PLC-BUS

In the PLC -BUS ( Power Line Communication Bus - also PLCBUS written ) is a powerline-based installation bus, wherein the switching signals over your existing house wiring to be sent, without new cables have to be laid.

Overview

In addition to data lines and wireless technology supply lines can itself serve as a communication medium, in the jargon Power Line Communication ( power line communications ). The advantages of this mode of transmission is its high reliability and low installation costs. The PLC system uses two-way communication bus and reaches a reliability of 99.95 %. This means max. 5 Error at 10,000 commands.

PLC-BUS accesses the addressing of X10 protocol and expands the 256 X10 addresses by a factor of 250 to 64,000 addresses. This is PLC-BUS within the space and unit code address- compatible with X10 and can incorporate a PLC-BUS/X10-Koppler X10 devices in the home automation. This is particularly of interest to users who have X10 in use.

The PLC - BUS system is very similar to the spread in the Anglo-American Universal Powerline Bus ( UPB ).

History

PLC-BUS was developed by the Dutch company ATS and is marketed as a technology since 2002. The Chinese company Shanghai Super Smart Electronics took over in 2005, the PLC -BUS technology in their home automation products, making PLC-BUS in Asia to one of the leading technologies for Home Automation.

Data transmission

The PLC- BUS uses the existing house wiring of the power grid. For data transfer, two different signals are required. The actual data signal and a carrier signal for synchronization. Without a carrier signal for transmission of data over long distances is not possible. The PLC bus uses the AC voltage of the power grid as a carrier signal for its own data. The alternating voltage in Germany based on a sine wave with a voltage of 230 V and a frequency of 50 Hz, a frequency of 50 Hz, means that any 50 second full-wave, each having a positive and a negative half-wave to be transmitted.

In this case, the data signal is by means of the pulse position modulation on the modulated carrier signal 230 V. In pulse phase modulation, data is transmitted by pulses which are modulated onto the carrier signal. By a time shift of the pulses and thereby different time intervals between the pulses, the information is encoded.

Corresponding to the PLC bus specification the data pulses are modulated within a defined time window in each half-wave of the carrier signal, the carrier signal reaches just before the zero crossing. Modulating the pulses at the end of the carrier signal has the advantage that this portion is mostly devoid of other interfering pulses and the sum of the carrier signal and the pulse does not exceed 230V. The window start 8.7 ms after the half-wave has passed through the zero crossing. The time window is divided into 4 parts, each fixed 275 ĩS. Each pulse must begin and end within one of the four sections. On the basis of pulse position two bits can be encoded and transmitted. During a full-wave comprising a positive and negative half-wave, as 4 bits can be transmitted. For transmission of a complete PLC bus data bytes of 8 bits or 40 ms two full waves are required. With a 230 V power supply with 50 Hz, this results in a data transfer rate of 200 bps.

The position of the pulse within the time window is interpreted by the receiver either as a 0, 1, 2 or 3 in accordance with the pulse position Tp0, TP1, TP2 and TP3, which corresponds to a two- bit code as follows:

With this modulation method, although only a very small data transfer rate is achieved, but this is the transmission of very robust and highly reliable. The signal can be transmitted in practice without a filter or amplifier over very large distances. Compared with the accessible in the Local Area Network data transfer rates it is very low, but sufficient for transmission of control commands from perfect.

Way communication

The communication according to the PLC -BUS specification is based on a start byte, which is sent before the actual data and prepared the receiver to receive data. The start byte always has the same structure 2-1-1-2 with respect to the pulse position ( Tp2 - Tp1 - TP1 - TP2 ). The definition of a start byte has the advantage that, when idle, no pulses are modulated onto the power lines.

Following the start byte of the five byte header data is transmitted. This header information includes information such as recipient address, sender address and the data length of the data below. Varies according to the number of bytes of the information to be transmitted and may be up to 18 bytes. The transmitted data frame is added to the circuit or by a one -byte checksum to detect errors in transmission can.

Digital transmission is the PLC-BUS technology is a secure and highly available bidirectional transmission based on the existing power grid dar. actuators can receive and execute its command to report back to the controller. A controller always has the possibility to selectively query the status of an actuator and thus to develop a visualization of the states in the house.

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