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Project Help and Ideas » Input Voltage Requirement for LED Array

August 17, 2010
by lavared
lavared's Avatar

Hi,

I have a LED Array 5x12 size which i'm trying to expand by adding 2 more modules of 5x12 size. How do I calculate what the required voltage that I should be providing for the 3 modules of 5x12 size running like a scrolling LED display.

Also is there a better way to fix the LED's to the board rather than using a foam board (i.e. a PCB or anything else). I checked the prices of the PCB fabrication for the size of the LED modules I have and they seem to be pretty costly.

Thanks

August 17, 2010
by hevans
(NerdKits Staff)

hevans's Avatar

Hi lavared,

The voltage you are providing to each array should stay the same. The chip runs off 5V, and in the case of our LED Array the chip is running the LEDs directly, this means all you need to do is make sure each chip gets the requisite 5V.

What you do have to worry about is the current draw from the LEDs as you start adding more panels. Take look at this thread where Mike explains about how much current runs through each LED in our LED Array. He comes up with about 6mA of current per LED when it is "on". For 120 LEDs that is about 700mA of current if all LEDs were to be on the whole time per LED Array. That is the theory of course, in practice the current draw is actually less due to resistances in the wires, breadboard, the inability of the chip to source that much current, and other factors. The best way to see it is by measuring the current with a multimeter. I was able to run our multi led array panel with 4 arrays off a wall wart rated for 300mA at 9V (going through the voltage regulator) however I do think I added a heat sink to the 7805.

Humberto

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