Subject:
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Re: Handyboard low voltage motor control
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 18 Oct 1999 19:38:25 GMT
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Original-From:
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Gary Livick <glivick@pacbell.netNOMORESPAM>
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Viewed:
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888 times
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Good point...
There is another way. You can build your own h-bridges using mechanical
relays and maybe a few diodes. They drop zero volts, which is good. However,
you obviously can't PWM the things. If you just want rudimentary speed
control, you could add another SPDT relay in line to add a dropping resistor
in series..... You can use the motor outputs right off the Handy Board to
switch your bridges.
If you want PWM, you can build your h-bridges from solid state dc-dc relays.
They switch in about a half microsecond, so are plenty fast. Some even have
flyback diodes built in, and only turn on when forward biased, which is great
for use in h-bridges. However, these will drop some voltage, so you have to
account for it when sizing your motor voltage supply. To control these, you
also use the outputs directly off your Handy Board. I've used the latter
method myself, and it works great.
Gary Livick
Paul Dito wrote:
> That'll work, of course, but that also means I'll be dissapating about 8
> volts at .5A through the resistor...
>
> Gary Livick wrote in message <380B55B1.1C3703C4@pacbell.net>...
> >
> > How about a resistor in series?
> >
> > Gary Livick
> >
> >
> >
> > Paul Dito wrote:
> >
> > > Hi All,
> > >
> > > Most of you guys seem to want more power to control motors, well, I want • to
> > > go the other way. I'm looking to drive 1.5v motors with the handyboard.
> > > The lowest voltage the L293 can take is 4.5v (Vmin of Vcc1), and that • still
> > > has my motors screaming, even with the minimum PWM from the controller.
> > > Obviously I can take the outputs of the handyboard to my own H bridge, • but
> > > I'm looking for an easier way out...
> > >
> > > Thanks,
> > > Paul
> >
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Message has 1 Reply:
 | | Re: Handyboard low voltage motor control
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| Well, I went with separate h-bridge to maintain PWM and it turns out that even though the motors are geared down, they still don't have enough torque to haul around all the batteries. Looks like I'll stick with 9v motors... Thanks for the (...) (25 years ago, 20-Oct-99, to lugnet.robotics.handyboard)
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