Automatic limit switch

[DominickC]

That sounds like a good job for a digital encoder.

[Alan Anderson]

Programming the robot to stop a motor when a digital switch activates is easy. See the attached snippet for an example of something that will keep a motor from going forward if the limit switch input is true.

However, what you're describing doesn't sound like something a digital switch can detect. Can you give some more information about how your limit switch is going to be physically activated?

[zaphodp.jensen]

An encoder would work best for this. To detect a bind, you would have the encoder, on a turn of the encoder, start a timer. If that timer reaches a certain value before the encoder triggers again, you would stop the motor. If it triggers, you would restart the timer again at zero.

If you wanted to stop after a number of revolutions, you would use a variable that would increment or decrement after a certain number of ticks, and if that number got to be higher or lower than a threshold, you would stop the motor in that direction, but allow it to turn the other way.

Sidenote about limit switches: Even easier, you could use the built in limit switch functions on the Jaguars to stop the motor. This wouldn't work for your application, but it is great for just about everything else! You just have to use a normally closed switch, and plug it into the limit switch ports (Removing the existing jumpers)! Simple, easy to use, save a DIO, and it relieves the cRIO of having to deal with the code!