Department of Electrical and Electronics PROJECT REPORT Nidhi T 1NH12EE030 Pooja Rani 1NH12EE034 Priyanka Agarwal 1NH12EE036 Modelling of automatic power switching control using ARM Microcontroller CHAPTER 1 INTRODUCTION The main aim of any electric power supply in the world is to provide uninterrupted power supply at all times to all its consumers. Although, in developing countries, the electric power generated to meet the demands of the growing consumers of electricity is insufficient, hence power instability or outage occurs. Power instability and outage in general does not promote development in the public and private sector of the country‘s economy. The investors do not feel secure to come into a country with constant power failure. These limit the development of industries , in addition, there are processes that cannot be interrupted because of their importance for instance, surgery operation in hospitals, transfer of money between banks and lots more. Power instability and outage creates a need for alternative source of power to backup the mains supply. A microcontroller-based automatic power switching or changeover finds a wide application scope wherever the reliability of electrical supply from the utilities is low and it is used in areas wherever continuity of power supply is necessary, for switching to an alternative source from main supply and vice versa. Figure 1.1 Electric Supply Lines Unlike a linear power supply, the pass transistor of a switching-mode supply continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. Ideally, a switched-mode power supply dissipates no power. Voltage regulation is achieved by varying the ratio of on- DEPT. OF EEE, NHCE Page 1 Modelling of automatic power switching control using ARM Microcontroller to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power conversion efficiency is an important advantage of a switched-mode power supply. Switched-mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight. Switching regulators are used as replacements for linear regulators when higher efficiency, smaller size or lighter weight are required. They are, however, more complicated; their switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have a poor power factor. 1.1 Existing system Mains power can be lost due to downed lines, malfunctions at a substation, inclement to ensure the continuity of power supply, many commercial industrial facilities depend on both utility service and onsite generation (generator set). Because of the growing complexity of electrical systems, it becomes imperative to give attention to power supply reliability and stability. Over the years many approaches have been adopted but current existing system is: Manually Controlled Changeover Figure 1.2 Manually Controlled Changeover DEPT. OF EEE, NHCE Page 2 Modelling of automatic power switching control using ARM Microcontroller 1.1.1 Manually controlled change over system Manual changeover switch system still remains the oldest changeover switch box used by majority of the electricity consumers. The switching obtainable from the changeover switch is usually manual, that is the user has to move a lever to change from one source to another. This is usually associated with time wasting as well as some health hazards like electric shock and trauma. This is usually accompanied by a loud noise and electrical sparks. Manual changeover switch box separates the source between a generator and public supply. Whenever there is power failure, change-over is done manually by an individual and the same happens when the public power is restored. 1.1.2 Limitations of manual change over system i. Manual changeover is time wasting whenever there is power failure. ii. It is strenuous to operate because a lot of energy is required. iii. It causes device process or product damage. iv. It has the potential to cause fire outbreak. v. It is usually accompanied by a lot of noise which may sometimes be psychologically destabilizing. vi. Maintenance is more frequent because the changeover action causes tear and wear. Figure 1.3 Electric shock DEPT. OF EEE, NHCE Page 3 Modelling of automatic power switching control using ARM Microcontroller 1.2 Proposed system In view of the limitation of above previous changeover systems, this project proposes and implements a power switching system that drastically reduced the shortcomings, the noise, arching, tear and wear, stress and time wasting associated with manual switch box. Also ARM LPC2148 microcontroller was also incorporated to help improve the speed of automation. The proposed system could efficiently and effectively manage energy consumption. The system can be used to avoid energy waste and saving energy consumption by a maximum of 68% in switching control during typical days[1].The system is controlled by a software program embedded in the microcontroller. Economically, this project is of affordable cost because of the use of integrated circuits (ICs) in place of discrete components. The major aim of this work is to exploit the ubiquitous microcontroller facilities in bringing about automation of the switching (changeover) process. One of the most critical needs of embedded systems is to reduce power consumption, space and time and this is achieved in this work. This system is designed to provide solution to the shortcomings of the already existing manual changeovers by performing power swap from mains power to solar panel generation automatically and vice versa. Figure 1.4 Automatic Power Supply switch DEPT. OF EEE, NHCE Page 4 Modelling of automatic power switching control using ARM Microcontroller The system is controlled by microcontroller used so there is accuracy in switching actions and there would not be over usage of light when not required. Around 65%-70% reduction in power consumption is achieved with this proposed system[2].The basic problem to be addressed here is how to connect two different sources of electrical power simultaneously to a single unit (automatic power changeover switch) that can serve as a link between these power sources and the load. Moreover, preference is given to the power source such that one source supplies the load at a time and when the first (mains) source fails, the link immediately connects the second (solar panel generation) source to the load. Constructing an automatic power switching system with a microcontroller that can toggle automatically will reduce the time and energy spent in changing over the switch box from time to time. This will allow the user to enjoy long term steady and uninterrupted supply of power. It has the following advantages: It minimizes damages on lives and equipments since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error and stress. It reduces its changeover timing to the minimum due to its fast response to power outage. 1.3 Significance of the work This work serves the purpose of saving the electrical appliances in a household and offices from power fluctuation-related damages which could be occasioned by overloading of unprotected changeover switches. Such a device protects electrical appliances from possible harmful effects of voltage sag. It provides an average user the comfort of enjoying the use of electrical appliances at home and offices without the interruption of work and switching over between the public power source and alternative power source. Convenience of not having to walk all the way to the alternative power supply source to turn it off or on is also provided. It can also create entrepreneurship opportunity for our teeming unemployed youths of the country owing to the large number of people that use alternative power supply that seek automatic switching(changeover) from the public power supply to the alternative power supply. DEPT. OF EEE, NHCE Page 5 Modelling of automatic power switching control using ARM Microcontroller 1.4 Literature Survey Power supply instability in developing countries creates a need for automation of electrical power generation or alternative sources of power to back up the utility supply. This automation becomes necessary as the rate of power outage becomes predominantly high. Most industries and commercial processes are partly dependent on generators and public power supply which is epileptic especially in tropical African countries where Nigeria forms a part. Therefore, if the processes of power change-over between these two power supplying sources are manual, human error during change-over connections may occur; leading to machine damage, electric shock/electrocution as well as increased down time consequently introducing massive losses. However, if the starting of the generator is automatically done by a relay which switches the battery voltage to ignition coil of the generator while the main power relay switches the load to either public supply or generator, the down time would greatly be reduced thereby maintaining the tempo of production in such industries. The first light switch employing "quick-break technology" was invented by John Henry Holmes in 1884 in the shield field district of Newcastle upon Tyne. The "quick-break" switch overcame the problem of a switch's contacts developing electric arcing whenever the circuit was opened or closed. In 1875 Henry Woodward patents an electric light bulb. In 1876 Pavel Yablochkov invents the Yablochkov candle, the first practical carbon arc lamp, for public street lighting in Paris. In 1879 Thomas Edison and Joseph Wilson Swan patent the carbon-thread incandescent lamp. Invented by Humphry Davy around 1805, the carbon arc was the first practical electric light. They were used commercially beginning in the 1870s for large building and street lighting until they were superseded in the early 20th century by the incandescent light.