Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!snorkelwacker!mintaka!streeter From: streeter@theory.lcs.mit.edu (Kenneth B. Streeter) Newsgroups: sci.electronics Subject: Re: 12V to 5V conversion (for TTL logic in car) Summary: Thanks for the suggestions Message-ID: <1990Jul24.125713.5495@mintaka.lcs.mit.edu> Date: 24 Jul 90 12:57:13 GMT Sender: daemon@mintaka.lcs.mit.edu (Lucifer Maleficius) Reply-To: streeter@im.lcs.mit.edu (Kenneth B. Streeter) Followup-To: sci.electronics Distribution: na Organization: Laboratory for Computer Science, MIT Lines: 42 Thanks for all of the suggestions that I've received for the 12V to 5V conversion in a car. What I've done is replace the 7805H (220 package) regulators with 7805KC (TO3 package) regulators to drive the logic circuitry. The logic draws relatively little current (each regulator needs to push about 150 mA) and the pair of regulators are probably actually overkill for this. To drive the current-hogging LEDs, I've used a LM323K (TO3 package) with a 3" x 5" finned heat sink. In this way, separate regulators drive the logic and the LEDs, so any power cycling that may occur due to the LEDs making the regulator too hot affects only the LEDs (a momentary loss of power to the LEDs doesn't hurt anything, whereas a momentary loss of power to the registers, etc, would lose the state information.) What I've done is basically the "simple" fix -- better, more robust suggestions were given, but I wanted to use the parts that I could find at local second-hand electronics stores and flea markets. I'd like to thank everybody that gave suggestions, especially: Tom Bruhns (tomb@hplsla.hp.com) Jeff DePolo (depolo@eniac.seas.upenn.edu) Mark Hoy (mark@retix.retix.com) Cary Logan (logan@titan.tsd.arlut.utexas.edu) Stephen MacMinn (macminn@powertool.crd.ge.com) Dana Myers (dana@devnet.la.locus.com) Phil Ngai (phil@brahms.amd.com) Steve Nuchia (steve@eddie.mit.edu) Dev Palmer (wdp@dukee.egr.duke.edu) Ahmed Shamim (ahmed@nicsa.ircc.ohio-state.edu) Norm Strong (strong@tc.fluke.com) David Thomas (bbx!yenta!dt@unmvax.cs.unm.edu) John Woods (john@frog.UUCP) -- Kenneth B. Streeter | ARPA: streeter@im.lcs.mit.edu MIT LCS, Room NE43-350 | UUCP: ...!uunet!im.lcs.mit.edu!streeter 545 Technology Square | (617) 253-2614 (work) Cambridge, MA 02139 | (617) 225-2249 (home)