Remote PLC system using GSM network with application to home security system

The focus of this paper is to present a low-cost and simple approach to designing intelligent home system using the concept of mobile-to-machine and machine-to-mobile communication. First, we develop a general purpose electronic circuit design that can control and monitor a variety of home appliances with interface that can be plugged into GSM handset unit. The design based on PLC comprises microcontroller, adaptation circuit, power circuit, and RS232 interface. Then, we develop prototype home security system as an application example of the designed PLC system. The system is completely built and tested and showed perfect operation. Introduction Global System for Mobile communication (GSM) has been one of the best trustable wireless communication systems that can be accessed and used very easily. It is cost effective either if we consider the price of its transceiver module (a simple cellular phone) or the subscription fees. With the trend of huge growing usage of GSM during the past decade, network services is extended beyond speech communication to so many other custom specified applications, machine automation and machineto-machine communication. This paper designs an intelligent home that can communicate with the user by using a mobile phone over GSM network. The interface and communication between home appliance the controlling circuit is the most important component in automation process. This function is implemented by using a Programmable logic controller (PLC) interfaced to a mobile phone. The user sends GSM data in the form of SMS (short message service) message to switch ON or OFF any appliance inside the home, like lamp, light, air condition, washer machine, TV, register, video ...etc. The appliance may also sends to the user its status and alarms. For instance, if some body tries to get into the home, then the home will automatically send alarm message to the user mobile phone or call the police station (if required). The system can be improved to provide the user with information about the status of each appliance, for example “Is the air condition ON or OFF?” A sketch of overall design of the PLC system is shown in Fig. 1. In the literature, there are few contributions proposed in recent years in machine-to-machine, mobile-to-machine, or machine–to-mobile communication. These include: designing prototype integrated mobile telemedicine system interfaced with sensors to a patient’s body using GSM simulation[Woodward, 2001]; designing mobile system with wireless LAN [Kugean, 2002]; implementing measurement system to monitor the ambient air quality using GPS, GPRS modem and advanced RISC machine [Sang,2 004]; designing remote control of sensors and actuators using GSM module [Aranguren, 2002]; and designing stand-alone human temperature and blood pressure system using microcontroller with embedded software [Al-Ali, 2003]. In line with these works, we describe in this paper simple guideline procedures to build general purpose hardware circuit and software algorithm of home appliance system. We first shed the light on the PLC system followed by describing the major components of the system: microcontroller, adaptation circuit, and power circuit. More detailed microcontroller operations with focus on AT commands transmission is presented in Section 4. In Section 5, we develop prototype home security system as an application example of the designed PLC system. Finally, Section 6 concludes the paper. purpose hardware circuit and software algorithm of home applianc system. We first shed the light on the PLC system followed by describing the major components of the system: microcontroller, adaptation circuit, and power circuit. More detailed microcontroller operations with focus on AT co mands transmission is presented in Section 4. In Section 5, we develop pr totype home security system as application example of the designed PLC system. Finally, Section 6 concludes the paper. PLC System The GSM network provides full duplex link to support the user requirement. The user can access the application remotely through SMS service where his message read and decoded by the microcontroller attached to the mobile set through a suitable interface, usually RS232 is used but also either Bluetooth or infrared links can be used. A resident assembly program on the microcontroller board allows it to transmit and receive data bytes to and from the attached GSM module under the control of the far end phone key board or upon receiving SMS from the remote mobile phone The decoded message is then processed and used to access the application using digital input /output or digital to analog converter. Adaptation circuits are also needed to provide suitable operating voltage level for the application. Examples of adaptation circuits are relay, power switch, power amplifier...etc. Fig. 2 shows the block diagram of the connection between the main components of the PLC system. In the figure, the level shifter is used to change the signal level in the serial port (12 volt for logic 0 and -12 volt for logic 1) to TTL level (5 volt for logic 1 and 0 volt for logic 0) to be compatible with the microcontroller. The used level shifter in this circuit is MAX232. The machine is the major part of the system because the overall system is built to control it. The machine can be either electrical or mechanical or any other type according to the user requirements. The machine includes all the necessary circuits and sensors needed to couple, apply input or output signals from the microcontroller to the units to be controlled. Among the circuit that may be employed in general are: �Different types of sensors, analog or digital, to sense temperature, pressure , speed, ...etc �Analog signal processing circuits �Programmable counters and timers, power switches: mechanical relays or semiconductor switches. �A/D and D/A circuits Controlling Circuit Home Appliance User Figure 1. Simplified block diagram of PLC system Figure 1. Simplified block diagram of PLC system 2 PLC System The GSM network provides full duplex link to support the user requirement. The user can access the application remotely through SMS service where his message read and decoded by the microcontroller attached to the mobile set through a suitable interface, usually RS232 is used but also either Bluetooth or infrared links can be used. A resident assembly program on the microcontroller board allows it to transmit and receive data bytes to and from the attached GSM module under the control of the far end phone key board or upon receiving SMS from the remote mobile phone The decoded message is then processed and used to access the application using digital input /output or digital to analog converter. Adaptation circuits are also needed to provide suitable operating voltage level for the application. Examples of adaptation circuits are relay, power switch, power amplifier...etc. Fig. 2 shows the block diagram of the connection between the main components of the PLC system. In the figure, the level shifter is used to change the signal level in the serial port (12 volt for logic 0 and -12 volt for logic 1) to TTL level (5 volt for logic 1 and 0 volt for logic 0) to be compatible with the microcontroller. The used level shifter in this circuit is MAX232. The machine is the major part of the system because the overall system is built to control it. The machine can be either electrical or mechanical or any other type according to the user requirements. The machine includes all the necessary circuits and sensors needed to couple, apply input or output signals from the microcontroller to the units to be controlled. Among the circuit that may be employed in general are: 1Different types of sensors, analog or digital, to sense temperature, pressure , speed, ...etc 2Analog signal processing circuits 3Programmable counters and timers, power switches: mechanical relays or semiconductor switches. 4A/D and D/A circuits 5Input output latch circuits. �Input output latch circuits. Hardware Construction This section describes in details the major hardware components in Fig. 2, namely: microcontroller, adaptation circuit, and power circuit. The integration of all these components will be also sketched. The Microcontroller The microcontroller is a programmable device that can be designed to work as the designer want. It acts as the brain of the system. This microcontroller is designed to be multi input multi output and general purposes microcontroller. To make this microcontroller works, the programmer writes a program that controls the overall system then downloads this program inside the microcontroller chip. This program must be a HEX file. The program is written using assembly language and then converted to HEX file. There are several types of the microcontrollers available in the markets. The easiest way of using the microcontroller is to replace it with the personal computer (PC). However, such approach is not efficient and even not cost effective. The optimum way is to use a small microcontroller instead of PC. In this paper, we adopt AT89C52 Microcontroller. The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using ATMEL high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 and 80C52 instruction set. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the ATML AT89C52 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. The 89C52 chip contains the following sections: �Standard 80C51 CPU RS232 Level Shifter Microcontroller