DMX512 signal line of lamplight, you pick the right? - China lighting network

As a result of the DMX512 simplicity, reliability and flexibility, it soon became the controller ( Such as lighting console) And dimmers and fog machine, intelligent lamp and other special equipment connected main method, has been developed into from the console using the standard digital interface way to control the dimmer. But although DMX512 beyond the simulation system, but it can't completely replace analog system. DMX512 using the EIA - on its physical layer 485 differential signaling, and combined with a variable size, communication protocol based on package. DMX512 does not include error checking and correcting automatically, thus for dangerous applications, such as fireworks or manipulation of the mobile stage, is not a proper control. Error trigger may be the electromagnetic interference, electrostatic discharge, improper cable termination, cable is too long or cable due to poor quality. Defined according to the standard DMX512 interface definition, at the same time, in order to distinguish between the traditional audio card nong interface, 3 core context defines the five core interface, but in recent years, the three core you interface also more and more applied in the DMX512 equipment, line 5 Pin sequence the following notice are different from traditional audio interface, contrary Pin2 and responsible for the positive and negative, and because the Pin 4 and Pin 5

to backup link is currently does not define, so usually can only meet Pin1 ~ 3. DMX512 special cables and maximum transmission distance DMX512 controller with 250 kbit/s differential serial data transmission, theoretically a bus link up to 1200 meters (longest

3900英尺) The longest, but that doesn't mean that a cable can be used 1200 meters, but add up to 1200 meters after the repeater. Transmission distance, the higher requirement for wire, can be on the premise of guarantee the characteristic impedance of 120 Ω bold cable. 3 core card card nong nong and 5 core interface can use 2 core with shielded twisted-pair cable, and cable must meet the characteristic impedance of 120 Ω, and characteristic impedance is one of the most important, do not match the characteristic impedance of distorts digital signal waveform, increase the error. Industry in many engineers use normal microphone cable or RVVP 2 x 0. 752 links, and the two cables are low impedance, impedance is almost 50-70

Ω, 120 Ω can not meet the standard demand, makes greatly increase the reflex, shorten the transmission distance, especially after more than 50 m, could be unpredictable and correction, irregular, or completely uncontrolled error signals, and even suddenly stop running. Using the microphone or line RVVP, even in the increasing conductor cross-sectional area can increase the characteristic impedance, which is even more coarse line cannot extend the transmission distance, so be sure to use professional DMX512 control line. What need reminds is, the appearance of this wire and the ratio of outer diameter to the microphone cable is very close, the scene must be bullish on the surface when using identity 'DMX512,' don't use the wrong. It is important to note the surface characteristic impedance of the cable electrical indicators, such as the characteristic impedance non-professional personnel by the naked eye is not see appearance. DMX512 link and end resistance DMX512 single bus (no more than 32 units on the network load A single device to connect) 。 If you need to use more than 32 unit load distributor communication, develop parallel network. Load links by RS485 chrysanthemum lotus, namely all the load series. Daisy chain what need reminds is, the last set of load, the need to link a 120 Ω end resistance and end resistance can be used with 120 nong Ω impedance card head, also can use small resistance element in the context of pin2 and responsible. Though normally, no end resistance, some system can run normally, but cannot guarantee system has been normal operation, and not, flicker, pause, random or not make lighting effects. Summary of 1, be sure to use professional DMX512 control line; 2, loaded with no more than 32; 3, be sure to use the last set of load 120 Ω end resistance. YanZhiXiang

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