Why is DMX protocol control so stable?

Introduction to DMX512

The DMX512 protocol was first developed by USITT (American Theater Technology Association) to control the dimmer from the console with a standard digital interface. DMX512 surpasses the analog system, but it cannot completely replace the analog system. The simplicity, reliability and flexibility of DMX512 have quickly become the protocol of choice when funds permit. In addition to dimmers, a series of ever-increasing control devices are evidence. DMX512 is still a new field in science, with various wonderful technologies based on rules.

DMX512 design standard

DMX512 is designed around the industry standard EIA-485 interface. EIA-485 belongs to the "electric" end of interface, voltage, current, etc.The system is established based on downward symmetrical transmission along the shielded conductor twisted pair. This winding structure ensures that the generated interference will act on both signals equally, thus ensuring consistent digital phasing. The wire used should be a suitable data wire composed of one or two twisted pairs, foil and woven screen. Symmetric audio cables cannot accomplish this task.

Normally, like any network segment, there should be two terminals at both ends of the wire. The lighting console usually serves as a terminal at one end, while the other end should only have a 120Ω resistor. The EIA485 specification only supports a "daisy chain" or a serial network composed of up to 32 "unit loads" on each segment. The manufacturer claims that each segment can be as long as 1000m. However, it should be particularly pointed out that the role of the repeater should be considered about 700m or 800m, which can prevent environmental abnormalities.

DMX512 performance parameters

　　 1. Comply with DMX512/1990 timing, respond quickly without missing frames. 3 or 4 PWM channels (prefabricated optional).

　　2, pulse width modulation signal is greater than 200Hz, 0-100% range 256 level output

　　3, linear dimming possible (prefabricated optional)

　　4, weak brightness without visible flicker.

　　5, support address burner address programming

　　6, 74HC165 extended dip switch input address

　　7, automatic serial addressing.

　　 8. Signal regeneration function. A maximum of 512 three-color decoding chips (512A) can be connected in series

　　 9. There is no DMX512 signal, which can automatically run the colorful gradient color demonstration program.

　　10. Working temperature: -40℃~85℃ The pins can be factory configured

How to use dmx512 system?

The first correct link method

DMX controller---receiving decoder---LED lamps or DMX controller---LED lamps (lamps with DMX signal receiving chip)The DMX signal is a 485 signal, which is a parallel signal. The installation looks like a serial installation. Many people think that the signal is serial. In fact, the DMX signal is parallel. All the receivers below are connected in parallel to the output of the DMX controller. Online, if the address code is not distinguished, different receiving ends cannot be distinguished. Only by distinguishing different receiving ends can a variety of regular change effects be formed.

DMX512 supports 512 channels. If your "unit load" occupies 16 channels, you can only connect 32 "unit loads". Like general full-color LED lamps, RGB colors occupy 3 channels, DMX512 Each output of the controller can connect 170 lamps. If the DMX512 controller has multiple outputs, you can connect N channels*170 lamps.

Generally, the receiving end 2 receives the DMX signal input from the upper receiving end 1, and then transmits it to the next receiving end 3. It is the "daisy chain" method you mentioned above. This is not a "serial network", and a serial network is not needed. The address code only looks like serial in design, but actually comes in parallel, but the parallel signal lines are routed through the receiving end inside, but it is beautiful and convenient to install.

It is not necessary to use the "daisy chain" method. You can also pull out a main signal line from the DMX controller, and connect all the "unit loads" to this main signal line in parallel.

The second correct connection method

Controller---Receiving terminal 1---Receiving terminal 2------Receiving terminal n---Resistance---GND

This is correct. The resistance standard is 120 ohms, which is only used in traditional applications. We usually do not connect the resistance and grounding in the application of LED products. It has no effect on the use, but any product equipment is theoretically grounded. All are good. Ground it if you like it. Is it possible to use separate power supplies for each? This is not certain, it just depends on how easy your receiving end design is, whether you use one power supply to connect many or one power supply for each lamp.

The receiving end of DMX sets different addresses according to the installation order. According to the normal installation method, if the LED lamp occupies 3 channels (address), then the start address of the first receiving end is set to 1, and the second receiving end is set to 4. Set the third receiving end to 7....... Always set it like this.

When the DMX receiving end receives the DMX signal, it converts it to an analog signal to drive the LED.

Note: PWM is the signal sent by the DMX controller to control the brightness of the LED. The receiving end does not do any processing. The following are all received by each receiving end. It is the same command, but the receiving end has different codes, and the signal from the receiving end to the LED is different, so the LED can be combined to produce different changes.