Subject:
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RE: power source
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 13 Feb 2002 19:30:32 GMT
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Original-From:
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Kingsley Gifford <KGIFFORD@nomorespamTHEZONE.NET>
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Viewed:
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772 times
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In reference to http://www.aaroncake.net/circuits/supply6.htm
I have an old transformer from a tape deck that produces 11.2V AC. (I
just checked it). Can I build the circuit on the above page and use this
transformer? Or do I need to get one that produces DC.
thanks
-----Original Message-----
From: Mathias Uhr [mailto:uhr@mathias.net]
Sent: Wednesday, February 13, 2002 8:41 AM
To: lego-robotics@crynwr.com
Subject: Re: power source
hi!
> What you do is you connect the positive wire from your power supply to
> pin 1* of the 7809. Then connect the ground of the RCX and the power
> supply to pin 2. Connect pin 3 to the positive battery terminal on the
> RCX. I also put a diode in between pin 1 and the power supply.
> Also note that your supply voltage needs to be at least 1.2 volts • above
> your output voltage. An unregulated 9v power supply should do fine,
> because they usually give a higher voltage.
if you use an unregulated supply, you need to add a big capacitator
in front of the ic (after rectifing of course)!
generally, they advice to use an electrolyt capacitator of sufficient
size (there are formulas for this) for filtering and a small tantalum
or ceramic one in parallel to smooth out fast peaks and avoid
oscillation.
usually, you add such a pair of (smaller) capacitators behind the
regulator too.
see a circuit schematic here:
http://www.aaroncake.net/circuits/supply6.htm
you will probably come to the conlusion that it is easier and safer
to buy a power supply that is cleanly regulated to 9v dc...
please note that power from the batteries is not regulated inside the
rcx! (on the contrary to the power plug of rcx 1.0) if you connect a
power source to the battery clips, you need to make sure that it is
well rectified and regulated!
(for more details about the rcx's internal power regulation see one
of my earlier posts at http://news.lugnet.com/robotics/?n=16677
hope this helps, greetings
mat
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