11-08-2014, 02:51 PM
SEMINAR ON EMBEDDED SYSTEMS
[attachment=66548]
INTRODUCTION
An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs pre-defined tasks, usually with very specific requirements. Since the system is dedicated to a specific task, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, so the cost savings may be multiplied by millions of items.
Handheld computers or PDAs are generally considered embedded devices because of the nature of their hardware design, even though they are more expandable in software terms. This line of definition continues to blur as devices expand.
Examples of embedded systems:-
• automatic teller machines (ATMs)
• avionics, such as inertial guidance systems, flight control hardware/software and other integrated systems in aircraft and missiles
• cellular telephones and telephone switches
• computer equipment such as routers and printers
• engine controllers and antilock brake controllers for automobiles
• home automation products, like thermostats, air conditioners, sprinklers, and security monitoring systems
• handheld calculators
• household appliances, including microwave ovens, washing machines, television sets, DVD players/recorders
• medical equipment
• handheld computers
• videogame consoles
CHARACTERISTICS
• 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.
• For high volume systems such as portable music players or mobile phones, minimizing cost is usually the primary design consideration. Engineers typically select hardware that is just “good enough” to implement the necessary functions. For example, a digital set-top box for satellite television has to process large amounts of data every second, but most of the processing is done by custom integrated circuits. The embedded CPU "sets up" this process, and displays menu graphics, etc. for the set-top's look and feel.
• The software written for embedded systems is often called firmware, and is stored in ROM or Flash memory chips rather than a disk drive. It often runs with limited hardware resources: small or no keyboard, screen, and little RAM memory.
• Embedded systems reside in machines that are expected to run continuously for years without errors and in some cases recover by them if an error occurs. Therefore the Software is usually developed and tested more carefully than that for Personal computers, and unreliable mechanical moving parts such as Disk drives, switches or buttons are avoided. Recovery from errors may be achieved with techniques such as a watchdog timer that resets the computer unless the software periodically notifies the watchdog.
BASIC ELECTRONIC COMPONENTS
Resistors are components that have a predetermined resistance. Resistance determines how much current will flow through a component. Resistors are used to control voltages and currents. A very high resistance allows very little current to flow. Air has very high resistance. Current almost never flows through air. (Sparks and lightning are brief displays of current flow through air. The light is created as the current burns parts of the air.) A low resistance allows a large amount of current to flow. Metals have very low resistance. That is why wires are made of metal. They allow current to flow from one point to another point without any resistance. Wires are usually covered with rubber or plastic. This keeps the wires from coming in contact with other wires and creating short circuits. High voltage power lines are covered with thick layers of plastic to make them safe, but they become very dangerous when the line breaks and the wire is exposed and is no longer separated from other things by insulation.
VARIABLE RESISTORS
Variable resistors are also common components. They have a dial or a knob that allows you to change the resistance. This is very useful for many situations. Volume controls are variable resistors. When you change the volume you are changing the resistance which changes the current. Making the resistance higher will let less current flow so the volume goes down. Making the resistance lower will let more current flow so the volume goes up. The value of a variable resistor is given as its highest resistance value. For example, a 500 ohm variable resistor can have a resistance of anywhere between 0 ohms and 500 ohms. A variable resistor may also be called a potentiometer (pot for short).
TRANSISTOR
Transistors are basic components in all of today's electronics. They are just simple switches that we can use to turn things on and off. Even though they are simple, they are the most important electrical component. For example, transistors are almost the only components used to build a Pentium processor. A single Pentium chip has about 3.5 million transistors. The ones in the Pentium are smaller than the ones we will use but they work the same way.
LDR(LIGHT DEPENDENT RESISTOR)
A Photoresistor is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electronsenough energy to jump into the conduction band. The resulting free electron (and its holepartner) conduct electricity, thereby lowering resistance.
A Photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire band gap. Extrinsic devices have impurities, also called dopants, added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction. This is an example of an extrinsic semiconductor. Photoresistors are basically photocells
INTRODUCTION TO MICROCONTROLLER
Microcontroller, as the name suggests, are small controllers. They are like single chip computers that are often embedded into other systems to function as processing/controlling unit. For example, the remote control you are using probably has microcontrollers inside that do decoding and other controlling functions. They are also used in automobiles, washing machines, microwave ovens, toys ... etc, where automation is needed.
The key features of microcontrollers include:
• High Integration of Functionality
• Field Programmability, Flexibility
• Microcontrollers sometimes are called single-chip computers because they have on-chipmemory and I/O circuitry and other circuitries that enable them to function as smallstandalone computers without other supporting circuitry.
• Microcontrollers often use EEPROM or EPROM as their storage device to allow fieldprogram ability so they are flexible to use. Once the program is tested to be correct then large quantities of microcontrollers can be programmed to be used in embedded systems.
• Easy to Use
8051 MEMORY ORGANISATION
The 8051 has a separate memory space for code (programs) and data. We will refer here to on-chip memory and external memory as shown in figure 1.5. In an actual implementation the external memory may, in fact, be contained within the microcomputer chip. However, we will use the definitions of internal and external memory to be consistent with 8051 instructions which operate on memory. Note, the separation of the code and data memory in the 8051 architecture is a little unusual. The separated memory architecture is referred to as Harvard architecture whereas Von Neumann architecture defines a system where code and data can share common memory.
STEPPER MOTOR
Of all motors, step motor is the easiest to control. It's handling simplicity is really hard to deny - all there is to do is to bring the sequence of rectangle impulses to one input of step controller and direction information to another input. Direction information is very simple and comes down to "left" for logical one on that pin and "right" for logical zero. Motor control is also very simple - every impulse makes the motor operating for one step and if there is no impulse the motor won't start. Pause between impulses can be shorter or longer and it defines revolution rate. This rate cannot be infinite because the motor won't be able to "catch up" with all the impulses (documentation on specific motor should contain such information). The picture below represents the scheme for connecting the step motor to microcontroller and appropriate program code follows.
The key to driving a stepper is realizing how the motor is constructed. A diagram shows the representation of a 4 coil motor, so named because 4 coils are used to cause the revolution of the drive shaft. Each coil must be energized in the correct order for the motor to spin
CONCLUSION
An engineer must have a good practical as well as theoretical knowledge. He must be technically sound as book knowledge is incomplete.
The technical training was an educative as well as interactive. We learned how to make the people learn. Technical lectures presented by the professional technicians on Embedded Systems and Embedded C were really interesting and healthy to learn the industrial trends.
Practical Training is a true platform to initiate the step towards professionalism in an engineer’s life. I am thankful to all the faculty members and Principal for supporting my work and for providing a right track.
[attachment=66548]
INTRODUCTION
An embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs pre-defined tasks, usually with very specific requirements. Since the system is dedicated to a specific task, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, so the cost savings may be multiplied by millions of items.
Handheld computers or PDAs are generally considered embedded devices because of the nature of their hardware design, even though they are more expandable in software terms. This line of definition continues to blur as devices expand.
Examples of embedded systems:-
• automatic teller machines (ATMs)
• avionics, such as inertial guidance systems, flight control hardware/software and other integrated systems in aircraft and missiles
• cellular telephones and telephone switches
• computer equipment such as routers and printers
• engine controllers and antilock brake controllers for automobiles
• home automation products, like thermostats, air conditioners, sprinklers, and security monitoring systems
• handheld calculators
• household appliances, including microwave ovens, washing machines, television sets, DVD players/recorders
• medical equipment
• handheld computers
• videogame consoles
CHARACTERISTICS
• 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.
• For high volume systems such as portable music players or mobile phones, minimizing cost is usually the primary design consideration. Engineers typically select hardware that is just “good enough” to implement the necessary functions. For example, a digital set-top box for satellite television has to process large amounts of data every second, but most of the processing is done by custom integrated circuits. The embedded CPU "sets up" this process, and displays menu graphics, etc. for the set-top's look and feel.
• The software written for embedded systems is often called firmware, and is stored in ROM or Flash memory chips rather than a disk drive. It often runs with limited hardware resources: small or no keyboard, screen, and little RAM memory.
• Embedded systems reside in machines that are expected to run continuously for years without errors and in some cases recover by them if an error occurs. Therefore the Software is usually developed and tested more carefully than that for Personal computers, and unreliable mechanical moving parts such as Disk drives, switches or buttons are avoided. Recovery from errors may be achieved with techniques such as a watchdog timer that resets the computer unless the software periodically notifies the watchdog.
BASIC ELECTRONIC COMPONENTS
Resistors are components that have a predetermined resistance. Resistance determines how much current will flow through a component. Resistors are used to control voltages and currents. A very high resistance allows very little current to flow. Air has very high resistance. Current almost never flows through air. (Sparks and lightning are brief displays of current flow through air. The light is created as the current burns parts of the air.) A low resistance allows a large amount of current to flow. Metals have very low resistance. That is why wires are made of metal. They allow current to flow from one point to another point without any resistance. Wires are usually covered with rubber or plastic. This keeps the wires from coming in contact with other wires and creating short circuits. High voltage power lines are covered with thick layers of plastic to make them safe, but they become very dangerous when the line breaks and the wire is exposed and is no longer separated from other things by insulation.
VARIABLE RESISTORS
Variable resistors are also common components. They have a dial or a knob that allows you to change the resistance. This is very useful for many situations. Volume controls are variable resistors. When you change the volume you are changing the resistance which changes the current. Making the resistance higher will let less current flow so the volume goes down. Making the resistance lower will let more current flow so the volume goes up. The value of a variable resistor is given as its highest resistance value. For example, a 500 ohm variable resistor can have a resistance of anywhere between 0 ohms and 500 ohms. A variable resistor may also be called a potentiometer (pot for short).
TRANSISTOR
Transistors are basic components in all of today's electronics. They are just simple switches that we can use to turn things on and off. Even though they are simple, they are the most important electrical component. For example, transistors are almost the only components used to build a Pentium processor. A single Pentium chip has about 3.5 million transistors. The ones in the Pentium are smaller than the ones we will use but they work the same way.
LDR(LIGHT DEPENDENT RESISTOR)
A Photoresistor is made of a high resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electronsenough energy to jump into the conduction band. The resulting free electron (and its holepartner) conduct electricity, thereby lowering resistance.
A Photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own charge carriers and is not an efficient semiconductor, e.g. silicon. In intrinsic devices the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire band gap. Extrinsic devices have impurities, also called dopants, added whose ground state energy is closer to the conduction band; since the electrons do not have as far to jump, lower energy photons (i.e., longer wavelengths and lower frequencies) are sufficient to trigger the device. If a sample of silicon has some of its atoms replaced by phosphorus atoms (impurities), there will be extra electrons available for conduction. This is an example of an extrinsic semiconductor. Photoresistors are basically photocells
INTRODUCTION TO MICROCONTROLLER
Microcontroller, as the name suggests, are small controllers. They are like single chip computers that are often embedded into other systems to function as processing/controlling unit. For example, the remote control you are using probably has microcontrollers inside that do decoding and other controlling functions. They are also used in automobiles, washing machines, microwave ovens, toys ... etc, where automation is needed.
The key features of microcontrollers include:
• High Integration of Functionality
• Field Programmability, Flexibility
• Microcontrollers sometimes are called single-chip computers because they have on-chipmemory and I/O circuitry and other circuitries that enable them to function as smallstandalone computers without other supporting circuitry.
• Microcontrollers often use EEPROM or EPROM as their storage device to allow fieldprogram ability so they are flexible to use. Once the program is tested to be correct then large quantities of microcontrollers can be programmed to be used in embedded systems.
• Easy to Use
8051 MEMORY ORGANISATION
The 8051 has a separate memory space for code (programs) and data. We will refer here to on-chip memory and external memory as shown in figure 1.5. In an actual implementation the external memory may, in fact, be contained within the microcomputer chip. However, we will use the definitions of internal and external memory to be consistent with 8051 instructions which operate on memory. Note, the separation of the code and data memory in the 8051 architecture is a little unusual. The separated memory architecture is referred to as Harvard architecture whereas Von Neumann architecture defines a system where code and data can share common memory.
STEPPER MOTOR
Of all motors, step motor is the easiest to control. It's handling simplicity is really hard to deny - all there is to do is to bring the sequence of rectangle impulses to one input of step controller and direction information to another input. Direction information is very simple and comes down to "left" for logical one on that pin and "right" for logical zero. Motor control is also very simple - every impulse makes the motor operating for one step and if there is no impulse the motor won't start. Pause between impulses can be shorter or longer and it defines revolution rate. This rate cannot be infinite because the motor won't be able to "catch up" with all the impulses (documentation on specific motor should contain such information). The picture below represents the scheme for connecting the step motor to microcontroller and appropriate program code follows.
The key to driving a stepper is realizing how the motor is constructed. A diagram shows the representation of a 4 coil motor, so named because 4 coils are used to cause the revolution of the drive shaft. Each coil must be energized in the correct order for the motor to spin
CONCLUSION
An engineer must have a good practical as well as theoretical knowledge. He must be technically sound as book knowledge is incomplete.
The technical training was an educative as well as interactive. We learned how to make the people learn. Technical lectures presented by the professional technicians on Embedded Systems and Embedded C were really interesting and healthy to learn the industrial trends.
Practical Training is a true platform to initiate the step towards professionalism in an engineer’s life. I am thankful to all the faculty members and Principal for supporting my work and for providing a right track.