Alt-BEAM Archive
Message #00709
To: beam beam@corp.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Sat, 20 Feb 1999 21:09:43 -0600
Subject: [alt-beam] Re: stepper motors
Here is a simple circuit to drive a stepper coil.
+5v
___
|
o-------.
| |
< |
1K > |
< /
470 | |<' 1N4001 or equivalent
o---/\/\/---o---| ,------|<-------.
from |\ | |
microcore `---o--o to coil o--o--.
MJ2955 |
or equivalent _|_
= Gnd
A typical 8 coil (4 opposite pairs) will use 4 of these circuits. You engage
each pair one after another. reverse the direction of the pulse to reverse the motor.
In the 8 coil (4 pair) stepper, each cycle (activate coils 1, 2, 3, and 4 in
line, or one microcore loop), the stepper will rotate 1/8 the way around. 8
cycles from 1-4 will give you one rotation. that's how disk drives can be so
precise. each pulse only moves the motor 15 degrees!
To reverse one stepper though, you need two reversers connected together.
Reverse the signals to coils 1 & 4 and reverse 2 & 3. that should reverse the
stepper's direction. I may try to make something from the NUMEROUS dead drive I
have, just to be able to say I have done it! hehe! (:
You can use that driver for any coil based device, I think. It takes and active
low input, so it matches the microcore's active output. If you need active high,
just throw an inverter on the input. I'm sure a transistor could do the job to,
if you don't want to add a chip. I forget what type of transistor is ideal for
that.
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://members.xoom.com/richfiles
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