A few questions concerning power injection on RGB pixels

[Reinout]

Hello everyone! My name is Reinout and I'm an art student from the Netherlands. I've always been inspired by all the amazing Christmas displays I've seen online and on this website. For my graduation project I'm planning to build an 6000 RGB pixel tunnel that reflects the beauty of light. I have only 3 months to build and program this 60 square meter display and I really need some help.

So, I'm not from Australia and I'm not working on something direct Christmas related... why am I here? Well; I figured that all the professionals on Christmas lighting are right here! Most of the information and tips I collected came from this forum so it was a logical step to me to ask you for help.

I will be building a modular system made from custom plastic sheets (I worked for a plastic extrusion company a couple of years ago). These sheets will be lasercut into nets that kinda look like HolidayCoro's Pixnode nets. Every net is 1 square meter and will contain 100 LEDs, that's a pitch of 10cm. I will use 5V pixel nodes and will run it at about 60%, so power injection every 100 LEDs should work out. I'm not entirely sure if my wiring is correct, this is a rough drawing I made to show you my plans.

(12v PSU should be 5V PSU)

I will use the T-500K controller, it has 8 channels each controlling 700 pixels. Every net of 100 pixels will have 2 input cables with 2 pins. 1 cable with negative and data from the previous net and 1 cable with positive and negative from the power supply.

These are the questions that I'm struggling right now:
1. Is my wiring correct or do I need to connect the negatives of the power supplies together?
2. Can I power 700 5V led's from 1 big power supply (with power injection every 100 pixels) and do I need a power distributor?

I'm hoping you want to help me out, even though this isn't 100% a Christmas project. And if people are interested in how this project turns out I'm more than happy to keep you updated.

Cheerio!

 

[AAH]

Hi Reinout
A couple of issues 1 of which you noted being the 12V power supply that you drew and noted below.
6000 pixels (at full 100% white) will draw around 330A so you will need several power supplies depending on what wattage they are. It's 1650W total so you will probably be looking at at least 6 of them assuming that they are 350-400W supplies and allowing for them not to be loaded to 100%.
You need a ground/-ve connection from the pixel inputs back to the T-500K
Depending on how far it is from the T-500K to the 1st pixel in a run you may need to put in a null pixel or something like my "null pixel buffers". A distance greater than about 5m can present problems.
You need fusing on the positives coming from the power supplies.
Ideally you should have power (- and +) injected at both ends of those strings of 100. If they were 12V pixels you could probably get away with powering from 1 end but with 5V you can only drop about 1V before you get into problems.
Safety-wise you are better off isolating the positives on each of those runs of 100 but performance-wise you will get a better voltage (most of the time) if you continue the 5V for the full pixel run and tap into it every 100 pixels. When you have the same brightness/current on each section of the run then there will be no benefit but when 1 section is using more current than another the current can be sourced via that connection.

In a shameless plug for something that may be handy for what you are doing my Power8 power distribution board has sufficient fusing, and also contains a null pixel buffer, in order to power 1000 pixels at 100% load.

 

[Reinout]

Thank you very much for your relpy, that's very helpfull to me! I got 9 power supplies, just to be sure for now. The null pixel story is absolutely new to me but I think the data cables are short enough to avoid any problems. I hope all the products come in next week. I did a test on the lasercutter and it actually worked quite well.

 

[Reinout]

I'm having some issues with the T500K LED controller right now. There is very little documentation online about this controller so this might bring some issues.
Will post some updates soon.