Alt-BEAM Archive
Message #00728
To: beam beam@corp.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Sun, 21 Feb 1999 09:31:06 -0600
Subject: [alt-beam] Re: stepper motors
As i said, I took i from my digital electronics book around 12:00 AM. The basic
schematic will work, throw any reasonably sized transistor in it's place and you
have a driver. I suppose the book assumes your driving a tank made with stepper coils.
I would assume most people would just throw in a transistor in it's place and
leave it at that. I saw why they put the pull up resistor in the whole circuit.
So maybe the microcore doesn't need it!
Try this then.
+5v
___
|
|
|
|
|
/
470 |<' 1N4001 or equivalent
o---/\/\/-------| ,------|<-------.
from |\ | |
microcore `---o--o to coil o--o--.
PNP |
transistor _|_
= Gnd
Wilf Rigter wrote:
>
> I would say Richard wastes about 0.8 ma since the 1K is across the
> base-emitter
> junction. However the TO3 MJ2955 is a monster, bigger than the MicroCore,
> has an max Ic of 15A and an hFE of about 30. A complete mismatch for the
> MicroCore drive capability. You want amps? You need a power mosfet !
>
> > 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
> >
>
> Why the 1K pull-up on the MJ2955 base? You seem to waste
> considerable current.
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://members.xoom.com/richfiles
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