pixel question

cam080

New elf
Joined
Jan 23, 2020
Messages
7
Hi All,

I'm in the process of putting together a mega tree.
I have set it all up on the ground to test it out just so I know it's working.
I found 3 dead pixels out of 2400, which I thought was quite good. They weren't completely dead, just not displaying a certain colour. I went ahead and replaced those 3 pixels.

When setting the strings back up and testing again, there seemed to be more dead pixels, approximately 3 again, nowhere near the original 3. These were definitely not there when I tested the first time and I definitely replaced the correct ones as I marked them while they were on.

Any ideas what could cause this?
 

djgra79

My name is Graham & I love flashing lights!
Generous elf
Joined
Dec 27, 2011
Messages
1,583
Location
Cranbourne West
Are these 5v or 12v pixels? Double check the voltage output form the PSU and at the pixels is not above what they are supposed to be.
 

cam080

New elf
Joined
Jan 23, 2020
Messages
7
They are 5v pixels.
If the voltage was over 5v and above what it should be wouldn't it effect more than approx 3 pixels out of 2400?
 

Dreamin

Full time elf
Joined
Dec 28, 2016
Messages
179
Location
Sunshine Coast
Causes could be plug issue (had that before), power related for 5v you should be power injecting every 100 pixels. I've had stuff where I plugged it in and it hasn't worked properly, then taken a step back and tested and checked and it was my fault, not a dead pixel.
 

cam080

New elf
Joined
Jan 23, 2020
Messages
7
I used one of the online calculators for voltage drop and it seemed I could have a string of 200 pixels and power inject at the end (200). So I can go 100 pixels up the tree then 100 pixels down, that way I don't have to do any injecting at the top of the tree.
This seems to work but just have these random 3 pixels out of the entire lot that seem to be having issues.
I may just end up putting up with it as I don't think I will have time to fix it up, slowly running out of time.

Same thing happens on lower brightness settings
 

cam080

New elf
Joined
Jan 23, 2020
Messages
7
Can't say I have tried that. I have a few, suppose it is something that's pretty easy to try
 

Dreamin

Full time elf
Joined
Dec 28, 2016
Messages
179
Location
Sunshine Coast
I used one of the online calculators for voltage drop and it seemed I could have a string of 200 pixels and power inject at the end (200). So I can go 100 pixels up the tree then 100 pixels down, that way I don't have to do any injecting at the top of the tree.
This seems to work but just have these random 3 pixels out of the entire lot that seem to be having issues.
I may just end up putting up with it as I don't think I will have time to fix it up, slowly running out of time.

Same thing happens on lower brightness settings
What you have to remember is power runs both way. I'm not sure where the random pixels are, but if they are around the middle between the power injection area that might be what's causing it. What percentage of power are you running your lights at? Is the lead to from the controller to the tree long? Remember this will have a voltage drop too. I might be barking up the wrong tree but one test I would do would be a white test and see if pixels before the ones appearing dead are showing signs of going pink/red as power drops off.
My 24x50px tree is 50 up, then cut 5V, and the next 100 pixels (ie at the bottom) are injected on a separate fuse 5V, then cut and next 100 the same. Probably OCD but it will run at 100% that way if I wanted it to and everything is fused separately. I run 3 ports of 400 for a 1200 tree off a differential receiver. The only issue I had with the tree was config in controller.
 

TerryK

Retired Elf
Joined
Feb 9, 2020
Messages
121
Location
West Central Ohio
I do not see it mentioned yet but with 2400 pixels you are using multiple supplies, yes? Are the supply's common (negative) connections tied together for a good data line reference?

If the pixels were replaced and the problems moved, assuming nothing else changed, my first suspicion would be a data line problem; noise, poor connection(s), negative reference, etc.

You mentioned that the pixels were not completely dead, just a color or two. If possible I would also suggest picking a color, say red, and increment the drive level slowly to determine if all the pixels show red. Starting slow will minimize voltage drop problems. Determine if 100% red works, then turn red off and do the same with green and blue. This will prove the pixels are all right and the problem lies within power injection, power supplies, cables, controller, and/or software.
 
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