From: "Jason McCullough"
Subject: Re: Timer circuit for relay?
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Thu, 03 Oct 2002 02:14:54 GMT
NNTP-Posting-Date: Wed, 02 Oct 2002 22:14:54 EDT
Organization: Road Runner High Speed Online -- Northeast Ohio
I've built several long delay circuits using the 555 timer, and just as
another person responded, the timing delay is very difficult to control over
those long periods. Temperature, component tolerances, etc. greatly affect
the precision of your timer. I'd recommend expanding on the idea suggested
about using a decade counter IC along with your 555 timer. You can make a
relatively short pulse timing with your 555 and then it would get divided
many times by how many decade counters you choose to use. Another bonus to
this setup would be that you could easily put little switches on some of the
outputs of the counter IC's and that would allow you to easily select your
shorter and longer time intervals! Good luck! The decade counters are
xxx4017 and should be available at any electronics store.
"DaveC" wrote in message
> Posted elsewhere in these groups is my original question, "555 Timer
> Well, I thought that there might be another way to approach this circuit.
> I need to turn on a relay once an hour for a few minutes. The "once an
> needs to be adjustable -- maybe between 45 and 75 minutes, and the "few
> minutes" should be between 5 and 20 minutes.
> How about running a 555 to generate a clock signal as in input to a
> which, once an hour, outputs a signal (ie, goes low). This triggers
> 555 which closes the relay for the shorter period.
> If the clock signal 555 is adjustable -- say, plus and minus 40 percent,
> "once an hour" output from the counter will change accordingly (ie,
> earlier or later).
> The relay-controlling 555 will be simple, adjustable 555 monostable
> Constructive criticism? Ways to improve on this?
> Note that my return address is corrupted in an attempt to reduce spam. If
> choose to e-mail me, please correct my address as described below.
> Dave Carpenter
> Sound Logic
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