LED comparison - 5mm to Cree XR-E High Power

[Waterproof]

I ordered a bunch of 5mm LEDs from deal extreme to compare the light output on a watt:watt basis. I used 50 of the 5mm white LEDs and compared them to a single Cree XR-E cool white LED. Here are the power specs:

 

Cree XR-E run at 3.7v and 1000mA = 3.7watts

 

50 x 5mm LEDs run at 3.3v and 20mA = 0.0726 watts each or 3.63 watts total.

 

Here's a shot of the two setups:

 

Fired up. The pic is off-angle, so this isn't a great comparison between the two. The color of the 5mm LEDs is very close to 10,000 K whereas the Cree is about 6,500 K.

 

I then placed each over an acrylic tube. I put a white plastic card on the bottom to compare the brightness under 12" of water.

 

Here's how the bottom of the tube was illuminated with each:

 

Cree XR-E

 

5mm Array

 

I'm not sure this is conclusive in either direction. The 5mm LEDs are very directional, whereas the Cree, without optics, has a fairly wide dispersion angle. For the above test, I fanned out the 5mm LEDs to get a spread as similar to the XR-E as possible.

 

I then shot the array at the ceiling, approximatley 5 feet above. In this case, the 5mm LEDs were much brighter. Once again this is likely due to the dispersion angle of the Cree XR-Es.

 

Cree XR-E on the left and 5mm LED on the right. There is little discernable projected light by the XR-E.

 

I put an 8-degree optic on the XR-E, which greatly increased the projected light by harnessing it into a tigher beam.

 

Finally, I put each over my biocube-14.

 

Cree XR-E

 

5mm LED array

 

If the above tank pics, I fanned out the 5mm LEDs even more to try to duplicate the spread of the XR-E. Even with the outter LEDs pushed pretty far out, the resulting light was still more concentrated in a smaller spot.

 

 

Overall, I'd say the 5mm LEDs look a little better in each test. So, why don't we use them in reefs? Well, the sheer number would make them a pain in the butt. To duplicate what I have in my BC-14, I'd need the equivalent of 11 LEDs = 550 LEDs. This would be a royal pain to solder! On a pico, however, I think the 5mm LEDs might offer some neat possibilities to the budget DIYer. I'm still a big fan of the Cree LEDs.

 

Please note, I have not evaluated the PAR coming off these LEDs. If anyone has an idea of another test, let me know, and I'll give it a shot.

[not_sponsored]

I have a PAR meter if you want to send the 5mm array to me I can test it against a CREE XR-E Q5.

[evilc66]

Some reasons we don't use 5mm LEDs:

 

- Big drop off in PAR. Much faster than a high power setup.

 

- Shorter life. High power LEDs are rated for 50,000 hours. 5mm are rated at 10,000 hours, but typically last much less than this.

 

- Binning, or lack thereof. Cheap LEDs will vary quite greatly in color.

 

- Color. Most of the whites have a significant green or purple halo with can look pretty crappy.

 

- Poor heatsinking. No easy way to heatsink these, and they will generate a decent amount of heat when tightly clustered, leading to failure.

[Waterproof]

I have a PAR meter if you want to send the 5mm array to me I can test it against a CREE XR-E Q5.

 

Thanks for the offer, but it's probably not worth the shipping. I know a person in town with one, so I might take it by his place. I'd be interested in seeing the dropoff.

[Waterproof]

- Poor heatsinking. No easy way to heatsink these, and they will generate a decent amount of heat when tightly clustered, leading to failure.

 

MAN, way to suck the fun out of my thread!

 

I did notice that the 5mm array puts off some decent heat. It would be nice to find an option for very small tanks (e.g., picos, 3gal minibow, etc.). The problem with the crees is that you need to add more over a shallow tank to get decent coverage. This is costly, and you end up running the XR-Es at about 350mA so that they aren't overly bright. Ideas?

[evilc66]

I have done tests very similar to what you are doing. 1/2W 10mm and superflux LEDs work out the best, but they still don't hold a candle to a Cree.

 

Another big issue is that you hit the performance ceiling right out of the gate with small LEDs. Even if you could match the PAR levels of a Cree, as soon as you add even an 80 degree lens, they get left in the dust.

 

There have been projects done here in the past that have used 5mm LEDs, and it never seems to be enough long term. It's nice that the LEDs have become cheaper now, but it's a lot of work wiring and soldering 100 LEDs for a small array.

 

Lets use a 3g pico as an example. You could easily need 200 LEDs (50/50 white and blue). 100 white will cost you $31 for 55Kmcd @ 20 degrees, and 100 blue will cost $21 for 10Kmcd at 20 degrees (these are not the 1/2W LEDs, but decent 20mA LEDs, not super cheapies). Building real current regulators and not using just resistor will cost about another $20. Pcb for it might be around $10 for a good sized one. Add a power supply for $15. Thats $97, and a lot of work soldering 200 LEDs.

 

8 Crees with heatsink, drivers and power supply is about $135 if you really skrimp, and it will have more PAR, higher reliability, and longer life, with much less labor.

 

Sure there are some cost savings there, but you lose the savings on your reliability and labor.