home made solar

[mossrisjhons]

Hello,
I am hoping that you would be kind enough to help me with a question. I would like to use 4 LED's for a solar powered lamp that I am building. Would you be able to tell me exactly what kind of rechargeable batteries I would need for the 4 LEDs and if I need resistors? Is it necessary to have a pcb board for this project? And finally, maybe it's a longshot but does anyone know if there was a kit available for an outdoor solar lamp? Using the solar path lights just wouldn't provide enough light in the lamp.
Thanks in advance.

[janneman]

Originally Posted by mossrisjhons

Hello,
I am hoping that you would be kind enough to help me with a question. I would like to use 4 LED's for a solar powered lamp that I am building. Would you be able to tell me exactly what kind of rechargeable batteries I would need for the 4 LEDs and if I need resistors? Is it necessary to have a pcb board for this project? And finally, maybe it's a longshot but does anyone know if there was a kit available for an outdoor solar lamp? Using the solar path lights just wouldn't provide enough light in the lamp.
Thanks in advance.

Well, I don't know which LEDs you will use, but obviously your battery voltage must be higher than the LED voltage. Or you can use a lower battery voltage and put the LEDs in series/parallel. Be aware though that LEDs need to be driven by a constant current because it is very difficult to drive them from a constant voltage due to their badly defined and steep V/I curve.

So at any rate you want some kind of adjustable current source; there are lots of ICs for just that purpose so a search on the net might be usefull.

Did you search the Elektor forum, they may have something like that already.

Jan Didden