DMX512

The DMX system was created by the United States Institute of Theater Technology (USITT) in 1986 to standardize lighting and stage effects control. It quickly became a universal standard and, after minor revisions, received the final name DMX512/1990 in 1990. In 2005, several changes were made to the standard's specification, and since then it has been called DMX 512-A. Currently, the system is used worldwide for lighting various artistic events (and beyond). Regardless of the event size, this solution is used at major concerts and festivals.

Basic Information about DMX512

One DMX line has a total of 512 channels, each of which can have a value between 0 and 255. Large concerts can use up to several hundred such lines. Of course, for small systems used by DJs or bands at various dance events, weddings, etc., 1-2 DMX lines are perfectly sufficient, especially since, according to the recommendations, one line can support up to 32 devices (PAR lights, moving heads, LED BARs, fog machines, etc.). The popular, free FreeStyler DMX software supports up to two DMX lines (Universe 1 and Universe 2), for a total of 1024 channels.

Connecting Devices via DMX

The system is connected in series, meaning that a break in the circuit will disconnect the devices after the fault. The order in which the devices are connected is not particularly important; rather, we should pay attention to aesthetics and hiding tangled cables (unless we want them to be visible ;) ). Devices "see" each other in the system only by their DMX address. For example, the first device connected by cables can operate at address 050, for example, and the fourth at address 001. The DMX address is one of the most important pieces of information required to run the system; you'll find more information later in this article. The system sends the signal in one direction, meaning the controller doesn't receive feedback on whether all the devices in the show are connected. This means that if we program scenes for four heads and only connect one, it will function correctly (aside from visual issues). The exception is the RDM system used in more expensive models; it allows for two-way information exchange, such as addressing and changing selected parameters from the controller. Devices should be connected using dedicated DMX cables. Because we're transmitting a digital signal, the cable should be shielded and have an impedance between 85-150 ohms. According to the standard, 5-pin XLR connectors should be used, but in practice, especially in cheaper devices, 3-pin sockets are installed. This allows for the use of microphone cables, which usually prevents system errors. The maximum total length of all cables in a single line is 300m.

Each DMX line, regardless of the number of devices, should be terminated with a DMX Terminator, a plug with a properly soldered 120-ohm resistor. This eliminates signal reflections, which in extreme situations can even cause signal loss. In practice, this is usually not necessary, but it's a good idea to have at least one in your cable kit for emergency use.

DMX Address

Devices connected to the controller operate on specific DMX channels; the specific number is described in the user manual. Each channel is responsible for a specific function, such as brightness, vertical or horizontal movement, strobe, etc., so the number of channels used will depend on the device's capabilities. For example, a simple RGB PAR spotlight will use at least three channels, separately for red, green, and blue. Channels for brightness, strobe, and additional functions such as auto programs or dimmer curves may also be added. A moving head will use at least a dozen channels, and the most complex devices can exceed a hundred channels. Why do we need this information? It's essential for correctly addressing devices in the system. Each device should be addressed to the first available channel, remembering that a single DMX line has a total of 512 channels. Example - we need to address 4 spotlights, each occupying 7 channels. The first spotlight will receive address 001, the second - 008, the third - 015, and the fourth - 022. As you can see, the address is the DMX channel number to which we assign the first channel of the next device. You can, of course, leave a blank space between the devices, for example, addressing the lamps from the example above to addresses 001, 010, 020, 030. However, it is not allowed to address them so that the channels overlap, e.g., 001, 005, 007, etc. Software controllers like FreeStyler automatically assign the next device the first available address when adding devices to the work window, so there's no room for error. The next step is to address the devices themselves. The address in the controller must match the device's address. It's important to pay attention to the appropriate DMX mode in the device – most models allow you to change the number of channels used, for example, they can operate as 10-channel or 14-channel devices. If the DMX mode doesn't match the one used in the library (fixture) or in the control software, this will change the function for that channel (e.g., instead of brightness, the lamp will activate a strobe), so this is very important. Addressing the device itself is as simple as selecting the appropriate address in the device's menu. If in doubt, it's best to consult the user manual. This is more difficult if you have switches instead of a display; positioning them correctly will address the device to the correct address. In this case, I recommend downloading a simple app on your phone – DMX Calculator. Enter the required address, and the screen will display the switch settings.

DMX Controllers

Controllers can be broadly divided into two groups: - Computer programs – these require a suitable USB interface or Art-Net gateway, or a dedicated wing, and, of course, a computer, to run the system. The cost of such a system depends on the program's DMX interface requirements. For example, FreeStyler, QLC, etc., work with many models from various manufacturers, with prices starting at around 100 PLN, such as the KaMOD 512 (USB DMX interface operating in the Enttec Open DMX standard) or the KWMATIK PROMYK (Art-Net gateway). There are also programs that require their own interfaces, such as ADJ MyDMX, Chamsys MagicQ Basic, and ChamSys MagicQ Compact Connect. These devices unlock the program's features; please note that they do not work with third-party software. - DMX consoles – these controllers do not require an external computer. Typically, these are more expensive solutions than software controllers, with costs ranging from a few hundred złoty to several hundred thousand złoty, such as the ChamSys QuickQ 10. Cheaper solutions tend to have fewer capabilities than computer controllers and are more difficult to program. However, the most expensive models are true powerhouses with powerful capabilities, used for applications such as large festivals, such as the grandMA3.