# powering LED haunt lighting



## wandererrob (Aug 8, 2007)

I've decided this year to ditch my old lighting (110v CFL's housed in PVC tubes with gels to color the lights) and go to LEDs. For this purpose I snagged a whole bunch of 3W LED flashlights off of eBay for short money.

They're perfect for the haunt because they're small, bright, weatherproof and already matte black. Threw some small circles of gel over the lenses and I've got a bunch in my main colors.

Now to power the buggers. Worst case, I just run them all on batteries (a single AAA or AA each). But ideally, I want to hardwire them so they can be powered from a central power supply. The question is, what's the best way to do so? And what size resistor would one install in them so they don't fry? That's the big question mark as I have no clue what the electronic voodoo inside them is doing with 1.5V to drive a 3W LED. And how many milliamps are they drawing? Not a clue.

Any thoughts, suggestions, ideas?


----------



## Allen H (Feb 13, 2010)

Let me preface this by saying I may be an idiot here. 
But its already made for an unregulated 1.5 V power supply, I would just attach speaker wire to the positive and negative battery connects inside the flash light and run that tou a 1.5V wall wart the Ma ought to be 60ma per light. are they one LED or 3?


----------



## corey872 (Jan 10, 2010)

Are you sure they are a single AA or AAA battery? You mention coloring them with gels so I'm assuming they are white, which is almost always a ~3.5V LED. Given that LED and the 3W rating, the only thing I've seen in that range is running 3 (or 4) AA or AAA batteries in series. The simple stuff uses 3 batteries to get ~4.5V which is actually about 3.6V once under load, and the high end stuff uses 4 cells with an actual voltage regulator to get steady light output over a long time.

But what ever the case, if it were me, I'd get some fresh batteries and hook the flashlight up as the mfr intended. Measure the current and voltage, then you know you should be safe up to those numbers. Decide what power supply you want to use and plug those numbers into a LED resistor calculator to match the resistors.

If you don't already have a DVM, a simple $5 meter can be pretty cheap insurance against blown parts and a handy tool for troubleshooting:

http://www.harborfreight.com/7-function-digital-multimeter-90899.html

[edit] Well, I stand corrected - I do see "3W LED Flashlight" on ebay with 1 AA battery. So don't know exactly what tricks they are using inside, but hooking up and measuring current/voltage would still be the best way to size a resistor for your power supply.


----------



## wandererrob (Aug 8, 2007)

Yes, they are 3W. The module containing the LED also has a driver board in it with a capacitor and what look to be surface mount resistors.

That said, I tested it with my multimeter and it claims it's pulling about 80mA, so I'll use 80mA and 1.5v on a sacrificial unit and see how it goes and adjust from there.


----------



## wandererrob (Aug 8, 2007)

Just to wrap this up, I ended up chopping out the joule thieves in the flashlights and wiring the LEDs straight to the 3.3V lead on an ATX power supply. They spent the evening tonight quite happily casting as nice, creepy moonlight blue glow on my cemetery.

For accent lighting, I'm powering 3W LEDs (proper ones on heat sinks) using LED drivers driven by the 5V ATX leads. After comparing the heat sink LEDs to the flashlights, an EE friend of mine says the flashlights are more likely 1-2W not 3W. But they still are working nicely for what I wanted them to do. 

Hey, whadaya want for $1 slowboat specials, right?


----------

