High power LED troubleshooting

[Ced]

Hi,

I've been struggling with my power LEDs for a while, and after reading a lot, I still don't know what's the problem.
I hope more knowledgeable people will find out easily :)

I am using a 10W white power LED (they're actually 3 leds in serie, voltage drop of about 9.9 V).

It is being fed by a 12V LED power supply (http://www.buyincoins.com/new_en/de...led-strip-light-display-10-product-12257.html
), and has a resistor of 2.2 kOhm in serie.

Should give it a bit under 1 Amp power, which seems to be going all right.
They're set on an aluminum rail, with silver thermal paste, so heat dissipation should be fine.

However, after glowing for some time (in the minutes range), it happens to dim a lot, and stay dimmed.

But, the strange thing is, if I only touch the LED or wire, it brightens again, staying bright for a while again.

Is it coherent with overheating ? overpowering ? my wire connection being fiddly (it's not welded, just tied wire) ?


(My multimeter is shot, so it's harder to test anything ;))


Thanks for your help !
Ced.

 

[Norm]

(it's not welded, just tied wire) ?

The joins need to be soldered, I'm sure your joins are going to be unreliable.

Norm

 

[Ced]

The joins need to be soldered, I'm sure your joins are going to be unreliable.

Norm

Thanks for your input, Norm.

It seemed to me like it was the issue, but I wouldn't really believe it as long as I didn't understand why they would stop conducting correctly.

Would you have an explanation ?



Thanks,
Ced.

 

[arek98]

I would say that resistor is not 2.2kOhm it would be way to big but this is not important here (could be 2.2Ohm) - if it works then it must have a proper value.

As for dimming, is resistor cooled properly/big enough? With 12V input it will disipate about 2W of power and need cooling. As it heats up resistance will go up, current will drop and LEDs will dim. By touching anything you may cool it down a bit and LEDs brighten back.

Check how hot is resitior when LEDs dim, touch it and see what happens.
If this is it you need to cool it down - attach to heatsink (should be attached anyway)

 

[Steve K]

some photos of your light, the connections, wiring, etc., would help give us some idea of what might be wrong. From the description, I'm inclined to blame the wiring connections too, but I wouldn't rule out the possibility that the power supply could be having some problem....