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From: roy@phri.nyu.edu (Roy Smith)
Newsgroups: sci.electronics
Subject: Re: 12V car --> 3V cd player
Message-ID: <1990Dec27.141809.2856@phri.nyu.edu>
Date: 27 Dec 90 14:18:09 GMT
References: <41842@ut-emx.uucp>
Sender: news@phri.nyu.edu (News System)
Organization: Public Health Research Institute, New York City
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elrond@ccwf.cc.utexas.edu (hlista) writes:
> Does anyone have a schematic for a 12V DC to 3V DC 600 mA?
> Thanks for any help.

	Seems like a perfect application for a 7803 three-terminal
regulator.  Can't get much simplier than that.  Should run you a couple of
bucks at Radio Schlock.  If they don't have the 7803 (it's an unusual
value), they will probably have the variable version, which just requires
adding a couple of passive components to set the output voltage.

	The only question is whether a 7803 is hardy enough to handle all
the horribleness that goes on in a automobile electrical system (I'm mostly
worried about voltage spikes).  You might want to protect it with something
like a 20V zeiner across its inputs, and a 1-ohm power resister in series
with the input, after the zeiner.

--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Arcane?  Did you say arcane?  It wouldn't be Unix if it wasn't arcane!"