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Please help with my calculations!

Discussion in 'Power Supplies' started by Dez, Jan 12, 2019 at 5:51 PM.

  1. Dez

    Dez Fueled by Christmas - Inspired by You! Generous Elf

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    Hi,

    I am wanting to create a pixel matrix which will be 1200mm x 1200mm and the I will be using WS2811 bullet pixels from Ray Wu spaced at 50mm apart.
    I am having some trouble working out how to calculate how many power supplies I will require. I am almost 100% confident that my calculations are incorrect. Where I have written "power" is where I plan on power injecting. Can someone please help me out here? Based on the attached drawing, below are a few questions I need answering and possibly explain how you got to this answer so I can better understand.
    1. Do I have the number of channels correct?
    2. How would you get Ray Wu to make up your pixels for this?
    3. What is the total light load and how to calculate?
    4. What strength power supply to use?
    5. Would you consider 5V a better option for this and why?
     

    Attached Files:

  2. Nuzzy

    Nuzzy Apprentice Elf

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    1/ Channels would be 484 x 3 = 1452
    2/ ask him to make up either 22 stings of 22 pixels or 11 strings of 44 pixels @ 3 inch spacing.
    3/ rough specs are approx 0.8w per pixel, 0.8 x 484 pixels = 387 watts.
    4/ assuming 80% efficiency for power supplies you would need 387 / 0.8 = 484 watt power supply rounded up to a single 500 or 2 x 250 or 300 watt supplies.
    5/ 5 volt uses 0.3w per pixel so it would be 484 x 0.3 = 145w, assuming 80% efficiency them you would only need 1 x 200w power supply.

    Power injection as per your drawings for 5 volt (every 44 nodes) or half as much for 12 volts (every 88 nodes).
     
    Last edited: Jan 13, 2019 at 4:28 PM
  3. OP
    OP
    Dez

    Dez Fueled by Christmas - Inspired by You! Generous Elf

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    Ok that makes sense. Thank you very much
     
  4. AAH

    AAH I love blinky lights :) Community Project Designer Generous Elf

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    1200 x 1200 at 50mm spacing works out to 25x25. (24 spacings of 50mm). This is 625 pixels and 1875 channels.
    Pixels are generally 55mA each regardless of the voltage. This means the full load current on white is 34A. A 12V 400W supply is rated to 33A so that's right at the upper limit. A 5V supply of 200W or more will do the kob.
    Strings of 50 at 3" spacing should do the job. The wire length is typically what the pixels are specified by so 4" wires is probably what you want.
     
  5. OP
    OP
    Dez

    Dez Fueled by Christmas - Inspired by You! Generous Elf

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    Ok thank you. When I say 1200 I was meaning from the outside of the material so I was allowing the outside pixels to be in from the edge but I understand what your saying.
     

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