5v WS2811 power injection

dariansdad

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Jan 16, 2012
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Knoxville, TN
In the attached drawing, I have a representation of one side of a burst I have built. There will be an identical left side but I didn’t want to clutter up the drawing more than it already is.
I know I have to inject power to these pixels as denoted in the top picture. The reason for injecting every 25 pixels is, there is a 4 foot gap between pixels 25 and 26, 50 and 51, etc. The wire running between these pixels is 16 gauge, 3 conductor, SPT-2
My question is:
Should I add a ground wire to the negative side of the pixel wires too, (as denoted in the bottom drawing), or will the SPT-2 and the actual pixel ground wire suffice? If my understanding is correct, this would be a common ground. If that is not correct, could someone please explain what a common ground is
Thanks for any insight,
Ron
 

fasteddy

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You need to connect both the +5v and the ground at the injection points assuming you are using one power supply to power this up, this ensures you complete the power injection circuit or else your strings will be taking the whole ground load to complete the circuit and you will still see voltage drop issues.
 

battle79

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Also note in your drawing, that the green lines in the bottom picture are ground/common. We don't have a -5V at any point. You need to connect to the 5V and the ground at each point of injection.

Generally, each injection point should run all the way back to the PSU as opposed to looping between the injection points. In your case the injection cables are short enough that you could probably ignore this if you using 16guage.

If using two separate PSU's, i.e. one for each half, you need to run a cable from one to the other ONLY on the ground. This creates the common ground you may be thinking of. If using two supplies make sure that the 5V from the first supply is not connected to the 5V from the second supply, especially in the middle of the pixels where you cross to the new PSU.

Hope that helps more than confusing,
Rowan
 

dariansdad

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Jan 16, 2012
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Knoxville, TN
5v and ground at each injection point and don't loop the 2. I think I have it figured out now. Once I get it wired back up ill test it to see if everything lights properly and check the voltage drop.
Thanks guys.
 
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