Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!sunybcs!kitty!larry From: larry@kitty.UUCP (Larry Lippman) Newsgroups: sci.electronics Subject: Re: A pathetically simple question... Summary: Delay-on-operate timers... Message-ID: <3422@kitty.UUCP> Date: 30 Sep 89 01:04:24 GMT References: <1989Sep28.122217.26867@watcsc.waterloo.edu> <4377@wpi.wpi.edu> Distribution: sci.electronics Organization: Recognition Research Corp., Clarence, NY Lines: 28 In article <4377@wpi.wpi.edu>, reynhout@wpi.wpi.edu (Andrew Reynhout) writes: > I need a circuit that will, on application of power, cause a delay of 5-20 > seconds before allowing current to flow (a different part of the circuit) > Basically, it should take, say, 12v, wait 10 seconds, then trip a relay. > It's for an alarm circuit. (I didn't see much point in paying $159 for $30 of > components and a few hours of work.) > I tried a deceptively complex setup with a FET and timing cap and all sorts > of other nasty things, but I can't get ANYTHING out of it. I am assumning that this is NOT for an OEM application where you must have this circuit function on a PC board along with other circuit elements. All you need is a time delay relay, with a delay-on-operate mode. The simplest time delay relay is of the thermal delay type, as manufactured by Amperite or GV Controls. You can often find such thermal delay relays (which are usually made for octal sockets, although 7/9-pin miniature also exists) in surplus stores for a buck or so. A far better approach is to use a solid-state timer, which can be purchased new for as little as $ 25.00, and surplus for $ 5.00 or less. Such a solid-state timer - which is available in many package types - will do EXACTLY what you want and will provide an isolated set of relay contacts. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"