Power injection help needed.

[mcompanik]

Bear with me as I try to explain what I am doing.  I am doing 2 DMX grids of 1696 12v nodes each for a total of 3392 from HolidayCoro. I am using their AlphaPix 16 controller for the grids because it can handle 5440 nodes (more than I need) with power injection. Here is how I have it set up: Each output controls 212 nodes. I am injecting power after the 26th node. Between node 26 and 27, I cut the power wire, capped the end that comes from the controller, attached the power from a separate 350w power supply, left the data wire alone, and spliced in the negative from the separate power supply. I do this 3 times with each 350w power supply. I also connected the negatives from each power supply together per HolidayCoro's diagram. The nodes that are connected from the controller and before the power injection are working fine, but after the power injection, they aren't lit. I know I am missing something here that must be fairly simple, but for the life of me, I can't figure out what I am doing wrong. Thanks in advance for any help or guidance you guys can give me.

[k6ccc]

In general terms, your procedure for power injection is correct with one exception.  If I'm understanding your description, on each string there are 186 nodes beyond the power injection point.  That is likely too long.  A good rule of thumb is to not exceed 100 nodes (at 12 volts) from where where ever power is being provided.  The reason for this is the amount of current that needs to be carried for the strip or string exceeds the current carrying capacity of the wires or PC board traces.  That results in excessive voltage drop to the end of the string.  However, this is not why it's not working.  From your description, I don't see any issues with the procedure.  Can you give a little more detail on how many power supplies you are using, and what the arrangement is.  By that I mean something like: "Power supply #1 feeds the controller only.  Power supply #2 feeds strings 1 - 4 from the 27th pixel to the end of those strings.  Power supply #3 feeds strings 5 - 8 from the 27th pixel to the end of those strings, etc".  Do you have a voltmeter and can confirm that the pixels are getting power of a reasonable voltage?

  If you have not read it, I would suggest taking a look at this explanation (starting about half way down the page): https://www.doityourselfchristmas.com/wiki/index.php?title=Power_Injection

 

 

[Dennis Laff]

4 hours ago, mcompanik said:

Bear with me as I try to explain what I am doing.  I am doing 2 DMX grids of 1696 12v nodes each for a total of 3392 from HolidayCoro. I am using their AlphaPix 16 controller for the grids because it can handle 5440 nodes (more than I need) with power injection. Here is how I have it set up: Each output controls 212 nodes. I am injecting power after the 26th node. Between node 26 and 27, I cut the power wire, capped the end that comes from the controller, attached the power from a separate 350w power supply, left the data wire alone, and spliced in the negative from the separate power supply. I do this 3 times with each 350w power supply. I also connected the negatives from each power supply together per HolidayCoro's diagram. The nodes that are connected from the controller and before the power injection are working fine, but after the power injection, they aren't lit. I know I am missing something here that must be fairly simple, but for the life of me, I can't figure out what I am doing wrong. Thanks in advance for any help or guidance you guys can give me.

Why are you injecting at pixel 26 you can inject at 100 should be fine 

[BMurray]

Like Dennis mentioned..Why at pixel #26. 12 volt are good for up to 100 pixels. In your case I would inject at the halfway point at the 107th pixel. I'm  not positive but I'm sure the end result to the last 6 pixels on either end would be negligible. Especially if your not running them at full power. I have some small matrices with 186 pixels each (my first year with matrices) . Myself,  I power inject at the end of my run at the 186th pixel. You may be able to try that instead. Instead of splicing in the middle inject at the end of the run...... ********make sure you put an in-line fuse to each of your power injection lines********. I am though using 1 power supply and an alphapix4  to run my 4 smaller matrices.  I'm sure there are different rules for using (2) power supplies

[mcompanik]

Here is my setup: Power supply 1 runs the controller and the first 26 nodes on all 16 outputs. Power supply 2 runs nodes 27 - 212 (186 nodes) on 3 strings. The reason I did that is if 50 nodes draw 27 watts (per HolidayCoro), I should be able to run 550 nodes under 300 watts and that gives me an extra 50 watts for power loss. Each power supply is running 3 strings from node 27 - 212, so a total of 558 nodes. This is repeated for power supplies 3-7 also. Since it should be fairly easy to do, I am going to cut the number of nodes from each power supply in half by injecting power at the end of the string and see if that helps. If it works, I'll just have to buy more power supplies. With that being said, I know I want the power supplies as close to the nodes as possible, but what would be the max distance I could go from the power supply to the nodes if each 350 watt supply was running 279 nodes using SPT-2 wire?

[TheDucks]

according to the Alphapix chart you should be able to run 100 8mm nodes ( up to 5A ) on all 16 outputs (80A PSU)

using a 350W PSU does reduce this to 1.5A / output. IF you are driving ALL WHITE.

Distance is your enemy a high current. SPT is 18 (or 16) Ga and will drop quite a bit every ROUND TRIP 10'  If you need distance (because you can't locate PSU's near injection), run heavy Ga wire to the point, then use a small gauge jumper to make the connection to the string. use copper wire

 

 

[Little_b]

I think you're on the right track.  With power supply #2 Pixels 27- 212, if I read it correctly you only have it connected at pixel 27.  You will need to connect it to pixel 212 (the end) as well.  I would also suggest connecting at least once more, if not in two spots, in the middle.  Do the same with the other power supplies.  I don't think you need to add power supplies, just the number of times you inject power from them.  I don't know how well these pics will be, but here is how I have part of my 63 x 126 pixel matrix wired.  I have 630 pixels powered on each power supply with a total of 12 power supplies.  I know it pushes the limits a little, but I don't use all white all at once.

[k6ccc]

I'll jump in here again to agree that you need to at the very least inject power at the end of the strings.  Note that if you are powering a string (or in your case, the last 186 pixels of a string) at multiple points but from the same power supply, you do not need to cut the positive at each injection point.  You only need to isolate the positives when it is from different power supplies (as is your case at pixel 27).

I agree that you have enough power supplies, it's just the distribution that needs some attention.  Also, as has been mentioned, make sure to include fuses.

 

[mcompanik]

In my original post, I said I must be missing something simple. I was. It was a polarity issue. I am so used to using 120v and regular strings where the polarity doesn't really matter. I went through and fixed everything, so now they all light the way they should. Now to tackle my setup issues with doing a matrix. I am going to start a new topic. Thanks to everyone for all your help.

[k6ccc]

4 hours ago, mcompanik said:

In my original post, I said I must be missing something simple. I was. It was a polarity issue

You are really lucky that you did not kill pixels!  With DC, polarity is VERY important!

Glad you got it working.