Alt-BEAM Archive
Message #00738
To: beam beam@corp.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Sun, 21 Feb 1999 14:16:33 -0600
Subject: [alt-beam] Re: stepper motors
I sent it as a general example. base resistor, transistor, coils(s), protection
diode. If you can "idealize" it for BEAM microcore use, go ahead.
> Presumably the `from microcore' is a push-pull output, in which
> case a pull-up should indeed be superfluous. But now that 470 ohms
> strikes me as rather small. Base current will be something like
> 9mA, which means that the kind of transistor I imagine you might
> need - like a good BC327 - is likely to oversaturate, and your
> microcore output may not like to sink 9mA anyway (4mA is about the
> most I'd want to ask of a 74HC output).
>
> It all depends on that stepper coil, of course. Perhaps I'm
> having a far too subtle featherweight `bot in mind...
>
> >
> > +5v
> > ___
> > |
> > |
> > |
> > |
> > |
> > /
> > 470 |<' 1N4001 or equivalent
> > o---/\/\/-------| ,------|<-------.
> > from |\ | |
> > microcore `---o--o to coil o--o--.
> > PNP |
> > transistor _|_
> > = Gnd
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://members.xoom.com/richfiles
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