Help with Mini Solar Charger

Discussion in 'General Electronics Chat' started by Knowlittle, May 18, 2016.

  1. Knowlittle

    Thread Starter Member

    Mar 16, 2016
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    0
    Hi all hope you can help. ..... i have a small 5v solar panel and want it to charge 2 rechargeable AA batteries. Whilst charging (while sun is shining) LED 1 Must be illuminated, whem the sun sets LED 2 must illuminate and LED 1 must switch off. Then when the sun comes up yhe following morning the cycle must start over ! Hope you guys can help (PLEASE MAKE IT SIMPLE ) Thanks.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,773
    931
    Simple would be a few diodes to drop the voltage and a direct connection to the batteries needing a charge.
    LED's that light and go off based on charging cycles is complex and requires a controller.
    Have you done ANY Google searching for charge control circuits?
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    1,103
    Unfortunately, to do what you ask reliably is not simple :(. To prevent battery over-charging or over-discharging you'll require a controller, as mentioned. You will also need a light/dark sensor with a certain amount of hysteresis to prevent flickering at dawn/dusk.
     
  4. jsallas

    New Member

    May 17, 2016
    9
    1
    Mr. Kermit is right. The simplest way is using diodes to drop the voltage. Of course this won't be an "smart charger" and won't prevent battery overcharge.
    Adding to this, you need to put some protection diodes to the lines feeding the panel. If you don't do this, the solar panel will behave as a resistive load when it is shadowed or not exposed to light, and it will drain your batteries.

    For the LEDs, you might need a controller or a voltage comparator and fix a treshold voltage (with hysteresis) to compare with the panel output.
    The comparator output should be able to drive an LED, or to switch a transistor if more LEDs are needed.
     
    Last edited: May 18, 2016
  5. Knowlittle

    Thread Starter Member

    Mar 16, 2016
    45
    0
    Ok let me explain differently, the sunlight will act as my "sensor", i will add additional resistors to the circuit to prevent overcharging i basically just want for the leds to charge in the day and as soon as the solar panel gets no more light for them to illuminate.
     
  6. Knowlittle

    Thread Starter Member

    Mar 16, 2016
    45
    0
    Ps its only a 5v panel.
     
  7. Knowlittle

    Thread Starter Member

    Mar 16, 2016
    45
    0
    And yes i have added a diode from the solar panel to the circuit.
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,773
    931
    Okay. Your device can be simpler than this but look it over to get an idea about block diagrams and the additional work involved in doing things like making lights blink conditionally and how a controller would work overall.
     
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