Re: E-Stop Revisited (PS on sherline auto changer)

James,

With servos you should short the leads so the motor "brakes"...

Ballendo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "jmkasunich
<jmkasunich@y...>" <jmkasunich@y...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo <ballendo@y...>"
> <ballendo@y...> wrote:
> > Peter,
> >
> > On small "desktop" machines, here's what I do:
> >
> > As soon as the estop is pressed; I cut spindle power(with a
> > "hockey puck" SSR), drop power to the optos so the steps stop
> > getting to the drives, begin a timing circuit set to the worst
> > case spindle run down time, and raise the voltage to a "1" on
> > the estop signal line going to the computer.
> >
> > Now the spindle is winding down, held in place by the still
> > active drives, and the computer has been "notified" that we
> > have a problem out here...
> >
> > When the timer times out, I can assume the spindle is no longer
> > turning, so the enable for the drives is turned off, allowing
> > free movement of the motors.
>
> A very well thought out system. I just want to point out that
> this system should only be used for stepper based machines.
> With servo motors there are failure modes that would cause the
> motors to run away at full speed even though the step inputs
> are blocked. If using servos, cut the servo motor power right
> away, don't just block the step pulses.
>
> John Kasunich