Comparison and advantages of Power Line Communication:
Power line carrier communication is used to transmit signals in the existing power lines, and its working principle outlined as follows: data or voice modulation in the range of tens to hundreds of KHz carrier frequency is sent through the power lines, the receiver will contain the power line signal receiver, which demodulates the carrier signal down to restore the original voice or data output. With this type of power line communcation the need for re-laying becomes unnnecessary as like that of the wired communications.In wireless transmission, the sending and receiving requires complex equipment to transmit information. But, the power line communication does not require additional set up lines of communication, and it is not taking up valuable radio spectrum resources. So, it is suitable for a small group of internal transmission or (typically a power transformer in the same room) the composition of local area network to achieve the purpose of data or voice transmission.
Applications of Power Line Communcation:
LM1893 National Semiconductor Devices, United States (National Semiconductor) which works for the development of power line carrier communication integrated circuits, designs integrated sending and receiving of data with all the functions through half-duplex serial data communication. Integrating a small amount of external components makes a complete power line carrier communication system, to suit for industrial automation systems, building the data or voice communication, household appliances, centralized control, the hospital’s emergency call system, fire alarm and computer data transmission applications.
Features of Power Line Comuncation:
- FSK anti-noise modulation technique
- Optional noise filtering of the pulse generator
- Data transfer rate up to 4.8kB
- Sine wave carrier frequency in order to reduce radio frequency interference
- RF power can be increased 10-fold
- Carrier frequency can choose between 50-300kHz
- Is compatible with TTL and MOS logic level
- Adjustable voltage to the power level
- To drive various existing power lines
The Pin diagram of LM1893 IC, which is used for Power Line Communication is shown below:
Working of LM1893:
LM1893 is integrated with the sending and receiving side divided as two separate parts. The sending part constitutes of the built-in FSK modulator, sine wave generator, current-mode controlled oscillator, automatic gain control circuit (ALC) and output power amplifier modules on the circuit. Receiving part consists of a limiting amplifier, phase-locked loop demodulator, low-pass filter, DC-clamp circuits and noise filters and other blocks. To send or receive a data, the TX / RX should be high. When the circuit in send mode, the data signal from the P17 inputs FSK modulator and it form a switch control current and drive the oscillator frequency with a deviation ± 2.2% triangle wave, sine wave by the sine wave shaping circuit output signal; and then the signal isamplified by the power transmitted by the coupling coil to the up going power lines. ALC (automatic gain control circuit) is to ensure that when the electrical wiring of the load changes, it makes the the output level of the carrier to maintain a certain level range.
When the TX / RX is low, the circuit in the receiving mode, and the the power line receives signal through the coupling transformer input. The process is as follows: LM1893 10 pin connected with the limiting amplifier amplifies the filtered signal of the DC component and 50Hz/100Hz power frequency signal , and then demodulated by a PLL circuit. The RC filter circuit is used to filter out high frequency components of output data signals, in order to maintain a reliable data signals. Then, the signal is carried out by the comparator and the noise shaping filter with and the output at pin 12 delivers a complete data signal.