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View Full Version : How much solar power do I need to run two IR LEDs?


tbaleno
12-23-2006, 11:29 PM
This project is going to be for in the house using ambient lighting to light 2 high output IR LEDs. I can't seem to find how much current is needed by these and I'm not sure what the typical solar cell radio shack puts out. Anyone have an idea of how much solar area from one of the pannels at radio shack I need to power two of the high output IR LEDs that radio shack sells?

The reason for the project is to create a wii "sensor bar" It can be mounted below a tv to potentially pick up light from the tv as a source of power if that would help. The "sensor bar" is basically an ir transmitter and not really a sensor bar at all.

There aren't any decent electronics stores near me so radio shack is my best bet for the parts (unless I go online).

Mike Dabrowski 2000
12-24-2006, 08:49 AM
Most high power IR leds run at between 30-50MA, and need between 1.2-2.5V. ~ .125W

A single solar cell will output .5V in sunlight, with the current dependent on surface area and the intensity of the light. To get the 2.5V to drive the IR leds, 5 solar cells in series would be needed.
While a tv set would seem to be pretty bright, you must remember that a CRT based tv is just a single pixel at a time that is being illuminated. Your eye has a fairley long persistance, and the slight persistance of the phospor makes it look like a full screen. Take a photo of a TV picture at 1/100th of a second or faster, and you will see only a partial picture, and if over 1/500th of a second, it will look more like a dot.
The solar cells would only see the light from one pixel at a time and therefore not produce much power, as only one of the 5 cells would be illuminated at a time. A single 60-100W bulb would do much better, as all 5 solar cells would be iluminated at the same time.
Plasma, LCD, and DLP TV work differently, but still do not produce much light.
Sunlight at most locations produces about 1KW/ square meter, the radioshack solar cells are likely about 10% efficient, so if you had a sq meter of the cells, you could produce 100W.
5-1A cells in full sun would produce 2.5W. The same cells with a 100W lamp 6" from the surface, may be able to light your leds.
I hope this has given you an approximate scale of things.

tbaleno
12-24-2006, 09:41 AM
It helps alot. Thanks.



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