RE: stepping motor driver, 8-pack, Phytron-ECT

[Peter Eng <eng@cars.uchicago.edu>]

> McNulty wrote:
> 
> with ACS microstepper drives. They work fine when they do 
> work and have
> not given us
> many noise headaches, but they are very sensitive to 
> power-cycling, hot-plugging
> motors, etc., i.e. the usual things one should not do but 
> which still occur.
> In particular, the microstepper drives frequently fail if one 
> does not switch
> off their motor current switches before switching off or on the
> ACS Step-Pak crate power. The failure mode usually manifests 
> as a 'busy' light

I have a lot of experience with the 'busy' light problem.  I have tried to
get Leo to fix the problem which is a CMOS chip used as an LED driver.  The
chip blows and then blocks the stepping signal!  There is a very quick and
dirty fix.  You take a pair of diagonal cutters and clip out the chip.  The
lights will no longer work but the driver will.  I have asked Leo to put
some more protection on the board since the CMOS is connected to the limit
lines directly!  He as been unresponsive to this problem.

One nice thing about the this driver is the ability to have the current set
back to very low values in a few msec.  This is very useful for in vacuum
motors, and we have been using them very successfully in our mono.  This
current set back feature in not well documented.  To use it you have to add
or remove jumpers.  Also the heart of the driver is an OEM module from
Intelligent Motion.  I have the manual for the module and found that you can
reduce the driving current to any value by adding your own reference
resistor.  You don't have to install current limiting resistors for small
motors.

If you are running small two phase bipolar motors like Micro Mo stepping
gear heads (found in the Newport MFN stages and CARS KB bender) and can live
with half stepping CARS has designed an 8 channel box with connections for
an OMS (using a CARS transition board) or E500.  It uses one DB25 for the
step and direction and one DB25 for limits and home (making installation
easier but trouble shooting harder) This driver is very hard to kill.  I hot
plug it all the time with no problem.  The University of Chicago JFI
electronics shop has built more then 25 of these units and the cost is about
$1700 including transition board.


	-Peter