Subject:
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Re: Using 12V supply with Expansion Board?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 25 Sep 1999 20:26:39 GMT
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Original-From:
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Giang Tran <GT4025@CHI.DEVRYspamless.EDU>
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Viewed:
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801 times
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At 12:13 AM 9/25/99 -0700, you wrote:
I've look at the electrical schematic for both the Handy Board and
Expansion and this is what I got.
Because the expansion board only share the handy board's motor output for
its Servo outputs, I don't think you would have a problem with the new
motor power source modication unless you're planning to use the Servo motor
supply and LEGO sensor outputs on the Expansion board.
If you want to use the Servo outputs on the expansion board, than you would
need to do some minor modifications. Since the original supply of 6V to the
servo motors on the Expansion board was from the 5 series diodes (used to
step down from 9.6v to 6v), you can either add 3 or 4 (each diode require
~.7v to conduct) more diodes to it to get the equivalent 6v from the new
12V or you can just use a different power source. I think using a different
power source would be a much wiser thing to do since adding the required
diodes would means you have to de-solder the last one and added the others
to it. And since servo motors are made to operate from around 4.8v to 6v
which means that if you intended to use it, you would have to cut the old
Servo Motors power trace on the Expansion Board and connect the new servo
motor source (a different 6V supply) onto it. The back of the Expansion
board labelled where to cut the trace for the new servo motors source.
Also, if you were to look at the Expansion board's electrical diagram, you
will also notice that the 3906 transistor with the series 47 ohms resistor
conneted to it, you would see that it share the Handy Board's motor supply
also. I am assuming since the 3906 collector input can handle the voltage
increase, I think the LEGO sensor input would also be ok though(not sure),
I am sure it wont get fried but not sure if it would still work with the
LEGO Sensors.
Words of wisdom, this is what I am assuming from my logical point of view.
I may be wrong so I suggest before making the modification, you should use
an external variable power source to test the sensor outputs first. I
suggest starting from 9.6V and slowly increasing it to 12V and check to see
if any components is getting hot.
Reference:
Expansion Board electrical schematic:
http://lcs.www.media.mit.edu/groups/el/projects/handy-board/hbexp30/expsch30
.gif
Handy Board motor trace cut:
http://lcs.www.media.mit.edu/groups/el/projects/handy-board/mods/hbmcut.html
Rob
> Hi - -
> It's NOT a stupid question ... I've been wondering the same thing.
> I'd like to have separate supplies both for the motors and for servo
> power. When you find the solution, please let me know what you
> discover.
> Thanks,
> - Nick -
>
> Giang Tran wrote:
> >
> > Hello 'Botter,
> >
> > I think I am about to ask a stupid question but as a precaution, will the
> > Expansion board be "ok" with a new 12V motor supply rather than the 9.6V
> > connected to the Power Expansion header (J13)on the HB since the Expansion
> > board and HB share the same header? Also, I'd be very appreciated for any
> > tips on how to modify the Expansion board to work with a the new 12V power
> > supply, if needed (does it?). Thanks alot guys.
> >
> > G. Tran
>
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