Experimental Physics and
Industrial Control System

[email protected] · Mon, 30 Mar 1998 18:34:59 -0600 (CST)

> Hubert, re...
> 
> > -- On Mar 27, 1998, [email protected] (Tim Mooney) wrote
> > > I should mention that glitches on the limit-switch lines can produce
> > > very similar behavior, and are by **far** the more common cause of it.
> > > So don't everybody with an intermittently jerky motor immediately assume
> > > their hardware is flakey.  You might just need some decoupling capacitors.
> > 
> > I'm not sure that this is true.  I've seen this behavior very regularly
> > (with the .27 release of the motor record, VME8-8 board).  I don't have
> > any limit switches in my system and limit-switch support has not been
> > enabled.
> 
> Wait a minute.  You can't enable or disable limit switch support, and the
> hardware doesn't care whether or not you actually have switches.

We have seen this behavior with the OMS boards when we were not using 
epics.  It can be tricky to diagnose since noise on the limit lines
gives a limit switch trip, but only an intermittant one, so that the
software doesnt actually have time to trap the error as a limit problem.
All you see is that the motor intermitantly stops.  Capacitors on the limit
lines (as close to the oms boards as possible as with Kurt Goetz's paddle
board) seem to cure this problem. OMS also claims that the MMI
PAL chips on the limit lines are particularly susceptible to the problem and
that switching to TI PAL chips limits the effect.

Larry

-- 
==================================================================
Laurence Lurio
IMM-CAT
Sector Number 8
APS/ANL
Building 400                               VOICE:     630-252-0281
9700 South Cass Avenue                       FAX:     630-252-0282
Argonne, IL 60439-1749                     EMAIL:  [email protected]
==================================================================

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System