help for led array?

Forum 2005-2010 (read only) Hardware Interfacing
#1

I've got a pcb that I'm thinking of turning into a oversized killer flashlight. ;D I'm trying to figure out what sort of power source I may need...

PCB: http://amplebiz.com/products/el025.html

LEDs: 3.3V at 2OmA continuous, 50mA for peak for 10% pulse width http://cgi.ebay.com/100-pcs-3mm-White-LED-Lamp-Ultra-Bright-200-Free-Resist-/160511173925?pt=LH_DefaultDomain_0&hash=item255f362525

I am still a n00b at figuring out this sort of stuff... can anyone talk me through what sort of battery pack I'd need? I'm simply trying to run 108 of those LED's in series and have decent battery life. N00b-comprehensible explanations appreciated. :D

#2

The PCB can hold 108 LEDs.

It depends if the PCB wires all the LEDs in serial or in parallel. I'd hope they'd wire it in parallel.

The PCB link you provided says the LEDs are wired in 2 different groups:

?2 different groups of LED with different forward voltages : Red, Orange, Yellow (ROY) need 1.8V to 2.0V forward voltage White, Blue, Green, UV (WBGU) need 3.0 to 3.3V forward voltage ?For ROY Group, apply 8VDC, total current for the Module is 540mA, power consumption about 5W ?For WBGU Group, apply 12VDC, total current for the Module is 540mA, power consumption about 7W

So it looks like you need a power supply (battery) that can provide 12V @ 1.08 Amps for however long you want the flashlight on.

#3

what sort of batteries/resistors combination would provide that? I probably have a wall adapter that provides that, but it needs to be battery powered to be portable

#4

The NiCad remote control car batteries will come somewhat close. They provide 7.2V at 700mA for an hour.

They're basically 6 AA batteries in a pack. Each AA battery will give you 1.2V, so you could increase that to 12V by using 10 AA batteries.

Another option would to be to tie two RC batteries in series for 14V. I'm not sure if that increases the mA/hours or not. Probably not.

It'll suck the life out of your batteries, so make sure to use rechargeables.

#5

I've got a wall adapter that I want to test this thing with... it's putting out 12V at 200mA. Is that enough to give this thing a try? I've got to think about what sort of batteries I can use to push this thing for a little while... I've got 2 remote control airplane batteries I should test

#6

also, if the voltage is correct, is it a problem to have too few amps on something, or does it just affect brightness?

#7

wow, I've got 2x 6V 300mAh rechargeables... would that total 12v 600mAh? Sounds like a perfect solution

#8

how do you measure amperage of a power source using a meter? sorry for all the n00by questions :slight_smile:

#9

Here you go

#10