When controlling lighting equipment, the compatibility of the lighting controller will be lost if the standard of the control signal is not unified for each maker. Therefore, a standard called "DMX512" was developed to unify the control signals of each manufacturer and lighting equipment. Let's study about such DMX512 this time.
DMX512 is a digital signal communication standard that was started and has been revised by the American Institute of Arts and Technology (USITT). One digital cable can exchange light control data for 512 channels, and can control the signal of each channel in 256 levels.
Normally, each piece of lighting equipment has an input terminal and an output terminal, and each piece of lighting equipment is connected in a daisy chain fashion. In addition, it is recommended to use a terminator (termination resistor) of 120Ω for the output terminal of the last lighting device in the chain. The terminator can be manufactured by using an off-the-shelf product ( HOSA DMT-414) or by connecting a 120Ω resistor to pins 2 and 3 of the XLR connector.
About connection cables DMX cable , and for XLR 3-pin digital cable of AES / EBU cable . If you use a microphone cable or audio cable instead of a DMX cable, the lighting equipment may malfunction because the data is prone to errors.
It is possible to connect up to about 400m, but it changes with the environment, the cable used, the number of lights to be connected, etc. If the number of lighting devices to be connected is large or the connection distance is long, it is recommended to use a buffer amplifier as needed.
The DMX lighting equipment handled by Sound House use XLR3 pin or XLR5 pin, and the phase of the signal is Pin 2 for DATA - and Pin 3 for DATA +. If you use equipment of a different phase in lighting from other companies, it is necessary to match the phase using a phase conversion connector etc.
The DMX channel settings to be used are set for each piece of lighting equipment.
※As an example, suppose that there are 3 devices that require 5 channels of DMX data to control the operation.
The number of DMX channels that can be output depends on the specs of each controller, but the controller sends the same data to all lighting devices, so the connection order of the lighting equipment is not decided.
When setting a DMX channel, there are cases where the setting is made with a small switch called dip switch, and when a number is displayed on the display and a DMX channel is set with the up / down button etc. In the case of dip switches, channel setting is performed by adding binary numbers. Refer to the table below for DMX channel settings using dip switches.
In general, the number of lighting devices and the number of channels are the criteria for controller selection. When there are few lighting fixtures or when performing dimming lights such as par lights that require a lot of control in real time, it is easier to control a controller with a fader for each channel, and channels used for moving heads, effects, etc. For machines with a large number of controllers, controllers with memory functions are more suitable.
DMX controllers output only DMX signals. Therefore, when controlling a light bulb such as a par light, it is possible to adjust the brightness by using a DMX-compatible dimming unit. The dimming unit can not be used for power transformers or motor control. It is necessary to perform ON / OFF control with a DMX compatible power supply unit with a switch function.
If it is a DMX compatible lighting device, control can be performed with the controller by connecting a digital cable and setting the channel.
* Some controllers may not be able to control without special settings on the controller side.
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