Control Condenser Charge and Discharge

Discussion in 'The Projects Forum' started by Justino, May 21, 2014.

  1. Justino

    Thread Starter New Member

    May 21, 2014
    Hi Everyone,

    I'm into this exercise where i have to accumulate charges on a condenser and discharge all the accumulated charges when it reaches a certain level.

    I have the following circuit, composed of sub-circuits A and B. I use a manual switch to open and close these sub-circuits.

    - +
    ---------|voltage source|----------
    | |
    | sub-circuit A |
    | |
    | - + |
    |---------|condenser|---------/ <----- switch
    | |
    | sub-circuit B |
    | |

    When sub-circuit A is closed the condenser is charging. When the condenser is charged i use the switch to open sub-circuit A and close sub-circuit B, thus lighting up the LED.

    I'm very lazy, so i'm looking for something that controls the switch automatically:
    1) when the condenser is charged the switch must open sub-circuit A and close sub-circuit B automatically to light the LED.
    2) when the condenser is "empty" the switch must close sub-circuit A and open sub-circuit B automatically to charge the condenser.

    Is there any eletronic component that can read the charge on the condenser and open and close a switch automatically?

    Than you
  2. pwdixon


    Oct 11, 2012
    Sounds just like a 555 timer circuit to me.
  3. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    Look up the Joule Thief circuit. It might be what you want. There are many resources once you know that is what you want to look for.
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    If you are happy with C charging to only 2/3 of V & discharging to 1/3 V, then go with pwdixon, or else list your requirements or make a simplified 555.
  5. crutschow


    Mar 14, 2008
    "Condenser". I haven't heard that term used since I was a kid, and that goes back a bit. ;)
  6. Justino

    Thread Starter New Member

    May 21, 2014
    Hi guys, thanks for the replies. I've done a sketch so it's easier to understand what i need..


    So i need some kind of voltage controlled switch that allows me to discharge the capacitor when it reaches a certain voltage level.
    I've read about the 555 which uses voltage comparators and flipflops. Is this the simplest solution? Any hints about how could this be implemented?

    Thank you
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Is there a purpose to this experiment?
    With 5 V battery, 555 trip points will be about 1.6 V & 3.3 V, so you will need to make your own @ 1 V & 4 V. You will need some resistance in series with LED, say 120Ω, & a resistor in parallel with LED to drop V down to 1 V. With 1000 μF LED will flash for about 1/10 sec.
    , recharge maybe 1 ms