Help need to discharge capacitor in given circuit

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mguptamel

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Hi all,

I am a newbie in electronics and trying to get grasp of capacitors. I am unable to discharge capacitor in attached circuit. So far the circuit is doing the following

1) RC network to turn-on LED after a given time, for example, T seconds.

2) Once LED is turned-on I want to discharge capacitor so that cycle begins again. But I am unable to do this at this moment. PLEASE HELP.

 

You need to connect a second transistor across the capacitor, emitter to earth, collector to the junction of the capacitor and the base connection. If you feed current into the base of this transistor then it will draw collector current and discharge the capacitor. If you connect the base to earth via a resistor then the second transistor will be turned off and the capacitor will charge up.
Frank
 

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