Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!husc6!mit-eddie!uw-beaver!tektronix!tekcrl!tekchips!jans From: jans@tekchips.TEK.COM (Jan Steinman) Newsgroups: sci.electronics Subject: Re: TTL Questions Message-ID: <1469@tekchips.TEK.COM> Date: Fri, 17-Jul-87 13:53:09 EDT Article-I.D.: tekchips.1469 Posted: Fri Jul 17 13:53:09 1987 Date-Received: Sat, 18-Jul-87 18:27:47 EDT Organization: Tektronix Inc., Beaverton, Or. Lines: 25 <<<1. What's the easiest way to go about interfacing a TTL output (from, say, a standard S or LS AND gate) to a relay, for controlling anything from automobile (12VDC)...>>> My favorite is TIP120 (?) which is a power darlington. With just one or two mA base current, it will drive 8 (?) or so amps. Who needs a relay? Just ground the emitter, hook you load between the source and the collector, and drive the base through about 4.7k. You can parallel them for more current if you put an anti-current-hog resistor between emitter and ground. About .1 ohm should do -- I simply put 10A fuses in each emitter, which seems to add a suitable resistance. <<<...to house (120VAC) environments?>>> Use a MOC2010 (?, available from RS) triac-opto-iso driving either another triac of the proper rating, or a relay. There's an ap note on the back of the blister-pack. <<<2. I've... seen that a no connection to inputs, such as a simple AND or OR gate, drives the input high. Is this guaranteed true?>>> I'm afraid I don't understand this at all! :::::: Software Productivity Technologies --- Smalltalk Project :::::: :::::: Jan Steinman N7JDB Box 500, MS 50-470 (w)503/627-5881 :::::: :::::: jans@tekcrl.TEK.COM Beaverton, OR 97077 (h)503/657-7703 ::::::