automatic light

Discussion in 'General Electronics Chat' started by aimaldaudkhan, Aug 9, 2013.

  1. aimaldaudkhan

    Thread Starter Member

    Jan 25, 2013
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  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    On first guess, the transistor will only turn on when the DC charging voltage drops below the battery voltage.

    It will likely turn on when there is a large draw from the battery and the capacitor is drained at each half cycle or if a connected battery has a voltage higher than the charger.

    R2 is insuring the base voltage is pulled low to turn on the PNP transistor.

    In the end, there is nothing to limit the base current at the transistor so I don't really like this circuit.
     
  3. aimaldaudkhan

    Thread Starter Member

    Jan 25, 2013
    38
    0
    why R2 is not working when main supply is on i use a simple wire instead of R2 it doesnot works but i take a resistor it starts work whats the main role of R2
     
  4. BobTPH

    Active Member

    Jun 5, 2013
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    As already answered, the purpose of R2 is to turn on T1. If you replace it with a wire, you have shorted the power supply. Do you normally decide components are not needed and short them with a wire?

    Bob
     
    aimaldaudkhan likes this.
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Thanks Bob ;),
    I don't know what was missing in my explanation but, since he gave you the "thanks", my dribble didn't seem to do anything for the OP! HAHAHA!

    This place is getting stranger and stranger!

    GT
     
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