PLC using GS with application to home security A. Alheraish, W. Alomar, and. Abu-Al-Ela Department of Electrical Engineering, King Saud University, Riyadh, Saudi Arabia PLC using GS Keywords Programmable logic controller, machine automation, GS, home security, microcontroller. Abstract focus of this paper is to present a low-cost and simple approach to designing intelligent home using the concept of mobile-to-machine and machine-to-mobile communication. First, we develop a general purpose electronic design that can control and monitor a variety of home appliances with interface that can be plugged into GS handset unit. design based on PLC comprises microcontroller, adaptation, power, and RS3 interface. n, we develop prototype home security as an application example of the designed PLC. is completely built and tested and showed perfect operation. Introduction Global System for obile communication (GS) has been one of the best trustable wireless communication s 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 GS during the past decade, 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 GS. interface and communication between home appliance the controlling is the most important component in automation process. This function is implemented by using a Programmable logic controller (PLC) interfaced to a mobile phone. user sends GS data in the form of SS (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. 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). 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 is shown in Fig.. In the literature, there are few contributions proposed in recent years in machine-to-machine, mobile-to-machine, or machine to-mobile communication. se include: designing prototype integrated mobile telemedicine interfaced with sensors to a patient s body using GS simulation[woodward, 00]; designing mobile with wireless LAN [Kugean, 00]; implementing measurement to monitor the ambient air quality using GPS, GPRS modem and advanced RISC machine [Sang, 004]; designing remote control of sensors and actuators using purpose GS module hardware [Aranguren, 00]; and software and designing algorithm stand-alone of home human appliance temperature. and We blood first pressure shed the using light microcontroller on the PLC with embedded followed software by describing [Al-Ali, the 003]. major In components line with these of works, the we describe in this paper simple guideline procedures to build general purpose hardware and : software microcontroller, algorithm of home adaptation appliance., We and first shed power the light. on the ore PLC detailed followed microcontroller by describing the operations major components with focus of the on : AT commands microcontroller, transmission adaptation is presented, and in power Section. 4. ore In Section detailed, microcontroller we develop prototype operations home with security focus on AT commands as application transmission is example presented of in the Section designed 4. In PLC Section., we Finally, develop prototype Section 6 home concludes security the paper. as an application example of the designed PLC. Finally, Section 6 concludes the paper. igure. implified lock diagram f PLC ystem Figure. Simplified block diagram of PLC User Controlling Home Appliance 8 th National Computer Conference 006 Saudi Computer Society PLC System GS provides full duplex link to support the user requirement. user
PLC System GS provides full duplex link to support the user requirement. user can access the application remotely through SS service where his message read and decoded by the microcontroller attached to the mobile set through a suitable interface, usually RS3 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 GS module under the control of the far end phone key board or upon receiving SS from the remote mobile phone decoded message is then processed and used to access the application using digital input /output or digital to analog converter. s are also needed to provide suitable operating voltage level for the application. Examples of adaptation s are relay, power switch, power amplifier etc. Fig. shows the block diagram of the connection between the main components of the PLC. In the figure, the level shifter is used to change the signal level in the serial port ( volt for logic 0 and - volt for logic ) to TTL level ( volt for logic and 0 volt for logic 0) to be compatible with the microcontroller. used level shifter in this is AX3. machine is the major part of the because the overall is built to control it. machine can be either electrical or mechanical or any other type according to the user requirements. machine includes all the necessary s and sensors needed to couple, apply input or output signals from the microcontroller to the units to be controlled. Among the that may be employed in general are: - Different types of sensors, analog or digital, to sense temperature, pressure, speed, etc - Analog signal processing s 3- Programmable counters and timers, power switches: mechanical relays or semiconductor switches. 4- A/D and D/A - s Input output latch s. - Input output latch s. GS V 0 0 0 Figure. block diagram of the PLC Figure. block diagram of the PLC Far end User -V RS3 AT Command Level Shifter AT Command icrocontroller achine Hardware Construction This section Hardware describes in Construction details the major hardware components in Fig., namely: microcontroller, adaptation, and power. integration of all these components will be also sketched. This section describes in details the major hardware components in Fig., namely: icrocontroller microcontroller microcontroller, is a programmable adaptation device, that and can be power designed. to work as integration the designer of want. all these It acts as the components brain of the will. be also This sketched. 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 icrocontroller the overall then downloads this program inside the microcontroller chip. This program must be a HEX file. program is written using assembly language and then converted to HEX microcontroller file. re are several is a programmable types of the microcontrollers device that can available be designed in the markets. to work as the easiest way designer of using the want. microcontroller It acts as the is to brain replace of the it with. the personal This microcontroller computer (PC). However, is designed to such approach is not efficient and even not cost effective. optimum way is to use a small microcontroller instead be multi of PC. input In this multi paper, output we adopt and AT89C general icrocontroller. purposes microcontroller. To make this microcontroller works, the programmer writes a program that controls the overall AT89C is a low-power, then downloads high-performance this program COS inside 8-bit microcomputer the microcontroller with 8K chip. bytes This of Flash program must be a HEX file. program is written using assembly language and then converted to HEX file. re are several types of the microcontrollers available in the markets. 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.
programmable and erasable read only memory (PERO). device is manufactured using ATEL high-density nonvolatile memory technology and is compatible with the industry-standard 80C and 80C instruction set. on-chip Flash allows the program memory to be reprogrammed in or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the ATL AT89C is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. 89C chip contains the following sections: - Standard 80C CPU - Full Duplex UART (Universal Asynchronous Receiver Transmitter). 3-3 programmable timers. 4-8 k byte Flash memory. - 4 I/O programmable ports 6- Crystal Oscillator where the crystal is connected externally. chip can also work from external clock generator while disabling the Crystal oscillator. functions of the microcontroller in the are: PLC using GS 3 a- Initiate the attached GS module and make it ready to communicate with the other phone by sending a confirmation either through SS or dialing the previously stored phone numbers list. This is important to acknowledge the far end control units that the is ready. This step is done once when power is turned ON, and each time the power is turned ON. b- Check the reception of any commands either in SS or by answering a call and waiting the commands from the far end mobile set. This also include sending a confirmation that the message is received. c- Process the received commands and produce all signals needed to physically execute this command. d- Perform any needed tests and acquire all possible signals that confirm the execution of the received commands. e- Send a confirmation message to the far end mobile set and return again in waiting state for another commands. Of course the above functions are general and the driving software may be written to adopt a specified application. One of the 80 s many powerful features is it s integrated UART, otherwise known as a serial port. fact that the 80 has an integrated serial port means that the programmer may very easily read and write values to the serial port. If it were not for the integrated serial port, writing a byte to a serial line would be a rather tedious process requiring turning on and off one of the I/O lines in rapid succession to properly clock out each individual bit, including start bits, stop bits, and parity bits. However, the programmer does not have to do this. Instead, he simply needs to configure the serial port s operation mode and baud rate. Once configured, all what he has to do is writing to an SFR (Special Function Register) to write a value to the serial port or read the same SFR to read a value from the serial port. 80 will automatically let the programmer know when it has finished sending the character he wrote and will also let him know whenever it has received a byte so that he can process it. programmer does not have to worry about transmission at the bit level--which saves him quite a bit of coding and processing time. microcontroller controller can accept TTL level in its input or output but most of the external s work in either olt or 0 volt and thus the microcontroller can not operate these s. To overcome this, the adaptation is used to convert the input or the output voltage level between the microcontroller and the external. adaptation consists mainly of relays and transistors. Fig. 3 shows the adaptation suggested in this paper. When the input to the adaptation is low then the output will be and the switch will be opened but when the input is high then the switch will be closed. reason behind using this type of the is to completely isolate the relay current from the microcontroller current. This method prevents the output voltage from dropping and prevents the microcontroller from producing a high current, which may damage the microcontroller.
is low then the output will be and the switch will be opened but when the input is high then the switch will be closed. reason behind using this type of the is to completely isolate the relay current from the microcontroller current. This method prevents the output voltage from dropping and prevents the microcontroller from producing a high current, which may damage the microcontroller. is low then the output will be and the switch will be opened but when the input is high then the switch will be closed. reason behind using this type of the is to completely isolate the relay current from the microcontroller current. This method prevents the output voltage from dropping and prevents the microcontroller from producing a high current, which may damage the microcontroller. Figure 3. Figure 3. Figure 3. Load Load 4.7k Relay Relay input 0k 4.7k 4 Figure 4. power Figure 4. power Figure 4. power Power input 0k required power to operate the microcontroller is volt (DC) but the available voltage supply is 0 volt (). must use a to covert the voltages to Power volt. consists of a transformer to change the voltage from () to required 6 volt power (), to operate a bridge the microcontroller to take the absolute is volt (DC) value but of the the available signal, voltage a capacitor supply is and 0 volt a (). regulator. Power Fig. must 4 use shows a the building to covert the of this voltages. to volt. consists of a transformer to change the voltage from () to 6 volt (), a bridge to take the absolute value of the signal, a capacitor and a regulator. required Fig. 4 shows power the to building operate of this the. microcontroller is volt (DC) but the available voltage supply is 0 volt (). must use a Input to covert the voltages to volt. output consists Regulator of a transformer m to change the voltage from () to 6 volt (), a bridge to take the absolute + value Bridge of the - signal, a capacitor and a regulator. Fig. 4 shows the building of this. Figure. integrated PLC + Bridge - Input Regulator Integrating the above main microcontroller m (AT89C), adaptation, and power as well as level output shifter Regulator + (ax 3) Bridgeis -illustrated in Fig.. In the figure, the is constructed to control and monitor m many machines () or home appliances. 7 3 4 Serial port Integrating the above main microcontroller (AT89C), adaptation, and power as well as level shifter (ax 3) is illustrated in Fig.. In the figure, the is constructed to control and monitor many machines () or home appliances. 000n 000n 40 39 0k Figure. integrated PLC 000n 3 000n 4 6 7 8 000n 6 4 3 0 9 AX 3 0.47m HELE.09HZ 30 AT89C 9 0 3 8 7 6 4 8 3 9 0.k k Relay 4.7k 0k icrocontroller Operation
Integrating the above main microcontroller (AT89C), adaptation, and power as well as level shifter (ax 3) is illustrated in Fig.. In the figure, the is constructed to control and monitor many machines () or home appliances. icrocontroller Operation AT commands (Attention commands) are commands that control the PLC. AT commands can be considered as a representation of the signal that passes inside the PLC. If the microcontroller is considered as the brain of the then the AT Commands act as the nervous of the. se commands are used to allow the connection between the data terminal equipment and the data communication equipments through any port like the serial port RS3. most commonly used AT Commands that are related to the SS message are the following: - AT+CGF= /* Setting the massage format to the text mode. PLC using GS - AT+CSDH= /* Setting the AT command to the mode that allows sending SS.. 3- AT+CSP=7, 67, 0, 0 /* Setting the text mode parameter, where the second parameter specifies the period for resending, meaning that 67 specifies that the time is 4 hours. other parameters are related to the coding protocols. 4- AT+CPS=<mem>, <mem>, <mem3> /* Preferring the memory location for the message storage. mem represents the type of memory to be used either SI card or mobile equipment which are indicated by S or E respectively. mem specifies the memory from which the message will be read and deleted. mem specifies the memory to which writing and sending operation are made. mem3 specifies the memory that the received message will be stored in it - AT+CGR= /* Reading the message, where is the number of the message in the memory. 6- AT+CGS= the phone number /* Sending the message. 7- AT+CGD= /* Deleting the message. Sending the AT Commands by using the microcontroller is not an easy job. This is because the designer has to understand the communication protocols that are used by the GS and by the mobile phone. Since sending the AT Commands will be through the serial port, the AT Command will be sent character by character. Once the mobile receives the character, it will use an error checking technique to check if the character was received correctly or there is error on it. technique used in the mobile is the echo checking technique. In this technique, the mobile will resend the same received character again to the microcontroller to check if the transmitted character was received correctly or not. procedure of transmitting the commands will be as follows. First, the microcontroller sends the first character of the AT Commands to the mobile. n, the microcontroller will wait for the mobile phone to resend the same character to prevent the collision between the transmitted and received signal at the SBUF (Serial Control, Addresses 99h). microcontroller will send the remaining characters by the same way. Once the AT Command has been sent completely, the mobile phone will send a response to the microcontroller. number of the character response will vary from At Command to other. microcontroller must wait until the received response finish completely. Home Security System A simple application of the above described is a home security as shown in Fig. 6. This enables the far end user through SS facility to monitor the state of home door and detect any illegal intrusion; select and change a certain password for key locking the door; and control the home lighting to give impression for the outsiders that there is somebody inside. password may be any four characters where their ASCII code is inserted in the deriving program either using the key pad or by sending a SS message from the far end mobile. intrusion detector is a simple LED (Light Emitting Diode) and an infrared sensors. se two elements are fixed across the door and send on/off signal in case of intrusion. sensor will be connected to the microcontroller and acts as a switch. sensor is read by the microcontroller that decode their reading and send it to the far end user through GS as SS. tice that the alarm of an illegal intrusion will be ignored when the program receive the correct password. Control of the lighting can be performed simply by using voltage controlled power switches connected shunt the usual on/ off switch of selected rooms and appliances in the house. control signals of these switches come from port C of the microcontroller as it programmed as an output port.
intrusion will be ignored when the program receive the correct password. Control of the lighting can be performed simply by using voltage controlled power switches connected shunt the usual on/ off switch of selected rooms and appliances in the house. control signals of these switches come from port C of the microcontroller as it programmed as an output port. dc power supply +/- V V 6 Level Shifter + RS3C Connector and Cable UART ATEL 89X icrocontroller Input Output Ports Start Figure 6. Block diagram of Figure 6. Home Block diagram security of Home security Initializing the icrocontroller Power Switch Initializing drivers the mobile & Status signals [AT+CGF=], [AT+CSDH=], [AT+CSP=7, 67, 0, 0], [AT+CPS="E", "E", "E"] Is there a thief? Lighting System and Home Is there a new appliances essage? Key Lock Control - bit Key Lock Solenoid Intrusion Detector -bit Sent SS to the user" there is a thief" Infrared Sensor Fig. 7 shows software implementation of the home security operation. Two implementation scenarios are considered: controlling the alarm (from user s remote mobile to the machine) and Save and read the message alarm notification Fig. 7 shows (from software machine implementation to user s remote mobile) of the For home the security first scenario, the user operation. sends SS Two message to the microcontroller. Is the password microcontroller correct? will then check for any new message. If there is a new implementation message, the microcontroller scenarios are sends considered: AT Command controlling that is specified the alarm for reading (from user's the message. remote Consequently, mobile the to the microcontroller machine) and will alarm save the notification message in (from its memory. machine n, to user's the message remote will mobile) be compared For with the other first messages scenario, that the Decode are the user stored message sends previously. SS Based message on this to comparison, the microcontroller. the microcontroller will microcontroller decide which will output then pins check have for to be any low new and message. which output If there pins is have a new to be message, high. the high signal will go to the adaptation Control the output of the icrocontroller and opens the switch causing the machine to work. received microcontroller message will be automatically sends AT Command deleted. For that the second is specified scenario, for the microcontroller reading the message. input is connected Consequently, to a switch. the switch microcontroller is Delete fixed the message in the will door. save When the the message door is opened, in its memory. the switch n, is closed the [AT+CGD=} and there message will be an will input be voltage compared to the with microcontroller. other messages microcontroller that are stored will previously. check its input Based and on sends alarm this comparison, message to the the user microcontroller as the designer will has decide programmed. which output Fig. 8 shows pins have a snapshot to be low of the and complete PLC. which output pins have to be high. high signal will go to the adaptation and opens the switch causing the machine to work. received message will be automatically deleted. For the second scenario, the microcontroller input is connected to a switch. switch is fixed in the door. When the door is opened, the switch is closed and there will be an input voltage to the microcontroller. microcontroller will check its input and sends alarm message to the user as the designer has programmed. Fig. 8 shows a snapshot of the complete PLC. Figure 7. flow chart of the home security Figure 8. Snapshot of the PLC AT+CGS Figure 8. Snapshot of the PLC
Start Initializing the icrocontroller PLC using GS Initializing the mobile [AT+CGF=], [AT+CSDH=], [AT+CSP=7, 67, 0, 0], [AT+CPS="E", "E", "E"] Is there a thief? Sent SS to the user" there is a thief" 7 Figure 7. flow chart of the home security Is there a new essage? Save and read the message AT+CGS Is the password correct? Decode the message Control the output of the icrocontroller Figure 7. flow chart of the home security Delete the message [AT+CGD=} Figure 8. Snapshot of Conclusions In this paper, we have developed an integrated PLC. is intended to be used in the PLC many applications where the user can monitor and control target machine remotely using GS. designed PLC is based on microcontroller and adaptation connected to various home devices. electronic design of each design element was described with economical and simple layout. was applied to an example of home security notification to monitor and control the home door alarm. has been implemented in laboratory and proved to be feasible by experiments. References Woodward, B. Istepamian, H. and Richards, C. (00) Design of a Telemedicine using a mobile telephone, IEEE Transaction on Information Technology in Biomedicine, Vol,, arch. Kugean, S. Krishnan, S. Chutatape, O. Swaminthan, S. Srinivasan, Wang, N. (00) Design of a mobile telemedicine with wireless LAN, International Conference on s and Systems, APCCAS 0, Asia-Pacific, Oct. Conclusions In this paper, we have developed an integrated PLC. is intended Sang, H. Lin, C. Youn, Z. (004) A wireless Internet-based measurement architecture for air quality monitoring, IEEE Conference Instrumentation and easurement Technology, ITC 04, ay. Aranguren, G. zal, L. Blazquez, A. and Arias, J. (00) control of sensors and actuators by GS, IEEE 00 8th Annual to be used in many applications where the user can monitor and control target Conference of the Industrial Electronics Society IECON 0, Vol. 3, v. machine remotely using GS. designed PLC is based on Al-Ali, A. Al-Rousan,. and Al-Shaikh,. (003) Embedded -Based obile Patient onitoring Device, 6th IEEE Symposium on Computer-based edical Systems, CBS 03, ay.