Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: XR-2240
Message-ID: <1990Mar15.171310.28917@utzoo.uucp>
Organization: U of Toronto Zoology
References: <3687@tukki.jyu.fi> <1617@argus.UUCP>
Date: Thu, 15 Mar 90 17:13:10 GMT

In article <1617@argus.UUCP> ken@argus.UUCP (Kenneth Ng) writes:
>One of my first electronics projects was the XR-2240!  After I found out
>that a 555 isn't too good for an 8 hour delay...

Actually, if you want long delays and don't insist on using a single chip,
much the simplest way to proceed is to build a reasonably slow oscillator
with a 555 or whatever and then just run the output into a CMOS counter,
e.g. 4040 or 4060.  The counter's power consumption is negligible and the
available counters go up to a division ratio of 2^16 or so.  Their main
limitation is that the division ratio has to be a power of 2.
-- 
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry henry@zoo.toronto.edu