An interesting thing happened this past Christmas. After retiring my show I got bored and needed to find something to do. I decided to decorate my 12’ Christmas tree with 850 RGB pixels and programed it with several patterns. For the fun of it, I posted it to my Facebook page and the response was huge. People started sharing it, and I started getting lots of questions about how I did it.
It was then I realized the challenge of explaining RGB and DMX to people who knew nothing about it. It also became apparent that people wanted to venture into RGB but were holding off because it all seemed very confusing. In actuality, it’s all quite simple when you have a basic understanding of how it works.
So you may be asking yourself what is RGB? RGB stand for Red, Green, Blue. With a combination of these three colors you can produce millions of colors when blended together. If you have ever used a program like Photoshop that lets you select different colors with sliders, you have been working with RGB and may not have realized it. By adjusting the red, green and blue sliders in these programs, you get different colors. Each one of these sliders has a range from 0 to 255. If all of the sliders are at zero, you have black. If all the sliders are at 255, you have white. Anything in between is a color.
Now that you have a basic understanding of what RGB is, let’s move on to what a pixel is. A pixel is grouping a red, green and a blue LED into a single light. There are many styles of pixels, and each one has its own advantage. All pixels work on the same principle. By changing the intensity of the red, green and blue LEDs in the pixel you get various colors. There are two categories of pixels: dumb and smart. If you have a strand of dumb pixels they will all be the same color at the same time. Smart pixels allow you to control each one individually. A majority of light show people use smart pixels.
Since smart pixels are individually controlled, and every pixel has a red, green and blue LED that can have 255 different intensities each, how in the world do you make all of that work? This is where DMX comes into play.
DMX is an industry standard way of talking to lights and staging equipment. It’s actually quite easy to understand. Here are the basics. DMX has 512 channels. Think of a channel like an individual slot, or a plug on LOR. Each one of the slots can have a value from 0 to 255. Sound familiar? Each pixel takes three channels. One for red, one for green and one for blue.
In most cases the first pixel in line grabs channels 1, 2, and 3. The next pixel grabs channels 4, 5, and 6, and it keeps doing this down the line. This is called auto-addressing and most pixel strands will do this. Not all DMX lighting auto addresses. An example of this would be RGB flood lights. These lights require you to tell it the Start ID for that fixture. For example if you have two RGB flood lights, you would set the Start ID to 1 on the first flood, and 4 and the second one.
Because DMX only allows up to 512 channels you can only have 170 pixels. How did I get that number? If you take 170 pixels and multiply it by 3, because each pixel takes three channels, you get 510. The last two channels are not used, because we do not have enough channels left to add another pixel so technically they get ignored.
You may be asking yourself, If you can only have 170 pixels, how do those mega holiday shows with thousands of RGB pixels control them all. That’s a good question, and it’s not as difficult as you would think. When you group the 512 channels together, you create a DMX Universe.
If you need to run more than 170 pixels, you simply add another universe giving you another 512 channels. If you combine universe 1 and 2 together, you can control up to 340 pixels. Still need more pixels; move to the next universe. The good news is many DMX controllers like GeekMyTree, SanDevices, and Light-O-Rama (LOR) Cosmic Color products handle all of this for you automatically. The more universes the controller can handle, the more pixels you can have. It is not uncommon for large RGB shows to have many controllers.
The last piece of the puzzle is how do all of these pixels know what to do? In order for you to create all of the amazing patterns and color sweeps, your DMX controller needs to know where every pixel is. This is called a pixel map. Pixel maps are created in the software you are going be to creating effects in. In most cases it’s as easy as telling the software how many strands you have, and how many pixels per strand. The most popular packages for controlling holiday RGB lighting are MADRIX, xLights/Nutcracker, Light-O-Rama Superstar, Hinkles Lighting Sequencer (HLS) and LSP. Each package has its unique advantages.
If you are like me and learn better visually, you can check out my RGB 101 video on YouTube by searching for GeekMyTree RGB101. If you are still confused, feel free to drop me an email at firstname.lastname@example.org
This article was included in the April 2014 issue of PlanetChristmas Magazine.
By Brad Boyink