Design of Power Line Carrier Communication System based

on FSK-KQ330 Module
Yin QUN, Zhang JIANBO (corresponding author)

Abstract

The power line carrier communication system is designed based on a FSK-KQ330 (carrier modulation and
demodulation module). The system uses STC microcontroller as the core processor and uses FSK-KQ330 as the
modem module. The system includes the zero-crossing detecting circuit, the magnifying circuit of triodes, the
resonant circuit and the transformer isolation circuit. Master-slave system can transmit data signals over
power lines. It not only can apply to intelligent home system, but also can be used for the remote control of
the intelligent switch and the intelligent equipment.

Keywords: FSK-KQ330, power line carrier communication, STC microcontroller

and it is easy to be implemented and be

1. Introduction extended[5]. Therefore,there is the
The power line carrier communication significance for the research of the power
(PLC) is a specific communication way of line carrier system.
the power systems. Power line carrier Currently, there are three types of
international major modulation technology
communication refers to the technology
which the high-speed power line carrier
which uses the existing power lines to
communication uses.They are three
transmit analog or digital signal by way of categories: single-carrier class, spread
carrier at high speeds [1]. The biggest spectrum class, and OFDM(Orthogonal
feature is that the system does not need to Frequency Division Multiplexing[6].).The
rebuild the network,and as long as there is paper analyzed and studied that the FSK
wire,data transmission can be performed single-carrier class is in the application of
[2]. the electric power carrier communi-
The current application areas are mainly cation[7].
concentrated in the intelligent home,
intelligent utilities (such as remote meter 2. Structure of the system
reading system, street lighting remote The system includes the STC
monitoring systems, etc.) and industrial microcontroller (the core processor), FSK-
intelligence (such as various types of KQ330 module (a modem module), the data
devices data acquisition). Technically, transmitting circuit, the data receiving
power line carrier communication is no circuit, the zero-crossing detecting circuit,
longer a point-to-point communications the magnifying circuit of triodes, the
category, but rather to highlight the resonant circuit and the transformer
concept of open network structure. Each isolation circuit. Master-slave system can
control node (controlled device) forms a transmit data signals over power lines to
centralized network[3]. The system uses achieve the remote control of the host
the existing power lines network, without machine. The core of the system includes
rearranging network cable, which helps to two parts: one is that STC microcontroller
save financial, material and human controls the power line carrier module FSK-
resources[4].At the same time,It is reliable KQ330 module to send and receive data;

the other is that Power line carrier part is

Yin QUN: Lecturer, City College of Kunming University of
Science and Technology; 455601875@qq.com composed of power line carrier module FSK-
Zhang JIANBO (corresponding author): Eng., Kunming KQ330 and peripheral circuit (resonance
University of Science and Technology Oxbridge College, detection circuit and amplifier circuit) [9].
1286#,Haiyuan Bei Road, National High-Tech industry
Development zone, Kunming, Yunnnan,China;
exnet@vip.qq.com
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2.1. Overall system design diagram

Figure 1. Overall system design diagram

The flow of data received is as follows:

2.2. The overall design concept of power
firstly, the resonance detection circuit
line carrier communication system
detects the received signal; secondly, after
The design of power line carrier the signal is isolated by transformer, the
communication system can be divided into waveform is shaped by the resonant circuit;
data transmission and data reception finally, the shaped signal is demodulated by
according to the data flow [10]. the data module of FSK-KQ330, after the
Data transmission flow is as follows: data is demodulated, it is sent back to the
firstly, the system uses the direct interface microcontroller through the serial ports [12].
(serial asynchronous communication) of SCM In the receiving-data part, it has a zero-
and FSK-KQ330 module; secondly, after the crossing detection circuit. The function of
transmission data is modulated by FSK- the circuit is to detect the frequency of the
KQ330 module, through the external circuit sine wave signal on the power line. When
(amplifier circuit and the resonance the level of the signal passes through the
detection circuit), the square-wave signal zero point, the microcontroller sends or
changes into the sinusoidal signal; finally, receives data.
after isolating the interfering signal, the The signal flow diagram of the carrier
signal is coupled to the power line [11]. module is shown below.

Figure 2. The signal flow diagram of the carrier module

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3. The design of system hardware circuit and the transformer isolation circuit.
circuit The resonant circuit enables waveform
signal more stable and no noise [13].
3.1. The data transmitting circuit
3.1.1. The transmitting circuit principle
The circuit is mainly includes the diagram
magnifying circuit of triodes, the resonant

Figure 3. Transmission circuit

3.1.2. Circuit analysis

3.2.1 The circuit principle diagram
In the power line carrier communication
system, the operation of the data
transmitting circuit is described as follows:
the FSK-KQ330 module's 8 pin outputs the
square wave signal, and then it is coupled
to the power line, after it is magnified and
detected. The role of R1 and C1 is limiting
the current. The transistor Q1 amplifies the
signal. L1 and C2 constitute a resonant
circuit. This role of the circuit is able to
change the output square signal form FSK-
KQ330 module's 8-pin into sine wave. Then
it amplifies the signal from the transistor
Q1;the function of the transformer is to
isolate the interference and let the current
to become lager [14].
Figure 4. The receiving circuit diagram
3.2. The data receiving circuit
This circuit is mainly includes the 3.2.2. Circuit analysis
magnifying circuit of triodes, the resonance
detection circuit [15], the transformer The workflow of receiving circuit is
isolation circuit, and the zero-crossing described as follows: firstly, the signal in
detection circuit. power line enters the receving pin (1 pin) of
Receving circuit is connected to power FSK-KQ330, after acrossing the peripheral
lines, and it sents the data signal to the circuits. The function of the peripheral
module. The main function of the receiving receiving circuit is that the resonant circuit
circuit is detection. When the waveform selects frequency. Namely, it uses FSK-
signal is detected and is amplified, FSK- KQ330 to identify the signal frequency.
KQ330 module can identify the normal state After the transformer isolating interrupt
[16]. signal and the resonant circuit selecting
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signal frequency and amplifying signal, it 3.2.3. Zero-crossing detecting circuit

uses two reverse diode which filter out the
The role of zero-crossing detecting
signal of too large magnitude to protect
circuit is to detect sine wave in the power
FSK-KQ330 module [17]. Secondly, L3 and
line. When the sine wave goes through the
C6 constitute the resonance circuit, it can
zero point, the data signals can be
let the wanted signal produce resonance.
transmitted stably and the waveform
The role of the resonance circuit is
amplitude does not change greatly. Zero-
amplifying signal and detecting signal. It is
crossing detecting circuit is shown below.
the same as the function of the radios'
resonant circuit which can extract the 3.3. FSK-KQ330 line carrier module
waveform of the singal; L2 and C5 also The module uses low voltage power line
constitute the resonance circuit. Its roles is as the media of the signal (data)
further amplifying signal and detecting transmission. The carrier frequency of the
signal to filter out the unusful waveform signal (data) modulated by the module is
signal [19]. The role of two reverse diode 50 kHz~350 kHz. The high frequency signal
(1N4148) is that limit the waveform in the low voltage power line can be
amplitude and let it is less than 0.7V transmitted to the distance.
voltage. Therefore, the circuit can identify The pin diagram of the module is shown
the useful waveform and protect the FSK- in figure 5.
KQ330 module effectively.

Figure 5. Zero-crossing detecting circuit

The 1pin is the foot of the input meet the communication format can trigger
data.The 8 pin is the foot of the output the corresponding function, which reduces
data. The operating voltage of the module the chance of error and data corruption.
is +5v. The communication protocol of the
system organizes data by packets and also
4. System Software Design sends data by packets. Data transmission
format is a frame format. When the carrier
4.1. Communication Protocol module is the sending-data state, data is
The system communication protocol is sent to the power line; when the data
mainly to ensure that the data which are transmission is complete, the carrier
transmitted will not be interfered with the module is set to the receiving-state. Data
data of other slave machines. It ensures the frame has a fixed format [21]. It includes
quality of the communication. In addition, the start code, the length code, the data
the agreement reduces the cost of content and the end code. The start code is
communication in some certain extent. It the head of each data packet, which is
helps identify the source of the signal and indicated as "#"; the length code is the total
realizes the exchange of the machines. length of the current packet; the end code
In this article, the communication is the end of each packet of data symbol,
protocols ensure the quality of data which is indicated as "$". Command packet
transmission. In the course of data format is shown in Table1.
reception, only the data packets which
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Table 1. Communication protocol packet format 4.2.2. Packet reception interrupt

Start code Length code Data End code program flowchart
#
0x length Content $

The way of the carrier module is a self-

defined way. If the data to be sent is # 0x06,
0x12, 0x34, 0x56, 0xFA, 0x91, 0x54$", so
0x06 is at the second place in the packet,
which indicates that the data content
length is six. The data behind 0x06 is the
data content, which is 0x12, 0x34, 0x56,
0xFA, 0x91, 0x54".
Because there are many interference
signals in the power line, the start code
shall be strictly determined. The serial port
baud rate is 9600 bps. When the start code
of the received data is # and the end code
of the received data is $, the data is valid
data. Otherwise, the data will be
abandoned and it re-searches the next start
code.
According to the data's transfer direction,
data communication can be divided into
three kinds of work mode: the simplex
mode, the half-duplex mode and the full- Figure 7. Packet reception interrupt program
duplex mode. In this paper, data flowchart

communication uses the half-duplex mode

which cannot send or receive data at the 5. Analysis of experimental results
same time [23].
By analyzing the experimental data
4.2. Communication Process achieved from the test, we found that the
actual signal values are close to the
4.2.1. The flowchart of send subroutine theoretical values. The system can work
stably.
5.1. The signal of FSK-KQ330 module
transmit-pin
When there is no data to be transmitted,
the signal in the transmit-pin is a straight
line. When data is transmitted, the signal in
the transmit-pin is a square wave signal. It
is as shown in Figure 8. Test point is in the
base pole of the transistor.

Figure 6. Zero-crossing detecting circuit Figure 8. Theoretical value of carrier module output
signal
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6. Conclusions
The low-voltage power line carrier
communication system is designed to
transfer 50 Hz power. At the same time,
more and more modern family use electric
equipment (such as microwave ovens,
induction cooker, electric power, washing
machine, computer, vacuum cleaners and
other equipment). The electric equipment
is mostly the inductance type equipment.
Because the electric equipment exists
the difference of quality and performance,
electric equipment itself can bring
Figure 9. The actual value of the carrier module
output signal interference to the power lines and
generate a lot of noise in power lines,
which restricts the quality of signal
5.2. The waveform received by carrier
transmission. This design uses the
module
multilevel filter amplifier circuit, which can
The signal received by the carrier effectively filter out noise and make the
module is a sine wave signal, which is received signal by the slave machines clean
filtered out from the 220V AC [24]. It goes and smooth. It is shown in figure 8,9,10 that
through the resonant circuit module. after the full control signal (square wave
After resonance filtering and waveform signal) is modulated by the master
processing, the signal is the stable sine machine, through the power line
wave. The actual signal values by testing transmission to the slave machine, the sine
are close to the theoretical values. wave signal can be demodulated by the
slave machine,which is close to clean and
smooth. The design of low-voltage power
Line carrier communication system based
on FSK-KQ330 module has the
characteristics of the simple hardware
circuit and low cost. The design can provide
reliable guarantee for data communication
based on single chip microcomputer . The
scheme can apply to intelligent home
system ,and It can also be used for the
remote control of the intelligent switch and
the intelligent equipment.
Figure 10. Theory carrier signal value at the
receiver module
7. References
[1] Yin Qun, Zhang Jianbo, "Design of control
platform systems based on object-oriented".
in International Review on Computers and
Software. 2012; vol. 7(no. 1): p. 438-442.
[2] Jianbo Zhang, Qun Yin, "Design of echo
cancellation based on FM1188". in
Electrotehnica Electronica Automatica. 2013;
vol. 61(no. 4): p. 41-47.
[3] Qi Jia-Jin, Chen Xue-Ping, Liu Xiao-Sheng, "
Advances of research on low-voltage power
line carrier communication technology". in
Dianwang Jishu/Power System Technology.
2010; vol. 34(no. 5): p. 161-172.
[4] Cai Wei, Liu Yi-Jun, Song Chun-Hui, Chen Lei,
Figure 11. The actual signal value at the receiver Le Jian, Jin Chao, "Overview of the channel
module
modeling methods of power-line carrier
 ELECTROTEHNIC, ELECTRONIC, AUTOMATIC, vol. 62 (2014), Nr. 3 141

communication". in Power System Protection June 10, 2003; vol. 27(no. 11): p. 16-20+33.
and Control. 2012; vol. 40(no. 10): p. 149- [15] Zhang Youbing, Cao Yijia, Cheng Shijie,
154. "Influence of synchronization errors on OFDM
[5] Chang Qing-Mei, Zhou Chang-Lin, Zhang based communication system for low voltage
Shao-Bo, Zhang Tong, "Elliptic filter design power lines". in Dianli Xitong
used for power line carrier communication". Zidonghua/Automation of Electric Power
in Power System Protection and Control. Systems. September 25, 2004; vol. 28(no. 18):
2011; vol. 39(no. 5): p. 144-147. p. 36-40.
[6] Wang Kuifu, "Complex signal processing and [16] Kuo H.C., Lin C.H., "Design and
its application in power line carrier implementation of wide area power line
communication". in Dianli Xitong insulation resistance measuring, monitoring
Zidonghua/Automation of Electric Power and control management system in Journal
Systems. Dec 20 2006; vol. 30(no. 14): p. 41- of Taiwan Society of Naval Architects and
45. Marine Engineers. February 2007; vol. 26(no.
[7] J. Michael, Whitney Bruce, "Evaluation of the 1): p. 19-27.
potential for power line carrier (PLC) to [17] Katayama M., "Introduction to robust,
interfere with use of the Nationwide reliable, and high-speed power-line
Differential GPS network Silva". in IEEE communication systems". in IEEE
Transactions on Power Delivery. April 2002; Transactions on Fundamentals of Electronics,
vol. 17(no. 2): p. 348-352. Communications and Computer Sciences.
[8] Wang Chang-Long, Ma Ai-Wen, Li De-Liang, December 2001; vol. E84-A (no. 12): p. 2958-
He Fu-You, "A Storage Alarm System Based 2965.
on Low Voltage Power Lines Carrier [18] Kuo H.C., Lin C.H., "Design and
Communication Using Spread Spectrum implementation of wide area power line
Technology" in Proceedings of the insulation resistance measuring, monitoring
International Symposium on Test and and control management system". in Journal
Measurement. 2003; vol. 5: p. 4236-4238. of Taiwan Society of Naval Architects and
[9] Xiao Yong, Fang Ying, Zhang Jie, Dang San- Marine Engineers. February 2007; vol. 26(no.
Lei, "Research on characteristics of low 1): p. 19-27.
voltage power line communication channel" [19] Katayama M., "Introduction to robust,
in Power System Protection and Control. reliable, and high-speed power-line
October 16, 2012; vol. 40(no. 20): p. 20-25. communication systems". in IEEE
[10] Fang Yong-Jun, Xu Zhi-Qiang, Zhai Ming-Yue, Transactions on Fundamentals of Electronics,
"Resource allocation for single user in power Communications and Computer Sciences.
line communication adaptive OFDM systems" December 2001; vol. E84-A (no. 12): p. 2958-
in Power System Protection and Control. 2965.
February 16, 2010; vol. 38(no. 4): p. 6-10. [20] Warudkar H.S., "Low voltage power line
[11] Tokuda Masamitsu, Hosoya Satoshi, communication: Applications in home
Yamagata Tom, Matsuo Takashi, "Conducted automation and energy management". in
interference immunity characteristics to Journal of the Institution of Engineers
high-speed power line communication (India): Electrical Engineering Division.
system". in IEEE Transactions on Electronics, December 2002; vol. 83(no. DEC): p. 250-256.
Information and Systems. 2010; vol. 130(no. [21] Xu Yiwen, Chen Zhonghui, Wang Weixing,
8): p. 1316-1326. Chen Wenxiang, "Multi-carrier FSK system
[12] Newbury J., Miller W., "Multiprotocol based on DSTFT and high-order moments for
routing for automatic remote meter reading LPLC communication". in Journal of
using power line carrier systems" in IEEE Computational Information Systems. October
Transactions on Power Delivery. January 1, 2012; vol. 8(no. 19): p. 8119-8127.
2001; vol. 16(no. 1): p. 1-5. [22] Kim Yong-Hwa, Lee Jong-Ho, "Comparison
[13] Xie Zhiyuan, Liu Qian, Guo Yihe, Wang Yan, of passband and baseband transmission
"Carrier signal transmission law of three- schemes for power-line communication OFDM
phase overhead power line". in Automation systems". in IEEE Transactions on Power
of Electric Power Systems. March 10, 2012; Delivery. October 2011; vol. 26(no. 4): p.
vol. 36(no. 5): p. 57-60. 2466-2475.
[14] Zhang Youbing, Cheng Shijie, Xiong Lan, [23] Yao Liang, Lai Qing-Huim, Lin Jun,
"Analysis and simulation of the OFDM based "Discussion on the multi-terminal trans-
communication over low voltage power line". mission line protection configuration in high-
in Automation of Electric Power Systems. voltage power grid". in Dianli Xitong Baohu
142 ELECTROTEHNIC, ELECTRONIC, AUTOMATIC,vol. 62 (2014), Nr. 3

yu Kongzhi/Power System Protection and Science and Technology.

Control. May 16, 2010; vol. 38(no. 10): p. 79- Her research interests include Embedded systems,
82+88. single-chip measurement and control field, the
[24] Zhao Hongshan, Liu Lifeng, Yang Qixun, computer control system, the interface control
system.
"Exploration of applying power-line spread
spectrum carrier technique to distribution
Zhang JIANBO was born in 1984.
automation". in Dianli Xitong Zidonghua
He received his Bachelor Degree in
/Automation of Electric Power Systems. Computer Software Engineering
2000; vol. 24(no. 12): p. 49-51, 68. from Oxbridge College, Kunming
[25] Franklin, Gregory A., "A practical guide to University of Science and
harmonic frequency interference affecting Technology, China in 2007, his
high-voltage power-line carrier coupling Master's degree in Computer Software Engineering
systems". in IEEE Transactions on Power from Yunnan University China in 2011.
Delivery. 2009; vol. 24(no. 2): p. 630-641. He is currently a lecture in Oxbridge College,
Kunming University of Science and Technology.
8. Biography His research interests include Computer software
engineering, information management systems,
Yin QUN was born in 1978. He and embedded systems.
received her Bachelor Degree in
Computer Science and Technology
from Kunming University of
Science and Technology, China in
2003, her Master's degree in
Management Engineering and Science from
Kunming University of Science and Technology,
China in 2008.
She is currently a lecture in Kunming University of