Count Down Timer Circuit

Posted on Aug 7, 2012

With switch SI in the off position, as shown, battery voltage is applied across timing-capacitor CI, which stays charged while the rest of the circuitry has no power supplied to it.

Count Down Timer Circuit
Click here to download the full size of the above Circuit.

Transistor Ql, and thus transistors Q2 through Q4, are kept in an off condition as long as CI has a sufficient charge.

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