capacitor charging and discharging

Discussion in 'The Projects Forum' started by Paul McD, Feb 9, 2012.

  1. Paul McD

    Thread Starter New Member

    Feb 9, 2012
    10
    0
    I've got an electrical problem with capacitors:

    I need to make a circuit for a solar car and I've been given a 10F capacitor, a motor and I can use other components if needs be. I need to be able to charge the 10F capacitor with a 3V solar panel, disconnect the solar panel, turn a switch and run the motor. I've tried to make a circuit on copper strip board but without success. I'd be extreamely gratefull on any assistance in charging and discharging capacitors. A circuit diagram would be perfect.

    Many Thanks.
     
  2. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    As a good starting place please show us what circuit you tried so we can help you build on that or give constructive suggestions based on what you did. It will help a lot.
     
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  3. Paul McD

    Thread Starter New Member

    Feb 9, 2012
    10
    0
    Attached is the circuit that I tried, but I couldn't get any output.

    Hope this is useful?

    I could do with a response promptly as I need to have the circuit built soon.

    Thanks
     
  4. BSomer

    Member

    Dec 28, 2011
    433
    106
    The first problem that I see is that your capacitor has no path to discharge its energy. When you close the switch all you are doing is connecting the + side of the motor to ground. Try it the way I have edited your drawing. :)

    Brian
     
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  5. MrChips

    Moderator

    Oct 2, 2009
    12,429
    3,360
    You need to provide some specifications on the motor. I don't think there is enough energy stored in the capacitor to run the motor unless it takes 1mA or less.
     
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  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    At 1mA, it would take over 8 hours to totally discharge a 10F cap.
     
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  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    If you want to disconnect the solar cell when you run the motor, use a SPDT switch.
     
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  8. Mark_T

    Member

    Feb 7, 2012
    47
    8
    In theory a 10F cap has 30 Coulombs of charge at 3V.
    A coulomb is 1 amp for 1 second.
    If the motor is say 0.5 amp (at 3v) then max of 60 seconds. BUT....
    As the cap discharges the voltage will fall off, quite rapidly.
    On the good side is, once the motor is moving the sustaining current can be relativly low. But if voltage falls to much it will stop.
     
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  9. Paul McD

    Thread Starter New Member

    Feb 9, 2012
    10
    0
    Thanks very much for all your sugestions, but I'm affraid I don't know the specifications of the motor that was supplied, all I know is that I should be able to realistically use a 3v solar cell, a 10F capacitor and the provided motor. The specifications for the challenge say that I can have 15mins of charging time with the solar cell and should then be able to travel 8m, up to three times (fastest time wins).

    If anyone can help more that would still be much appreciated.

    Thanks very much for your help and kindness so far.
     
    Last edited: Feb 9, 2012
  10. Mark_T

    Member

    Feb 7, 2012
    47
    8
    Well I think the 8m means 8 metres not miles.
     
  11. Paul McD

    Thread Starter New Member

    Feb 9, 2012
    10
    0
    Yes, the car must travel 8meters not 8miles, up to three times on one charge.
     
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