Controller based Temperature Monitoring System Jay H. Bhut1, Dharmrajsinh Parmar2 1ME student of MEFGI, Rajkot, Gujarat - India. Email: [email protected] 2M.Tech. Student of CSPIT, Changa, Gujarat - India. Email: [email protected] Abstract:Monitor and control the temperature is an important factor in industrial environments. Sensors are widely used for measurement of temperature. This paper describes a temperature controller where the user can pre-adjust the temperature or can give a condition to maintain the temperature of an instrument or of any instrument body. In addition it records temperature variations in PC using serial communication. The controller can be easily adapted to different environment and actuating systems to fulfil the local requirements. Keyword: Microcontroller (PIC), Temperature Sensor (LM35), ADC. INTRODUCTION The temperature is one of the important factors which need to control and monitor as it often affect some scientific experimentsand instruments reading inthe laboratory where an investigation performs.There are many different cases where the quality of theexperiments depends on a reliable Temperature control [2]. There are the adaptive requirements which lead us to include different hardware components as: 1.A controller board, 2.A Temperature Sensor, 3.A Personal Computer, and 4.The appropriate Software. From these a controller board is required to control the peripheral activity which connected to it. A temperature sensor is mainly used to measure the temperature of aninstrument body where it connected and it gives the output in an analog form and output of that given to A/D IC to convert it into digital form. From this one can maintain a temperature through coil, heater or fan by keeping a condition in controller. A personal computer is used to display and store the temperature and to provide quick and easy access using the RS232 cable of a serial communication to the mentioned board. Software used to calculate the temperature through pin connected with a sensor and set the parameters and maintain the constant temperature by triggering voltage of the pin which connected to heater or coil. Software also used to display the recorded information of temperature variations and serve a communication link between the control board and the PC. This paper is organized as follows: in the first section itdescribes the sensors and control board, which form the hardware of the system. In the following one that gives an outline of a mathematical calculation for calculating the temperature. In the next following section brief intro of software is provided. Finally, in the last section it concludes the paper. TEMPERATURE CONTROLLER USING PIC: The controller used in this work is microchip’s PIC controller which is more popular one among the other controller so,it also called as industry standard controller. The other main thing to use PIC controller is it has inbuilt analog to digital channel which removes the requirement of an external Analog to Digital (ADC) IC to convert analog output of a sensor into digital to give it to a controller as an input [3]. Fig 1: Functional Block Diagram of Temperature Controller Sensors are widely used to measure the room temperature or of an instrument body. Usually, temperature sensors are of two types by seeing its output as some gives voltage whereas few give in current. LM35 is a one of the popular temperature sensor which gives its output by converting temperature into appropriate voltage. In this presented work temperature controller describes based on PIC16F887 and LM35 temperature sensor. A description of a simple temperature measurement and a display system is described in this paper. The above functional block diagram shows a temperature controller system which having different blocks which connected to the controller to perform different functions as explained below. 5V power supply connected to controller to supply the power and reset circuit used to reset the circuit. Here from above block diagram Crystal frequency block connected to controller is optional as PIC controller has also an internal crystal oscillator of up to 8MHz. Personal computer is used to display and store the temperature data into database throughout the whole day using serial communication. One can also use a LCD display and keypad to only display the temperature without using any serial port. At last Coil or Heater used as a cooling part to keep maintain the temperature of an instrument body as per controller instruction through software. The 10 bit of inbuilt ADC converter is used in PIC controller to convert the analog output of LM35 into equivalent digital sequence and which removes the requirement of an external ADC IC as it need in other low level controller. LM35 temperature sensor’s pin configuration is as shown in below figure. LM35 temperature sensor gives temperature in voltage which is linearly proportional to the temperature in oC (centigrade). Thus, this is one of the advantages of LM35 over other which gives temperature in tooK(kelvin), as the user need to convert it to centigrade [4]. Fig 2: LM35 Pin Diagram MATHEMATICAL CALCULATION For each degree Celsius change in temperature, the sensor output changes by 0.01V due to LM35 Sensor has a linear 10mV/oC of scale factor. So, one can say that there is a 0V for 0oC and 1V for 100oC [4]. The microcontroller has 10 bit of A/D converter which gives equivalent digital 10 bits of output which need to convert into appropriate temperature using some mathematical calculation as given below [1]. Here reference voltage taken as 5V which is same as supply voltage of the controller and if we say the digital 10 bits of output as ADCVoltage then the voltage comes from the pin is as calculated below. Voltage (V) = ADCVoltage/1024 X 5……1 Here 1024 is the 210 as controller has 10 bits of inbuilt analog to digital channel. So, ADCVoltage divided with 210 bit and multiply with the reference voltage of 5V. So, the voltage comes from the calculation is equivalent to the temperature which comes from the temperature sensor. Now as the linear scale factor of LM35 is in the mV so to convert the above voltage into mV it multiplied with the 1000 as shown below. Voltage (mV) = ADCVoltage/1024 X 5 X 1000….2 Now as we know the scale factor of LM35 is 10mV/oC. It means that 10mV of temperature varies per oC (Simply 10mV = 1oC). So, to get above equation in degree centigrade we divide it with 10 as from its scale factor. Temperature (oC) = (ADCVoltage/1024 X 5 X 1000)/10….3 The simple explanation of above equation can be drawn as by showing it as simple calculation as “If 1oC for 10mV then how many centigrade for above given voltage in equation 2.” So, at final the simple equation can be drawn from above is written as below equation 4 for reference voltage of 5V. Temperature (oC) = ADCVoltage/1024 X 500….4 SOFTWARE DESCRIPTION The software code is used to done all this mathematical calculation as shown in above section. The software code in present work is written in ‘C’ language using Hi tech c compiler in MPLAB X IDE. The MS Visual Studio used to create a GUI and to store temperature data into database. The RS232 port is used for make serial communication between controller and personal computer. The flow chart for software steps is as shown in below flow chart. Fig 2: Flow Chart for temperature monitoring system CONCLUSION The work, presented here drawn from the investigations and implementation that have been done so far and it is also intended to be of some use in Small Scale industries, laboratories, or in small research organization, etc. because Instrument Automation is often Requirement by industry especially in smaller research institutions where the cost is matter. This paper designed in such a way so thatit will helpful to user to make temperature controller and monitoring system usingany different peripheral and controlleralso by taking the basic idea given in presented work. REFERENCES AnshumAn BezBorAh, “PIC16F877A-based Temperature monitoring system”, Electronics for you magazine, www.efyMag.coM R. López, S. Galindo, E. Gaytán, R. Juárez, TEMPERATURE AND HUMIDITY LABORATORY REMOTE CONTROLLER, Journal of the Mexican Society of Instrumentation, Vol. 3 Nr. 6/1996, pp 14-20 PIC16F882/3/4/6/7 Datasheet – Microchip Technology http://ww1.microchip.com/downloads/en/DeviceDoc/41291D.pdf LM35 Datasheet – National Semiconductor http://pdf1.alldatasheet.com/datasheet-pdf/view/8866/NSC/LM35.html