hardware orientation embedded systems

8/9/2019 Hardware Orientation Embedded Systems

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HARDWARE ORIENTATION

EMBEDDED SYSTEMS


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There are many types of power supply. Most are designed to convert highvoltage AC mains electricity to a suitable low voltage supply for electronicscircuits and other devices. A power supply can by broken down into a seriesof blocks, each of which performs a particular function


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The regulated DC output is very smooth with no ripple. It is suitable for allelectronic circuits.


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Batteries come in all shapes and sizes. They store electrical charge and as we allknow when they are put into an electronic device such as a portable radio, theyprovide the power. The usual battery sizes are seen opposite. These are the typeused in school projects and range from 1.5 volts to 9 volts.

School projects are powered by batteries because they are safe, easily boughtand safe.


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Light Emitting Diodes (LED) are very rugged, they last a very long time and theyare an optical source. (ALIGHT SOURCE)LEDs produce red, green, yellow, or orange light. They are used in a range ofproducts. Can you name any ?

InfraredL

EDs are also available although light from this type cannot be seen bythe human eye. These are used in security devices.LEDs are part of the diode family, consequently they must be connected theright way round or current will not pass through. They are usually protected bya resistor. (See DIODE information sheet).


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LDRs or Light Dependent Resistors are very useful especially in light/darksensor circuits. Normally the resistance of an LDR is very high, sometimes ashigh as 1000 000 ohms, but when they are illuminated with light resistancedrops dramatically.

The animation oppositeshows that when the torchis turned on, theresistance of the LDR falls,

allowing current to passthrough it.


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When the light level is low the resistance of the LDR is high. This preventscurrent from flowing to the base of the transistors. Consequently the LED doesnot light.

However, when light shinesonto the LDR its resistancefalls and current flows intothe base of the first transistorand then the secondtransistor. The LED lights.


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A relay is an electromagnetic switch. In other words it is activated when a currentis applied to it. Normally a relay is used in a circuit as a type of switch (as you willsee below). There are different types of relays and they operate at differentvoltages. When you build your circuit you need to consider the voltage that willtrigger it.


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This simple circuit activates the relay only when the LDR is dark (covered). Thiscould be used as part of an automatic animal feeder. For instance, if the animalwas fed at night the circuit above would activate the relay. A second circuit,connected to the other side of the relay releases food into a dish.


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Transistors can be regarded as a type of switch, as can many electroniccomponents. They are used in a variety of circuits and you will find that it is rarethat a circuit built in a school Technology Department does not contain at leastone transistor. They are central to electronics and there are two main types; NPN

and PNP. Most circuits tend to use NPN. There are hundreds of transistors whichwork at different voltages but all of them fall into these two categories.


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The circuit shown in is based on an NPN transistor. When the switch is presseda current passes through the resistor into the base of the transistor. Thetransistor then allows current to flow from the +9 volts to the 0vs, and the lampcomes on.

The transistor has to receive avoltage at its base and untilthis happens the lamp does notlight.

The resistor is present to protectthe transistor as they can be

damaged easily by too high avoltage / current. Transistors arean essential component inmany circuits and aresometimes used to amplify asignal.


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The circuit to the right shows a single transistor. When the switch is pressedcurrent flows from the 9v to the 0v and also to the base of the transistor.This allows the transistor to switch and in turn, current / voltage flowsthrough the bulb, which lights.

However, there is a potential problem with this circuit. The signal / currentat the base of the transistor may be too weak to switch the transistor andallow the bulb to light or it may flicker on and off.


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A possible solution is seen tothe right. A second transistoris added to the circuit, the

circuit is now likely to workas the original signal /current is amplified.

The amount by which theweak signal is amplified iscalled the GAIN.


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Below is a system designed to monitor the temperature of a car radiator. When theradiator temperature becomes too high the voltage from the temperature sensorand sensor unit changes. The comparator detects this change in voltage andactivates the darlington pair. The darlington pair driver provides enough amplifiedcurrent for the motor to operate, cooling the car radiator. .


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The single transistor does not amplify the current to the motor. As a result themotor does not spin. Control Studio software allows experimentation, withoutthe need to build a real circuit using actual components. It saves time and moneyas components are not


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The packages of popular integrated circuits used in schools and colleges aresometimes called a Dual In-Line Packages. They are also called either DIPpackages or DIL packages and two examples are shown opposite. The PICAXE18 is a DIL package with 18 pins and its smaller relation is the PICAXE 08 with

8 pins.


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This integrated circuit is used for timing. Many circuits are composed oftimers and the most common of them all is the 555 Integrated Circuit. It isused in many commercially manufactured items such as video recorders andtimers.


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When the 555 IC is used to produce an MONOSTABLE circuit - it will onlypulse once. Monostable circuits can be used to turn lights/LEDs on or offjust once. They are also used in many more school based circuits.


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4029 CMOS counter IC count up or down, and in either decimal or binarymode. It can also be preset with any initial count, and is designed so thatmultiple 4029 ICs can be cascaded and still maintain fully synchronouscounting either up or down.


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We require numerical counting in several operations.This requires just sevenLEDs (plus an eighth one for the decimal point, if that is needed). A commontechnique is to use a shaped piece of translucent plastic to operate as aspecialized optical fiber, to distribute the light from the LED evenly over a fixed

bar shape. The seven bars are laid out as a squared-off figure "8". The result isknown as a seven-segment LED.


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The 4511 a BCD to 7-segment decoder driver. Its function is to convert the logicstates at the outputs of a BCD counter like the4029 into signals which will drive a7-segment display. The display shows the decimal numbers 0-9 and is easilyunderstood.


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y TRACKING(REVERSE ENGINEERING)

y TESTING AND DEBUGGING

*CONTINUITY CHECKING

*LOOSE(DRY) SOLDERING*VOLTAGE CHECKING


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y AN EMBEDDED SYSTEM IS MAINLY A COMPUTERSYSTEM WHICH IS DEDICATED TO PERFORM ONEOR FEW TASKS USUALLY IN GIVEN REAL TIMECONSTRAINTS.

y WHEREAS THE GENERAL PERSONAL COMPUTERSARE VERY FLEXIBLE AND THEY SERVE WIDERANGE OF END USER`S NEEDS.


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y PERFORMS SINGLE SET OF FUNCTIONS

y WORKS IN TIME CONSTRAINED ENVIRONMENT

y HIGH PERFORMANCE AND RELIABILITY

y LOW COSTy CERTAIN EMBEDDED SYSTEMS ALSO HAVE

MECHANICAL MOVING PARTS..


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EMBEDDED SYSTEMS Vs. GENERAL COMPUTINGSSYSTEMS

ES HAVE VERY FEW RESOURCES..*LIKE LESS MEMORY CAPACITY

*LESS PROCESSING POWER

THE MAIN CHALLENGE IS DEVELOPING AN

EMBEDDED SYSTEM APLLICATION


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y IT IS A RAPIDLY GROWING INDUSTRY .SONUMEROUS GROWTHOPPORTUNITIESAND SO NO DEARTH OFJOBS

y ITS ALMOST INSEPARABLE PART OF OURLIVES

y TO REALLY UNDERSTAND THE WHOLEELECTRONICS SCENERIO


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y MICROCONTROLLER


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MICROCONTROLLER

y NO ON CHIP RAM,ROM,I/O,TIMER,SERIAL PORT

y

USED IN GENERAL PURPOSEAPPLICATIONS

y NO DATA STORAGE FACILITY

y ON CHIP RAMROM,I/O,TIMER,SERIAL PORT

y

USED IN SPECIFIC PURPOSEAPPLICATIONS

y PROVIDES DATA STORSGEFACILITY

MICROPROCESSOR


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y 4-BIT

y 8-BIT

y 16-BIT

y 32-BIT


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y Speed

y Packaging

y Power consumption

y

The amount of RAM and ROM on chipy The number of I/O pins and the timer on chip

y How easy to upgrade to higher- performance or lowerpower-consumption versions

y Cost per unit

y Availability of software development tools, such ascompilers, assemblers, and debuggers.


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y NOTES

y EMTECH MANUAL

y 8051 MICROCONTROLLER BY MAZIDI

y

INTERNET

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