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Are 12v LED strips damaged w 9v Adapters?

Posted by MarkMurphyTX (My Page) on
Wed, May 22, 13 at 16:18

First time poster. Reading previous LED posts - excellent group. While waiting on ebay 12vDC LED 5050 and 3528 strip reels delivery from China, I am pondering, researching; getting confused and questioning.

The question I cannot find an answer for is: Will 12v LED strips be damaged or significantly reduced hour lifespan IF powered by a general purpose wall adapter rated less than 12vDC? Will a 9vDC or 6vDC wall wort adapter hurt the LED strip?

If YES or NO, can you explain in DIY homeowner language please?

I think the 5050 SMD is a 3 diode / resistor strip designed to run at 12vDC constant voltage.

I understand that using more than 12vDC will burn out or shorten the diode hours - like a 5amp 18vDC power supply from old laptop is a bad choice.

Yes I know the LED vendors sell new 5 amp 12vDC wall adapters for powering the whole 5 meter reel (16+ feet). I may end up buying new but prefer free.

If I want shorter LED lengths, I desire to reuse DC wall adapters from old electronics IF it doesn't damage the LED strips. ( I have a box of adapters kept from old... printers, phones, cable devices, alarm systems, keyboards, gaming systems, etc) .

I just bought from ebay auctions: 1 reel of 300 LED SMD 5050 $11.50 and 1 reel of 600 LED SMD 3528 $8.01. ($19.51 no tax no shipping - doing this on the cheap). Cool White. 1 reel is 5 meters long (16+ ft) LED flexible strip lighting with 3m tape backing.

The rating for these is 12 volts DC. Ebay merchants indicate the SMD5050 working curent is1.2 amps (1200mA) per Meter (39") of LED strip. The strips can be cut every 3 leds which is .05 meters (2 inches) which therefore uses 60mA per 2 inches.

If my calculator is correct; a 12" long strip is 360mA (.36 amps) 12vDC. Seems like overkill to use a big 5 amp wall adapter. I have an old uniden 9vDC 360mA and would like to reuse it.

The SMD3528 LED strip working current is even less - about .8 amps per meter.

Thanks in advance for your thoughts and comments. I know one of you is shaking your head right about now but constructive feedback would be appreciated.

Cheers - Mark

Other sidebar question is how do you know if a power supply adapter is regulated or unregulated? I read somewhere to only use regulated adapters (don't know why). I think the old Malibu low voltage lawn lights power is 12 volts but not sure if it is ok for LED strip lights.

Follow-Up Postings:

RE: Are 12v LED strips damaged w 9v Adapters?

You aren't going to get so much light out of them if you drop the voltage to 9V, but it will not hurt anything.

Is that Mailbu 12v DC? It needs to be, connected with the correct polarity.

RE: Are 12v LED strips damaged w 9v Adapters?

It looks like the leds have been pre wired with a resistor under the Heat shrink tubing.
It is stated that the current would be 30 mA at 9 Volts.

Here is a link that might be useful: The led strips I got from

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