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LED Christmas Lights Power Calculations

LED Christmas Lights Power Calculations


Although the WS2812B LED strips use tiny LEDS, and the power draw is relatively small, when you start multiplying that times hundreds of them, the current needs climb quickly.

Most sources will tell you that the RGB LED in the WS2812B strips require 20 milliamperes per color at full brightness.  A milliampere is 1/1000 of an amp and also referred to as mA.  So an LED running just red at full brightness will draw 20 mA... full brightness red and blue to make purple would require 40mA... and all three colors to create white, at full brightness, needs 60mA.  I've read people's real-world tests that come under 60mA, but I'd rather plan for the maximum and have some wiggle room.

Based on my rough measurements, I'm guess-timating that I'll need 45 meters of LED Christmas lights, and I'm using WS2812B strips that have 30 LEDs per meter.  That gives me a total of 45 x 30 = 1350 LEDs.  1350 multiplied by 60mA results in 81,000mA or a huge 81 amps!

With the tests I did earlier, I know that running the LED Christmas lights at half brightness will still give me a great effect, and I doubt I'll ever want all the LEDs to be white, at full brightness, at the same time.

So, as far as my particular project is concerned, I'll look at providing 40 amps for the entire project.  My power source will be a computer PSU converted to a standalone power supply.  PSUs have a lot of amperage.  Another bonus is that on top of the 5-volts they provide, I can get 12-volts as well.  Some of my wire runs will be long enough that I may have to account for voltage drops.  So, instead of running 5-volts to distance LED Christmas lights and finding out I only have 4-volts or less at the strip, I can run 12-volts (that will also lose some voltage, but stay much higher than 5-volts) and use a 5-volt converter just before the strips.

I will also be running a lot of parallel wires, rather than one wire and splitting it into a bunch of connections further down.  This will let me keep the amp load on each wire down, and will also let me add an additional PSU for more power and amperage if I want or need to.

Although I'll have about 45 meters of Christmas LEDs, about half of that will be on the garage soffit and the power supply will be in garage as well.  So I BELIEVE I'll be able to power all those with the 5-volt source on the PSU.  For the Christmas lights on the rest of the house, I'll probably rely on the 12-volt dropped to 5-volt method.  I'll have to start experimenting to see if I should buy adjustable buck converters, or if I can whip up a simple converter that will consistently put out 5-volts, regardless of the input voltage.