Drive A 5w Led

[camilozk]

Hi!

I bought some 5W cool white leds (http://www.ebay.com/itm/5-10-50-pcs...var=420747181213&_trksid=p2057872.m2749.l2649)

in the specs at ebay says that "Cool White: 4 Chips,Voltage6V~7V),Current: 700mA", and since I learnt thay these kind of led needs constant current, I overviewed the voltage rating and I used a 700mA constant current driver (http://www.ebay.com/itm/Sure-Boost-...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649)

I burnt it. two of them.

What am I doing wrong and how do I correctly drive these leds?

thanks in advance!

 

[Alec_t]

What heat sink did you use?
It's not clear from the write-up if the 700mA rating for the LED is for some specific set of conditions, e.g. a brief burst of current, continuous current, forced-cooling of the LED, .......
Personally, I would never drive a LED at the stated maximum current. Vendors/manufacturers figures can be a tad optimistic. It's safer to allow a decent margin.

 

[kellys_eye]

What heat sink did you use?

I'm guessing 'none'....

 

[Tha fios agaibh]

The Chinese are horrible at instructions.

I wouldn't trust the specs given. They could mean to use a700ma rated power supply instead of saying it has a forward current of 700ma?

I would apply 6vdc and measure the actual current.

I'm guessing your constant current driver went well above the rated forward voltage of 7 in order to maintain a current of 700ma.

 

[camilozk]

As for heatsink I used one of these typical aluminium stars (http://www.ebay.com/itm/50-x-LED-He...530734?hash=item2a6fdf496e:g:26IAAOSwOdpXyabt). @kellys_eye ; unnecessary useless comment...

@Alec_t, thanks for your comment

@Tha fios agaibh, this is indeed probably what happened. As a matter of fact I asked the manufacterer of the 700mA constant current driver, and he answered "It is a boost led driver ,you use 12v to power, the output voltage will be higher than 12V the led (6V~7V) will be burned". I will apply 6vdc and measure current and come back with the results.

 

[(*steve*)]

As for heatsink I used one of these typical aluminium stars

That's not a heatsink, that's what you mount on a heatsink.

unnecessary useless comment...

Not really, more an observation based on plenty of experience.

 

[BobK]

If you apply 6V you may well burn another one.

LEDs cannot be reliably run from a voltage source, the current would be too varisble. You had the right idea with the constant current source. You just need one that can run in the range of 6 to 7 volts.

And you do need a hear sink if you want to run it at more than about 1 Watt.

Bob

 

[camilozk]

thanks bob for sharing your thought!


And about "I'm guessing 'none'....", even if it is an accurate observation, it plays no role in trying to help the community finding solutions.

 

[(*steve*)]

Have you read the resource on LEDs?