Subject:
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RE: Small battery box into 9V powersource?
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 5 Oct 2004 19:07:46 GMT
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Original-From:
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Gunnar Konráðsson <postur@NOSPAMmail.dk>
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Viewed:
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3126 times
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-----Original Message-----
From: news-gateway@lugnet.com [mailto:news-gateway@lugnet.com] On Behalf Of
Rob Hendrix
Sent: 5. október 2004 18:40
To: lego-robotics@crynwr.com
Subject: Re: Small battery box into 9V powersource?
"Brian Davis" <brdavis@iusb.edu> wrote in message
news:I547MA.6n7@lugnet.com...
> I'd like a small powersource I can plug into a wall, and I've got a
> small 9V
> battery box that seems to have gone bad. The idea is to use a standard
> "wall
> wart" transformer to feed 9-12V DC into the small battery box. But, with
> all
> that lovely room in there, it would be nice to add a rheostat of some type
> to be
> able to dial up the voltage I really want (think very poor mans train
> transformer).
> First, has anybody done this? I'm assuming the gear motors still run
> just
> fine on "pure" wall wart output (as oppossed to RCX / control center /
> train
> drivers), but I'm more concerned with two other aspects of this: (1)
> should I
> leave in the thermal fuse (actually, I suspect this is the part that may
> have
> failed, so I may have to work without it in the circuit), and (2) if I
> just
> throw a good old variable resistor in the circuit, what sort of heat
> dissipation
> within the small batter box am I talking about? Damaging?
> Speak to me oh Modding Masters!!
>
> --
> Brian Davis
I'm not that gifted in electronics so my knowledge is limited. I'd use a 9
volt voltage regulator inside the battery box, but I'm guessing there's an
easier, more efficient, and better way...
9v regulator:
http://www.mouser.com/index.cfm?&handler=data.listcategory&D=*lm7809*&terms=
lm7809&Ntt=*lm7809*&Dk=1&Ns=MfgrPartNumber%7c%7cSField&N=0&crc=true
datasheet: http://www.nteinc.com/specs/1900to1999/pdf/nte1910.pdf
-Rob
If you choose to use a variable resistor, you are burning off the same
fraction of power you´re utilizing, that is, if you just want half the
voltage you get from the "wall mart" transformer, you are burning as much
power in the variable resistor as your´re using in your motors.
I´m not sure of the efficiency of the regulator, but I would guess it would
be somewhat better solution, but IMO, the best solution would be, to buy a
"wall mart" transformer with a selectable DC output voltage.
GHK
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