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What is DMX512? How does DMX512 controller work?

Views: 0     Author: Anny     Publish Time: 2021-05-12      Origin: https://www.suntechleds.com/

DMX512 is a digital communication network standard commonly used to control stage lighting and effects. Originally intended as a standardized method of controlling dimmers, it is now the primary method of connecting controllers and dimmers, as well as more advanced fixtures and special effects equipment.


1. What is DMX512 ?


DMX stands for Digital Multiplex or Multiplexed Data Transmission. It is a digital communication network protocol used to control lights, such as stage lights and fog machines. The DMX protocol is how your lighting system gets information about operations from your console or software.


DMX applications cover everything from indoor and architectural lighting to electronic billboards. Others include controlling Christmas lights, bridge lighting, stadium lighting and arena concerts.


  • It uses the electrical standard RS485. This is a two-wire balanced system - logic "1" has 5V on line A, line B is 0V, and logic "0" has 0V on line A and 5V on line B. (Actually only a 0.2V difference is needed between A and B). The system is very robust and can withstand a variety of failure conditions.


  • The DMX wires should be terminated with a 120 ohm resistor on the A and B wires of the last fixture (in real life this is usually not installed and everything still works).


  • It is an asynchronous (non-clocked) serial protocol with 8 data bits.


  • It runs at 250KBaud (bits per second).


  • Up to 512 control channels can be sent over the wire.


  • Each control channel can carry a value from 0 to 255.


  • The start of each "packet" of 512 channels is marked by an "break time", which is a logical "0" lasting at least 88 microseconds.


  • If more than 512 channels are required, use a second DMX line (another physical line). Each 512-channel block is called a "DMX universe".


More read: How to choose a power supply for your LED strip?


Analysis of DMX512 protocol format

The DMX512 control protocol stipulates that data is sent in the format of a data packet, and each data packet contains several data frames. The format of the data frame is shown in the figure below:


1


(DMX512 data frame format)


The DMX512 protocol has certain requirements for the data transmission rate, the typical transmission rate is 250kbps. The corresponding duration of each bit is 4μs, and the duration of each data frame is 44μs, and the protocol also stipulates that each DMX512 data packet supports a maximum of 512 frames of data transmission at a time. The format of DMX512 data packet is shown in the figure below:


DMX512 data packet format

(DMX512 data packet format)


The DMX512 protocol stipulates that data packets must be transmitted in accordance with the specified format and transmission baud rate. The format of a complete DMX512 data packet consists of an MTBP (Mark Time Between Packages) signal, a BREAK signal, a MAB (Mark After Break) signal and an SC (Start Code) signal, and other data frame. 

More read: How does the WS2812B LED light work?


2. DMX controller


Modern RGB lighting offers a variety of options for home, commercial and architectural applications, and when combined with control methods such as DMX, can reach its full potential. Controllers are usually divided into four control modes, which are:


- Zone or circuit selection (select individually addressed cells or circuits)

- Color selection

- Dimming/Fade Control

- Program selection (Chase, Strobe, etc.)


The first step is to select the unit or unit selection you wish to control, depending on the DMX controller, how many individual selections you can control.

You can then choose the color you wish to set, which is covered in more depth in the "Packet Architecture" section below, but the base controller uses a rotary dial to make this selection, and the more advanced allow you to enter specific values.

The dimming and fading aspects of the controls can then be set, which combined with the color selection can produce the exact shade of color you want to achieve.

Finally, any programmed "effects" you wish to use can be set. Again, depending on the controller, basic effects (like chasing) can be set up, or on more advanced models you can program your own.




3. DMX512 controller module function


The DMX512 controller is divided into the following 6 functional modules, and the functional requirements for each functional module are as follows:


(1) LED light strip:The LED light strip is the main part of the controller that needs to be controlled. It is made up of full-color LED lights connected in parallel or in series. The display data is transmitted on the light string through the data line, so that The LED light string displays a specific effect.


(2) Manual control: The manual control part realizes manual control and adjustment of the controller, such as menu selection, switching of presentation effect files and adjustment of refresh rate between data packets, etc. Manual control is realized by buttons.


(3) LCD status display: The LCD part is mainly to provide a friendly operation interface through which the user can see which effect file is currently being demonstrated, the basic information of the effect file, and the refresh rate of the current demonstration file.


(4) SD card data: SD is used to save effect files, so if you want to replace the original demonstration effect, you only need to save the newly generated demonstration effect file to SD without modifying the controller and light string.


(5) PC-side online debugging: The PC-side online debugging is mainly to download to the controller immediately when a demonstration effect is generated, which facilitates the design and modification of the effect file. If the demonstration effect is ideal, the effect can also be directly saved to SD Card.


(6) Controller software: The control software part is the core part of the controller system. The main function of the controller is realized in this part, and other functional modules of the controller are combined and called to realize the controller's control of the LED light strip.


DMX controller connection line


This article provides a basic overview of DMX light controllers and how they work. You can apply this information to your settings. DMX light controllers can be used in a variety of environments, from large installations to intimate lighting setups.

If you have any other questions or further requirements, welcome to contact us. We will be glad to help you with any problems.



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