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Power calculation

Discussion in 'Power Supplies' started by dpavisic, Jul 27, 2014.

  1. dpavisic

    dpavisic Full Time Elf

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    I have the following lights and am just wanting to check my calculations for how much power they will use and what power supply I will need.

    http://www.aliexpress.com/snapshot/6008549881.html. These lights are 12 v

    According to the website they use 0.30 watts per light so for every string of 100 they will use 3.0 watts. If I use a 600watt power supply @80% load this gives me 480 watts of usable power. In other words I should be able to run around 160 strings (with suitable power injection) from the one power supply.

    This seems like a huge amount of lights from the 1 p/s but I would like someone to please confirm this as power is not a strong point for me. I think I followed the formula in the 101 manual but maybe I stuffed up somewhere.

    Many thanks
     
  2. David_AVD

    David_AVD Bite my shiny metal ass!

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    Umm... 100 x 0.3W = 30W, not 3.0W but may be a typo so you'll have to revise that calculation.

    I made a LED current calculator that may be of interest. it's on my web site here.

    I don't know if I'd trust the wattages quoted on Ray's site.
     
  3. OP
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    dpavisic

    dpavisic Full Time Elf

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    Umm no that was not a typo and was exactly the mistake I could not see. Feel like an idiot but at least I got a calculator for future reference :)

    Thanks so much
     
  4. davrus

    davrus Silent Elf

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    You will be safer using 0.6W for each node. In real life, 100 pixels will use about 5.5 A when all are white. (I am just testing mine right now). So I calculate 6A as the draw for 100 pixels when sizing my power supplies.
     
  5. David_AVD

    David_AVD Bite my shiny metal ass!

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    My calculator shows the 2811 strings to be 5.55A per 100 pixels, so that's good to get confirmation with a real world example. :)
     
  6. OP
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    dpavisic

    dpavisic Full Time Elf

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    David your site is fantastic and full of very useful ideas.

    Thanks again
     
  7. plasmadrive

    plasmadrive Full Time Elf

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    Not strings but strips (should be close) I measured 3.3 to 3.6amps with all white, center fed between two one meter sections of Plasma Icicles.

    So actual per meter of WS2812 (5v) strips was 1.15-1.3amps per meter (including drop for connectors, cable and flexible PCBs), no more than one meter length from any power injection.
     
  8. David_AVD

    David_AVD Bite my shiny metal ass!

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    Obviously any strip figures will vary a lot depending on how many LEDs per metre.
     
  9. plasmadrive

    plasmadrive Full Time Elf

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    Aaahh.. good point.. mine were 30 LEDs per meter.. and 5v type.

    I also found that some strip manufacturers use heavier copper... They cost more, but they don't have as bad of voltage drop issues for longer strings.
     

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