How to properly drive and power a COB LED

Thread Starter

Dritech

Joined Sep 21, 2011
901
Hi all,

I intend to use a COB LED like this one.
The information I found on the internet is not clear and there is a lot of mixed opinions.

I am not sure about the below:

1) Is a current limiting resistor necessary for driving this type of LED? I already powered this without any current limiting resistor and so far they are still working : )
2) Can I drive these directly from a PWM module? (i.e. without using their dimmable controller/remote, which is most likely a PWM module)
 

Audioguru again

Joined Oct 21, 2019
5,414
The ebay ad says to use a 12V 15W Constant Current driver/transformer (with a fan?) as is shown on your video.
The ad for the COB says, "It's better to add heatsink / radiator".
Since you must "weld" the wires to the COB then the COB and the remote controller are two separate items.

If you use your own PWM controller then you must limit the output power to 15W, and cool the COB properly.
 

Marley

Joined Apr 4, 2016
489
It says it's 12V 15W so should be OK to power directly from a 12VDC supply without a series resistor. 15W means it will draw 15/12 = 1.25A so make sure your power supply can do this. Make sure the the power supply is close to 12V and regulated (stays close to 12V under changes in load). Do not use a car battery which will be 13.5V or more.
Yes, you will need to mount it on a heatsink. The lower the operating temperature - the longer the lifetime of the COB LED.
If you want to dim this, PWM is the the way to do it. A simple series MOSFET driven by some kind of PWM circuit (555) or microcontroller should do it.
 

ronsimpson

Joined Oct 7, 2019
2,525
If you have a bench supply with adjustable Current Limit, then set the current limit to 1A to 1.25A and set the voltage to 13V. The supply should run in CL mode.
 

MisterBill2

Joined Jan 23, 2018
13,750
Really, you need to know the current that the specific LED is intended to operate at. Then either a resistor to limit the current OR a current regulating power supply.
 

Tonyr1084

Joined Sep 24, 2015
7,198
Do not use a car battery which will be 13.5V or more.
A fully charged 12V car battery will be 12.6V. If operating in a vehicle, with the engine running, the voltage can go as high as into the 15V range, but I've never seen that personally. I HAVE seen B+ go up to 14.5V. But once the battery is fully charged then the maintained voltage of the 12V system will be from 13.6 to 13.8V while the engine is running.

A car battery by itself (not on any chargers) will give you low 12 volt ranges. As power depletes the voltage will drop down into the 11V range. Deeply depleted will be in the upper 10V range
 

Tonyr1084

Joined Sep 24, 2015
7,198
I once accidentally shorted a car battery with a 20 gauge wire. It instantly melted down. I don't know how much current it saw but it was instantaneously. In fact, it burned the wire so fast the insulation hardly had time to melt. A small wire won't limit current like a resistor will. In the event of drawing more current than the wire can handle will result in a "Fuse" like action, in that it will burn out when its ability to conduct is exceeded.
 
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