injecting power for modules on p12r

candlelight

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Feb 4, 2012
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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...
 

j1sys

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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
 

lithgowlights

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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.
 

candlelight

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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..
 

j1sys

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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
 

fasteddy

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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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