Re:low cost stepper driver

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "John Dammeyer" <johnd@...> wrote:

>
> You cannot guarantee that when you unplug a powered stepper motor that the
> connector or switch won't have the contacts bounce on/off for a few
> micro-seconds or even milli-seconds. During that time the stepper motor
> windings behave just like the ignition coil and the resultant high voltage
> spike will kill the drives.
>

This is what I was wondering. I appreciate that you get a back-EMF spike when it's disconnected, but it's *DISCONNECTED* - it's not the driver transistor switching off so it shouldn't reach the driver. But intermittent connections (or a spark that jumps the gap, as Tony suggested) is possibly the reason.

I note that some good quality drivers have tranzorbs which can presumably absorb more energy than the internal diodes (and also don't dump it into the power supply).


-adrian