Cheap Cree P4 LEDs: Good for fixed lighting lm/$ ?

[MrNaz]

I was thinking of using these:
http://www.dealextreme.com/details.dx/sku.2134
In a fixed lighting application, specifically, for creating a flood light for my backyard. Driven at 700mA each, they should put out about 100-120lm. I would use them without any optic, so that the maximum light output was achieved.

I would like to know if this deal represents a good deal in terms of lumens per dollar. Is the P4 is still a decent LED to use, or is it now hopelessly outdated?

 

[clg0159]

P4's are excellent LED's for your purpose. In response to your question they are a great deal in terms of LM/$. Here is the breakdown:
P4's=bin minimum of 80.6lm
at 17.81/5 each LED cost is $3.56
so....80.6lm/$3.56= 22.6lm per dollar

now consider the brighter Q5 that DX offers:
Q5's=bin minimum of 107lm
at 6.27 per LED
so....107lm/$6.27= 17.06lm per dollar

To be fair though you would only need 4 Q5's to achieve the same(actually slightly more) total output, but 4 Q5's= $25.08 so the cost for parts is still higher.

However, this does not factor in the power consumption costs in the long run, which will be slightly higher considering 15W(5XP4s) vs. 12W(4XQ5s).

 

[LukeA]

You'll get a lot more than 120 lumens at 700mA from a P4. More like 175.

P4 is fine for fixed lighting. You have to use the light a lot to save enough energy to get back the money you'd spend for higher bin LEDs.

 

[MrNaz]

Thanks for the reply guys. Another question, these P4 LEDs are a WD bin. That tint is probably a bit better than the cool WC bin Q5s I've got here. However, if I were to light, say a bedroom with WD bins, would that be too cool a light for that setting? Perhaps a bathroom would better suit that tint?

 

[LukeA]

I have a night light in a bathroom running a P4 7A at 350mA and I think it's very good.

WD is a little on the cool side, but you should like it at a low enough light level.

 

[clg0159]

I agree with LukeA, I prefer the P4 7A-C tints. They will cost more, but it is worth it for a light you will use often. I believe DX has warm white Crees but I don't think they specify the bin.

 

[Mr_Light]

I have been buying lots of the Q2 CREEs at DX for home lighting projects. The tint seems pretty neutral. If you use the "bulkrate" pricing they cost just a tiny bit more than the P4s.
http://www.dealextreme.com/details.dx/sku.2395

 

[SafetyBob]

May I just put in a plug for you to consider using some sort of spot optic. I have some of the Ledil optics for the cree leds. I got all the kinds that were available for the XR-E at the time and tested the capability of them all. (from Brum)

I think you may be happier with the results especially in the back yard with "real" spot optics that could really flood the back yard with light exactly where you want it. That would require your fixture to be made with the led's angled in the right direction for the coverage you would like to have.

I think you will find that the bare led will flood maybe a little to good close in and not nearly well enough for 15 or 20 feet out (if you need to get out that far). Depending how you will mount it you may be lighting the bottom of your roof better than 15 feet out into the yard. Perhaps a combo of spot (think wide spot) and bare led for close in flood would be the perfect combo.

I don't get off on this whole topic lightly. I too have been looking at every single commercially built flood and led street light (and components) that are out there for sale (and most not available yet to the general public yet). Proof of concept that we can do this and do it well is out there. I looked at a $465.00 led work light for a service truck application a couple of days ago at a place in town that sells all that stuff. I could not believe the price with a small mill or even without.....just a chunk of aluminum, some black paint, P4's, optics, some BuckPucks and I believe we would be in business. Workable and better looking only based upon how much equipment and/or time and/or skill you have.......

Promise me once you get yours done you will post pictures of what you do. Your exact opinion on how they turn out too, will pretty much tell me exactly what I need to do and stop B.S.ing myself trying to get it right the first time.

Bob E.