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INTRODUCTION
1.1 EMBEDDED SYSTEMS
Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real time performance constraints that must be met, for reason such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs.
An embedded system is not always a separate block - very often it is physically built-in to the device it is controlling. The software written for embedded systems is often called firmware, and is stored in read-only memory or flash convector chips rather than a disk drive. It often runs with limited computer hardware resources: small or no keyboard, screen, and little memory.
Wireless communication has become an important feature for commercial products and a popular research topic within the last ten years. There are now more mobile phone subscriptions than wired-line subscriptions. Lately, one area of commercial interest has been low-cost, low-power, and short-distance wireless communication used for “personal wireless networks". Technology advancements are providing smaller and more cost effective devices for integrating computational processing, wireless communication, and a host of other functionalities. These embedded communications devices will be integrated into applications ranging from homeland security to industry automation and monitoring. They will also enable custom tailored engineering solutions, creating a revolutionary way of disseminating and processing information. With new technologies and devices come new business activities, and the need for employees in these technological areas. Engineers who have knowledge of embedded systems and wireless communications will be in high demand. Unfortunately, there are few adorable environments available for development and classroom use, so students often do not learn about these technologies during hands-on lab exercises. The communication mediums were twisted pair, optical fiber, infrared, and generally wireless radio.
1.3 APPLICATIONS OF EMBEDDED SYSTEMS:
Some of the most common embedded systems used in everyday life are
Small embedded controllers: 8-bit CPUs dominate, simple or no operating system (e.g., thermostats)
Control systems: Often use DSP chip for control computations(e.g., automotive engine control)
Distributed embedded control: Mixture of large and small nodes on a real-time Embedded networks. (e.g., cars, elevators, factory automation)
System on chip: ASIC design tailored to application area. (e.g., consumer electronics, set-top boxes)
Network equipment: Emphasis on data movement/packet flow. (e.g., network switches; telephone switches)
Critical systems: Safety and mission critical computing. (e.g., pacemakers, automatic trains)
Signal processing: Often use DSP chips for vision, audio, or other signal Processing (e.g., face recognition)
Robotics: Uses various types of embedded computing (especially Vision and control) (e.g., autonomous vehicles)
Computer peripherals: Disk drives, keyboards, laser printers, etc.
Wireless systems: Wireless network-connected “sensor networks” and “Motes” to gather and report information
Embedded PCs: Palmtop and small form factor PCs embedded into Equipment
Command and control: Often huge military systems and “systems of systems” (e.g., a fleet of warships with interconnected Computers)
Home Appliances: intercom, telephones, security systems, garage door openers, answering machines, fax machines, home computers, TVs, cable TV tuner, VCR, camcorder, remote controls, video games, cellular phones, musical instruments, sewing machines, lighting control, paging, camera, pinball machines, toys, exercise equipment.
Office Telephones, computers, security systems, fax machines, microwave, copier, laser printer, color printer, paging
Auto Trip computer, engine control, air bag, ABS, instrumentation, security system, transmission control, entertainment, climate control, cellular phone, keyless entry.
1.4 OBJECTIVE OF THE PROJECT
The main objective of the metal detector robot is used to detect the metal and if the sensor found metal near to it, the robot stop moving and on LCD screen it is displayed as metal detected.
1.5 HARDWARE REQUIREMENTS
Micro Controller (AT89S52).
Metal sensor.
LCD
L293D
Gear Motors
Regulated Power Supply
1.6 SOFTWARE REQUIREMENTS
The KEIL MICRO VISION IDE where KEIL C51 Product is a complete software development environment for the8051 microcontroller family.
MICRO C Flash+ Ver. 4.0.0 programmer for MCS51 microcontrollers developed by UC micro systems
OPERATION:
Regulated Power Supply feeds power required for Metal Sensor, Micro controller, LCD unit +5V DC source, Motor Driver IC and Gear Motors requires +12V DC power source. A Metal Sensor is used to scan for a metal identification, LCD is used for Display about the status of operation of the system, Gear motors are attached to Robot to make the Robot body to move in different directions, to drive motors in different directions and to ON and OFF a driver IC is used, a Micro Controller is used as a control unit to activate the sensor and drive input and output devices.
When the system is initiated by the regulated power supply then micro controller activates the motor driver IC so that the motors comes to ON state and make the Robot to move in forward direction as programmed for Micro controller. The Micro controller makes the Robot to move, parallel it monitors the metal sensor. When the metal sensor identifies any metal in front of it then the signal is fed to micro controller, which in turn makes the motors OFF such that the Robot waits for few seconds and later it keeps moving as usual. If metal sensor don’t identify any metal in front of it then the controller makes robot to move as usual.
2.2 REGULATED POWER SUPPLY
The power supplies are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronic circuits and other devices. A RPS (Regulated Power Supply) is the Power Supply with Rectification, Filtering and Regulation being done on the AC mains to get a Regulated power supply for Microcontroller and for the other devices being interfaced to it.
A power supply can by broken down into a series of blocks, each of which performs a particular function. A dc power supply which maintains the output voltage constant irrespective of ac mains fluctuations or load variations is known as “Regulated D.C Power Supply”
2.2.1 Transformer
A transformer is an electrical device which is used to convert electrical power from one Electrical circuit to another without change in frequency. Transformers convert AC electricity from one voltage to another with little loss of power. Transformers work only with AC and this is one of the reasons why mains electricity is AC. Step-up transformers increase in output voltage, step-down transformers decrease in output voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains voltage to a safer low voltage. The input coil is called the primary and the output coil is called the secondary. There is no electrical connection between the two coils; instead they are linked by an alternating magnetic field created in the soft-iron core of the transformer. The two lines in the middle of the circuit symbol represent the core. Transformers waste very little power down current is stepped up. The ratio of the number of turns on each coil, called the turn’s ratio, determines the ratio of the voltages. A step-down transformer has a large number of turns on its primary (input) coil which is connected to the high voltage mains supply, and a small number of turns on its secondary (output) coil to give a low output voltage.
2.2.3 Filter:
A Filter is a device which removes the a.c. component of rectifier output but allows the d.c. component to reach the load.
Capacitor Filter: We have seen that the ripple content in the rectified output of half wave rectifier is 121% or that of full-wave or bridge rectifier or bridge rectifier is 48% such high percentages of ripples is not acceptable for most of the applications. Ripples can be removed by one of the following methods of filtering.
(a) A capacitor, in parallel to the load, provides an easier by –pass for the ripples voltage though it due to low impedance. At ripple frequency and leave the D.C. to appear at the load.
(b) An inductor, in series with the load, prevents the passage of the ripple current (due to high impedance at ripple frequency) while allowing the d.c (due to low resistance to d.c)
© Various combinations of capacitor and inductor, such as L-section filter section filter, multiple section filter etc. which make use of both the properties mentioned in (a) and (b) above. Two cases of capacitor filter, one applied on half wave rectifier and another with full wave rectifier.
Filtering is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output. Filtering significantly increases the average DC voltage to almost the peak value (1.4 × RMS value).
To calculate the value of capacitor©,
C = ¼*√3*f*r*Rl
Where,
f = supply frequency,
r = ripple factor,
Rl = load resistance
Note: In our circuit we are using 1000µF hence large value of capacitor is placed to reduce ripples and to improve the DC component.
2.2.4 Regulator:
Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or variable output voltages. The maximum current they can pass also rates them. Negative voltage regulators are available, mainly for use in dual supplies. Most regulators include some automatic protection from excessive current ('overload protection') and overheating ('thermal protection'). Many of the fixed voltage regulators ICs have 3 leads and look like power transistors, such as the 7805 +5V 1A regulator shown on the right. The LM7805 is simple to use. You simply connect the positive lead of your unregulated DC power supply (anything from 9VDC to 24VDC) to the Input pin, connect the negative lead to the Common pin and then when you turn on the power, you get a 5 volt supply from the output pin.