Hi, every one, I am planing to buy some led lights from china, Can anyone offer some good supply. anh how can i kown if they are good or bad.

One of my friend suggest buy from them because he bought them already:

www DOT lighting-cree DOTcom

anyone know this company or can anyone suggest a good manufacturer

Thank you so much

my email:ledjackk@hotmail.com

I would suggest that you buy a couple of samples and compare them with what is available, at their prices you will not lost much if they prove to be duff.

I notice that their ratings of between 3 and 9W seems pretty interesting since looking directly into a 6W LED lamp will dazzle you, equivalent to 50W halogen, also they will produce a considerable amount of heat so will need ventilation similar to the GU10 halogen.

Life expectancy of an LED light is >100,000 hours, some of the lights advertised have ratings of < 35,000 hours. I would imagine that the cheaper the lamp the lower the MTBF.

So start from the premise that their cheapness will reflect on their longevity.

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."

Have a look at candlepowerforums, pages of LED tech advice

hi, thank you so much

i think i would ask for samples firstly.

i want some down lights for my bedroom which is around 12square meters.

Any suggestion of power consumption of light ?what power can light up my bedroom?

i think their 9W LED Down Light9w down light is good

this is a nice site to learn LED Technology

Hi,

We have done a small amount of work with LEDs over the last few years and have discovered the following when putting together luminaires:

The lumen outputs of LED datasheets are notoriously misleading. The problem is that the LED is a bright point source of light and not a distributed source.

Also the lumen output from the luminaire is often not measured - only the theoretical lumen output from the LEDs used in it. This is now being addressed with energystar rating system which has just recently been nailed down. And longevity is way overestimated unless you can seriously liquid cool the LED junction - also longevity was specified as time to reach 60% initial lumens compared to 80% in longevity specifications for SON-T lamps.

Output listed in datasheets is often from a brief flash of light in an integrating sphere which differs significantly from output in typical applications where Tj is never 25C.

Also best efficiency has often been running at 65% of rated power on very high specification heatsinks, at least the big manufacturers are learning this now and not pushing the LEDs so hard (also helps with thermal issues generally).

Reflected light is nicer on the eye but requires significantly more lumens to acheive good standard desk lumen levels of 300. Point source lighting from direct viewed high brightness LEDs will leave persistence spots on your retina - like seeing stars - usually not dangerous unless you stare long and hard at close range! There were some guidance documents beginning to appear on this topic when we were doing our development work.

My advice would be use reputable reliable LEDs from established manufacturers, run at 65% of rated power, properly thermal bond to high specification heatsinks, feedback heatsink temperature (from as close to the LED as possible) to your control circuit in an attempt to limit Tj and promote LED longevity and concommitent lumen output.

If you want a good result that will last then good design and a healthy bank account are essential I think.

Hope this helps.
Regards
E.

-------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The meaning of life is a blank sheet; write on it wisely. ~ M.Cutler.

if you use 9w leds,and 50 0f them that will give you 450 watts of light,running that from a step down transformer,via a separate 6a mcb,in cu,make sure you wear sunglasses if you use white ones

I agree with Legh, you'd better order samples first and make comparison with suppliers, in order to find the right supplier.