I am trying to build a circuit that is able to turn a relay on and off at specified times. I have been working with a 555 timer, and it will do the job, but I want the circuit to be fully adjustable. I want to be able to have on and off times of up to 20 seconds, and I want to be able to have off times longer than on times. Can anyone point me to the right direction?
The 555 timer can be configured so that high time and low time are each adjusted by their own rheostat (potentiometer). The trick is to use a diode in parallel with R2. The timing capacitor, C, is now filled only through R1 and emptied only through R2. Check out the following excellent explanation.
Substitute a potentiometer for a resistor in your 555 circuit.
JM
Thanks! this is what I was missing, two pots and a diode will do the trick
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