PV Gap

Jessie Said:

solar panel to power 20 LEDs?

We Answered:

If you know electronics what do you need to know? This is about as basic as it comes. Panel needs to go to a regulator, regulator needs to go to a battery, the battery needs to go to the leds.

You should be able to get every part you need from radioshack.


20 leds at 20ma at 3.5 volts is 1.4 watts of power. Make sure the panel is rate for about twice this size.

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Your setup depend a lot on how efficient and how much money you want to spend.

Best setup would be to buy a 2 watt panel then connect it to a Adjustable-Voltage Regulator like a LM317T (radioshack) this regulator supports over 1.5 amps(5.25w)this will easily power 1 watt of leds. Setup the regulator to output 3.5 volts. If you dont care if it runs at night connect the small power capacitor rate for more than 3 volts. If you want it to run for a little longer at night connect it to a larger capacitor. If you want it to run for a long time connect it to 3.5 volt worth of rechargeable batteries.


easier and less efficient way would be connect the panel to a preset voltage regulator like a 5volt connect this to your power source that you pick. Then put a resistor on every led so they can run off the 5volts.
If you led is 3.5 volt and needs 20ma you would need a 250 ohm resistor on every led. (5v/0.02amp=250ohm)


Easist and not the best would be to buy 12volt solar battery charger. Connect the charger to a motor cycle battery. Connect 600 ohm resistor on every led and your done.

Just make sure the panel doesn't output voltage higher than you regulator supports. This shouldn't be a problem with small panels.You could all so skip using resistor on every led and hook some or all of them in series but its not as easy.