Bob said:
>This cap could be replaced with an electrolytic as any leakage would not
matter.
That depends on the time delay you need - leakage in a normal electrolytic
may be too much if you want a longish delay. Somewhere, I have some
MPF121if you really want to try, but I've just gone through this exercise,
and the better answer is a piece of 4000 CMOS logic, the number of which I
can't remember. It consists of an R-C oscillator and counter, and I use a
transistor after it to drive a relay. If you're interested, I can send you
the circuit as a Word document. I think it's a far more satidafctory
approach than the analogue one - and it takes a lot for me to approve of
anything digital!
73
Peter G3RZP
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