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170 pixel P12R limit and 7.5A conflict?

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by nutz4lights, Jan 21, 2013.

  1. nutz4lights

    nutz4lights Full Time Elf

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    Hey all,

    I have been trying to do some planning for this year and I'm stuck on one thing. I have another thread related to the specific application, but this is more of a general power draw and J1SYS P12R question. DISCLAIMER: I do understand where I need power insertion below, even if I don't specifically mention it.

    The P12R has twelve fused outputs. The outputs are fused at 7.5A per output. There are two banks of six outputs, each bank can do a max of 30A. So, there seems to be a common recommendation toward 5V when using WS2811 pixels (in regards to the 12V pixels generating excess waste heat and maybe not lighting the LEDs as bright if I understand the gist of the sticky thread '12V versus 5V lighting'). The P12R also can connect up to 170 pixels per output, and that is where my problem lies.

    For my application, I want to have 300 WS2811 pixels on an artificial tree around 2m high. 300 pixels x 0.3W per pixel is around 90W. Now, ideally, I would be want to use two outputs from the P12R so that I could put six of these trees on one P12R controller (the trees will all be within a 5m area). The P12R can do 150 pixels per output, which is great! Only problem is if I use the 5V WS2811 pixels... 150 pixels is 45W (150 x 0.3W / pixel) and using 5V would require 9A on one P12R output... which is fused at 7.5A. I assume someone has run into this type of thing already, right? What is the general thought here? I know I could use three outputs with 100 pixels on each output which would be 30W (100 x 0.3W / pixel) requiring 6A @ 5V), but then I would need to buy four of the P12R units instead of two (an additional $350 + power supply + casing).

    Of course, I could go with 12V WS2811 pixels. I would run two outputs with 150 pixels on each, which still requires the same 45W per output (150 x 0.3W / pixel), but because of the 12V pixels, I would only use 3.75A per output, well within the 7.5A fuse limit... but then I have the issues associated with 12V pixels. The 12V pixels also cost $0.06 additional each, which is $200 more for all the trees (still less than purchasing two extra P12R units, with a power supply, with a case, etc).

    So, I am looking for some recommendations here on how to proceed. I am ready to order pixels and am stuck on which approach to go with... are the 12V pixels really that bad?

    Thanks!

    -Louie
     
  2. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    If you refer to the P12R manual it will show some examples of connecting the P12R, the examples you may be needing is option 4 (pg 11) and option 6 (pg 12) This shows you how you can use multiple supplies to your pixels.
     
  3. OP
    OP
    nutz4lights

    nutz4lights Full Time Elf

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    Thanks Eddy. That looks like a great option and got my brain going in a different direction that I was this afternoon... I have one more question. In order to make the cabling a bit easier, is there any reason I can't feed the data/clock/ground in at one end (pixel #1 let's say) and the power in at pixels 50, 100, & 150? Let me know if that doesn't make any sense and I will try to create a picture of what I'm talking about.

    Thanks,

    -Louie
     
  4. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    You can do it that way as well, just make sure that the voltage drop as the begining of the string is low enough that it doesnt cause data issues.
     

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