Solar panel to LEDS, no battery, how to?

Thread Starter

scrufdog

Joined Aug 27, 2015
2
This is an office project, for my new desk. Its basically a small terrarium that will be lit up by 10 LEDs running at 18ma.

I want to power this using a 10 watt (21.6v/0.58A) solar panel, and no batteries or external power. This is so the LEDs only light when the office is 'open' with lights on. So, the panel will sit a few feet under the light on top of a cabinet. Not the most efficient for a solar panel, but its what I got.

I originally was thinking about using a zener to limit the voltage of the solar panel, but my knowledge of zeners is not what I thought it was, and I cant get anything to work that way. Now I'm considering just a voltage regulator, but I need one that can support a 3vDC output and an input range from 1-20vDC.
I feel like this 'simple' project is running away from me.

So, I'm looking for guidance in designing this circuit. Seems like it should be a relatively simple circuit, but I guess I'm missing something. be it zener or voltage regulators or whatever. I dont necessarily need all the work done for me, advice or a direction to start would be cool.

Thanks
 

Bernard

Joined Aug 7, 2008
5,288
I would use a boost converter, constant current, constant V with output set @ 35 V & 18 mA with white LEDs in series. Might measure panel output in place to see if 1 W is available.
 

Bernard

Joined Aug 7, 2008
5,288
My constant current converter turns out to be just buck so would change to just a V adjustable buck converter
with LEDs wired 2 in series with 55 ohm, 1/4 W R , 4 strings. Adjust output to 9 V.
LM2596 Buck Converter, US $ 1.45 to 2.99 on Amazon.
 
Last edited:

oz93666

Joined Sep 7, 2010
672
You cannot get enough light to realistically energize a panel with indoor lighting , the power output will be well below 1% compared with the panel being outside ....

But basically it's very simple to link leds directly to a panel ,no circuitry is needed. First you have to match the leds voltage to that of the panel ... 12V led strip or led chip/s would match well with a 12V panel (that's 17 to 20 V open circuit) ... then just make sure the max power from the panel does not exceed the max power the leds can tolerate .... All the power will go to the leds , they will fade up and down with passing clouds .

If you are really determined to do this indoors then just wire the leds in series , enough so they start to light up at about 12V . if they are white and you have 10 then put 5 in series ... twice.. and connect directly to panel ...
 
Last edited:

Thread Starter

scrufdog

Joined Aug 27, 2015
2
Yeah, I measured the output and its just enough to wire 2 LEDs across the output, any more than that and the voltage falls out.

This might be of interest.
Thanks for this, I'll definitely be using this in future projects

Thanks everyone, I'm going in a different direction than I originally thought, but these answers are all good ones.
 
Top