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Circuit including a solar cell?

kwells7504

New Member
Hi!

I am a complete beginner at circuits(no experience), but I am making a project and I would like to know if this circuit idea is possible and if it is, how do I make it?

So I am going to make a small wireless lamp, but I want it to be solar powered - using mini project solar cells (is that even what you call them?)
I would also like it to have a switch included so it can be switched on/off.

Would I need a battery as well as the solar cells?

If you are able to, could you create a circuit diagram for me and explain what I would have to buy, and if you're willing to, guide me through how I connect everything (soldering I assume?)

Thank you so much, sorry that I'm asking for a lot but I need help quickly as I have to submit my project idea soon!

(Things I would like in it, solar cells, switch, light bulb, battery(?) )
 

rjenkinsgb

Well-Known Member
Most Helpful Member
The simple circuits used for solar cell garden lights are the easiest and cheapest to reproduce.

Just add a switch in series with the LED to shot it off when not needed.
Example - the top shows the working principle, the lower is a functional circuit:

That is from this page, which also has other examples and working circuits:

Use high efficiency "ultra bright" LEDs to maximise the light output for a given current drain from the battery.
 

kwells7504

New Member
Thanks for replying.

I looked on the website link but I'm confused because I'm an absolute novice and have no idea what some of the components are :D

From the website, I picked out that I need a rechargeable battery?
Is it even possible to have a switch on a circuit like this?
What type of wire would I need to connect if all?

Sorry but you'll have to dumb everything down for me as I'm hopeless:(
 

cowboybob

Well-Known Member
Most Helpful Member
Welcome to ETO, Kwells7504!

How much are you willing to spend?

Reason I ask is that this kit is probably the cheapest you'll find with all the parts needed to make what you have described. And no soldering necessary, just "wire nut" it all together: Its $19.95 plus shipping. I don't think you could buy the individual parts needed for that amount of money...
118727
I can work up a schematic for this circuit, if you like.
 
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kwells7504

New Member
This looks perfect!

However, is it possible to get a bigger bulb as I'm making something which will need more than just those little LEDs. (Of course I'll buy them additionally to the kit)

If you don't mind,
Thanks so much for your help!!
 

kwells7504

New Member
Sorry I pressed send before I completed it, if you don't mind could you make a diagram for me?I watched the video on the website but it would be easier if I could see it easily!
 

rjenkinsgb

Well-Known Member
Most Helpful Member
However, is it possible to get a bigger bulb as I'm making something which will need more than just those little LEDs.
You can use as bright or as many LEDs as you like, if connected appropriately.

However you must have a large enough solar panel to recharge the battery in whatever time is allowed in sunlight, to make up for the total power used by the lamp(s) in whatever time they are switched on.

If you want to power a large lamp for long periods, you need a big! solar panel, plus a battery big enough to run the lamp for as long as needed between having sunlight to recharge it.


Note that for any significant power use, the solar panels must be in direct sunlight to provide practical levels of power for battery charging; the energy from direct sunlight is around 1000 Watts per square metre, so even though solar cells are not very efficient, you can get a decent amount of power from them under those conditions.

In artificial light, the power output is trivial - eg. in a typical room, the electric lights may give about 10 - 20W total light output, over the entire area of the room. The solar panel gets a tiny amount of that and converts a few percent of what it does get to electricity; small fractions of a watt.
 

kwells7504

New Member
Hi,

I'll stick to LEDs then!

Could someone tell me what voltage the LEDs are from the solar panel kit above?
(If the voltage is higher, is the light brighter?)

Also, would it be possible for someone to create a basic circuit diagram for the kit above?

Thank you!! :)
 

cowboybob

Well-Known Member
Most Helpful Member
....
Could someone tell me what voltage the LEDs are from the solar panel kit above? ...
Typically, the forward voltage of an LED is between 1.8 and 3.3 volts. Judging by the battery complement above and that the , I'd guess 3.3VDC
(If the voltage is higher, is the light brighter?)
Within limits. Generally, max LED output is determined by rated max forward voltage of the LED
...
Also, would it be possible for someone to create a basic circuit diagram for the kit above? ...
118756
The ground symbol (118759) is only shown because the simulation software (TI TINA) requires it.
 
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rjenkinsgb

Well-Known Member
Most Helpful Member
LEDs run at somewhere between 1.8V - 3.5V typically; Red are the lowest, then yellow - green - blue/white.

The LED efficiency and current determine the brightness. Typical older or panel indicator LEDs are just a visible light point at 20mA, some newer ultra-bright white ones are literally painful to look at, at the same current.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
That "kit" circuit needs a diode (preferably a schottky rectifier) adding between the solar panel and the battery, or the battery will discharge through the cells when there is no light.
 

kwells7504

New Member
Actually last question, could someone recommend what schottky rectifier diode is a good one to buy for this circuit?
 

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