Right power supply for 5050 led strip

Question

I have 5050 led strip 60 led/m, and I have a power supply I want to use to power it on Now I got some specs online (not sure if right ones?) for 5050 which say:

150 LED Count: 36W

Now, say I want to have a strip of 50 leds. Does it mean they will draw 12W? My power supply says PSA15W-120. Does it mean 15 watts at 120V?

• How do I know that this power supply will not burn the leds?
• Why don't I need a limiting resistor here?

Some other specs for this strip will talk about current consumption, but not sure how to go about it in calculation.

Now if my power supply is 12V and leds draw 12W, will the current be 1A? Now I have to say that ofcourse I did connect the strip to the supply and it works, but how do I know that neither is get damaged over time?

I know there are a few questions here, but for a seasoned electonicist probably are no-brainer. I appreciate any help or reference to a relevant article.

Answer 1

For your LED strip you need to know if it is supposed to be constant current or constant voltage supplied. Luckily it says DC12V on the strip itself, so it's constanst voltage with 12V.

You don't need limiting resistors as they are built on the strip (see those three little black things near the LEDs? Those are the limiting resistors).

You power supply has it's specs on the label: 12V 1,25A. So it has a maximum power of 15W.

The voltage is okay. As for the power, that's a bit difficult without knowing the exact specs of the strip, but if we take those you linked, you have calculated correctly - 50 LEDs will take 12W, which is 1A on 12V.

You are supplying the right voltage and you don't draw to much current, so everything is within specification and I don't see how there should be any premature aging happening here if the strip stays cool (glue it on an aluminium profile for example).