Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers.rutgers.edu!mit-eddie!uw-beaver!tektronix!reed!percival!bucket!chrisb From: chrisb@bucket.UUCP (Chris Bradley) Newsgroups: sci.electronics Subject: Re: TTL Questions Message-ID: <426@bucket.UUCP> Date: Sun, 19-Jul-87 15:36:56 EDT Article-I.D.: bucket.426 Posted: Sun Jul 19 15:36:56 1987 Date-Received: Tue, 21-Jul-87 00:44:37 EDT References: <1395@crash.CTS.COM> Reply-To: chrisb@bucket.UUCP (Chris Bradley) Organization: Rick's Home Grown Unix; Portland, OR Lines: 30 In article <1395@crash.CTS.COM> rpluth@pnet01.CTS.COM (Ron Pluth) writes: > > I have a couple questions about TTL logic that I hope can be >answered here... > > 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) to house (120VAC) >environments? These are two *different* situations. I'm look >ing for hardware that can be easily picked up at Radio Shack >(gasp!)... if anyone would even happen to know part numbers from >such equipment, this would also be great. Well, it all depends on how much currentthe coil in the relay needs to activate. I'll assume that your digital output is around 5 volts, and that your relay coil needs to support at least 3 amps. If you can, use relay (Cat. # 275-214 - $4.69). Then, you need some sort of transistor that will support (E) 5 / (R) 150 = (I) 33.3 Ma. The transistor doesn't have to be very powerful in terms of wattage, so we'll use the NPN transistor (Cat. # 276-2030 - $.79). Now, connect the collector at +12V. Connect the emitter to one of the coil leads on the relay. Connect the remaining lead to ground. Now, connect the base to the output wire of your digital logic circuit. You can now figure out how to wire the rest of the relay up yourself. You're looking at about 5 bucks total, but you can cheapen the price if you need less than 3 Amps. If you don't need that much current, use a smaller comparable one - There shouldn't be any problem in current handling in the transistor. -->Chris ..tektronix!reed!percival!bucket!chrisb