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?
Simple On/Off timed circuit
Dec 11, 2007
4 Replies
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.
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Substitute a potentiometer for a resistor in your 555 circuit.
JM
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Thanks! this is what I was missing, two pots and a diode will do the trick
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