Answered Grounding question when using multiple power supplies

[johnson8ryley]

I couldn't really find a concrete answer on this but I think I know the right answer.
I'm outlining my roof this year in 12V INK1003 5m pixel strips (600 pixels total) and I plan to inject power at the end of each strip (there are 4 strips connected in series along the roofline).

Since my roofline is long, I plan to use 2-3 different power supplies located at each strip to inject power instead of trying to inject power from one power supply possibly 60ft away to the last strip.
The question I have though is: to ensure all power supplies have the same ground, do I simply run a wire to connect all the power supplies ground together? I have some 16/4 security wire that I plan on using and I think that would be sufficient to tie all the grounds together.

I'm sure this question has been asked somewhere but I couldn't find it upon searching and I just want to be safe than sorry. Thank you guys in advance!

 

[LightmeupAucklandNZ]

I just run all my data and ground wires together then when i want to inject i used the extra red and white wire at the end of my strips to inject but i make sure that the positive from last PSU isnt connected. So pretty much just use a new PSU and have the ground and data flow through. I dont ground all my PSU as there all connected to the same power source. Correct me if im wrong but thats what i been doing and it seems to work all fine

 

[TerryK]

Ground (which refers more to the AC supply side) isn't quite the correct word to use, but yes, as a general rule the DC negatives are tied together to form a DC Common. The 16 AWG is a bit light I think. I suggest using several if not all 4 conductors although it would depend somewhat on distance between supplies and what their wattage ratings are.

 

[johnson8ryley]

I just run all my data and ground wires together then when i want to inject i used the extra red and white wire at the end of my strips to inject but i make sure that the positive from last PSU isnt connected. So pretty much just use a new PSU and have the ground and data flow through. I dont ground all my PSU as there all connected to the same power source. Correct me if im wrong but thats what i been doing and it seems to work all fine

I'll wait for others to chime in but that's why I'm not sure if I even need to connect my grounds together is because technically all of my power supplies are connected to the same power source (my house). So they are all getting their grounds from the same source theoretically, but I wasn't sure if their individual grounds needed to be tied together to ensure a "good ground" amongst the whole pixel rooftop.

Your layout and wiring sounds very very similar to what I have in mind so I'm glad its working for you! Thats good news for me I think

 

[johnson8ryley]

Ground (which refers more to the AC supply side) isn't quite the correct word to use, but yes, as a general rule the DC negatives are tied together to form a DC Common. The 16 AWG is a bit light I think. I suggest using several if not all 4 conductors although it would depend somewhat on distance between supplies and what their wattage ratings are.

Each PSU is 350W and they will be spaced about 30ft apart approximately. And thank you for the clarification because I was referring to the grounds as I thought all grounds needed to be shared. But it's actually the DC negatives (aka -V) that need to be tied together?

 

[LightmeupAucklandNZ]

This is my whole display i only used 2x 350watt PSU all my pixels were at 20% brightnes. So with me it was less PSU.

 

[johnson8ryley]

Ahh I think I see what LightmeupAucklandNZ was referring to. But if this is the case, I don't see a point of running a wire to tie the DC negatives of the power supplies together.



Edit: wow I guess I went overkill on buying 4 350W power supplies for my roof alone

 

[TerryK]

I'm sure you will get other individuals opinions.

You're in the US. To maintain NEC Code compliance, the power supply's AC Ground terminal (different from the DC - or negative terminal) really should be properly connected to an earth ground system. In the US, that is the 'U' shaped post of the standard 120VAC plug. At the other end, a green wire, bit rare but possibly green/yellow.

The DC minuses, or negatives in most cases are tied together. Refering to the graphic you posted; first the use of GND is not correct. Next, as the DC negatives are not directly connected, there is no DC common as such. Connection of the DC negatives is indirect through the negative pixel string wire. That means that whatever voltage drop (rise) exists in the pixel string negative wire is effectively shifting the next supply's negative upwards (positive) as referenced to the previous supply.

BTW. Does the website work (lightsoflincoln)?

 

[johnson8ryley]

I'm sure you will get other individuals opinions.

You're in the US. To maintain NEC Code compliance, the power supply's AC Ground terminal (different from the DC - or negative terminal) really should be properly connected to an earth ground system. In the US, that is the 'U' shaped post of the standard 120VAC plug. At the other end, a green wire, bit rare but possibly green/yellow.

The DC minuses, or negatives in most cases are tied together. Refering to the graphic you posted; first the use of GND is not correct. Next, as the DC negatives are not directly connected, there is no DC common as such. Connection of the DC negatives is indirect through the negative pixel string wire. That means that whatever voltage drop (rise) exists in the pixel string negative wire is effectively shifting the next supply's negative upwards (positive) as referenced to the previous supply.

BTW. Does the website work (lightsoflincoln)?

I think I follow what you're saying Terry and I really appreciate your knowledge. The first graphic is actually pulled from the AusChristmasLighting guide. But I'm assuming when you say "the use of GND is not correct" that the picture should be labeled with DC negative and not actually GND.

Secondly, I follow what you're saying how the only DC common is indirect from the connection of the new power supplies between each strip and the negative pixel wire string. However, I don't know enough about circuity to understand why the voltage drop rise in the negative wire affects the next supplies negative upwards. But I think that is beside the point.

To be safe and compliant, you're saying I should run a wire similar to the new diagram below were all of the PSU DC negatives are connected directly
Edit: yes, all of my power supplies will have a 3 prong AC ground connected. I'll be using the standard 120VAC plugs to supply power and ground to all PSU's.


lightsoflincoln.com doesn't work just yet but it will be up here soon I have a friend of mine building the website for me hopefully in time for the show.

 

[Dez]

We ensure all the ground wires are interconnected through the pixels then into the power supplies. No need to run a seperate wire between power supplies outside of the pixel strings

 

[ezellner]

The issue of V- varying between power supplies is that the data signal needs to have a common base. If the V- varies from one power supply to the next, the data signal will have a different V- reference for each leading to pixels not reading the correct data. By tying the V- of all power supplies together, the base for the data signal is the same throughout.

 

[TerryK]

Each PSU is 350W and they will be spaced about 30ft apart approximately. And thank you for the clarification because I was referring to the grounds as I thought all grounds needed to be shared. But it's actually the DC negatives (aka -V) that need to be tied together?

When connecting DC negatives, if the supplies are in close proximity I definitely would. If spaced further apart it becomes more difficult to determine which is best, connect or not connect. For supplies separated 30 feet I probably would follow what Dez suggested, that is let the pixel string negative wire couple the power supply's negatives albeit indirectly. Why or why not? Because that will create a circular current path in the negative power circuit and circular current paths are just about always never good.

 

[johnson8ryley]

You guys are awesome, this is why I love this forum.
So essentially I "could" run into data problems by not tying the V- together, but I should be fine since each PSU is only about 30 ft apart from one another.
Also Ezellner thank you for your explanation about why different V- references impact data signals. That makes more sense now.



So I could follow this diagram and be safe hopefully? Let data and V- pass through from pixel to pixel but don't inject +V when using multiple power supplies.
If I have any problems with this setup, then I know my problem is because I didn't directly connect my DC negatives

 

[johnson8ryley]

I'm glad I'm getting this clarified now because I also have 6 holidaycoro candy canes where the first cane will be powered from the controller, but the other 5 will be powered from a separate power supply