Designing a Low Cost Electronic Devices Switching System Controlled by Short Message Service

Zahariah.M, Mardiana.B, Hazura.H, Fauziyah.S, Hanim.A.R Faculty of Electronic Engineering & Computer Engineering

Universiti Teknikal Malaysia Melaka (UTeM) Melaka, Malaysia

zahariah@utem.edu.my, mardiana@utem.edu.my, hazura@utem.edu.my, fauziyah@utem.edu.my, hanim@utem.edu.my

Abstract— This paper explains how a Short Message is used as a command to remotely control a switching system. There is a great demand for applications that can remotely control electrical or electronic devices. Over the last decade, the implementation of this concept has been attempted by using the Internet and through power-line modems. However, these solutions are not only complex but also require a physical connection to access those devices. A simple, cost-effective solution is proposed here, by which devices as mentioned above can be controlled remotely while the user is anywhere across the globe. Short Message Service (SMS) is a mechanism of delivery of short messages over mobile networks that are widely spread all over the world. A mobile phone which is connected to a PC is used to receive commands from the owner. After receiving the text commands, the received data will be analyzed by the PC program and then PC will set the status of its parallel port data pins to high or low. The switches of all the controllable devices are connected to the PC parallel port. Therefore, by sending appropriate data via SMS, the devices can be switched ON/OFF remotely.

Keywords-component; electronic devices, switching, SMS

I. INTRODUCTION In today’s world, there is a great demand for applications

that can remotely control electrical or electronic devices. These devices include household appliances such as televisions, refrigerators, lighting appliances, air-conditioners and washing machines. There are researches have been carried out for this purpose by implementing this function through the Internet and power-line modems. However, these solutions are not only complex but also require a physical connection to access those devices. In the case of controlling electronic circuits through the Internet, the main problem is that each controllable device requires separate Ethernet card and IP address. It also requires Internet connection to each device. A simple, cost-effective solution is proposed here by which devices as mentioned above can be controlled remotely, while the user is anywhere as long as the service is available.

Nowadays, Short Message Service (SMS) has become very popular since it is cheaper when compared to voice services. It is a store-and-forward way of transmitting

messages to and from mobiles. Each short message can be no longer than 160 characters. These characters can be text (alphanumeric) or binary Non-Text Short messages. An interesting feature of SMS is return receipts. This means that the sender has the option of receiving a receipt notifying that the SMS was successfully delivered to the intended recipient. Since SMS uses signaling channels for its transmission/reception as opposed to dedicated data channels, these messages can be sent/received simultaneously with the voice, data or fax services over Global System for Mobile Communication (GSM) networks. Moreover, SMS supports national and international roaming. With Personal Communication Services (PCS) networks based on all the three technologies which are GSM, Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA) supporting SMS [1], SMS has been rendered a universal mobile data service.

Power can be wasted in houses and offices due to forgetful nature of users not switching off appliances after use. There is also the risk of over-heating and hence, damage caused to household appliances like water-heaters due to such common human errors [2]. By the solution proposed, such power wastage can be minimized in homes and even work places can be controlled by a common remote-switch by appropriate networking. In this method the switches will be controlled by SMS messages.

II. BACKGROUND STUDY The beauty of SMS is the ability to send and receive text

messages to and from mobile telephones. The text can comprise of words or numbers or an alphanumeric combination. SMS was created as part of the GSM Phase 1 standard. Each short message is up to 160 characters in length when Latin alphabets are used and 70 characters in length when non-Latin alphabets such as Arabic and Chinese are used.

Mobile phone users to communicate with each other routinely use the SMS. Typically, such person to person messaging is used to say hello or prompt someone for something or arrange a meeting or tell someone something.

2009 International Conference on Computer Technology and Development

978-0-7695-3892-1/09 $26.00 © 2009 IEEE

DOI 10.1109/ICCTD.2009.166

292

2009 International Conference on Computer Technology and Development

978-0-7695-3892-1/09 $26.00 © 2009 IEEE

DOI 10.1109/ICCTD.2009.166

292

Serial Port

AT Commands

Parallel Port

Control Circuit

Send an AT Command to modem

Any command message?

Initializing serial port: baud rate, flow control

NO

• Read the SMS message content. • Analyze the command. • Check authentication parameters • Write the required data to the Parallel Port.

YES

Start

Check Timer > 1 minute?

YES

NO

End

Such messages are usually originated from the mobile phone keypad.

When the information to be communicated is short or it would take too long to have a full conversation or someone is traveling overseas or not available to take a voice call, SMS is an ideal messaging medium. For example, network operators typically charge the same to send a short message to someone in the same room as they do to someone traveling overseas with their mobile phone. Because short messages are proactively delivered to mobile phones that are typically kept in the user's pocket and can be stored for later reference, SMS is often more convenient than email or data to communicate amongst distributed and mobile groups of people.

These specialties of SMS make the system interesting to be explored and exploited to run other applications apart from doing its original purpose. One of the potential applications is to control remote circuits for the purpose of monitoring or for the safety reason.

III. METHODOLOGY The implementation of this solution is depicted by Fig.

1. The system consists of three major elements which are a hand-phone, a personal computer (PC) and an external control circuit.

The short message (command message) to control the devices is sent from any remote cell or land phone network to a pre-determined mobile number, which is connected to the PC.

A. Software Development The hand-phone which acts as a modem is connected to

the PC through the serial port. The serial cable functionality is established by using HyperTerminal. The firmware that reads and analyzes the command messages is developed by using Visual C++. This program periodically sends an AT Command to the modem to check for incoming command messages. If there is a command message received, the modem will respond to the PC. Based on the command messages received, the program will on/off the specific device by sending the high or low inputs to the parallel port data pins. The flow chart in Fig. 2 explains the program of the firmware.

Figure 1. The block diagram of the system.

Figure 2. The flowchart of the firmware program.

Basically, the program that was developed is not standalone software. This program requires other software to be installed in the same PC namely Nokia Data Suite Version 2.0.This program will enable the program to configure the serial port via the F-bus cable.

B. Hardware Development The electronic or electrical devices to be controlled are

connected to the parallel port of the PC through an external control circuit. The I/O voltage level of the parallel port is 5V Max and 3mA current can be drawn from the port [3]. If the device is an electronic device that needs only 5V to operate, then this can be directly controlled from the parallel port.

The control circuit contains eight identical relay that act as switches. Each relay is connected to one electrical appliance. As a precaution, a UPS is used to keep the computer operating in the case of a mains power supply failure or the board is accidently disconnected.

IV. RESULTS An experiment prototype of the system has been

successfully developed as shown in Fig. 3. In this prototype, bulbs are used to represent electrical appliances. An analysis has been conducted to test the functionality of the system.

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Figure 3. The experiment prototype of the system.

Table I shows the pin configurations for the parallel port of the PC which enable the PC to communicate with the external circuit. Table II shows the output of the experiment.

To activate Device 1, a command message containing a ‘1’ is sent to the modem. The firmware will activate pin D0 to trigger relay 1. While to activate Device 2, a command message containing a ‘2’ is sent to the modem. The firmware will activate pin D1 to trigger relay 2. For the subsequence devices, the same process needs to be done by sending a number according to the device’s number. To OFF all devices, a command message containing a ‘9’ is sent.

Fig. 4 shows the code that is translated by the Hyperterminal when command ‘1’ is received by the modem while Fig. 5 shows its execution status. Fig. 6 demonstrates the output of the relay circuit when command ‘1’ is sent to the modem.

TABLE I. THE PIN CONFIGURATION FOR THE PARALLEL PORT

Pin Number Device Connected

D0 Device 1

D1 Device 2 D2 Device 3 D3 Device 4 D4 Device 5 D5 Device 5 D6 Device 6 D7 Device 7

TABLE II. THE OUT PUT OF THE EXPERIMENT

Command Message Device Respond

1 Device 1 ON 2 Device 2 ON 3 Device 3 ON 4 Device 4 ON 5 Device 5 ON 6 Device 5 ON 7 Device 6 ON 9 All devices OFF

Figure 4. Program reading message ‘1’.

Figure 5. Program executes command ‘1’ and displays command.

Figure 6. Device 1in the ‘ON’ condition.

From the results of the experiment, we can say that all devices able to respond to the corresponding command messages.

V. CONCLUSION With the success of this experiment, we conclude that

SMS can be used to control the switching system of electrical devices. This outcome can be implemented in several applications such as in controlling house lights or switching ON the air conditioner. This approach may leads

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to energy saving and prevent damages caused by excessive heating.

REFERENCES

[1] Siang, B.K. Bin Ramli, A.R. Prakash, V. Bin Syed Mohamed, S.A.R. “SMS Gateway Interface Remote Monitoring and Controlling via GSM SMS”, Proceeding 4th National Conference on Telecommunication Technology 2003.

[2] Alheraish, A., “Design and Implementation of Home Automation System”, IEEE Transaction on Consumer Electronics, Nov 2004.

[3] Hutchinson, Sarah E. Sawyer, Stacey C., “Computers, Communications, and Information: A User's Introduction. Comprehensive Version”, 7th Edition, 2000.

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