I have a question about PI from the rear.

S

Srmorgan

Member
I have a 12v run that wraps around 3 sides of my garage. I forget how many but I don’t think that matters. I have it running off of 2 power supplies. One on each end of the run. I know I don’t have to use two but I was new to the hobby. The first PS was already powering a bunch of lights and I didn’t want to run any long PI lines. The last 2/3 of the run is powered from the rear and the middle of that rear section(so about 1/3 the way from the back of the run). I kept having problems in the middle section that was only powered from the rear. I only had pixels go bad in that section. And I created problems for troubleshooting when pixels would burnout because it wouldn’t pass the voltage down the line so I would have to hook to the front section and unplug the rear power supply to figure out where the bad pixel was. I noticed this section had multiple pixels burn out over the years. The last time I had one burn out and I hook it up with the front section everything worked fine. When I took it back apart and hooked up the rear power supply again the pixels stopped working again. Hooked up to the front power supply and they all worked again. I have adjusted my PI since then and made everything PI’d from the front. I was wondering, does PI’ing from the rear cause problems for the pixels or cause them to burn out prematurely?
 
No, the pixels don't care where their power comes from. You might want to count the number of Pixels you have in that area, as you may be able to power them all if you run power around 20%. I have been amazed at how many Pixels I can run on one port at 20%. 280 - 300 no problem, many folks claim they have even more on one port with no PI.
 
Another thing to check would be the output voltage of the Power supply. They usually have a adjustment screw somewhere.
Check the voltage at the PI point, could be a problem with wire or connection. Good Ground?
And like stated above, I run most everything at 20%. Full brightness in most cases is just overkill. I keep my flood lights
and arches that have pixels in Pex tubing up around 100%.
Anyway, let us know what you find.
 
After reading through several times, and I'm still not clear, is this what you had.
A string of pixels powered from both ends from 2 different power supplies?
Wouldn't you have to cut or break the V+ in the string so the 2 PS's would not oppose each other?
Is that what you did? A pixel going bad usually stops Data from flowing not Power. Or am I wrong?
 
That is correct. I think there is about 270 pixels.I don’t remember the correct count but let’s say it’s 100 pixels. 1-33 is powered from the first power supply. The + is cut and the - is still connected. 34-100 is powered from psu 2 connected at 100 and 66. The middle section is the problem area. I’ve had them up for 4 years now and the middle is the only are to loose pixels. I could definitely run the whole string from psu 1 at 20% but I was excited and decided to overdo it a bit. I lost a pixel last month and noticed that that section would work fine if powered from the beginning so I adjusted it so that the 1st and 2nd section was powered from psu 1 and it works fine now. I was just curious why it was happening. What would happen was I would loose a pixel half way through the middle section. So the pixels from the front of that section to the bad pixels would turn off and behind the bad one would stay on but not change. I think what was going on was that the pixel wasn’t sending the power to the front so everything ahead of it would turn off. And with them off there was no more data to control behind. It’s not a big deal I’ll just make power from the beginning a standard practice. Just curious if there was more to this that I didn’t understand, or if it was a bad practice.
 
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