View Full Version : Feedback

02-02-2014, 12:19 PM
Hi ive been sat thinking about the cnc machine in the garage, and came to the conclusion that mach3 would continue to run the program even if the axis have stopped moving.

This got me thinking to how to have feedback from the steppers to say its still moving, or would an encoder be needed.

02-02-2014, 03:49 PM
There's probably at least 3 kinds of 'stopped'

1. The axis is physically jammed but the stepper is still trying to turn.
2. The stepper is at standstill with the driver holding it there
3. The is no power to the stepper motor

An encoder would indicate all of these conditions but you would have to compare it to the current instruction being issued by Mach3, i.e. is Mach3 telling it to stop ?
Some drivers issue an alarm signal if there is a problem so this could be used.

You could attach a small motor to the end of the ball screw, as it turned it would generate a small voltage that you could detect, then you need a way to compare it to what Mach3 is asking for by maybe looking at the step/dir signals to the driver. If step/dir = YES and feedback volts= 0, then problem.

Edit: Mach3 brains idea no good because DRO moves at Mach request not feedback from stepper, what was I thinking about :disgust: