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I purchased one of these cheap LED panels to light a room. One review suggested that it's important to put a resistor on it, to keep it from frying itself. But, he didn't list what resistor to use.

I've searched around and found a lot of discussions of resistors for individual LEDs. But, I haven't stumbled onto the right page for this situation.

I have a UNI-T multimeter. I saw "Easy way to figure out a LED's Vf in order to pick an appropriate resistor", but putting my multimeter into what I think is diode mode stayed stuck at 0L. (I was careful about polarity.)

This is my first encounter with "forward voltage" so, it's a bit overwhelming.

Thanks.

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I understand that you can't give me a definitive answer. But, does anyone have a Scientific Wild Ass Guess? Something along the lines of, probably higher than this. I'd be surprised if higher than that. And, likely around here? Just a ballpark number that has a reasonable chance of being safe?

And, I haven't ever bought something like this. A suggestion or two on a source would help me out.

I appreciate everyone's input. I understand that not having a data sheet makes this a pain. But, this is just a DYI thing, and they're so inexpensive that it's hard for me to pass them up.

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closed as off-topic by Jasen, Finbarr, JRE, RoyC, Warren Hill Apr 29 at 9:46

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Jasen, Finbarr, JRE, RoyC, Warren Hill
If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ That you get 0L is probably because your multimeter's power rail is less than the forward voltage, see my related question: electronics.stackexchange.com/questions/431009/… \$\endgroup\$ – Michel Keijzers Apr 15 at 22:31
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    \$\begingroup\$ that looks like as assembler lamp module designed for direct connectio to 12-14VDC/ \$\endgroup\$ – Jasen Apr 16 at 0:57
  • \$\begingroup\$ I doubt it needs any resistor. It probably contains current limiting resistors already or, more likely, a constant current circuit. \$\endgroup\$ – Warren Hill Apr 29 at 9:46
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The ad (not the same thing as a datasheet) tells you that it is 12 V and 70 W. From this we can work out that at 12 V you will need a 70 / 12 = 6 A, 12 V power supply. The current limiting resistors are, hopefully, built in.

No datasheet? No sale!

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  • \$\begingroup\$ Yes, I purchased an appropriate power supply, and I've mounted a heat sink to it. I've tested it for a few seconds. Very bright. I think it's going to work well where I want to use it. I just need to get the resistor figured out, so I don't kill it quickly. It's very low profile, so I can't see where they would include a resistor within the package. \$\endgroup\$ – Mighty Apr 16 at 3:02
  • \$\begingroup\$ The device says "Plug and Play" which is why T says the resistors are hopefully built in. A power LED device can't be "Plug and Play" if it doesn't have current control. Unfortunately whatever control circuit/resistors are on the device are obscured by the lens. In one of the images it has a device labelled "LED Controller" inline, so if that isn't included in your module, and it is itself the current control, you may need to get a driver. \$\endgroup\$ – K H Apr 16 at 3:53
  • \$\begingroup\$ That controller doesn't come with it. The lens is translucent enough that I can see the individual LEDs. I can see that there is no other circuitry nestled in. They're only $10. I should probably just rip one apart and see how they're connected and if there's anything else there. \$\endgroup\$ – Mighty Apr 16 at 4:06

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