Hbridge

[Chris Loper]

Thanks for the replies.
Please pardon the slowness of my response
as I get the piclist in the digest form.

>From Dwayne and Chance, it seems that I will not
likely do better than the $75 Hbridge on eBay
(even if I build it myself).

Thanks to Olin, Dwayne and Martin K.,
I realize that my assumption that I need an Hbridge is wrong.
If I decide to pursue the relay / mosefet option,
can anyone venture a guess on how the cost
for the relays, mosfets, etc might compare
to the $75 mark set by the eBay Hbridge?

I've found a lot of good information here
   http://buggies.builtforfun.co.uk
I'll be researching for a while.
Thanks again.
--Chris
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[Gaston Gagnon]

You may look this group up for very sound expertise:
http://groups.yahoo.com/group/osmc/
Gaston


Chris Loper wrote:

> Thanks for the replies.
> Please pardon the slowness of my response
> as I get the piclist in the digest form.
>
> >From Dwayne and Chance, it seems that I will not
> likely do better than the $75 Hbridge on eBay
> (even if I build it myself).
>
> Thanks to Olin, Dwayne and Martin K.,
> I realize that my assumption that I need an Hbridge is wrong.
> If I decide to pursue the relay / mosefet option,
> can anyone venture a guess on how the cost
> for the relays, mosfets, etc might compare
> to the $75 mark set by the eBay Hbridge?
>
> I've found a lot of good information here
>    http://buggies.builtforfun.co.uk
> I'll be researching for a while.
> Thanks again.
> --Chris
>  

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[Olin Lathrop]

Chris Loper wrote:
> I realize that my assumption that I need an Hbridge is wrong.
> If I decide to pursue the relay / mosefet option,

You may not need a relay if you can find a big enough DPDT switch.  A big
double knife switch should be fine for what you want.  Those used to be more
common.  It's the kind of item a old surplus place might have.  The switch
will last longer if you aren't stepping on the accellerator when switching
directions.  This is a go cart, so that sounds like a reasonable thing to
expect the user (you) to do.

Once the relay or switch is switched to a particular direction, you've got
the motor in series with the power supply and the power FET.  Only a single
power FET is needed topologically, although multiple FETs may make it easier
to get to the desired current rating.  The rest is just a little firmware in
a PIC with a A/D and PWM module.

What is the maximum motor current?


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[M.L.-2]

On Tue, Jun 30, 2009 at 2:14 PM, Gaston
Gagnon<gaston.gagnon@...> wrote:
> You may look this group up for very sound expertise:
> http://groups.yahoo.com/group/osmc/
> Gaston
>

They once told a man that he should use an OSMC for the starter motor
on their car. I would not recommend them for "sound expertise." If all
you have is a hammer ...

-
Martin
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[malvira]

On Tue, Jun 30, 2009 at 01:49:01PM -0400, Chris Loper wrote:

> Thanks for the replies.
> Please pardon the slowness of my response
> as I get the piclist in the digest form.
>
> >From Dwayne and Chance, it seems that I will not
> likely do better than the $75 Hbridge on eBay
> (even if I build it myself).
>
> Thanks to Olin, Dwayne and Martin K.,
> I realize that my assumption that I need an Hbridge is wrong.
> If I decide to pursue the relay / mosefet option,
> can anyone venture a guess on how the cost
> for the relays, mosfets, etc might compare
> to the $75 mark set by the eBay Hbridge?
>
> I've found a lot of good information here
>    http://buggies.builtforfun.co.uk
> I'll be researching for a while.
> Thanks again.
> --Chris
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

I've built a PWM driver for a go-kart around this size (1.3kW stalled)

   http://dspace.mit.edu/bitstream/handle/1721.1/33705/64667085.pdf?sequence=1

See Section 5.1 page 43. (and page 39 for the shoot-through delay
circuit)

You can do without the output filter --- we just had that to have the
students practice inductor design.

Also I don't say it in the writeup, but you need need good heat-sinks
on the FETS.

-Mar.
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[Alan B. Pearce-2]

>I've found a lot of good information here
>   http://buggies.builtforfun.co.uk
>I'll be researching for a while.

Hey, that has some fun projects ...

That's another hour lost to the ether ...
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