Pixels Not Lighting Up White

[Max Kabilafkas]

Hi

I have the following channel in my display. Each of the tree strings are 50 node 5v pixels.


When I try to turn all three strings on to a white or near-white colour, strings 2 and 3 do not turn on (string 1 lights up fine). When I switch to any other solid colour, all three strings light up correctly.

I know that white draws more power than other colours so I have double checked my power injection wiring to string 2 and it all seems to be connected correctly.

Also I am running the pixels at 30% brightness which should be way below the power limit of the power supply.

Any suggestions to what I am doing wrong?

Thanks

 

[djgra79]

Have you placed a multimeter or clamp meter on the 2nd or 3rd strings to see what the voltage measures, to confirm your checked wiring? If running at 30%, that might be enough to power the single colours but not white which is a mix of all 3.
Are you sure the controller output is setup correctly for the number of nodes connected? Maybe an off channel is to blame. Not sure just throwing it out there.

 

[Max Kabilafkas]

I'll check that out djgra79.

Also I just realized that this might be a problem? Is it bad that my power supply which is doing the power injection is also connected to a different channel (also 5v)?

 

[djgra79]

Is that power supply also powering and supplying pixel power via the controller output, or is it a different PSU? If the latter, are you able to show that in your diagram?

 

[i13]

In your diagram, I can't see a reason for the problem that you're describing but there is room for improvement. Looking at that diagram, the question that I immediately want to ask is whether the same thing happens on both outputs of the controller.

In order to reduce the maximum distance from the power supply to the furthest pixel, I have attached a diagram showing power injection in both directions. In your current setup, the furthest pixel is 100 pixels away from the injection point. In the setup that I have drawn, the furthest pixel is 50 pixels away from the injection point. I don't think this is the cause of your problem but keep it in mind if you see voltage drop problems at the end of string 3. I'm anticipating a possible future problem here, not suggesting that this would fix your current problem.

Addressing your current problem, you do have a negative loop. At worst, this might cause a very slight flicker in rare cases so I wouldn't worry about it. It is, however, possible that the negative wire is broken somewhere. My guess is that it is broken between strings 1 and 2. If so then you have a circular path so that the negative can circumvent the breakage. This could cause the symptoms that you're describing. In order to follow the circular path and get around the breakage, the current needs to travel around a longer path, resulting in more voltage drop and a poor data reference at the beginning of string 2. You're seeing this when the pixels are turned on white because that's when there's the most current and therefore the most voltage drop.