Step 1 – Check if the input of your strip is 12V

Step 2 – Check how many watts per meter your LED strip will consume

Step 4 – Calculate the estimated power usage

 -Total length of led strip of 30 led/m used for progect is 10m :  10m x 7.2w = 72w

Step 5 – Understand the rule of 80%

 -When choosing a power unit, it’s a good idea to make sure you are only using 80% of the rated power maximum to increase longevity          of the power supply and keep it cool to prevent overheating:  72w / 0.8 = 90w

Step 6 –  Put it all together to determine the amps of power supply you need

 -Amps = Power / Volt       90W / 12V = 7.5 A

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10 Answers

Steuk. (anonymous) 0 Comments

Thank you for this.

I have a question : The power supply will also power arduino nano, asl shield, 2 PIR, 1 light resistor…So we need to add some watts I guess. How many ?

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Arduino with all  this stuff will consume around 60 mA or less.. So no need to worry ..

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Steuk (anonymous) 0 Comments

Indeed, it’s nothing. But to know it is important !

Thank you for this information.

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John (anonymous) 0 Comments


You talk about 5050 LEDs. Consumption is about 0,2W per LED.

In my case, I have 15 stairs. I think I will put a 300LED/roll. So I’ll have 40 LED/stair. My total consumption will be 0,2*40*15 = 120W.

But I see that 3825 LEDs’ consumption is about 0,08W (per LED).

With this, it would be 0,08*40*15 = 48W…Better.

My questions are :

  1. Is my calculation correct ?
  2. Are the 3825 LEDs sufficient ? (since it’s only to have light at night I guess it’s OK, but maybe I’m wrong)
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Anonymous 0 Comments

Hi. Sorry for my late reply.

Here is some comparition between those two types.


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