Re: 10 amps to drive steppers

Posted by Mo

on 1999-06-14 18:50:11 UTC

> From: Jon Elson <jmelson@...>
> A properly designed stepper driver shouldn't be troubled by operating
> with no load. Unplugging or plugging in the motor while the driver is
> active could cause some arcing that might cause damage, but just running
> the driver with no motor connected shouldn't be a problem.

Jon, unfortunately both types of board I have here warn that this is a
certainty
and I believe the Camtronics boards are the same. I have inadvertantly
killed one that way.
It must be in the design, as you say. Where a manufacurer warn specifically
that their design
will be seriously damaged by this - it is good to take the precaution.

> Here's what I did, although it is on a servo system, but the problems are
> similar. The E-stop signal on my system releases a pair of relays (one
> a signal size, the other a power contactor). When these relays are
> released, they connect a power resistor to the servo amps power
> input, discharging the power supplies. When the relays are engaged,
> first the signal relay closes, connecting the same power resistor in
> series with the DC supply and the servo amps. Another contact on
> this relay connects power through to a time delay circuit. After
> a 1 second delay, giving time for the resistor to ramp up the
> voltage in the servo amps, the power contactor closes, delivering direct
> power to the servo amps. When this relay closes, it also connects
> the enable input to the servo amps to +12, turning them on.
> This gets rid of all the high DV/DT transients when powering things
> up and down, and makes sure that whenever there is a fault, everything
> is powered down in a controlled manner.

Perfect power up and enable sequencing. The power bleed resistors are the
absolute
minimum needed for those that do not have a similar set-up and are still in
the process of playing around with their assembly.
Jon do you have a schematic for that set-up - if not I could knock something
up and put it on Tim's site for members who would like to go that route.

Mo

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