Solar Panel Charing Indicator LED

Discussion in 'General Electronics Chat' started by RodneyB, Sep 27, 2015.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    I want to add a very simple if possible LED circuit to my solar panel to tell me if it is charging. Basically when the voltage is 14 Volts and above I would like an LED to Light when the panel voltage drops below 14 Volts I would like the LED to Switch off.

    I have fitted a 30 Watt solar panel to my gate motor, the motor has 2x 12 Volt 7 Ah batteries in parallel. I just want a visual indicator that the solar panel voltage is above 14 Volts. The maximum voltage of the 30 Watt panel is 17.4 Volts according to the specs on the back of the panel
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    Does it have to be precisely 14V or it can be 13.7V-14.5V.
     
  3. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Hi It does not have to be precisely 14 Volts 13.7V to 14.5V is fine Thank you
     
  4. ISB123

    Well-Known Member

    May 21, 2014
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    Try this:
    charger indicator.png
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Thank you so much for your help. Its greatly appreciated.
     
  6. ISB123

    Well-Known Member

    May 21, 2014
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    Use 1-2W components so they don't overheat.Transistor is BC547/546.
     
  7. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Thank you is 1N4001 diodes correct for D2 and D3
     
  8. ISB123

    Well-Known Member

    May 21, 2014
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    Yes,they drop around 0.7V at low currents,the LED should turn on at 13.9V-14V.
    I'll breadboard the circuit in few minutes to see if it works properly.
     
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  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,997
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    Or, if you have an op amp and a Zener, you can do this.

    OP amp is powered by the panel, the Zener is 10V and the pot is 1k linear.

    image.jpg
     
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  10. dl324

    Distinguished Member

    Mar 30, 2015
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    Diode selection isn't critical. Any silicon diodes you have available or you could substitute a single LED for the two diodes.
     
  11. ISB123

    Well-Known Member

    May 21, 2014
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    Can't breadboard it.Only have 3.6 Zener diodes I though I had some 12V but I guess I lost them.Tried modifying the circuit with 3.6V ones but It doesn't work properly.
     
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  12. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    I will build it and let you know how it works out

    Thanks for the help
     
  13. ISB123

    Well-Known Member

    May 21, 2014
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    OK,it's working on simulator but I don't know if it will in real life.
     
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  14. dannyf

    Well-Known Member

    Sep 13, 2015
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    2x diodes + 1x 12v zener = ?

    X diodes + Y 3.6v zener = ?
     
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  15. dannyf

    Well-Known Member

    Sep 13, 2015
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    Have you thought about using a mosfet?

    BTW, a tl431 is essentially a comparator and can be made to work here.
     
    Last edited: Sep 27, 2015
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