PC based Temperature Monitoring and Alarm System

Indian J.Sci.Res.3(2) : 17-20 , 2012 PC BASED TEMPERATURE MONITORING AND ALARM SYSTEM 1 I. OGHOGHO Department of Electrical and Information Engineering, Landmark University Omu-Aran, Kwara State, Nigeria E-mail : [email protected] ABSTRACT A PC based temperature monitoring and alarm system has been designed, constructed and tested. The system uses a linear and highly sensitive temperature transducer whose analog output is converted to digital format using an 8 bit analog to digital converter (ADC) before the digital signals are fed to the personal computer (PC) through the parallel port for display on the monitor. A program was written using Visual C++ which provides a user interface through which a predefined temperature limit can be set so that the threshold alarm is triggered when this limit is exceeded. A database to record the temperature readings for a o o certain period of time is also incorporated in the program. The device was tested within a temperature range of 25 C to 150 C while o varying the threshold temperature. From the results obtained the alarm was triggered at ± 0.1 C of the selected threshold temperature. The system finds application in power plants, laboratories, workshops and domestic kitchens. The system can also be adopted for multiple zone temperature sensing such as the simultaneous temperature measurement of automobile radiators and engines and measurement of boiler temperatures in power plants. KEYWORDS: Temperature,Alarm, PC, Monitoring,System The last decade has seen a large-scale growth in the requirement of temperature detection for industries, residential and commercial complexes and educational institutions (Chenetal, 2005; Prajaetal, 2011 and Mahanandiaetal 2008). Proper control and monitoring of temperature in these locations is necessaryto reduce failure rates because adverse temperatures in some of the systems will affect their functionality and availability. The need to monitor and control the temperature of equipments (whose functionalities depend on temperature) on real-time basis is necessary to avoid complete or partial loss of performance, accidents and damage of valuable machines which would take a lot of money and resources to restore to a good working condition. In power generating plants, for example, the output voltage produced is relatively affected by the temperature of the generators hence precise temperature sensing and control is very important (Alrashidi et al., 2009,Averyanova et al., 2011) In temperature monitoring systems, temperature is first converted to electrical signals using temperature transducers. The output of the transducers are conditioned and processed to give the output in the desired format. The output can be displayed on liquid crystal display (LCD) screens or on the PC monitor. The use of the PC has more advantages because, with the aid of a written program, it provides a user interface through which a predefined temperature limit can be set so that an alarm is triggered when this limit is exceeded. Temperature values can also be 1 Corresponding author stored and easily retrieved and modifications can easily be made to suite the particular equipment or system whose temperature is being monitored. The system can be easily interfaced with other PC based control systems in a larger perspective such as combining two machines. The PC based temperature monitoring and alarm system does not control temperature but monitors the temperature of the equipment and gives a warning when the threshold temperature is exceeded. MATERIALSAND METHODS In order to achieve the aim set out, existing systems were studied and various design options were considered (Praja et al.,2011;Averyanova et al.,2011;Wara et al., 2009; Agarwal and Pal ,2011;Dadji et al., 2009; Jovanović and Jevtic, 2011). The system was broken down into four sections: The power supply unit, the temperature sensing unit, the data acquisition and control unit and the output unit. A program in C++ required by the PC to monitor and control the device was developed after which the hardware and software parts of the system were integrated. The integrated module was tested and the results obtained were analyzed. The output voltage of the temperature transducer at different temperatures was tested. The equipment used for this purpose were; thermometer, heat source, a voltmeter and light emitting diodes (LEDs). The voltmeter was connected across the transducer (LM35) to measure the output voltage. OGHOGHO : PC BASED TEMPERATURE MONITORING AND ALARM SYSTEM The LEDs were connected to the output of the ADC to temperatures below the threshold,a yellow LED is lit for determine their state. The thermometer was used to temperatures equal to the threshold anda red LED is lit for determine the temperature of the soldering iron used as heat temperatures above the threshold. When the threshold source. At selected temperatures, the soldering iron was temperature has been exceeded, the last signal sent out from placed on the LM35 and the output voltage and the the PC is to the optocoupler energizing it thus causing it to temperature were read from the voltmeter and the PC trigger the buzzer. respectively and then recorded. The digital output of the ADC was read from the LEDs states, where ON represents RESULTSAND DISCUSSION HIGH and OFF represents LOW. Principle of Operation of the System The diagram of the system is shown in Fig.1. The system is powered by rectified and regulated 12V and 5V The recorded values of the results obtained from the tests are given in table 1. The thermometer and digital (ADC) temperatures versus output voltage is shown in Fig.2. D.C. power sources. The temperature sensing unit The temperature output of the PC compares well comprises of the temperature transducer and the analogue to with that obtained from the thermometer (± 0.2 C). The digital converter (ADC0804). Temperature is sensed by the alarm was triggered at ± 0.1 C of the threshold temperature. transducer and converted to an analog voltage by a It was observed that the ADC output in decimal differed transducer. The voltage from the transducer is passed to the from the thermometer reading by 10 C. This was due to the ADC which produces digital signals which are sent to the end error reading from the LM35 and the ADC. The end PC via the parallel port. The PC is the data acquisition and error reading was found to be 10%. Since it is the binary control unit. Signals from the ADC are transferred to the PC equivalent of this ADC output that is fed into the PC, the for processing via the data pins parallel ports. From the program was written to display the temperature taking into written program of Visual C++, the signal received, is consideration this end error reading of the LM35 and the executed pulse by pulse to convert the temperature sensed to ADC. The program was adjusted to ensure that the 10 C end a visual form where it can be monitored. The predefined error was subtracted from the measured temperature before limit of temperature that is to be monitored is achieved by it will be displayed on the PC screen, hence the temperature the Visual C++ program. A data base to record all the displayed on the PC screen compares well with that of the temperature readings for a certain period of time is also Thermometer despite the end error of the LM35 and the incorporated in the program. ADC. o o o o The PC reads the value of the analog to digital The device is able to measure and monitor converter output then interprets it to graphic User Interface temperature, display the value on the PC monitor and keep a (GUI). The value of the temperature is read on the monitor record of measured values. An alarm is triggered when the of the PC. The program has the following features: a selected threshold temperature is reached. Due to the Centigrade Scale, Data logging on easily readable text file, temperature transducer used, the device range is limited to sampling rate of 1, 5, 30 or 60 seconds: this feature enables −55° to +150°C. Another temperature transducer will have the operator to determine at what rate the temperature to be used for temperatures outside this range. The system should be monitored. Easily upgradeable source code for finds application in power plants, laboratories, workshops further capabilities: additional programming can be done on and domestic kitchens. The system can also be adopted for the existing one because of this important feature of the multiple zone temperature sensing such as the simultaneous program. temperature measurement of the radiator and engines in Based on signals sent out by the PC which depends on the monitored temperature, a green LED is litfor 18 automobiles and the measurement of boiler temperatures in power plants. Indian J.Sci.Res.3(2) : 17-20, 2012 OGHOGHO : PC BASED TEMPERATURE MONITORING AND ALARM SYSTEM Table 1: Test Results ADC Output (Digital PC Temperature Reading Thermo Temperature) LM35 1st test (Selected threshold 2ndTest (Selected threshold o Alarm o ( C) Output Temper o temp = 40 C) Temp meter temp = 80 C) LED type Temp Alarm o ON ( C) Decim Voltage Binary ature LED type al (V) (oC) ON OFF Green 30.1 OFF Green 30 0.37 00101000 40 39.9 ON Yellow 39.8 OFF Green 40 0.47 00110010 50 50 ON Red 50 OFF Green 50 0.58 00111100 60 60.1 ON Red 60 OFF Green 60 0.67 01000110 70 69.8 ON Red 70.1 OFF Green 70 0.78 01010000 80 80 ON Red 80.1 ON Yellow 80 0.87 01011010 90 90.1 ON Red 90 ON Red 90 0.96 01100100 100 L ED LE D Con verte r Dig it al Ana log ue to L ED 1 k 1k di spla y) DB1 DB0 and moni to r DB2 LM35 Vin(+) DB3 DB4 co ntr ol unit (pa ral lel po rts Co mputer D5 Vcc D7 Vcc(b) Vcc( b) Tx So ur ce AC D6 Pe rsona l 1 k Power Su pply Un it C1 Bri dge Rec tifie r From p le r Op tocou L7805 L7812C Vcc ((a ) Buzzer Vcc(a) Vcc( b) 30.1 Fig. 1: PC Based Temperature Monitoring and Alarm System Indian J.Sci.Res.3(2) : 17-20, 2012 19 OGHOGHO : PC BASED TEMPERATURE MONITORING AND ALARM SYSTEM Fig.2: Thermometer and Digital (ADC) temperatures versus output voltage ACKNOWLEDGEMENT I acknowledge the contributions of EngrAbayomiAlli Adebayo, Prof Wara S.T andEkpenyongU. in formatting, discussing, and in design and development of this work respectively. 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