How much heat sinking is enough for Cree P4 at 700ma?

I am looking to make a fixed lighting light that has one of the Taskled.com CC5W drivers to run 2-3 Cree P4 LEDs.

These are going to be used in a low voltage track light and be a replacement for MRbulbs.

Source voltage is 12V.

So this should be fine to run them since they are 3x = < 14.2V-11.5V?
So this should be fine to run them since they are also 2x = < 14.2V-11.5V.

I can not go 4x because that is more then 12V source. Unless I switch to the MAXflex2.

I am planning to run them at 700ma. So this is a little overdriven, but not too bad if I heat sink them. Now the question is how much heatsinking is practical to extend life?

In realistic terms, what sized Computer heatsink am I going to need to find to use to support 2 LEDs?

In realistic terms, what sized Computer heatsink am I going to need to find to use to support 3 LEDs?

I am talking about computer heatsinks because they are readily available and come in quite a few sizes. Or is just a piece of aluminum U-channel going to be enough? But the LEDs are going to inside a fairly small glass light enclosure.

Before we can give you a firm opinion, could you tell us what/where you are going to use the lights?

Bob E.

Edited first post.

Then I can answer this now. I have used a single Cree Q5 running at 1 full Amp on a smaller Pentium 3 heatsink for testing runtimes on my battery setups for awhile. It gets warm, perhaps 100 degrees after an hour at that full 1Amp. While taking some overall effeciency off the project, I would think if you had any heatsink in the P3 or P4 size (or equivalent AMD series (have those too)) and you could use the heatsink fan at reduced power (think quiet) you would have no heat issues with 3 or 4 LEDs on a computer heatsink. Without a fan, my recommendation would be to go with one per heatsink, however, make a sample 3 LED heatsink, no cooling and give it a try. With 12VDC power, you have plenty of options.

Let us know how this comes out and we want pictures too. Many of us are considering this for our homes.

Bob E.

SafetyBob said:

LMany of us are considering this for our homes.

Click to expand...

yes, especially as DX now have this: http://www.dealextreme.com/details.dx/sku.10852 (mains voltage LED Current Driver)

My advice would be to actually try to see how much illumination you get at 350 and 700mA, and see if you really need 700mA.
In my experimentations, I found that running crees at 700mA gives a significantly higher heat output, for less than double the light. I can run 7-8 crees, on a 1 meter U channel aluminum strip which barely gets warm at 350mA.
SO give it a practical test, since you might cut yourself a lot of hassle if you dont really need the high current.

As Mash stated better to have more LED's running at lower current than trying to squeeze every last lumen out of them. You could always run 6 LED's 3 in series in parallel with another 3 in series.
Norm

It might be very nice running at 500ma then that the task LED 5W module outputs for 2 Cree p4 on 1 pentium 3-4 heatsink inside a light with MR16 plug mounts.

So hide this inside a scone where the you can't see the light, it might work very well.

my whole room will be using 2x 15W CFL on 1 circuit for general light and project work and entertaining. Low level light would be 5 lights with 2x crees P4 modules at 500ma running inside them with a cpu heatsink to keep it reasonably cool. But i might even be able to go to the 350ma load based on what some people have said.

Interesting enough I used a Zebra Q5 light on HIGH to show the wife as a rough estimate to see if we liked this light level. This was 1 CREE Q5, so 2 Cree P4s should be more light and a bit brighter as one module for use to use to compare with.

Dx do a 1W mains driver now so less heat to deal with! should help such projects! http://www.dealextreme.com/details.dx/sku.11077

maybe you should just use two of these http://www.dealextreme.com/details.dx/sku.6076 in series and save the hassle of building something similar from scratch. and probably a lot cheaper too.