Re: Re: testing steppers

I smoked one Gecko when I started out because a winding in the motor shorted
out while running. It seems that coil inductance is essential to current
limiting with these devices. You will want to check the readings on each
winding for a resistance value, not just continuity or the lack of it.

HTH

Ray

>    From: "caudlet" <tom@...>
> Subject: Re: testing steppers
>
> --- In CAD_CAM_EDM_DRO@y..., Steve Ross <sross@m...> wrote:
> > Hello All
> > 
> > Recently I had a brand new driver box go up in smoke. It turns out
>
> a
>
> > stepper motor was the problem. How can you test a stepper motor
>
> before you
>
> > smoke the box?
> > 
> > Steve Ross
>
> An ohmmeter test to determine the windings followed by checking for
> shorts between windings and a winding shorted to the case should root
> out most of the destructive overloads.  An open winding won't
> overload the card but will case the motor to just sit and vibrate.
> If you are still concerned put a power resistor in series with the +
> side of the motor DC power that will limit the current to within the
> rating of the driver.  Use the age old formula of R = E/I where R
> equals the value of the resistor in ohms, E is your applied voltage
> and I is the max current rating of the driver card.  Power is
> calculated by using the formula Wattage = current(I) squared times
> the resistor you just calculated.
>
> IMHO It should be difficult to destroy a well designed driver card
> with pulse by pulse current limiting that is being run within the
> voltage specs of the card.