magicode said.

Another option is the HiTechnic Angle Sensor which will keep track of the angle of the motor even if the robot has been turned off:

http://www.hitechnic.com/cgi-bin/commer ... ey=NAA1030

Hi dimastero.... Thanks thats handy and will work in my situation!