Homemade Painting Light

[Carbon2010]

Hey guys new to the forums and the modding world so bare with me.

A friend came to me and asked me to build him a light so he can paint at night. His requirements were quite simple:

-Make it a white light.
-Make it bright.

I opted to use around 8-10 Cree XR-E Q5's. There rated at:
-3.7V
-Up to 1A
Around 225Lumens at 1A

Well I would like to under-drive everything and mount it on quite a big heat sink to keep temps down and total life of the leds at there best.

My question is this, How exactly do I create a driver for theses guys. I was going to use this technique using a LM317 as a regulator (beings as these LEDS are quite intensive)
http://www.instructables.com/id/Super-simple-high-power-LED-driver/
It seems simple enough but i'm still a little confused and don't want to burn out 50$ worth of quarter sized lights.

~How would you guys recommend hooking up this setup. ideally I would like to run at around 800mA and if possible use a potentiometer to control the brightness of the leds.

Thanks!

 

[John_Galt]

Youa re going to want to look at High CRI LED's from Nichia instead. They are rated at a 92CRI, whereas Cree XR-E's are about 80CRI. Also, a neutral tint would probably also help.
Otherwise, his colors will be off.

 

[LukeA]

If he's not mixing his colors by the light, it won't matter at all, and even if he was, the colors wouldn't vary nearly as much from the color rendering characteristics of the light as they would from variance of intensity of the light source, say from daylight to indoors.

As for creating a driver (presumably from a wall outlet), I would go even simpler than you have. I'd take a power supply capable of supplying the appropriate voltage and amperage (maybe a computer one) and make some equal strings of LEDs, select a resistor for each string such that the value is appropriate for ~750mA, and assemble.

 

[Carbon2010]

See here's the thing. I can't find anything that will work. I'm basically trying to figure out if I suply this circuit with more current and amperage will it fry the LEDs or will the lm317 put out 800mA (with the right resistor) and the LEDs draw 3.7v. The remaining voltage and amperage be dissipated as heat?

Thanks

 

[LukeA]

I wouldn't use LM317s. The resistors would set the current. Computer power supplies and wall warts vary their current according to load. The resistors burn in watts the difference between the voltage under load of the power supply and the total forward voltage of the LED string multiplied by the LED current in amps.

 

[Carbon2010]

Woah...Sorry you kinda lost me. Again i'm just starting out with electronics...

 

[Lighthouse one]

First..buy a 500 watt work light at the hardware store...
Second...buy a Zebralight headlight to wear while painting. I use one and they are great for close up inspection while you work. You can see any missed spots by just leaning in closer to the wall. They have single AA, single cr123 and now an 18650 model with a long runtime- and more power.

 

[Carbon2010]

Thanks guys, although being my first big project, I would love to give my new soldering gun a go.

Question now is, if I supply the lm317 with more power and current then required, will the extra current and voltage be dissapeted as heat?
Example:
The leds draw 3.7V and 800mA(1A max); the lm317 has a voltage drop of 3V. I'm hooking up two leds in series.
3.7+3.7+3 = 10.4V
I then just use a rated resistor to achieve 800mA. The Lm317 always trys to output 1.25V so by doing a simple calculation:
1.25/.800 = 1.56Ohms....Making a 1.6Ohm resistor closest to my achievable output.


If I supply the LM317 with say...12V and 2A will this be allright and not produce excessive heat?

Thanks.

 

[marokero]

Perhaps this link can give you some ideas:

http://www.reefcentral.com/forums/showthread.php?s=&threadid=1587273

Not that you should use the same LEDs, you're free to choose whatever you want, but I thought that was a nice idea to use those big heatsinks and fans.