Re: [CAD_CAM_EDM_DRO] Re: Lost steps

In a message dated 8/23/00 2:00:36 PM Central Daylight Time, Ozzie@...
writes:

<< Any thoughts? >>
I was just beginning to cobble-up a little interface-circuit to make an LPT-1
("parallel printer port") output drive some opto-isolator inputs on a
store-bought bipolar-chopper stepper drive, and I have a "digital counter"
which will count "square waves" as narrow as a hundred pico-seconds (a
guess), and I was getting SEVERAL more steps "per 1000" in tests, from zero
to dozens, and NO changes! Then, I tried tying .001 caps from each LPT-1
line (carrying step-pulses) to ground, and ALL FIXED! Seems the
"twisted-pair cable" from the puter's backside to the interface is not very
"signal-friendly", so, causes "hash" (lookit on a 'scope! NASTY!). The .001
rounds that off SHAMEFULLY, but it DO fix the problem!

Another way is to use a 74HCT4538 dual monostable for each pair of "pulsed
lines", and make the R/C for each monostable result in a retriggerable
output-pulse of at least 100 microseconds. That is enough "cover time" for
the hash to settle, before "expecting" the next legit pulse to come through.
WORKS! (the '4538 is the most wunnerful IC since garlic bread!)

A machinist with an electronic breadboard, a 'scope, and little brain is a
dangerous entity!

Jan Rowland