Newsgroups: comp.robotics
Path: brunix!uunet!europa.eng.gtefsd.com!howland.reston.ans.net!torn!watserv2.uwaterloo.ca!watmath!mwtilden
From: mwtilden@math.uwaterloo.ca (Mark W. Tilden)
Subject: Re: disk drive steppers
Message-ID: <CBM2FE.z8@math.uwaterloo.ca>
Sender: news@math.uwaterloo.ca (News Owner)
Organization: University of Waterloo
References: <1993Aug11.150046.26203@newshub.ariel.yorku.ca>
Date: Wed, 11 Aug 1993 20:04:25 GMT
Lines: 39

In article <1993Aug11.150046.26203@newshub.ariel.yorku.ca>
cs911225@ariel.yorku.ca (KEN E WILLMOTT) writes:

>I've seen a lot of posts about using disk drive stepper motors,
>and I wonder if anyone has tried using the existing driver board
>to power the stepper. It should be easy, since the Shugart
>interface has a TTL input for direction, and another one that
>produces a step when a pulse is applied. Anyone out there try
>this? I have seen some cheepo drives that I've wanted to try
>this with, but haven't had the time.

Three problems: finding the interface protocol to run the drive chips,
overcoming the electronic limits to protect the heads, and getting the
drives and drivers to handle a load larger than the small heads they
are optimized to move.

The last is the biggest bugger, because you often won't notice it until
the first two are compensated for.  We've found that old drives work
best because the steppers were distinctly over rated, but as
manufacturers got smarter, they realized they could save quite a bit by
custom winding their own motors which just don't have the yarbles for
most robotic work (especially in variable load environments).

Case in point, those neat little worm-gear steppers you'll find in dead
3.5in. floppies.  Absolutely pig useless for anything other than moving
heads.

So the moral of the story is, best to make/get your own controller, and
use old drives for the best power/weight ratios (typically, look for
steppers which have coil impedances of 5.6 ohms or less, or pancake
designs with high shaft torque).

Is all.

-- 
Mark W. Tilden.  "Gomi no Sensei des"       _    _    ________________________
MFCF, Un. of Waterloo, Ontario, Canada.    / \  / \  /________________________)
519/885-1211 <mwtilden@math.uwaterloo.ca> //\ \//\ \// ___o___________________
#include (standard.disclaimer);          //  \_/  \_/ (_______________________)
