My first LED lamp project.. Power supply questions???

[714guy]

Hello there..

I've been wanting to make an LED lamp for my desk for some time now. A few days ago I saw this Lamp and that's very similar to what I want. After reading up on it and I have some understanding on the basics about LED voltage, current, and resistors. But I am still unclear about the power supply and what I need to have so I can just plug it into the wall.

My plan is to use a aluminum C-channel to mount the LEDs in twos and staggered them. I want about 140 LEDs, 2 in series and then 70 pairs in parallel.

THE SPECS from http://led.linear1.org/led.wiz

• each 330 ohm resistor dissipates 132 mW
• the wizard says the color code for 330 is orange orange brown
• the wizard thinks 1/4W resistors are fine for your application
• together, all resistors dissipate 9240 mW
• together, the diodes dissipate 8960 mW
• total power dissipated by the array is 18200 mW
• the array draws current of 1400 mA from the source.

I was looking at AC power supplies that would output 12v and handle the 1.4 amp load, but is that all I need? LINK to one of them
Today I read about bridge rectifiers and capacitors to smooth out the flickering of LEDs on AC power. Would I also need this?

Well anyways I am sure there are many ways to power this lamp, but what would be the most stable and easiest and cheapest solution to power this lamp?

Thanks a lot for the help.

Jason

 

[Gunner12]

I'm also planning on making a LED desk lamp, but I'm using a single high power LED (Cree XP-E Q5) powered by this driver. I'm still searching for a suitable but simple way of keeping the LED cool, a copper cap could work. It's something different then what you are trying to build though.

I'm not sure what will work with your setup though.

:welcome:

 

[714guy]

Thanks for the help.. I will look into that. I am still trying to figure out the power supply. It seems that I need a power driver for the LEDs to keep the current constant so that it will be at max efficiency. But I figure I'll just play around a little first and see what works. I'll report back what I find.

Can't wait to learn more about the Cree's.. I always see it on DX but have no clue how to wire them up or use them. Eventually I want to make a headlight for my loupes.

jason

 

[Gunner12]

Cree is a company that makes LEDs. Common models are the XR-E, XP-E, XP-G, and MC-E.

The XR-E, XP-E, and XP-G have two contact points, one positive, and one negative, then bottom is for heatsinking. There are indications on the LED for which size is which. If you get it on a star or board, there should be labels on the board that tell you which contact is which. For the MC-E, it has 4 individually addressable dies, so there are 4 contacts on each side, one side is positive, the other side is negative. They are pretty easy to wire up.

I'm guessing that you are using 5mm LEDs? I don't recall a AC to DC driver that has a low output current, but if the LEDs are close in Vf, then you can wire then up in parallel and drive them that way.

 

[714guy]

Cool.. thanks for the info.

Yes i am using 5mm LEDs.. I will be connecting them in parallel. I am going to try it out to see how it works. I really just like the design and look of the LEDs but if it's not bright enough then I'll switch over to the cree's.

jason