DMX512 System Introduction of led lighting

DMX512 protocol is the first USITT (United States Theatre Technology Association) to become the standard digital interface from the console control dimmer way. DMX512 beyond the simulation system, but can not completely replace the analog system. DMX512 simplicity, reliability (if correctly installed and used it!), And the flexibility to quickly become the choice of funds under the agreement allows, in addition to the dimmer, the range of control equipment is growing evidence. DMX512 is still a new field of science, based on the rule has generated all kinds of wonderful technology. EIA485 (RS485) DMX512 is built around industry standard EIA485 interface design. EIA485 are interfaces, voltage, current, etc. “electric” side. System is based on the downward along the shielded twisted pair conductor established symmetric transmission. This spiral structure to ensure that the interference generated by the same act on the two signals, thus ensuring a consistent number of phase. Wire should be used by one or two twisted pair, foil and braid screen composed of the appropriate data cable. Audio cable symmetry can not finish the job. Normally, the same as any network segment, the wire ends should have two terminals. As usually in a lighting console terminal, and the other end should be only one 120Ω resistor. EIA485 specification only support the “daisy chain” or up to a maximum of 32 on each “unit load” posed by the serial network. Each manufacturer can claim up to 1000m. However, to highlight that the role of repeaters should be considered about 700m or 800m, which can prevent abnormal environment. XLR connector pins as follows: needle shield to the signal 1 / 0 V 2 internal conductor (black) data – 3 internal conductor (white) data + 4 internal conductors (green) secondary data – 5 internal conductor (red) secondary data + DMX512 control cable with 5 pin XLR (sometimes 3-pin) to connect devices (Table 1); parent interface for the transmitter, and the public interface for the receiver specification recommended a two pairs of wires (4 connector ) to achieve shielding, although only need one pair. Second pair of wires for the optional unspecified occasions. Should be noted that some of the dimmer use of these lines to indicate the fault and status information. Used if Dimmer second channel, you need specially configured splitter and repeater. The cable to the logic level of the safest method is to use a “standard” interface IC-TexasInstruments the SN75176B, if you want to achieve connectivity and isolation, Burr-Brown’s ISO485P is a good choice. Method of using these interfaces to provide a rating for each device unit load, these devices allow you to install up to 32 segments receiver. Across the line is not recommended to connect through a direct high-sensitivity direct-line optical isolator interface mode, it provides load than normal load on the receiver is 5 times, thereby reducing the segment can be installed on the receivers. In addition also cause distortion, increasing the risk of errors and lead to meet the EIA485 receiver fails, these are bad news! Data is based on an 8-bit data to send asynchronous serial protocol, with a start bit (low) and two stop bits (high), no parity. Thus, a data frame with 11 bits. Since the width of each is 4 Uu, it needs to send a frame 44 Uu time. If the line you want to send a continuous stream of data, it will produce 250000b / s data rate, or 250k baud. 8-bit word for each dimmer allows the range of 0 to 255 to send 256 separate levels. Start and stop bits for the transmitter and receiver synchronization. Data lines are usually at a high level; in fact it is high when idle state (more often in this state.) The emergence of the start bit to work to promote the receiver, behind the 8-bit data to be scanned and decoded (hopefully). Then the receiver waits the arrival of stop bits, stop bits will be again after this process. We need to stop bit for two reasons: so that the receiver has sufficient time to process the input data; to the state line is high, so the next “start” can be detected. Figure 1 depicts a frame inside the bit level, this frame contains the data “0” and “255.” So far has been very clearly explained, but not yet finished, DMX512 can support up to 512 dimmers, and now we have only seen the first one, then how to deal with all dimmers information? The answer is simple, just repeat the process! Yes, it is that simple. But now the situation is not so simple, we made the segment a data stream, but there is no way to identify which frames belong to which the dimmer. See “DMX Pack” section of the prompt. DMX512 “package” DMX512 package is the core of this standard, which consists of a deep set of synchronization information frame structure, in which the depth information is a “Break” and a “Mark-after-break”. That this information will enable the receiver to detect the start of a frame, it can handle the received data. Frame timing test shows the longest line at a low level of 4 Uu (start bit) +8 × 4 Uu (data bits) = 36 Uu, but a “Break” contains at least 88 Uu a “low”, which the difference can easily be detected, the dimmer can be used for synchronization. “Mark-after-break” on the line is “high” state, the width of at least 8 Uu time, “Mark-after-break” is necessary because in order to detect the “Break”, otherwise the frame will be followed by the start bit “Break”, the line has been caught in the low state. At this point will be very confusing! A description of “package” of Figure 2 helps to explain the above problem. “0” value indicates the back of the frame contains information on the dimmer level. 255 additional code is not defined in the specification, but some manufacturers have used the other code to send the product specific information. Non-zero start code of a receiver dimmer “will” ignore the rest of pack, but be careful, it will not always be checked to! Timing summarized as follows: Minimum Maximum Break 88μs 1 秒 Mark-after-break 8μs 1 Second  Inter-frame-time 0μs 1 Second  “Inter-frame-time” used to reduce data rate. Some dimmers can not handle high speed data, or other tasks at the same console used for “insert” the transmission. Its value can be from 0 to 1 seconds. Specification set some restrictions for the time. It can be seen from the above, the data rate is very scalable, but to note that the state does not allow continuous line in the “high” or “low” state than a second time, and error conditions should be considered at this time. DMX512 system in the almost all of misuse are lack of knowledge from the system. A place that is causing the problem in the signal separation. Remember, the end section of the system to run. Simply the Line separation (seems logical) volume due to the repeated changes in ohms and can not work. To do so easily lead to the destruction of the signal. Solution is to use the “splitter” and “repeaters” power equipment “listen” segment of the data, and then broadcast, or as needed in the next paragraph to “reproduce.”


Why to choose long-life led driver

There are two primary factors in the justification of most solid state lighting systems.The first is energy savings. However,there are other alternative lighting technologies that offer high efficiency for lower initial costs.The second justification,lower maintenance costs,is therefore critical.LEDs have the advantage of much longer life than most other lighting technologies. Reduced replacement and/or maintenance costs can be a very significant factor.However,if the power electronics in the system does not match the life/reliability of the LEDs then the justification of the system is in jeoprdy.

The life of an LED driver is mainly determined by the life time of the electrolytic capacitors employed.Therefore,to achieve long life of LED drivers,it is critical to select long-life,quality electrolytic capacitors.Also,since the life of electrolytic capacitors drops by half for every 10C increase in operating temperature,thermal management of these components is important.Two key factors for reducing the temperature of the capacitors are high efficiency design and thermal design.

How to choose a reasonable led power system

Choose how much amount of product, how the connections, the control system design, if not the AC product, to choose a good power system. This is a more complicated link.
A. First, determine the number of products to be LED, and the arrangement. Is best arranged by rendering exactly the same, which they have used the design effect.
B. If it is low voltage products, we will choose the power, we should pay attention to choose a power supply to the following aspects:
1. High reliability: in particular the drive power as the LED lamp, installed in the high altitude, convenient repair and maintenance cost is also large.
2. High Efficiency: LED energy-saving products, driving higher power efficiency. Installed in the fixture for the power structure, is particularly important. Because the LED luminous efficiency with LED temperature decreased, so the LED’s heat is very important. Power efficiency High rate of depletion of its small power, heat in the fixture on the small temperature rise will reduce the lamp. LED light on the slow decline favorable.
3. High Power Factor: Power factor is the power to the load requirements. 70 watts under normal use of electrical appliances, there is no mandatory targets. Although power is not a single factor with a lower electrical power has little effect on the power grid, but at night we light lamps, similar The load is too concentrated, would produce power more contaminated. 30 watts to 40 watts for the LED drive power, it is said in the near future, perhaps there would be power factor requirements of certain indicators.
4. Driving mode: now prevailing in two ways: one is a constant voltage constant current source for multiple sources, each current source separately to each channel LED power supply. In this way, the combination of flexibility, all the way LED failure does not affect the LED’s work, but the cost will be slightly higher Point. The other is a direct constant current power supply, LED series or parallel operation. It has the advantage of lower cost, but flexibility is poor, but also to resolve a fault LED, LED operation does not affect other issues. These two forms coexist in a period of time. Multi-channel constant current output power supply, cost and performance will be better. Perhaps the mainstream of the future
5. Surge Protection: LED Surge capacity is relatively poor, especially the anti-reverse voltage capability. Enhance this protection is also very important. Some LED lights installed in the outdoors, such as LED lights. Since the start grid load rejection and lightning sensors, from the grid The system will invade a variety of surge, the surge can cause some damage to LED. LED drive power should therefore inhibit the surge of the invasion to protect the LED from damage ability.
6. Protection: the protection of power in addition to conventional features, the best increase in the constant current output LED temperature feedback, to prevent the LED temperature is too high.
7. Protection: the lighting and outdoor installation type, the power structure should be waterproof, moisture, shells and Fast.
8. Drive power of power: the power of the power of our choice when we must remember to stay in power margin can not be overloaded. I am here to give you an empirical formula: power = LED lighting power supply power ⅹ 1.2
9. To comply with safety regulations and electromagnetic compatibility requirements.
LED power supply selection is very important to determine whether normal and stable throughout the project work. Therefore, there must be careful in the choice.

What is the distribution curve

Light distribution curve of the definition:
Distribution curve is actually a lamp or light source that emits light in the space distribution. It can record the luminous flux of lamps, light quantity, power, power factor, lamp size, lamp efficiency, including lamp manufacturers, models and other information. The most important thing of course, recorded the light in all directions the light intensity.
Light distribution curve of the Category:
Distribution curve according to their symmetry properties can generally be divided into: axial symmetry, symmetrical and asymmetrical light distribution.
Axial symmetry: rotational symmetry is also called, refers to all directions with all the basic symmetrical light curves, the general downlight, mining lamps are like light distribution.
Symmetry: When the lamps and C180 ° C0 ° light distribution profile symmetry, while C270 ° C90 ° and symmetric profiles with light, such a distribution curve is called symmetrical with light
Asymmetric: means C0 ° – 180 ° and C90 ° – 270 ° with any one section of light asymmetry.
Distribution curve in accordance with its beam angle is usually divided into:
Narrow light distribution (40 °)
Wide light distribution (> 40 °)
In fact, there is no strict definition of the various manufacturers of wide, middle and narrow definitions are slightly different.

Understanding and application of PWM

PWM this term, because in our drive PWM often used inside.
PWM Dimming (PWM), is the best LED grayscale adjustment method. PWM say more easy to understand, is to control the LED on and off the time scale, the proportion of time on and off divided into several levels, LED will show a corresponding number of gray. PWM frequency: just said PWM LED is on and off the proportion of time to achieve, but the switching frequency can not make too low, at least to be deceived eyes. learn from the experience of generally greater than 100Hz TV Some LED display will be the camera shot, conditional on the proposed design is more reasonable 300-500Hz. In the three-color design application is usually by adjusting the LED current to achieve the expectations of the white balance and maximum brightness, by controlling the PWM to gray level to achieve. LED numbers of gray levels the field and 7-color, 8, 16, 32, 64, 128, 256, 512 and other ways. it can be different orders of magnitude, these numbers the main level is to facilitate the digital line data processing only. such as have to be divided into 100, it is also possible. the product of three primary colors of the gray level, is the product number theory can reproduce the colors, we usually say that the number of colors. For example: Single color is 256 colors, red 256 (grade) × Green 256 (grade) × Blue 256 (level) = 16777216 (16KK colors).