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The power line home automation type communication system for voice communication and data transmission using an existing power line Md. Imamul Arefeen1, *Md. Abdus Samad2, Md. Asadujjaman Nur3 Electronics and communication Engineering Khulna University of Engineering & Technology Khulna, Bangladesh 2 [email protected] Abstract—This paper states about the voice communication and data transmission at a time on a single existing power line that reduces the complexity of so much wires used in communication system and it is applicable in a large automated area with low cost and easy installation process. The message (voice, tone or digital data) is modulated with a high frequency carrier by frequency modulation (FM) or frequency shift keying (FSK) process and after amplification it passes to the power line through the bidirectional coupler. At the receiver section the signal (FM or FSK) is recovered by coupler and then demodulated. The demodulated signal is then passed through the low pass filter to recover the voice or tone signal and a comparator is used to recover data signal. Here the authors use different carrier frequencies for different users and also use corresponding filter and comparator. A trap circuit is used here to localize the communication area which obstructs the transmitted signal to pass out of that area and hence losses are reduced. Keywords—modulation, filter, carrier; I. coupler, comparator, trap-circuit, INTRODUCTION Power line communication (PLC) technology defines transmitting of message through power line using carrier modulation. PLC can control and diagnose information such as temperature monitoring, vibrations measurements etc. are measured by various sensors convert to power and transmit through power cable [1]. The external electrical grid helps in many applications and provides opportunities for equipment for vendors [2]. It can provide broadband connection to rural or remote areas specially where telephone and cable connection do not have existence and also provide data services (broadband Internet service, VoIP service, remote metering, light control at street, home security and so on) [3]. In PLC communication the major drawbacks are noise influence, signal attenuation, and multipath feeding and reflection [4]. Broadband over power line (BPL) gives the opportunity of broadband marketplace and increase its demand widely [5]. Wireless local area network (LAN) can also attach with wireless modems that connects to one or more wireless hubs (infrastructure-based) or to each other. This is 978-1-4799-6062-0/14/$31.00©2014 IEEE used as a communication tool especially at telecommunication sector, at home automation and network access technology as its popularity is increased for using RF frequency. The wireless system is used for less number of nodes in the small network such as home or office and it also requires wireless networking hardware and software which is typically based on the IEEE 802.11b standard [6]. External plant applications of PLC are practicing widely. Now a days PLC systems have made vast popularity at Neighborhood Area Network systems in Europe and also at North America [7]. The field of power line communications has recently seen a revival of interest, with increased research activities, as well as new standards and products being introduced. The authors use here 150 KHz carrier for a single voice communication for hardware implementation and use different frequencies for transmitting more messages over a single power line. For each carrier the recovered message signal is found noiseless. The message recovering performance is excellent and the data recovery also shows better performance. This communication system is mainly home appliance based i.e. it is used at home, office or an institution automation for voice and data communication for no bill cost except only use of low power. This also can be used between the two power line substations. Limitations and difficulties which can obstruct communication are also revealed here. And also possible solutions are discussed here about the mismatch probabilities of coupler, different carrier frequencies related problems. II. SYSTEM DESIGN The total system runs at three parts named transmitter part, power line carrying part and the receiving part. At transmitter part the signal is modulated with carrier and then it is transmitted through power line. At receiver the modulated signal is received from power line with the help of coupler and then message signal is separated from carrier by demodulation and finally the message signal is recovered through filtering. In a PLC user module both transmitter and receiver circuit exists for bidirectional communication. Power line isolator which works for bidirectional coupling. comparator input and pin-4 is VCO output. The pin-3 & 4 must be shorted and the VCO output can be found here. If the FM modulated frequency is greater than VCO output, then the PLL gives a higher voltage according to the frequency variation and if the FM modulated frequency is less than VCO output, then Fig. 3. Circuit diagram of FM demodulation. Fig. 1. Functional block diagram of power line communication system. A. Modulation CD4046 IC can easily perform modulation. It contains a VCO (voltage control oscillator) which gives oscillating frequency according to voltage given at pin-9. At pin-4 free running oscillation occurs if any voltage isn’t provided at pin9 but if voltage is provided(message signal) at pin-9 then CD4046 gives modulated output in the manner that free Fig. 2. Circuit diagram of FM modulation. running frequency will be high if signal voltage is positive and low if message signal is negative. Simply, pin-3, 5,8,14 should be grounded, pin-11, 12 should contain resistors, a non-polar capacitor should be inserted between pin-6 & 7, message signal should be given in pin-9 with the addition of dc voltage to get modulated output. B. Demodulation For demodulation, the FM modulated signal should be given at pin-14 and the demodulated signal will be found at pin-10. The pin-5 & 8 should be grounded. A capacitor should be inserted between pin-6 & 7. Here, pin-3 is a phase the PLL(Phase-Locked Loop) gives a voltage according to the frequency variation. This demodulated output contains high frequency components. So a low pass filter is needed to recover the original message signal. C. Power line isolation This is the most important part of PLC that should be designed very carefully. As the modulated signal is transmitted over power line and a 220Vac (50 Hz) already existing there so it is needed to isolate the 220Vac (50 Hz) from our transmitter and receiver circuit for protection. To isolate the 220Vac (50 Hz) signal it is needed to apply a high pass filter to allow the high frequency modulated signal to pass through while blocking the low frequency signal. Here a high voltage low valued capacitor is used in series with a coupling transformer between the power line and Fig. 4. Circuit diagram of power line isolation. the transmitter or receiver. This will block any signal of a frequency lower than the cut off frequency and allow passing any signal having a frequency greater than the cut off frequency. D. Line Trap Circuit: The line trap circuit is used for allowing the transmitted signal to receive over a limited area such as a building, institution, market or a town. There may thousands of devices connected over the power line at a time. So there may have a great signal loss of our transmitted signal. To reduce this loss it is needed the line trap circuit. The line trap circuit has been used in series with the power line which actually consists of 150 KHz. But in Fig. 9 it has shown modulated signal with a low frequency carrier for easy realization of FM signal using TABLE I CIRCUIT SPECIFICATIONS Imp edan ces Fig. 5. Connection diagram of line trap circuit. a parallel inductor and capacitor. For the 50 Hz ac signal of power line it gives a very lower impedance but for our 150 KHz carrier signal it gives high impedance. So there is no restriction for 50 Hz ac signal of the power line but due to high impedance for carrier signal the line trap circuit will not allow to pass the transmitted signal out of the area bounded by the line trap circuit. The impedances can be easily calculated from the following equations XL=2πfL, XC=1/2πfC, III. Z= (XL* XC)/ (XL+XC) HARDWARE IMPLEMENTED CIRCUIT The transmitter circuit modulate the message signal with carrier and mix with power supply and the receiver act reversely and recover message. XL1 XL2 XC1 Transmitter/Receiver side coupler (for 50 Hz AC voltage) 0.01 Ω 2.2 Ω 31.83 kΩ (for 150 kHz carrier voltage) 6.6 kΩ 28 Ω 10.61 Ω Power line AC voltage (p-p) Modulated signal voltage(p-p) at FM input side Modulated signal voltage(p-p) at power line part 622 V 8V 2V same circuit. As Capacitor shows high reactance (31.83 kΩ) at 50 Hz and secondary inductance shows very low (.01Ω) reactance at 50 Hz frequency (TABLE I) so almost all the 50 Hz AC power line Voltage is seized at capacitor C1 and hence we get almost zero ac power line voltage at primary side and isolates the circuit from power line. Due to mismatch of power line and transmitter-receiver impedances the carrier wave shape is slightly changed as shown in fig. 10 but original carrier is recovered at receiver by the use of comparator. Peak to peak 50 Hz power line voltage ac voltage is 622V and the transmitted modulated peak to peak signal is only 2V and has no adverse effect on the devices connected with power line. Fig. 8. Waveform of Carrier signal. Fig. 9. Waveform of audio signal(1) and FM modulated signal(2). Fig.10. Coupling effect of carrier signal. Fig.11. Input signal(1) and demodulated signal(2) without power line. Fig. 6. Transmitter circuit. Fig. 7. Receiver circuit. IV. RESULT ANALYSIS The power line communication circuit carries 1.5 KHz message signal given from signal generator and a carrier of Waveform of input signal shown at fig.10. and also the demodulated signal without power line. The fig. 11 and fig. 12 shows that the output doesn’t changes and hence has no effect on PLC communication using power line with the circuit discussed here. Normally power line voice communication performance of the device. The 98% noise free efficient data transmission possible here. The coupling effect and the crosstalk two problems appear here. This can affect a bit in the output data. The PLC technology can be used in a home (Home networking (LAN)) to interconnect home computers and peripherals, and home entertainment devices that have an Ethernet port. Power line adapter sets plug into power outlets and establish an Ethernet connection using the existing electrical wiring in the home. (Power strips with filtering may absorb the power line signal.) This allows devices to share data without the inconvenience of running dedicated network cables. Fig. 12. Waveform of input signal and final demodulated signal using power line. needs 20-200 KHz carrier. The proposed circuit shows good performances at 20-160 KHz range shown at fig.13. Fixed amplitude message signal of 800mV is used for various carrier frequencies and graph shows corresponding outputs. At various frequencies the output voltage varies but provides ACKNOWLEDGEMENT This work was conducted in the Electronics and Communication Engineering department laboratory (MECE laboratory) at Khulna University of Engineering and Technology (KUET) at Khulna and in collaboration with the Department. REFERENCES [1] Output Voltage(mV) 1400 1200 1000 800 600 400 200 0 [2] 0 50 100 150 Carrier frequency(KHz) noiseless better output between 20 KHz to 160 KHz and output amplitude can be amplified to desired level by using amplifier. As at high frequencies (>160 KHz) CD4046 performs poor and hence lower the output. At lower frequencies C1 gives greater attenuation and hence outputs of low amplitudes. Maximum transmitted digital data using the designed circuit is 10Mbps and then only coupler and comparator is enough as it is high frequency. The circuit gives better performance than the others as almost noise free voice and data recover is done. The circuit installation cost is quite less than the others. V. [3] J. J. Lee, C. S. Hong, J. M. Kang and J. W. K. Hong, “Power line communication network trial and management in Korea” International journal of network management,Int. J. Network Mgmt 2006; 16: 443– 457,Published online in Wiley InterScience, (www.interscience.wiley.com) DOI: 10.1002/nem.632 [4] H. He, Student Member, IEEE, S. Cheng, Senior Member, IEEE, Y. Zhang, and J. Nguimbis, “Home Network Power-Line Communication Signal Processing Based on Wavelet Packet Analysis” IEEE transactions on power delivery, vol. 20, no. 3, pp.1879-1885; July 2005. [5] S. M. Singh, Esq.Ratepayer Advocate,State of New Jersey,Division of the Ratepayer Advocate, 31 Clinton Street, 11thFloor, Newark, New Jersey 07102;”Broadband over power lines A white paper”.pp. 35; [6] M. K. Lee1,n,y, R. E. Newman, H. A. Latchman, S. Katar, and L. Yonge, “HomePlug 1.0 powerline communication LANs}protocol description and performance results.” International journal of communication systems, Int. J. Commun. Syst.2003;16:(in press) (DOI: 10.1002/dac.601,pp. 16-20; A. A. Atayero, A. A. Alatishe, and Y. A. Ivanov, Members, IAENG, “Power Line Communication Technologies: Modeling and Simulation of PRIME Physical Layer” Proceedings of the World Congress on Engineering and Computer Science 2012 Vol II, WCECS 2012, October 24-26, 2012, San Francisco, USA, ISBN: 978-988-19252-4-4,ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online). 200 Fig. 13. Output voltages with the variation of carrier frequencies. CONCLUSION Power line communication (PLC) technology adopted in transmitting the message signal this paper shows this in a secured way. Efficient transmission is ensured by the output N. Ginot, M. A. Mannah, C. Batard, and M. Machmoum, “Application of Power Line Communication for Data Transmission Over PWM Network’’ IEEE transactions on smart grid, vol. 1, no. 2,pp. 178-184, september 2010. J. Serrao, A. Fakih, R. Khatik, ‘'Transmission of data using power line carrier communication system’’ International Journal of Electronics Communication and Computer Technology (IJECCT),Volume 2, pp. 280-283,Issue 6 ,November 2012. [7]