Views: 0 Author: Site Editor Publish Time: 2021-08-03 Origin: Site
Lighting control is the use of automatic control technology and intelligent management technology to control and manage the opening, closing, adjustment, combination, scene mode, etc. of the light source or lighting equipment of the building and environmental lighting to achieve the linkage of building energy conservation, environmental art and sensing,etc.
1. Lighting control method
There are many types of lighting control methods, and the common ones include the following:
This is the simplest and most common control method: on/off, turn the light on/off, this is also the way to switch household appliances.
A more common dimming method has the advantage that it does not require a signal line, the cost is relatively low, and the installation is relatively simple.
0~10V is also a kind of control signal, used to control the power supply part of the lamp, so that the lamp can receive a signal of 0~10V. The simple understanding is to adjust the voltage to adjust the brightness. For example, when 0V, the power output is zero; and when 10V, the power outputs is 100% .
DALI system is mainly used as a control system for hotel and indoor lighting. Its biggest feature is that a single lamp has an independent address, and a single lamp or lamp group can be accurately dimmed through the DALI system.
DMX512 is mainly used for stage lighting and outdoor lighting. The specific control form is: WiFi, infrared sensor, remote control, human body sensor, etc.
Now, I will share the relevant content of DMX512 with you.
2. What is DMX512?
DMX512 in English is Digital Multiplex With 512 pieces of information (multiple digital transmission).
The DMX512 protocol was first developed by the USITT (American Theater Technology Association) to control the dimmer from the console with a standard digital interface. Contrary to DALI, which is used to express static effects, DMX512 is mainly used to express the dynamic effects of the illuminated object. That is, the lights controlled by DMX give people the feeling that they are constantly changing, mainly color changes, suitable for rendering atmosphere, so general applications In landscape lights and stage lights.
DMX512 control system: There are several RGB lights, each of which contains a DMX module. This module will drive the LEDs to change brightly and darkly when it receives the power supply and the controller signal adjust the color change at the same time.
3. Features of DMX512
Each output loop supports a maximum of 512 channels; Each output loop supports a maximum of 512 channels. According to the number of channels occupied by a single device, the maximum number of devices that can be carried by each port is determined.
For example, the output circuit is the general, the communication is the soldier, and the equipment is the dormitory. The headquarters stipulates that each general can command a maximum of 512 soldiers. According to the number of soldiers accommodated in each dormitory, the number of dormitories under each general's jurisdiction is determined.
RGBW lamp connection diagram
So how many lamps can one DMX512 port carry? How is the channel calculated?
256-level dimming grayscale (0-255)
Each DMX control byte is called a command frame, which is called a control channel, which can control one or several functions of the lighting equipment. A DMX command frame is composed of 1 start bit, 8 data bits and 2 end bits, and it adopts unidirectional asynchronous serial transmission.
The SC in the control command in the above figure is the start bit, and the width is one bit, which is the start mark of the controlled lamp ready to receive and decode the control data; E is the end bit, and the width is two bits, indicating the end of a command frame.
D0 and D7 are 8-bit control data, and their level combinations are from 0000-1111 1111 to a total of 256 states (corresponding to decimal numbers 0-255). When controlling the brightness of the light, 256 brightness levels can be generated, 0000~ (0) Corresponding to the darkest light, 1111 1111 (255) corresponds to the brightest light. The bit width (per bit width) of the DMX512 command is 4s, the width of each frame is 44s, and the transmission rate is 250 Kbps.
Standard EIA485 interface: The wiring method is a bus topology structure, and does not support ring or star networks. Up to 32 nodes can be connected on the same bus.
Structures: DMX512 must follow the first bus structure, with a head and a tail.
Transmission rate 250Kbps: Bit rate refers to the number of bits transmitted per second, bps (Bit Per Second). The baud rate is closely related to the construction specifications, and the anti-interference ability of high baud rate signals is relatively poor.
4. DMX512 precautions:
In actual operation, it is not enough to just understand the characteristics of DMX512. In order to avoid engineering accidents, we must remember the following 5 points for attention:
(1) The transmission distance of the super five network cable is not more than 100 meters;
(2)When the distance between controllers exceeds 100 meters, use optical fiber;
(3) The EIA485 protocol stipulates that the number of nodes carried by each repeater shall not exceed 32;
(4) The wiring of each control loop must follow the bus structure layout;
(5) The signal wires and power wires should be laid separately.
Even if you use the DMX512 control system according to the steps and standards, you can always encounter various problems.
2. Common problems and solutions in engineering commissioning.
(1) What should I do if the entire control loop lights flash uncontrollably?
Confirm that the controller signal output is normal
When the entire control loop lamps are not controlled, if conditions permit, first use a temporary controller to test whether the loop is controlled separately:
a. Controlled-the original controller's signal output has problems (or wiring file problems, or port hardware problems, or port wiring problems);
b. Out of control-continue to investigate;
c. Turn off the lights after the first lamp, and test the first lamp separately to determine whether it is a controller problem or the signal interference effect caused by the following lamps;
At this time, the first light is usually OK.
Troubleshooting nodes or lights
When the controller signal output is normal, slowly increase the lamps to find out the nodes or lamps that cause the loop signal to be abnormal; usually, the "disection method" is faster.
(2) Uncontrolled flashing of individual lamps in a certain control loop
Confirm whether the controller wiring is in place
The number of lights in the wiring file of the controller must be the same as the number of lights installed on site.
Test with full wiring file
First use the test program to perform the control test, that is, the single-port wiring file is filled with 1-512 channels.
a. Random flashing lamps are controlled. At this time, rewrite the code for the loop lamps and the problem can be solved;
b. Individual lamps are still uncontrolled. Check whether the signal output terminal of the uncontrolled lamps is wired correctly or the lamps themselves have quality problems.
(3) Under what circumstances do I need to add a signal amplifier?
One function of the signal amplifier is to amplify the signal and restore the weakened signal to the strength of the starting point; the other function is to isolate the signal to prevent damage to the controller caused by lamp failure.
In the standard case, according to the EIA485 protocol, a signal amplifier needs to be added for every 32 nodes. In order to avoid the lamp signal from becoming weak in rainy weather or other conditions, the lamp will flash randomly.
More than 32 DMX decoders need to be connected with a signal amplifier, and the signal cannot be amplified more than 5 times continuously.
When the signal line is long or the quality of the wire material causes the signal kickback effect to affect the use, you can try to connect a 0.25W 90-120Ω terminal resistor to the DMX decoder or the signal terminal of the power supply at the end of each signal line.
(4) How many nodes can the output port of the sub-controller with amplifier have?
In the current standard specified in the EIA485 protocol, the general recommendation is to add an amplifier to 32 nodes. However, in actual operation, there can be more than 60 nodes, but there will be a safety hazard of unstable signal.
We generally recommend that customers add signal amplifiers if the number of DMX exceeds 32. This is very important.
(5) The signal line has no shielding function, can the signal still be transmitted?
Many domestic projects use network cables for signal lines, which are basically unshielded, and the transmission distance will definitely be discounted, but the specifics still depend on the project used to make the decision. The farthest distance can generally reach about 100m.
Therefore, we would recommend that customers use shielded twisted pair signal cables for DMX signal lines.
(6) What should I do if the time of each DMX circuit is not synchronized?
There are several different ports in the same divider, and some of the individual ports will have a significant delay in output signal. At this time, all you need to do is to reset the parameters of the controller. The most likely reason for this situation is that the controller's own parameters have caused the output frequency of each port to be different, which results in the signal output of each port being out of sync.
(7) If the transmission rate is reduced, will the synchronization be affected?
The transmission rate of DMX512 is 250Kbps. This cannot be reduced. If the transmission rate is reduced, it is another system. Another set of systems will have another set of protocols, which will not have any impact on the synchronization of the lamps.