Introduction: Temperature Control System Using Labview (Atmega32)
This work describes a framework of ON/OFF, proportional and linear temperature control systems. The design and implementation of this process is done using LABVIEW, virtual workbench software. The project involves includes data acquisition, data processing and the display of data. At the initial stage Data Acquisition is replaced by a microcontroller system as a cost effective measure. A ON/OFF controller system is designed using particular Relay element which controls the heating coil and LABVIEW virtual instrument is used to control the temperature and ensure that the temperature does not go beyond a certain set point. Feedback control is used in industry to improve and regulate response and result of a number of processes and systems. This project gives us an idea about the development and design of a feedback control system that keeps the temperature of the process at a predefined set point. The system contains data acquisition unit that gives input and output interfaces in between the PC, the sensor circuit and hardware. A proportional, integral, and derivative controller is implemented using LabVIEW. The project provides details about the data acquisition unit, the implementation of the controller and also presents test results.
The most significant and driving force which encouraged us towards the fulfillment of this project was to meet industrial requirements and standards with application specific, precise and cost effective tools which facilitate towards lesser time and labor consumption thereby providing results virtually which holistically used to cost a debt. In the extravagant field of Calorimetry, Physicist James Maxwell, in his 1871 classic Theory of Heat, states Temperature as a measure of the total kinetic and potential energy within an object. Today this degree of hot and cold stands as the most fundamental pillars of the laws of nature. Almost every industry shop floor deals with various actions of temperature and hence the control of these actions of temperature motivated us to design the temperature control system and to provide it with the new touch of virtual era, the
“Laboratory Virtual Instrument Engineering Workbench” came into picture.
1.2 Problem definition
Although our country is rapidly adapting modern industrialization, we are evolving as one of the major leaders in innovating more and more simpler measures in technology. Today still when it comes to industrial brazing and smelting we are prone to use the holistic approaches we have been carrying out for years. To solve this problem and establish continuity in providing simpler measures in industrial applications as responsible technologists we take a step ahead in reforming this problem definition.
1.3 Objective of Project
The basic objective revolves around the concept of data acquisition and processing and controlling the heating mechanism which further facilitates in disciplined temperature control. The heating coil which operates on 230V AC is governed by a control pulse from the controller system which is further connected to LabVIEW over which we obtain the temperature results in proper graphical format and also a virtual control block which controls the heating.
1.4 Limitations of the project.
As we saw above as stated in the objective we are dealing with data acquisition and processing which is best braced by a data acquisition system. Data acquisition (DAQ) is the process of acquiring an electrical or physical phenomenon such as voltage, current, temperature, sounds or pressure with a computer. A DAQ system consists of a DAQ card or sensor, hardware from which data is to be acquired and a computer with associated software. A DAQ card has various features which can be designed for different purposes. For data involving very high accuracy the sampling rate of the card should be high enough to reconstruct the signal that appears in the computer. NI USB-6363 DAQ can be used to get data related to impulse voltage which require very high accuracy. Sampling rate of this card is 2MS/s (mega samples per second). For acquiring data from high voltage system, first the system parameters should be scaled down to values supported by the DAQ card. So the high voltage system should be connected to instrument transformer to scale down the voltage as well as current. For remote control of a system (stand alone mode), CompactRIO can be used which provides embedded control as well as data acquisition system. The Compact RIO system’s tough hardware configuration includes a reconfigurable field-programmable gate array (FPGA) chassis, Input/output modules, and an embedded controller. Additional feature of Compact RIO is, it can be programmed with NI LabVIEW virtual instrument and can be interfaced. But when we come to designing point of view as responsible technologists, building a system which is accessible and usable to all economically is also one of the biggest factors to be undertaken. The cost of using a Data Acquisition system which provides very high accuracy and other flourished features has to be compensated with the use of a Micro controller system.
In this chapter, the overviews of the different controllers are described. Literature survey of the work has been discussed. The objective of the thesis is explained. At the end organization of thesis has been presented.
1.1 INTRODUCTION TO LABVIEW
LabVIEW TM (Laboratory Virtual Instrument Engineering Workbench), a product of National Instruments, is a powerful software system that accommodates data acquisition, instrument control, data processing and data presentation. LabVIEW which can run on PC under Windows, Sun SPARstations as well as on Apple Macintosh computers, uses graphical programming language (G language) departing from the traditional high level languages such as the C language, Pascal or Basic. All LabVIEW graphical programs, called Virtual Instruments or simply VIs, contain a Front Panel and a Block Diagram. Front Panel has various controls and indicators while the Block Diagram consists of a variety of functions. The functions (icons) are wired inside the Block Diagram where the wires represent the flow of data. The execution of a VI is data dependant which means that a node inside the Block Diagram will execute only if the data is available at each input terminal of that node. By contrast, the execution of programs such as the C language program, follow the order in which the instructions are written.
LabVIEW manages data acquisition, analysis and presentation into one system. For acquiring data and controlling instruments, LabVIEW supports IEEE-488 (GPIB) and RS-232 protocols as well as other D/A and A/D and digital I/O interface boards. The Analysis Library offers the user a comprehensive array of resources for signal processing, statistical analysis, filtering, linear algebra and many others. LabVIEW also supports the TCP/IP protocol for exchanging data between the server and the client. LabVIEW v.5 also supports Active X Control allowing the user to control a Web Browser object.
The version used for our project is LabVIEW 2013.
1.2 INTRODUCTION TO THE CONTROLLER UNIT.
The Atmel®AVR®ATmega32 is a High-performance low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega32 achieves throughputs approaching 1 MIPS per MHz allowing the system designed to optimize power consumption versus processing speed. It bears High Endurance Non-volatile Memory segments. The Atmel®AVR®AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the Arithmetic Logic Unit, allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers. The ATmega32 provides the following features: 32Kb of In-System Programmable Flash Program memory with Read-While-Write capabilities, 1024bytes EEPROM, 2Kb SRAM, 32 general purpose I/O lines, 32 general purpose working registers, a JTAG interface for Boundary scan, On-chip Debugging support and programming, 3 flexible Timer/Counters with compare modes, Internal and External Interrupts, a serial programmable USART, a byte oriented Two-wire Serial Interface, an 8-channel, 10-bit ADC with optional differential input stage with programmable gain (TQFP package only), a programmable Watchdog Timer with Internal Oscillator, an SPI serial port, and six software selectable power saving modes. The Idle mode stops the CPU while allowing the USART, Two-wire interface, A/D Converter, SRAM, Timer/Counters, SPI port, and interrupt system to continue functioning. The Power-down mode saves the register contents but freezes the Oscillator, disabling all other chip functions until the next External Interrupt or Hardware Reset. In Power-save mode, the Asynchronous Timer continues to run, allowing the user to maintain a timer base while the rest of the device is sleeping. The ADC Noise Reduction mode stops the CPU and all I/O modules except Asynchronous Timer and ADC, to minimize switching noise during ADC conversions. In Standby mode, the crystal/resonator Oscillator is running while the rest of the device is sleeping. This allows very fast start-up combined with low-power consumption. The device is manufactured using Atmel’s high density nonvolatile memory technology. The On chip ISP Flash allows the program memory to be reprogrammed in-system through an SPI serial interface, by a conventional nonvolatile memory programmer, or by an On-chip Boot program running on the AVR core. Software in the Boot Flash section will continue to run while the Application Flash section is updated, providing true Read-While-Write operation. By combining an 8-bit RISC CPU with In-System Self-Programmable Flash on a monolithic chip, the Atmel ATmega32 is a powerful microcontroller that provides a highly-flexible and cost-effective solution to many embedded control applications.
1.3 ORGANIZATION OF THESIS
Besides the first chapter which gives us an introduction to the thesis, the thesis consists of three other chapters. The second chapter deals with the market survey. The third chapter describes the implementation and operation of proportional and linear temperature controllers. It also gives an idea about how they are controlled using LABVIEW. The final chapter quantifies all the results and conclusions are drawn based on the observations.
2.1 EXISTING TEMPRATURE CONTROL SYSTEMS AND SOME OF THEIR DISADVANTAGES .
FTSS Temperature Control Chronicle 7 series
SS Brewing Technologies headquartered in the United States has been one of the leaders in the industry of brewing since a decade. Their temperature control systems have been widely and prominently used in the market. The FTSS Temperature Control Chronicle 7 series system is the current trending of the family which still supports a numeric display for control and monitoring.
Honeywell’s T775 Series 2000 electronic remote temperature control system
The T775 electronic temperature controller are the next generation of commercial and agricultural controls capable of sensing of temperature but again virtual remote graphical analysis is a limitation.
Also German Instrumentation tycoons OMEGA, Enivronnment.SA of France, Johnson Controls have prominently been constructing application specific Industrial temperature control Systems over the years.
3.1 Analysis and Design
a) Block Diagram :
As we see in the block diagram, let us explore each and every block of the system. We are using a Heating coil which is placed in a tank of water constructed of glass. To sense and communicate the temperature we are using a LM35 precision centigrade temperature sensor.
LM35 precision centigrade temperature sensor: The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly- proportional to the Centigrade temperature. The LM35 device has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The LM35 device is rated to operate over a −55°C to 150°C temperature range, while the LM35C device is rated for a −40°C to 110°C range (−10° with improved accuracy). The LM35-series devices are available packaged in hermetic TO transistor packages.
The description of Labview and Atmega 32 Microcontroller is already covered in the Introduction. Please refer page - 8 &9
Relay Circuit : We make use of a Relay circuit which is placed between the microcontroller block and the coil which operates at 230V AC as this relay circuit accepts a 5V trigger input which activates and controls the switching ON/OFF operation of the circuit.
Serial Communication using RS232:
Serial communication is basically the transmission or reception of data one bit at a time. Today’s computers generally address data in bytes or some multiple thereof. A byte contains 8 bits. A bit is basically either a logical 1 or zero. Every character on this page is actually expressed internally as one byte. The serial port is used to convert each byte to a stream of ones and zeroes as well as to convert streams of ones and zeroes to bytes. The serial port contains an electronic chip called a Universal Asynchronous Receiver/Transmitter (UART) that actually does the conversion.
b) LabVIEW Front Panel :