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injecting power for modules on p12r

Discussion in 'EthConGateway by Joshua 1 Systems' started by candlelight, Mar 17, 2012.

  1. candlelight

    candlelight New Elf

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    i plan on building a matrix using modules on a p12r board. I also plan on injecting power every 40 or so pixels, question is when attaching the wires to the p12 board, should i just connect the clock and data wires to the board since i'll be supplying the strings of modules with their own power source?
    I will supply the p12r board with a seperate power feed for the logic.

    Seems like i wouldn't want to connect power to the board since i'll be using three power supplies...
     
  2. j1sys

    j1sys There are no rules, and those are the rules. Community Project Designer

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    you will also need to connect a common ground connection. all signal levels need a signal ground to work properly.

    -ed
     
  3. lithgowlights

    lithgowlights Senior Elf

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    I recently tested a similar setup. 2 5v supplies, one powering the P12R and one at the far end of the pixel string. I left the ground connected but split the +V line so the second half of the string was powered by the far end supply and it worked well.

    I did have a few misfires and they disappeared when I put a slightly thicker wire between the 2 negative connections on the supplies.
     
  4. OP
    OP
    candlelight

    candlelight New Elf

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    so are you thinking i need to connect all three V- on the 3 power supplies together? I thought it was a no no to connect power suplies together, or does that only apply to the V+ connection? I'm completely new to RGB so i'm still absorbing all the info I can....

    need to hookup the lights to see how much they pull, but there are 4 leds per module, and i'll have 12 strings of 40 modules each (12v ws2801)...

    i was thinking i'd hook up 4 strings (160 pixels) to each power supply..
     
  5. j1sys

    j1sys There are no rules, and those are the rules. Community Project Designer

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    yes. for most practical uses ALL grounds (-V) have to be common. some times people call ground/-V common for this reason. We've run a 1.5A 5V supply for P12R, 30A 5V for strings 1-6, and 30A 12V for strings 7-12. ALL have their grounds tied together on our circuit board.

    -ed
     
  6. fasteddy

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

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    By connecting the grounds/negatives together with the power supplies is just ensuring that all the power supplies have the same potential. This doesnt actually 'connect' the power supplies together as the + positives are not connected together. This is OK to connect this way and in fact is best practice

    So when connecting between strips, connect both the negative/ground wire and data wires together. Keep the positive + wire seperate for each strip and connect the positive + from the second power supply directy to the second strip only. Then connect/inject negative/ground from the second power supply to both the first strip and second strip which is connected together.
     

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