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I have this circuit for charging a capacitor: capacitor charge circuit

What I need is a circuit for discharging the capacitor after 'V' (the voltage across the 100 µF capacitor) has reached the maximum value of 2V. I know a discharge circuit can be implemented by NPN transistors, but I am not getting how. Guidance required.

The capacitor should only discharge when 'V' reaches 2V.

ctype.h
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BLOB
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  • Do you want this to happen automatically/repetitively? Or like a camera flash where you press a button to discharge when the cap is charged up? – Oli Glaser Jan 13 '13 at 13:05

1 Answers1

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You cannot measure the voltage over the capacitor unless it is separated from the battery. In theory it is possible when you make a discharge circuit which 'cuts' the charge wires, but it won't work with your circuit.

  • there should be some way i can harness the charge stored by the capacitor when it is fully charged... Something like camera flash circuit.. – BLOB Jan 13 '13 at 09:13
  • There is a difference between _charge_ and _voltage_, you know that? Voltage is an electrical power, while charge is the amount of electrons stored. –  Jan 13 '13 at 09:50
  • I know.. How do I implement something like "camera flash circuit" using simple BJT's? – BLOB Jan 13 '13 at 11:35
  • You might want to ask a new question about that, since it is really a different question. List the requirements, etc. –  Jan 13 '13 at 12:04