"Pete" wrote in message ...
"Rob Paisley" wrote in message
om...
You could adapt these time delay and missing pulse detector circuits.

http://home.cogeco.ca/~rpaisley4/LM555.html#20

http://home.cogeco.ca/~rpaisley4/LM555.html#22

Right if I want to use a pulse time of about 10mins (not critical) am I
right in thinking that I can use a 10M resisitor and a 50uF capacitor?
(would give about 550 seconds) Is this pulse too long for the 555, and does
it matter what combination is used between resistor/capacitor?

I would use a 1M resistor and a 500uF capacitor. The time will most
likely run longer than calculated so a 500K pot and a 470K resistor in
series would be a more practical choice.

Rob.