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I have two LED stips salvaged from a LED TV. I only have these to LED strips and the ribbon cable that was connected to them from the TVs screen and not other PCB boards or components to help power the LEDs.

I would appreciate if someone can help me figure out how to power these two LED strips. I have very little electrical experience. Most Google searches for Led strip calculation are based on the length of a strip, but these are not the normal led strips from a roll.

The LED stips have various codes printed on them, but the code CL-550-072-V1-L and Google pointed me to this page whith what is seems the exact same model: https://eastern-star.en.made-in-china.com/product/UXyxNGmKYMYf/China-Es-Eled-063-Cl-5500-72V1-R-L-Eled-TV-Backlight-Use-for-Phi-Lips-Cl-55-Inch.html

From that page I gather:

  • Power: 0.5W/LED
  • Voltage: 3V/LED LED
  • Quantity: Rigth:72 LEDs Left:72 LEDs

I could not find information if the LEDs are in series or parallel.

Here is an image of the power connector on one of the LED strips: https://imgur.com/Jrz7pz4

Not the best picture. But each connector has only 1 row of connectors. The connector has a single connector with a pair of (+) and (-) on the strip, and an un-used connector in the center (the cable has no wire there). Additionally what looks like single (+) and (-) exposed for soldering?.

Questions:

  • Does that mean each LED needs 0,17 Amps (0.5 Watts / 3 Volts)?
  • How do I calculate the power requirements for the whole strip or both strips?
  • Any recommended power supply / driver that supports dimming?

Update

I borrowed a multi meter and measured the continuity of the strip. It seems that a single strip of 72 leds are wired in 4 series sets of 18 Leds each. There was continuity between diodes 01 - 19 - 55 - 72.

Could that mean that my required power supply should be the following?

Volts
18 Leds * 3 V = 54 V

Watts
72 + 72 Leds * 0.5 W = 72 W
+ 20% overhead = 90 W

Amps
90 W / 54 V = 1.66 A

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    \$\begingroup\$ What's the motivation for using these likely unknown and under-specified LED strips? If financial then what's the risk of not having any reliable information or guarantees? \$\endgroup\$ – Andy aka Mar 16 '20 at 13:33
  • \$\begingroup\$ @Andyaka: I have a very dark area in my apartment and wanted to try out this experiment (youtu.be/8JrqH2oOTK4?t=22). I tried using a 12v led strip as mentioned in the video but that was far-far from bright enough. So I thought why not just use the TVs LEDs that I assume would be brighter and will hit the acrylic and diffuses correctly. \$\endgroup\$ – Skuli Axelson Mar 16 '20 at 13:51
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Edit: I didn't see that you calculated for 2x72 leds or 8 series, so your calculation is correct. 2x36.72W You can buy two supplies of 1A each or one supply of 2A. Here is the calculation I did: 0.17A for each serie of 18 LEDs. Each serie being 54V (this is true), the power for each serie should be 0.17*54=9.18W. Four series in parallel would need 36.72W and a total of 4*0.17A=0.68A at 54V. You will need for this a 54V supply with at least 1A (You don't need twice as much, that's a rumour.)

I strongly recommend an adjustable supply (most supplies are adjustable) and to regulate the voltage to less than 54V (for example 50V or 52V if it's too dim) to be safe with temperature. Maybe a 48V supply would be enough if you can regulate it to 50V. (ask/check before buying)

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Does that mean each LED needs 0,17 Amps (0.5 Watts / 3 Volts)?

P = V * I <=> 0.5 W = 3 V * I => I = 0.5 W / 3 V = 0.17 A

So, yes.

How do I calculate the power requirements for the whole strip or both strips?

72 + 72 leds * 0.5 W = 144 leds * 0.5 W = 72 W

Any recommended power supply / driver that supports dimming?

Use a power supply that has some headroom (more power than you need). For dimming, I cannot give an answer.

However, as AndyAka says in his comment, you can better buy a new one, knowing the specs. From China, these are very cheap anyway.

Update

About the amperage … if the LEDs are 3 V, you should use a 3V power supply (although I never saw LED strips with 3V).

For the amperage, you can use P = V * I again:

72 W / 3 V = 24 A

And to have some headroom, use e.g. 30 A.

Actually this is really a lot, but 3 V is very low. You might even think about using some transformer from e.g. 24 V or 12 V to 3V and using a lower amperage.

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  • \$\begingroup\$ Thank you for the answer. What would the Amperage requirements be for the power supply? \$\endgroup\$ – Skuli Axelson Mar 16 '20 at 13:53
  • \$\begingroup\$ I'm asking the above because power supplies have output ?V by ?Amps = 72W (+power overhead of maybe 10-20%). \$\endgroup\$ – Skuli Axelson Mar 16 '20 at 14:35
  • \$\begingroup\$ I updated my answer \$\endgroup\$ – Michel Keijzers Mar 16 '20 at 14:49
  • \$\begingroup\$ I borrowed a multi meter and measured the continuity of the strip. It seems that a single strip of 72 leds are wired in 4 series sets of 18 Leds each. There was continuity between diodes 01 - 19 - 55 - 72. \$\endgroup\$ – Skuli Axelson Mar 16 '20 at 16:48
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    \$\begingroup\$ Does that mean that the input voltage should be 18 * 3 V ? Maybe a good idea to get some lab power supply and gradually increase the voltage. \$\endgroup\$ – Michel Keijzers Mar 16 '20 at 17:32

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