Laurence Taylor wrote:
Dave Plowman (News) wrote:

The trouble with this approach is that it is best for short time delays.
Ten minutes is a relatively long time, so circuit leakage may cause the
delay to be longer than what you would calculate based on the R-C time
constant.


If you use the CMOS version - usually 7555 - the low current allows times
of much more than 10 minutes.

The problem is that you end up needing absurd component values - ten
minutes delay would need 1.2Mohms and 470mf, for example, and the
latter is likely to be inaccurate and probably variable.

You can use two of them (or a 556), or there used to be a chip that
would work up to many hours delay, the number of which I cannot
recall; I think it was a TDA- something.

--

rgds
LAurence


Well letcher laurence....
Does everyone know that you are a pedophile?
laurence likes to **** children.....
alt.support.boy-lovers