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A temperature monitoring system which can be used to monitor the temperature of industrial processes has been designed and implemented in the course of this project. This system relied upon a controller which is connected to temperature sensors. The controller compares the actual temperature to the desired control temperature, or set point, and provides an output to a control element. Mostly the control element is a heater. The controller is connected to a Personal Computer (PC) using RS232 protocol, so that the current temperature can be seen on the PC. This system offers flexibility to controlling operations by providing a user-interface from which the temperature set-point can be easily changed. It is believed that this project will remove rigorous and unnecessary monitoring and controlling activities and hence ensure cheaper and faster product output.
1.1 Background of the project
Cutix Plc Nnewi, a leading manufacturer of indigenous cables, produces all kinds of cables ranging from house wiring cables to aluminum and copper conductors for high tension installation. Cutix was founded back in 1981, and started actual production in 1984. The company has many production machines which are highly durable and rugged.
A production chart of Cutix Plc Nnewi reveals that a finished product must have passed through the stages of wire drawing, first and second insulation, spark testing and the finishing (coiling and sealing) line. More critical of these is the first and second insulation stages which make use of high temperature to melt polyvinyl chloride (PVC) materials required for coating the cables. Such situation requires a given temperature to be kept stable to ensure smooth and uniform insulation.
Cutix, like most other manufacturing industries, makes use of analog temperature controllers. Such controllers can accept thermocouple or RTD inputs and offer imprecise temperature control over a range such as 75°C to 100°C. This seemed to pose no disadvantage to them since their products still sell in the market. However, this type of controllers used by these industry, unknowingly, possess no readable display, lack of sophistication for more challenging control tasks, and no communication ability, all of which most often expose the industry to the following problems:
• non-uniform heating rate for a point that requires more than one heating element, thus causing delay in start-up of production.
• wastage of raw of materials in test-running the line to ensure that the temperature has reached the minimum required value.
• poor package outlook because the sealers are not heated uniformly.
• extra man-power for each extrusion line- one at the take-off and another at the panel- to ensure that the machine is stopped immediately there is a sign of poor quality due to failure of one or more of the heaters.
• frequent damage of heating elements as a result of no precision in control which often leads to over-heating the elements beyond upper temperature range.
In view of the above limitations, and more, a pc-based automatic multi-point temperature monitoring and control is hereby proposed to remove the limitations of analog controllers and even add flexibility to the control process.
Today, with the continuous price erosion and performance increase of pc, industrial control is moving from an expensive, analog proprietary hardware base to one with foundation of pc-based software. Pc-based temperature control runs on personal or industrial hardened computers and provides answers to initiatives for lean control program.
With the inherent advantages of a pc-based control which include flexibility, high performance, customization, convenience, easier development, better integration with existing hard wares, portability and access, the proposed system should be able to help
Cutix (and other manufacturing industries) solve their problems by providing uniform heating, precision in measurement and control, self monitoring and extension of usage to remote, inaccessible locations in the manufacturing floor.
1.2 Aims and Objectives
This project “PC-based automatic multipoint temperature monitoring and control” is aimed at designing a temperature monitoring and control device which can be used to monitor and control the temperatures of industrial machines. Thus, the completed work can be viewed as a system having three main features which serve as the objective of the work.
•PC-based temperature monitoring and control.
•Automation facility, which enables the system to be self monitoring.
•Multi-point approach, a feature that makes it possible for more than one point to be monitored.
Hence, this project is meant to offer flexibility to monitoring operations by allowing or providing a PC-interfacing feature which allows an operator to monitor the ongoing process from his PC located at amore convenient and easy-accessible place. It is believed that this project will be able to remove the rigorous activities of monitoring temperatures by personnel, and engage him with other production activities, all aimed at ensuring cheaper and fast product output.
1.3 Significance of the Study
The beginning of a sweeping change is upon the control and instrumentation world with the availability of robust hardware, open technology and real-time, window-based operating system. PC-based control is emerging as a new control paradigm for increasing manufacturing productivity. PC-base automatic multi-point temperature monitoring and control offers open and more intuitive traditional solutions at a lower total system cost and easier migration to future technologies. Easier development, integration, portability, and access, ensure a flexible and efficient solution. Some of the inherent advantages of PC-based automatic multipoint temperature monitoring and control include the following:
•Custom user-interface for supervisory control.
For low-end PID (Proportional Integral-Derivative) controllers to high end programmable logic controllers (PLC) system, visualizing the control application can be very challenging. Many stand-alone controllers have fixed digital displays for configuring control set-points and viewing I/O values. PC-based automatic multipoint temperature controller, being an advanced system, on the other hand, have no display and typically requires a separate software package and human machine interface (HMI) to view and interact with automation systems.
•Easy integration with existing system
One may already have a control system that works well for most needs but could benefit from additional measurement I/O or advanced control functionality to optimize certain specialized tasks. A big advantage to using data acquisition hardware and an open PC platform is the number of options you have for connecting to existing equipment. Whether you are communicating with process instrument, PLC, or single loop controllers, you have a variety of ways to integrate a PC-based control system with existing hardware, this is exactly what a PC-based automatic multipoint temperature monitoring and control does in the case of temperature measurement.
•Software-defined control flexibility.
A PC-based automatic multipoint control system offers you complete flexibility in defining system functionality and I/O operations. In addition, even without prior technical skill in wiring a temperature controller, PC-based automatic multipoint control system enables an operator to carry out initial installation since the system just requires relocating it to another sight without rewiring process . Also such unskilled operator make changes in the initial setting using the window-based control interface.
•Multipoint monitoring and control for performance and reliability.
Beside single point digital temperature controllers which can control only one process, multipoint digital temperature controllers control more than one point, meaning they can accept more than one input variable. Generally speaking a multipoint controller can be thought of as a device with many individual temperature controllers inside one chassis. These are typically mounted behind the panel in some industrial applications, as opposed to the front-to-panel (FTP) . Multipoint temperature controllers provide a compact more modular system that operates either within a stand alone system or in a PLC environment. They provide a single point of software to access all control loops.
PC-based automatic multipoint temperature monitoring and control systems also have enhanced security such as not having buttons for a person to use and change critical settings. By having complete control over the information being read from or written to the multipoint controller, the machine builder can limit the information that any given operator can read or change, preventing undesirable conditions from occurring, such as setting a set point too high to a range that may damage products or the machine.
Today, manufacturers around the world look to PC to play a bigger role in their control systems. PCs are already an accepted platform for supervisory control, monitoring and reporting, as well as off-line data management and analysis. Manufacturers have already realized the flexibility of the PC and the easy-to-use open architecture of window-base software applications for manufacturing environment.
Following the trend, PC-based automatic multipoint temperature monitoring and control has emerged to facilitate efficient monitoring and control process for manufacturing industries. Such temperature controllers are used in a wide variety of industries to manage manufacturing processes or operations. Some common applications include the following.
•Heat Treat/ Oven
Temperature controllers are used in ovens and in heat treating applications within furnace, ceramic kilns, boilers and heat exchangers.
Temperature controllers must maintain a uniform level at designated temperatures and process time length. This helps to ensure a high quality product output.
Temperature control in the plastic industry is common on portable chillers, hoppers and dryers, and molding and extruding equipment, temperature controllers are mused to precisely monitor and control temperatures at different critical points in the production of plastics.
Temperature control is required in laboratory and test equipment, autoclaves, incubators, refrigeration equipment and crystallization growing chambers and test chambers where specimens must be kept or test must be run within specific temperature parameters.
•Food and beverage
Common food processing applications involving temperature control include brewing, blending, sterilization and cooking and baking ovens. Controllers regulate and/or process time to ensure optimum performance.
Insulation materials require a specific temperature which must be maintained uniformly throughout the barrel and nozzle zones to ensure good quality of product. Efficient temperature monitoring and control systems are required to achieve this.
Finally the steps taken to incorporate PC to temperature monitoring and control is one of the many steps required for a complete computer automation of industrial processes. Thus other parameters, such as pressure, colour, texture and so on, can be computerized, providing a platform for a unified process control.
1.4 Scope of the work
This work covers the following areas.
Temperature sensors are reviewed and choice made on the most applicable sensors. The sensor measures the temperature of the points and converts the reading to a voltage value. This value is then sent to the microcontroller which compares it with the set-point value, takes appropriate action in order to restore tolerable limits.
High level C-programming language is used to develop codes for the microcontroller to enable it read the values sent by the sensors and take appropriate actions. The Visual Basic Window-based software will be used to communicate with the PC operating system and the C program running on the hardware in order to read the user set-point values and current temperatures.
•Window-based software programming.
Communication between the hardware and the PC (serial communication) is facilitated by programming the PC to be able to communicate with the serial port. The Visual Basic Window-based software will be used to communicate with the PC operating system and the C program running on the hardware in order to read the user set-point values and current temperatures.
In order to ensure a compatible voltage level between the hardware and the PC, the MAX 232 technology is employed. This converts the hardware voltage level to a voltage which can be handled by the serial port in the PC.
A temperature control system relies upon a controller, which is connected to a temperature sensor. It compares the actual temperature to the desired control temperature, or set point, and provides an output to a control element. Mostly the control element is a heater. The controller is connected to a Personal Computer using RS232 protocol. The Current Temperature can be seen on the PC. Whereas the Temperature Set Point can also be changed through the PC. The different sections of this project are:
2. Analog to Digital Converter (ADC).
3. Temperature Sensor.
5. MAX 232.
It is the heart of the unit. It performs all the functions like getting data from ADC, Comparing the current temperature to set temperature, Turning ON/OFF the relay & communicating with the PC.
Analog to Digital Converter
The ADC Converts the Analog voltage received from the Temperature Sensor into digital format and gives it to the microcontroller.
The temperature sensor measures the current temperature and sends value in form of voltage to the microcontroller. Some IC (e.g. LM35) sensors have output proportional to the input temperatures.
Communication with the PC is done through the SERIAL PORT. The protocol of serial port is RS-232, for interfacing the controller to the PC using RS 232 protocol we require MAX 232 IC.
1.6 Project Report Organization
The design and implementation of the project, PC-based automatic multipoint temperature monitoring and control system, followed a systematic approach which reveals a step by step analysis of an existing system, taking Cutix Plc Nnewi as a case study, until a realizable, better system is arrived at. This report covers the entire steps followed to arrive at the complete envisaged system. Diagrams and tables are employed, where necessary, to illustrate facts and results.
Chapter one of this report is an introduction to the project. It covers the following areas: the project background, aims and objectives of the work, justification and scope of the work, and the block diagram overview of the project stages.
Chapter two is a literature review of related works. In this chapter, the general concept of temperature control is x-rayed; different technologies of relevant components are also reviewed.
In third chapter, the temperature control technique as used by Cutix Plc Nnewi is analyzed and shortcomings of the existing system outlined. Different methods of achieving a better system are also explored. Then, choice is made among all the available options. The option chosen is basically dependent on the nature of the envisaged system.
Chapter four describes the proper system design. The input, output and software interfaces are systematically modularized and designed. The block diagram of the modules (put together) is also given towards the end of this chapter.
The whole of chapter five is concerned with the implementation of the designed system. This involves the wiring schedules, full schematic diagram and integration of the different modular designs and schematics, testing and performance evaluation, costing and deployment of the achieved work.
Finally, the last chapter deals with the summary of achievement, problems encountered during the project design and implementation stages and the solution proffered.
Recommendations and suggestions for further improvement are also included.