# Help me identify these LEDs

#### wayneh

Joined Sep 9, 2010
17,152
I've got a couple LEDs that I know very little about. I'm hoping they look familiar to someone.

The smaller one on the left lights up if I supply 12V thru a 220Ω resistor. Vf = 8V. I suspect it can get a lot brighter but I have no idea of the max current rating.

The big one was in a bag labelled "150W 6000-6500K". I have no idea how to light that one up.

#### wayneh

Joined Sep 9, 2010
17,152
Yes, although the Vf doesn't match up. A lot of the other 10W COB pieces are rated to 900mA, so I think that's a decent assumption for the one I have. I'll try 0.5A and see what happens.

I think the big one you linked may be spot-on. I'll need to up the voltage somehow to get >30V. Not sure how I'm going to do that. I suppose I could put one in series with a 60W bulb and use rectified mains.

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#### MisterBill2

Joined Jan 23, 2018
8,500
NO!!! Do NOT use rectified mains power. The voltage will be excessive . Until you know the proper forward voltage there is a chance of doing damage, and with am LED device like that it is a fair amount of money's worth. There is also the problem that LEDs can easily fail from excess reverse voltage, which might even be less thatn the normal forward voltage. I followed the one link and looked at that chart and that gives a forward voltage of 30 to 34 volts. and a current of several amps. Now that the smaller one lights, you can see which side gets the positive, and there may be a similar physical clue on the larger one. Then you can experiment with applying a lower voltage to seewhat makes it light.
Another caution is that with that much power input it will get very hot very fast and so you do need a serious heat sink.

#### ElectricSpidey

Joined Dec 2, 2017
1,575
The smaller one is the 10 watt version.

The larger one looks like 100 watts, probably around 32 to 34 volts vf.

10 x 10 rows...150 watts is 10 x 15 rows

Although the bigger one could be 150 watts.

#### Wendy

Joined Mar 24, 2008
22,381
You could always put a bunch of batterys like 9V (Qty 4) in series to test it out.

#### Kjeldgaard

Joined Apr 7, 2016
450
As @MisterBill2 writes, whether it is a 10W or 150W type LED, a large/huge heat sink is needed.

#### Wendy

Joined Mar 24, 2008
22,381
Only if you feed it a lot of current, 20ma is always a good test current.