DMX-512 (Digital Multiplex) is a standard for digital communication networks that are commonly used to control lighting gear such as LED fixtures, dimmer packs, lamp remote heads and more – the DMX receivers,
A single DMX network (aka “DMX universe”) can control up to 512 channels.
Most likely a lighting console is used to control the DMX channels along with its parameter 0 -100% level for each channel. With a lighting console this parameter is typically varied by a fader.
A single channel parameter has a resolution of 8 bits > 256 steps available, commonly used for dim control.
Because the DMX-512 standard is a serial signal all DMX receivers need to be daisy-chained in one line. From the DMX output of the transmitter the DMX cable is hooked up to the first DMX receiver at the DMX input. From its DMX output it´s linked to the next receivers´DMX input, etc.. Never mind the order of the DMX receivers!
A maximum number of 32 DMX receivers may be used in one DMX universe.
The DMX address
Each DMX gear needs to be addressed – the DMX channel. Commonly you need to define the “DMX start address” for each unit. LED fixtures often use more than one channel. The additional channels are used for the adjustments of dim control, color temperature, green/magenta, etc. This “DMX map” of a gear mode defines a function for each channel. Here you can see two examples of a DMX map of Arri´s Skypanel-C.
If the sent DMX address matches the receivers´DMX address its channel parameter from the sender will be applied.
The last DXM gear in the serial line should be terminated in order to prevent a malfunction caused by signal reflection in the DMX cable. Either there is a “Termination” switch or it´s auto-terminated, you need to do this! If there is no such function of the fixture you should plug in at the very last DMX output a “terminator plug”.
A DMX plug should NEVER be pulled off during operation!
Regulated within the DMX specifications the last command will be hold until it´s overwritten with a new signal.
It means if you pull the DMX plug on hot signal you will not be able to control the lamp unless a new DMX signal will overwrite it, or you reset the unit.