Subject:
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Re: Increasing current output to motors on HandyBoard
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 10 Apr 1999 00:25:29 GMT
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Original-From:
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K.L.McKinnon <klmckin@magmacom.com{NoMoreSpam}>
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Viewed:
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1633 times
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Haven't actually tried it, but I was thinking of the same sort of thing.
Use a FET for PWM and a DPDT relay for direction. practically speaking,
if you only switched the relay when the FET was off, no power
transition, etc....
If your 'bot moves forward more than back than using a default state
(N/C) for the forward motion, means current to the relay is only
consummed during the reverse movement.
A single FET with a relay s(w)hould prove to be quite a bit more space
conservative and likely cost effective as well.
Comments?
K.L. McKinnon
MAR ERICSON wrote:
>
> I wonder if this would last since a relay is mechanical and I would
> assume that it would wear with all that "switching". Doe anyone have any
> experience with this?
>
> Thanks.
>
> -----------
> ericson mar
> Robotics Consultant
> mar@cooper.edu
> (212)353-4356
>
> Department of Mechanical Engineering
> The Cooper Union for the Advancement of Science and Art
> -------------------------------------------------------
>
> On Thu, 8 Apr 1999, Gary Livick wrote:
>
> > Another solution to this which is easier but more expensive is to use the
> > output of the motor driver chip to drive solid state relays. You need the
> > relays that use 5 volts for control and that will switch DC. The relays I use
> > have flyback diodes in them, but I don't know that all do so a user would need
> > to add them if they were not included.
> >
> > Four are needed.
> >
> > Gary Livick
> >
> >
> > Chuck McManis wrote:
> >
> > > At 11:46 PM 4/8/99 -0400, Ian Nieves wrote:
> > > > ...Is there
> > > > some stacking that would allow more current to pass safely? (I am
> > > > looking for a relatively simple solution that can be implemented quickly
> > > > and easily.) Can i stack two TI sn754410ne on top of each other?
> > >
> > > Stacking the chips is doable but you will toast them when you get near
> > > their current limit. An easier solution is to use the TI chips to drive
> > > power transistors that are acting as voltage followers. This lets them take
> > > the current. Alternatively you can pull the L293 chips out of the board and
> > > wire the sockets up to some National LM18200 H-bridges that will handle
> > > these motors at 12volts.
> > >
> > > --Chuck
> >
> >
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