>I am trying to create a long high pulse (around 10 minutes), then falling
>edge. Then have the process start over.
>I did not find any astabel circuits that could produce a very long pulse
>without additional ICs. I did find some long pulse monostable circuits, but
>am having trouble getting the timing to be consistent.
>In my sample circuit I have decreased the RC values just for testing.
>Sometimes the pulses are consistent, other times they appear to be at fairly
With the long time constants needed capacitor leakage can
become a problem. You might try using use a CD4060 (a quite common
IC or its later equivalents). This is a 14-stage binary counter
with an internal oscillator so that you may make use of a much
higher oscillator frequency (shorter time constants) and the
easier adjustment so afforded.
Cheers - Joe