Re: Homebrew STG card - 8254

["Steve Carlisle" <quatsein-at-island.net>]

Ther is a chip set similar to the one from Rutek, it is
avaialble from PIC-SERVO, for servo control, with an
option chip to control it from a step/direction source.
Most of the servo driver suppliers offer a pulse driven
servo driver, so that idea is not to off the wall.

Steve

----------
From: bfp <bfp-at-earthlink.net>
To: Multiple recipients of list <emc-at-nist.gov>
Subject: Re: Homebrew STG card - 8254
Date: Wednesday, March 01, 2000 1:50 AM


Hello all,
 I just dropped in from [CAD,CAM,EDM,DRO] and caught the tail end of this
thread ,I've been working on a similar idea myself and I had some random
thoughts on the 8254 timer chip.
I've done some work with these chips before on a hobby project and have
seen
a few others
using them on the web, to stop the timer output you can use a buffer with
an
enable pin like
the 74als244 or an AND gate & one bit from a digital port like the original
pc speaker did
I like the idea of using it to clock a stepper board,that got me thinking
about another use for it,
a company called Rutex in Australia makes an external board  that
translates
step+dir commands
into a +-10v servo reference signal by using a PIC chip to generate a PWM
signal and pushing it
thru an integrating op-amp[LM358] to get the +-10v output for the servos
it seems to me that using the 8254 to generate the PWM(mode1) would only
require a software
change,and an op-amp on the card or on a breakout board near the servo amp
might provide
a "clear upgrade path from steppers to servos"
another possibility is to feed a pulse string (mode2)or square wave
(mode3)into an  LM2917
frequency to voltage converter
I know its a bit unorthodox but does this sound reasonable?

Brian

ref:
http://www.boondog.com/tutorials/8254/8254.htm
http://www.rutex.com/990/990000.htm