Long duration timer

Posted on Apr 16, 2012

The time circuit can provide a time delay of up to 20 minutes. The circuit is a standard relaxation oscillator with a FET current source in which resistor Rl is used to provide reverse bias on the gate-to-source of the JFET. This turns the JFET off and increases the charging time of Cl.

Long duration timer
Click here to download the full size of the above Circuit.

Cl should be a low leakage capacitor such as a mylar type.

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