Power Injection — Ground needed?

Eebado

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Nov 27, 2021
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Maybe a stupid question, but do you have to run a ground wire to power inject? (when injecting from the same run and power supply).

As in, if I split my line after the fuse, ran one side to pixel 1, and the other side to pixel 100, would I need to connect ground or would just running the 12v line be enough and safe?
 

AussiePhil

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You ALWAYS should run the pair of wires, this is not really optional as current always flows on both pairs and without the second ground wire you just double the current on the single ground and hence increase further the voltage drop on the ground circiut.

Cheers
Phil
 

Eebado

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Nov 27, 2021
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You ALWAYS should run the pair of wires, this is not really optional as current always flows on both pairs and without the second ground wire you just double the current on the single ground and hence increase further the voltage drop on the ground circiut.

Cheers
Phil
The part about doubling the current on ground makes sense. I wouldn't say its "not really optional", as it is optional as long as the gauge of wire on the other ground has the ability to carry the additional current.

So technically, it's feasible. It's not a great idea as it could cause the other ground wire to fail and it shouldn't be done.

But, it could be done...
 

CargoLights

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Interestingly, it can sometimes be enough just to run an additional ground wire, but if you're running positive you almost certainly need to run an additional ground. Further, if you are using a separate power supply, you have to tie the grounds together at some point as well. Keith Wesley did a good video that goes over what is needed for power injection (and why) very well:

View: https://videos.xlights.org/vcs-2020-ever-wonder-why-you-pixels-flicker-and-how-to-fix-it-keith-wesley_5e9cff233.html
 

AussiePhil

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The part about doubling the current on ground makes sense. I wouldn't say its "not really optional", as it is optional as long as the gauge of wire on the other ground has the ability to carry the additional current.

So technically, it's feasible. It's not a great idea as it could cause the other ground wire to fail and it shouldn't be done.

But, it could be done...
quite honestly "not really optional" = "technically it's feasible"

for the sake of KISS principle the pos/neg should be run as a pair in DC systems like we use.
 

raymondclow

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Nov 25, 2021
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just to chime in and maybe kill two birds with one stone....i watched the above video in search for my issue of flickering, i then just ran a ground wire to the end of the pixel string and the flickering stopped since i remember watching a video that mention that sometimes is the ground that needs to be doubled up! now...does it matter where I inject ground on the string of lights or does it have to be at the end? can it be doubled at the port in the falcon? dont mean to highjack the thread but seems like it's in the same area. thanks!
 

i13

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Jul 5, 2013
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A risk that has not yet been mentioned here is that if you power through the controller at the beginning of the string, you should always inject the negative if you inject the positive. This is because if you inject only the positive, the only path for the current to complete the circuit through the negative is through the controller. Controllers generally aren't fused at the negative so that'll potentially be the failure point.

raymondclow, I think your flickering issue might have been caused by a poor negative reference for the data. You might have a bad negative connection somewhere. Sometimes connecting the negative elsewhere will compensate for this but it won't actually fix the bad connection. The negative can be injected anywhere but I would suggest having the nearest negative injection point to the controller no further than the nearest positive injection point for the same reason as above. I would not add additional wires to the Falcon's negative output port unless you do the same thing with the positive again for the same reason.

In summary: You don't want the negative current flowing through the controller to be more than the positive current because only the positive is fused there.
 
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