Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!att!cbnewsc!psfales From: psfales@cbnewsc.ATT.COM (Peter Fales) Newsgroups: sci.electronics Subject: Re: 555 IC Timer help needed Message-ID: <3481@cbnewsc.ATT.COM> Date: 26 Sep 89 17:19:20 GMT References: <169@uwm.edu> <568@limbic.UUCP> Organization: AT&T Bell Laboratories Lines: 53 In article <568@limbic.UUCP>, gil@limbic.UUCP (Gil Kloepfer Jr.) writes: > In article <169@uwm.edu> duc@csd4.csd.uwm.edu (Duc Minh Tran) writes: > > > > Vcc > > |__________ > > | | > > / __|__ > > R = resistor (R1) __|_____|__ > > C = capacitor \____| 4 8 | > > | |7 | (Output) __ __ > > / | 3|---------> __| |__| |__ > > (R2) | (555) | > > \____| TIMER | > > | + |2 | > > | |__| | > > | |6 1 5|---> ??? > > -+- |_____+_____| > > (C1) __|__ > Also note that, although I don't see it in this data sheet, that in all > other places I've read it is unwise to make R1 any smaller than 1K ohm. I > may be wrong about this, but I thought I read it somewhere. It's probably > a good rule of thumb. The reason for this is that during the discharge portion of the cycle pin 7 is connected directly to ground. You have 5 volts on one end of R1 and ground on the other. f i l l e r f i l l e r f i l l e r -- Peter Fales AT&T, Room 5B-420 2000 N. Naperville Rd. UUCP: ...att!peter.fales Naperville, IL 60566 Domain: peter.fales@att.com work: (312) 979-8031