Alt-BEAM Archive
Message #00735
To: Richard Piotter richfile@rconnect.com
From: Steven Bolt sbolt@xs4all.nl
Date: Sun, 21 Feb 1999 21:04:03 +0100 (CET)
Subject: [alt-beam] Re: stepper motors
On Sun, 21 Feb 1999, Richard Piotter wrote:
> 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!
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
>
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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