Building a Q5 Desk Light

[infection0]

Hi everyone, I am trying to build a simple, energy efficient CREE Q5 desk light that will be within my limited electronics experience. So I am planning on buying a simple Q5 star, heatsinking it with a piece of metal, and driving it with a wall plug DC converter (inverter?)

Here's the shopping list:

Power Supply: 3.5v 1A DC Supply.
Emitter: CREE Q5.
Heatsink Compound: Generic DX Compound.
Heatsink: The underside of my loft bed.

With everything I know about electronics, this should work. But I don't know much. A lot of people suggest resistors with LEDs, but the power supply is guaranteed to be constant.

So, I've got 4 questions for all of you pros:
1) Will this even work?
2) What voltage power supply should I get if I want to output 700-800mA?
3) That paint on my bedframe won't impact heatsinking too much, will it?
4) I've heard that you can control the current instead of the voltage. What kind of device to I need to do that?
5) Any other considerations for this light (maybe color temperature)? I would like a warm tint but don't know where to look.

Thanks for your help!

 

[SafetyBob]

After the wall wort or the LED burns up, I highly encourage you to look into Advances transformers or the MicroDriver9. You can get them with different power ranges and they would be much, much more effecient than your very cheap, very ineffecient wall wort.

You could also get BuckPucks that would give you 1000mA from AC power, you could get the wiring harness that controls dimming and you would have one terrific light.....and that would last for a long, long time too.

Lets talk heat. Go ahead and get the real thing....Artic Alumia Thermal Adhesive......THE only way I have ever installed an led. You can still pop it off the metal if it dies....but 100% transfer of heat is what you want and what you get and you don't have to do anything but keep the LED still for about 5 minutes and you never have to do anything again, no screws, no holders, springs.....nothing. Please use it. You will never regret it.


Bob E.

 

[LukeA]

With a thin enough layer, almost anything will work. The Fujik stuff is very good and works very well.

There aren't buckpucks for 120VAC.

 

[infection0]

Dang SafetyBob, I can tell you never settle for second rate!

So this wall plug is probably no good? It'll just burn itself out or the LED? I never knew that an inexpensive converter could be so bad... how much energy does it waste compared to better ones do you think? I've already bought it.

 

[SafetyBob]

LukeA is correct, my mistake you will need to get some sort of transformer to take 120VAC down to whatever you like....You should be able to find 12, 16, and/or 24 volt stepdown transformers.

With just an led or two, you would not need a huge one like a doorbell transformer, a tiny one used for smaller appliances or stereos would no doubt work. You will need to start reading and looking at the big supply houses for what they have....Digikey, Mouser, and Allied Electronics are the three I mainly use.

Since you are going to use a star (and a wise choice for all but the crazy modder) your compound will work fine as Luke has already mentioned, but I really have to tell you I love working with Artic Alumina Thermal Epoxy. Just a little bit holds everthing down perfectly, no screws, clips....nothing. Use your paste for now and see what you think.

Now, one last suggestion. If your "mount" to your bed with tilt, rotate, anything, I highly recommend you to look at "Brum"s thread I think in the B/S/T forum or the light/sell thread in the marketplace. He has different plastic lenses that will go over your LED so you can focus the light into a spot (for incredible reading lamp...maybe to spotty though) or you can get one with a diffused look to it (and I would recommend this one for now, but get both so you can compare)

OK, that should get you started. Good luck, and PLEASE post those pics of your completed project. We all love to see other's handywork and generally it gives us more ideas on projects we need to build for ourselves.

Bob E.

 

[Scott Packard]

I'm starting to see a proliferation of USB power supplies (to charge iPods and phones?) so I'd probably buy one of those (5V@2A).
You could then use run-of-the-mill USB cables to go from the wall to the light box, and limit the voltage and current within the box.

Later, when you're showing off your light and your friends want you to build them one too you'll have a versatile enough design that they can power it from their USB power supply.

http://iqpowersupplies.com/usb_power_adapter-dual.htm for an example of how USB is popping up.

 

[SafetyBob]

Definately worth at try........

Actually, I may give this a very close look. Thanks for bringing this to our attention.

Bob E.