Issue Wiring Up CREE Aquarium Light

Ok, so I purchased a Jansjo desk lamp from Ikea with the intention of using it as a light for a 5 gallon desktop aquarium.



Well I am trying to grow plants, and the stock LED was far too warm for that purpose. So I ordered a Cree XM-L2 in 6500k to replace it. Well what I didn't realize was that the existing chip/LED in the Ikea lamp has built in driver/voltage control functionality and that I would need a separate driver to run my new Cree LED.

So, I went to FastTech and ordered a 3v-4.2v 1-Mode LED Driver Circuit Board and a different 3v-4.2v single mode driver. The idea was that these would reduce the stock input voltage down to the ~3.2v-3.6v needed to drive this LED. Well it doesn't work that way. When hooked to either driver, the LED just blinks.

So I busted out the old Multimeter and checked things out.

The specs for the power supply on the Ikea lamp is below:



When I connect the multimeter to the power supply I get a consistent reading between 4.2v-4.6v. The LED drivers should be putting out around 3v, and for sure less than 4v. Instead, I get the following results when power is applied:



and




I am baffled as to why the voltage would go up. Can anyone offer any suggestions?

Thanks
[h=1][/h]

First off, you can't check the output voltage on an LED driver without a load.

Second, have you checked the output voltage of the power supply with a load on it? It could be a cheap unregulated supply that will have a higher voltage with no to little load, and as a result, will go beyond the input voltage spec of the driver, causing the problem you are seeing.

Without an LED connected, I am unable to test under load. Since the LEDS I have won't operate with this setup, I don't believe I can pull an accurate reading while they are blinking. I am happy to order a driver, I just am not sure which I would need- apparently outside of flashlight applications these 3w LEDs aren't often ran individually.

The vast majority of ALL leds are used outside of flashlight applications. However when you get into DIY circles things are very different. You are right to think you are in a different world, but this world DOES include substantial support for single 3W LEDs.

It's really hard to know what that power supply is actually capable of. The ratings give some hint, and your measurements add some, but that's still not enough to do a reliable design with it. We'll have to make some educated guesses and experiment.

It may well be that the power supply was designed to work in conjunction with a very common driver type used with single LEDs: an AMC type driver designed for 1A, 1050 mA, or anything close to that. This could be verified through testing.