Correct operation network DMX512 (especially when using long cables) is possible only in the case where the transmitting device to the host is a single line. In line can be included up to 32 devices located arbitrarily along its entire length. The allowable number of devices will decrease if the lines are used in devices that do not meet standard EIA485. The devices must connect to the line of very short cables (not longer than 30 cm (12 inches)) in order to avoid Y-splitting. In practice, however, this length may be increased up to several meters. Typically, the line also takes place inside the device, connecting its input and output connectors, and thereby allowing the device to form a chain.
Standard EIA485, used DMX512, able to work with lines of up to 1 km. This value is the recommended maximum. In practice, it is recommended to use the line length not exceeding 500 m. In the opposite case we must consider the possibility of using signal amplifiers (repeaters).
When building systems with long lines should be very careful when choosing a cable, which must have a suitable cross-section. Used cable must provide, at a nominal value of 120 ohm terminator at the far end of the line voltage is not less than 0.2 V in the event that the output voltage of the transmitting unit is only 2 V. It is not recommended to use cables in which the number of American assortment of wires is less than 22 AWG. The resistance of the cable to the DC should not be confused with the wave resistance. Resistance at dc can be measured by conventional ohm-meter and should not be greater than 200 ohms for each wire.
Y-cable is the cable that connects one plug (connects to the console), and two sockets (connected to the dimmer). In this case, pins 1 combined for all three connectors, pins 2 - too, and so
Using Y-cable in the line of DMX512, especially at large distances from the transmitting device, leads to a complex set of reflected signals that turn causes serious distortion of signals and increase the number of failures throughout the system.
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