Alt-BEAM Archive
Message #01431
To: beam@corp.sgi.com
From: Steven Bolt sbolt@xs4all.nl
Date: Wed, 10 Mar 1999 15:18:30 +0100 (CET)
Subject: [alt-beam] Re: Surface mount H-bridge chip
On Wed, 10 Mar 1999, Ben Hitchcock wrote:
> What I do for a solar powered reversing circuit is to have an enable
> transistor that switches the power on to the H-bridge when the motor needs
> to be run.
---8<---
The disadvantage of that idea is that you get three instead of two
VCEsats in series with your motor. Yes, it's only another 0.1V or
0.2V, normally, but when the `bot really needs power it will add
up to between 0.5V and 1V or even more.
If solar power is used, imho it is best to drive all four bridge
transistors individually, using 74HC logic to get the states you
want. For instance, if `non-smoke' is required you might do something
like this:
http://www.xs4all.nl/~sbolt/Other/Hlp-bridge.gif
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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