30-04-2014, 02:29 PM
AUTO POWER SUPPLY CONTROL FROM 4 DIFFERENT SOURCES: SOLAR, MAINS, GENERATOR & INVERTER TO ENSURE NO BREAK POWER
AUTO POWER SUPPLY CONTROL.docx (Size: 633.46 KB / Downloads: 89)
ABSTRACT
The main objective of this project is to provide uninterrupted power supply to a load, by selecting the supply from any source out of 4 such as mains, generator, and inverter and solar automatically in the absence of any of the source. The demand for electricity is increasing every day and frequent power cuts is causing many problems in various areas like industries, hospitals and houses. An alternative arrangement for power source is a must.
In this project uses four switches to demonstrate the respective failure of that power supply. When any of the switches is pressed it shows the absence of that particular source, switches are connected to microcontroller as input signals. A microcontroller of PIC family is used. The output of microcontroller is given to the relay driver IC, which switches appropriate relay to maintain uninterrupted supply to the load. The output shall be observed using a lamp drawing power supply from mains initially. On failure of the mains supply (which is actuated by pressing the appropriate switch) the load gets supply from the next available source, say an inverter. If the inverter also fails it switches over to the next available source and so on. The current status, as to which source supplies the load is also displayed on an LCD. As it is not feasible to provide all 4 different sources of supply, one source with alternate switches are provided to get the same function.
INTRODUCTION TO EMBEDDED SYSTEMS
EMBEDDED SYSTEM:
Embedded System is a combination of hardware and software used to achieve a single specific task. An embedded system is a microcontroller-based, software driven, reliable, real-time control system, autonomous, or human or network interactive, operating on diverse physical variables and in diverse environments and sold into a competitive and cost conscious market.
An embedded system is not a computer system that is used primarily for processing, not a software system on PC or UNIX, not a traditional business or scientific application. High-end embedded & lower end embedded systems. High-end embedded system - Generally 32, 64 Bit Controllers used with OS. Examples Personal Digital Assistant and Mobile phones etc .Lower end embedded systems - Generally 8,16 Bit Controllers used with an minimal operating systems and hardware layout designed for the specific purpose. Examples Small controllers and devices in our everyday life like Washing Machine, Microwave Ovens, where they are embedded in.
Characteristics of Embedded System:
• An embedded system is any compute system hidden inside a product other than a computer
• There will encounter a number of difficulties when writing embedded system software in addition to those we encounter when we write applications
– Throughput – Our system may need to handle a lot of data in a short period of time.
– Response–Our system may need to react to events quickly
– Testability–Setting up equipment to test embedded software can be difficult
– Debugability–Without a screen or a keyboard, finding out what the software is doing wrong (other than not working) is a troublesome problem
– Reliability – embedded systems must be able to handle any situation without human intervention
– Memory space – Memory is limited on embedded systems, and you must make the software and the data fit into whatever memory exists
– Program installation – you will need special tools to get your software into embedded systems
Bridge rectifier:
A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current (AC) input into a direct current (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center-tapped secondary winding.
According to the conventional model of current flow (originally established by Benjamin Franklin and still followed by most engineers today[2]), current is assumed to flow through electrical conductors from the positive to the negative pole.
Voltage Regulator:
A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
Electronic voltage regulators are found in devices such as computer power supplies where they stabilize the DC voltages used by the processor and other elements. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant. In an electric power distribution system, voltage regulators may be installed at a substation or along distribution lines so that all customers receive steady voltage independent of how much power is drawn from the line.
7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs. The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide. 7805 provides +5V regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels.
CIRCUIT DESCRIPTION:
Here is the circuit diagram of a simple 100 watt inverter using IC CD4047 and MOSFET IRF540. The circuit is simple low cost and can be even assembled on a veroboard.
CD4047 is a low power CMOS astable/monostable multivibrator IC. Here it is wired as an astable multivibrator producing two pulse trains of 0.01s which are 180 degree out of phase at the pins 10 and 11 of the IC. Pin 10 is connected to the gate of Q1 and pin 11 is connected to the gate of Q2. Resistors R3 and R4 prevents the loading of the IC by the respective MOSFETs. When pin 10 is high Q1 conducts and current flows through the upper half of the transformer primary which accounts for the positive half of the output AC voltage. When pin 11 is high Q2 conducts and current flows through the lower half of the transformer primary in opposite direction and it accounts for the negative half of the output AC voltage.
Notes:
• B1 can be a 12V/ 6Ah lead acid battery.
• Q1 and Q2 must be fitted to a proper heat sink.
• T1 can be a 9-0-9 V primary, 230V secondary, 150VA Transformer
• Do not expect much from this circuit. This is very simple one suitable for low grade applications.