Pixels a beginners guide
This is the place to start off learning about Pixels. NOTE: individual controllers, pixel strips / nodes, troubleshooting, and other non basic items will not be covered on this page please look for the correct page for your specific questions.
So you're interested in learning about pixels, they are an amazing technology that is growing rapidly in DIY lighting. Throughout this intro there will be some concepts that may be difficult to soak in all at once, refer back to this as necessary.
Terminology: A basic list that you should become familiar with when using dc RGB systems
Dumb RGB: these are known as dumb strips and can also just use the term RGB. In a dumb RGB strand positive voltage is applied to all lamps, the colors and intensity is selected by the resistance of the ground felt on 3 wires labeled r, g, and b. As resistance is increased on one colors ground wire, all the elements in the string of that color are dimmed. In Dumb rgb the entire string is controlled as one, individual lamp control is not possible.
RGB Pixel: these are known as smart pixels and can also just use the term pixel. In a RGB pixe strand positive and ground are applied to each lamp and each pixel has an ic chip that controls the resistance of ground felt on the color elements, in this way each ic chip can be individually addressed and the lamps that that ic chip controls can be different than the ones before or after it. When buying strips you may see notes like 30/10 or 60/60 these numbers represent the number of lamps per meter / the number of ic chips per meter, if the numbers dont match then lamps are grouped having one ic chip control more than one lamp. In a 30/10 strip of 5 meters, there is 150 lamps (30*5) but only 50 ic chips or pixels (10*5) so in this case each pixel is 3 lamps. In a 60/60 strip each lamp is individually controlled (5 meters would be 300 pixels and lamps).
Also when buying strips you will see that the lamps come in 2 sizes 5050 (5.0 mm x 5.0 mm) and 2832 (2.8 mm x 3.2 mm) do not confuse this number with the number of lamps / ic per meter this is simply the size of the lamp. You also will see the term smd, all this means is surface mount device... all flexible strips have all their stuff surface mount so this is not really needed to be said.
A basic idea of how RGB work versus the more traditional lighting in computer controlled shows:
Traditional lighting and its controllers function like a dimmer switch on the wall: the light is on or off and varies in intensity based on the position of the dimmer switch. Each dimmer switch is its own channel and a show consists of several to several hundred switches. To help ease the amount of boxes most of these switches are conveniently placed in groups of them on a board, you will find boards that have 4, 8, 12, 16 or even up to 48 switches on a single board, allowing for one connection to control a great number of lights.
NOTE: There are some controllers that do not support dimming but they are not mass produced by the DIY community anymore.
These boards are controlled by a signal generated by a computer running software that sends the signals, the boards figure out which switch is being referenced in the signal and adjusts the correct switch making all lights plugged into the switch dim/brighten.
Pixels are different in that one switch does not control the whole lamp; instead each pixel is comprised of 3 lights, one red, one green, and one blue. So each pixel needs 3 "switches" to make it function.
How the lamp is controlled defined as either dumb rgb or rgb pixels.
In a dumb RGB strand/strip, the 3 switches control the entire string of lamps, these are usually located on the board much like traditional controller boards. Like traditional lights the entire string lights up the same color, though they can be any color you choose. We generally cannot use a dumb rgb board to control rgb pixels, nor can we use a rgb pixel board to control dumb rgb.
NOTE There are a few boards available that do have the ability to control either but they are usually 1 or 2 output boards and are used infrequently in the DIY community.
In a smart pixel, in these there is a chip that controls each of the red, blue, and green elements in each pixel. (so Pixel No. 1 can be red, Pixel No. 2 can be green and Pixel No. 3 can be — well, any color you want). In a smart pixel string there can be a lot of smart chips emulating several hundred switches depending on the number of pixels. Smart pixel controllers send a signal down a wire that makes sure each light element gets the signal that is supposed to go to that element. Smart pixels each pixel can be any color at any time.
All rgb either dumb or pixels run on direct current (DC) this is not the household electricity in a wall socket or light bulb, household electricity is alternating current (AC) and the wall socket can be 110 volts - 220 volts depending on what country you live in. RGB need a power supply much like in your computer or cell phone charger, this converts the AC in your home wiring to DC and at the correct voltage. RGB run on either 5 volts or 12 volts, a 12 volt board will burn up a 5 volt pixel string so its very important to match the board to the RGB voltage.
RGB also come in a variety of profiles:
- RGB bullets look something like traditional lights — there is a "bullet" and then a run of wire and then another pixel "bullet," and so on. But remember, each one can change color.
- Square RGB are like bullets, except each lamp is a one-inch by one-inch by one-quarter-inch plastic box. Again, box and then a run of wire and then another box and so on.
- Pixel bulbs look like traditional C7 or C9 bulbs — about 1-1/2 or two inches long with a frosted or faceted cover. Like bullets and squares, each element is separated by a length of wire.
- RGB strips (which come as either rigid or flexible) are long, narrow printed circuit boards that have lamps attached every few inches. The lamps can be close together or far apart — space is varied by what you want or is available.
It is up to the individual as to whether to use bullets, squares, bulbs or strips based on how you want your lights to look. All function the same, only their appearance is different.
As you can see, there is a lot to consider when opting for RGB.
A quick overview of how the boards receive their signals
There is a myriad of different protocols that are used today, think of different cell phone companies, there is no right or wrong protocol just as there is no right or wrong cell phone company. The protocol is just a way of getting the signal from your computer to the controller board. The pixels themselves have their own native language they speak, but just like your cell phone its range is limited, usually less than 20 feet between individual pixels. The protocol then is used to carry that native language to the various controller boards, and is able to cover the distances needed between controllers and computer. Some boards will need a bridge to convert the carrier protocol to a signal that can communicate with the board, check with your individual board to see what is needed.
Identity and pixels
How does each switch know what part of the signal applies to it? For illustration here we will use the addressing system used in DMX protocol this should give you a general knowledge of how addressing works. Here we need to think of your phone number, each switch is assigned a number by the computer software, just like a phone number there can be enough different numbers that it will be hard to know what is what. We have area codes on our phone numbers to help distinguish what goes where, in the DMX world we divide switches up into a 512 switch grouping and call that a universe. When talking about a signal each switch is referenced as a channel. We then assign the bridges or boards to "listen" to certain universes. We can even assign boards to only select certain channels inside of that universe. Note: Some of the protocols do use a different addressing system, while the number of channels grouped together may vary depending on the protocol used the application is the same.
So we have an idea of how the pixels and protocols work, now lets cover some basics about the controllers that manage them.
Please note specific boards is beyond the scope of this wiki and will not be answered
In a dumb RGB board the board is assigned what universe and what start channel it is supposed to use. In a dumb controller, output 1 is the first 3 channels assigned to the board, output 2 is the next 3 channels assigned to the board and so on. Dumb RGB controllers can, for example, control 3 channels (a single strand) to 27 channels (9 strands) and beyond. You can hook together more than one strand just like you can hook traditional lights together, all strands connected together will be the same color.
In a RGB Pixel controller board the board is not directly assigned universe or channel numbers, instead each output on the board is assigned what universe and channel number it starts with. Instead of having the switches on the board there are smart chips in the individual RGB pixels directing the settings on each of the 3 elements (red, blue, and green), so the board sends a native language signal out on each output that starts with the correct universe and channel that is assigned to the output, the data is sent along a wire ensuring each RGB pixel gets the correct channels to the correct pixel elements. You can connect several strings of lights together using this, additional strands are still individual pixel controlled.
So we have covered the general concept of pixels hopefully this will help to clear some of the fog.
Further reading
Please look over these wiki's they expand on some of the topics mentioned in this.
A little more advanced reading these get into the "meat" of these topics
The next wiki in this series