1. 1 Introduction to Embedded system
An embedded system is a special-purpose computing machine system designed to execute one or a few dedicated maps. [ 1 ] frequently with real-time calculating restraints. It is normally embedded as portion of a complete device including hardware and mechanical parts. In contrast. a all-purpose computing machine. such as a personal computing machine. can make many different undertakings depending on programming. Embedded systems control many of the common devices in usage today. Since the embedded system is dedicated to specific undertakings. design applied scientists can optimise it. cut downing the size and cost of the merchandise. or increasing the dependability and public presentation. Some embedded systems are mass-produced. profiting from economic systems of graduated table.
Physically. embedded systems range from portable devices such as digital tickers and MP4 participants. to big stationary installings like traffic visible radiations. mill accountants. or the systems commanding atomic power workss. Complexity varies from low. with a individual microcontroller bit. to really high with multiple units. peripherals and webs mounted inside a big human body or enclosure.
In general. “embedded system” is non an precisely defined term. as many systems have some component of programmability. For illustration. Handheld portion some elements with embedded systems — such as the operating systems and microprocessors which power them — but are non genuinely embedded systems. because they allow different applications to be loaded and peripherals to be connected.
1. 2 Examples of embedded systems
Embedded systems span all facets of modern life and there are many illustrations of their usage. Telecommunications systems employ legion embedded systems from telephone switches for the web to mobile phones at the end-user. Computer networking utilizations
dedicated routers and web Bridgess to route informations.
Consumer electronics include personal digital helpers ( PDAs ) . mp3 participants. nomadic phones. videogame consoles. digital cameras. DVD participants. GPS receiving systems. and pressmans. Many family contraptions. such as microwave ovens. rinsing machines and dish washers. are including embedded systems. these are used to supply flexibleness. effiency. truth and other characteristics which made human life easier.
2. Undertaking DESCRIPTION
2. 1 Background of innovation
A big assortment of electrical contraptions are found everyplace. While the presence of those contraptions ensures that undertakings are performed more safely and expeditiously. the effectivity of those contraptions depends on commanding and bespeaking their operational position. For illustration. if an contraption is left turned on long after the user has finished with it. careless individual may fire themselves on the exposed het surfaces. Hence. an automatic control for closing off the contraption every bit good as for bespeaking that the contraption has been shut off would avoid this and other safety hazards. In add-on. the controller/indicator would cut down extra wear and rupture on the contraption. every bit good as save electricity. Another job created by the absence of indexs or controls stems from the fact that contraptions frequently require a short period of clip to make a ready or operational province. In such cases. the user must sporadically prove the contraption to see if it is ready. By supplying a control circuit for and index of a ready province. nevertheless. the user avoids losing the clip exhausted proving the contraption. Although some contraptions are equipped with control and bespeaking circuitry that automatically turns the contraption off or indicates that the contraption is ready to utilize. such circuits have tended to affect comparatively complex designs that have non to the full solved the jobs discussed supra.
Furthermore. the contraptions known in the anterior art do non automatically close off after a preset period of clip regardless of any usage during that period of clip. So in our undertaking we use Real Time clock to command the contraptions or to provide tonss at different intervals of clip.
Power Salvaging Using Time Operated Electrical Appliance Controlling System is a dependable circuit that takes over the undertaking of switch on/off the electrical devices with regard to clip. This undertaking replaces the Manual Switching. It has an Inbuilt Real Time Clock which tracks over the Real Time. When this clip equals to the programmed clip. so the corresponding Relay for the device is switched ON. The switching clip can be edited at any Time utilizing the computer keyboard. The Real Time Clock is displayed on four 7-segment show. The programmed clip can be predetermined by the user i. e. the user set clip as he requires. He may besides alter the scenes when of all time wants to make so.
2. 2 Block Diagram
Fig 2. 2. 1
2. 3 Block diagram description
The type of power supply we use is the LINEAR POWER SUPPLY. Linear power supply
An AC powered additive power supply normally uses a transformer to change over the electromotive force from the wall mercantile establishment ( brinies ) to a different. normally a lower electromotive force. If it is used to bring forth DC. a rectifier is used. A capacitance is used to smooth the throbing current from the rectifier. Some little periodic divergences from smooth direct current will stay. which is known as rippling. These pulsings occur at a frequence related to the AC power frequence ( for illustration. a multiple of 50 or 60 Hz ) . The electromotive force produced by an unregulated power supply will change depending on the burden and on fluctuations in the AC supply electromotive force. For critical electronics applications a additive regulator will be used to stabilise and set the electromotive force. This regulator will besides greatly cut down the rippling and noise in the end product DC current. Linear regulators frequently provide current modification. protecting the power supply and attached circuit from over current. The simplest DC power supply circuit consists of a individual rectifying tube and resistance in series with the AC supply.
[ 1 ] The Transformer
[ 2 ] The Rectifier
[ 3 ] The Filter
[ 4 ] The electromotive force regulator
The Transformer-usually steps up or step down the incoming line electromotive force depending on the demands of the power supply. This alternating electromotive force is so fed to the rectifier.
The Rectifier is a rectifying tube circuit that converts the Ac to throbing District of Columbia. This throbing District of Columbia is so applied to the filter.
The Filter is a circuit that reduces the fluctuations of the in the District of Columbia electromotive force. It can include one or several inactive
The electromotive force regulator is used to keep a changeless electromotive force at the power supply end product. It besides provides a farther smoothing of the dc electromotive force. We will be utilizing a zener rectifying tube as a electromotive force regulator. Modern twenty-four hours circuits have superceded the zener rectifying tube regulator with more modern integrated circuits. Since the zener rectifying tube is the simplest of these circuits to understand. we will analyze it as a requirement to the more modern circuits available.
In our undertaking we are utilizing the AT 89S51micro-controller. The AT 8051 micro-controller provides following standard characteristics: 4k of brassy memory. 128 bytes of random-access memory. 32 I/O. two 16-bit timer/counters. five vector two-level interrupt architecture. a full semidetached house consecutive port. o bit oscillator And clock circuitry. In add-on. the AT 8051 micro-controller is designed with inactive logic for operation down to zero frequence and supports two package selectable power salvaging manners. The idle manner stops the central processing unit while leting the random-access memory. counters. consecutive port and interrupt system to go on working. The power –down manner saves the RAM contents but freezes the oscillator disabiling all other bit maps until the following hardware reset.
Real Time Clock DS 1307
The DS1307 Serial Real-Time Clock is a low-power ; full binary-coded decimal ( BCD ) clock/calendar plus 56 bytes of NV SRAM. Address and informations are transferred serially via a 2-wire. bi-directional coach. The clock/calendar provides seconds. proceedingss. hours. twenty-four hours. day of the month. month. and twelvemonth information. The terminal of the month day of the month is automatically adjusted for months with fewer than 31 yearss. including corrections for leap twelvemonth. The clock operates in either the 24-hour or 12-hour format with AM/PM index. The DS1307 has a constitutional power sense circuit that detects power failures and automatically switches to the battery supply.
The back-up used here is of 3v which is used provide back-up for RTC in times of power failure
A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric stuff to make an electrical signal with a really precise frequence. This frequence is normally used to maintain path of clip ( as in quartz wrist watchs ) . to supply a stable clock signal for digital incorporate circuits. and to stabilise frequences for wireless senders and receiving systems. The most common type of piezoelectric resonating chamber used is the quartz crystal. so oscillator circuits designed around them were called “crystal oscillators” .
A reset circuit is like a switch which is used reset the circuit. It is connected to trap 9 of the accountant.
Liquid crystal show ( LCD )
Frequently. a microcontroller plan must interact with the outside universe utilizing input and end product devices that communicate straight with a human being. One of the most common devices attached to any microcontroller is an LCD ( show ) . Some of the most common LCDs connected to the microcontroller are 16?2 shows. means 16 characters per line by 2 lines. A criterion exists which allows us to pass on with the huge bulk of LCDs regardless of their maker. The criterion is referred to as HD44780U. which refers to the accountant bit which receives informations from an external beginning ( in our undertaking. AT89S52 ) and communicates straight with the LCD. Relaies
A relay is an electro-magnetic switch which is utile if you want to utilize a low electromotive force circuit to exchange on and off a light bulb ( or anything else ) connected to the 220v brinies supply. The current needed to run the relay spiral is more than can be supplied by most french friess ( op. As. 8051 etc ) . Relays let one circuit to exchange a 2nd circuit which can be wholly separate from the first. For illustration a low electromotive force battery circuit can utilize a relay to exchange a 230V AC brinies circuit. There is no electrical connexion inside the relay between the two circuits. the nexus is magnetic and mechanical. [ movie ]
Fig 2. 3. 1
The tonss here we use are Led’s and a fan.
3. Hardware description
3. 1 POWER Supply:
The type of power supply we use is the LINEAR POWER SUPPLY. Linear power supply
An AC powered additive power supply normally uses a transformer to change over the electromotive force from the wall mercantile establishment ( brinies ) to a different. normally a lower electromotive force. If it is used to bring forth DC. a rectifier is used. A capacitance is used to smooth the throbing current from the rectifier. Some little periodic divergences from smooth direct current will stay. which is known as rippling. These pulsings occur at a frequence related to the AC power frequence ( for illustration. a multiple of 50 or 60 Hz. The electromotive force produced by an unregulated power supply will change depending on the burden and on fluctuations in the AC supply electromotive force. For critical electronics applications a additive regulator will be used to stabilise and set the electromotive force. This regulator will besides greatly cut down the rippling and noise in the end product DC current. Linear regulators frequently provide current modification. protecting the power supply and attached circuit from over current. The simplest DC power supply circuit consists of a individual rectifying tube and resistance in series with the AC supply.
Block diagram of power supply
Fig 3. 1. 1
3. 1. 2 Transformers
The first constituent of the power supply is the transformer. Using magnetic yoke between twists. the transformer is used to insulate the rectifier from the brinies electromotive force. and to cut down the electromotive force to something the regulator can digest. The primary twist will be rated at 220 0V AC and the secondary will be a more user friendly ( or less user hostile ) electromotive force to accommodate the application. DC Output: The DC end product is about equal to the secondary electromotive force multiplied by 1. 414. but as we shall see. this is a instead simplistic computation. and does non take the many variables into consideration. At light lading. this regulation can be applied without fright. and it will be accurate plenty for most applications. When an appreciable current is drawn. this simple attack falls level on its face. Mains fluctuations: These occur in all state of affairss. and the brinies electromotive force at any point in clip will normally be slightly different from the nominal electromotive force quoted by the provider. Any fluctuation of 10 % or less can be considered “normal” . and greater fluctuations are non at all uncommon. Losingss: Since all transformers have losingss. these can non be ignored in the design stage. Magnetising loss ( AKA iron loss ) is the current that is required to keep the design value of magnetic flux in the transformer nucleus.
There is nil you can make to impact this loss. as it is dependent on the size of the nucleus and the design standard of the maker. Large transformers will hold a larger magnetising loss than little 1s. but will be less affected by it due to the larger surface country which allows the transformer to stay cool at no burden. Small transformers have a greater loss per VA than bigger 1s. and this is one of the grounds that little transformers run rather warm even when unloaded. The Fe losingss are greatest at no-load and autumn as more current is drawn from the transformer. Copper losingss are caused by the opposition of the twist. and are negligible at no burden. and rise with increasing end product current. There is a all right balance between Fe and Cu losingss during transformer design. A comparatively high Fe loss means that Cu losingss will be reduced ( therefore bettering ordinance ) . but if excessively high. the transformer will overheat with no burden. A full description of the magnetising current and its consequence on ordinance is outside the range of this article. and since there is small you can make about it. it shall be discussed no farther.
Mains noise: Noise can easy acquire through a transformer. both in transverse and common manners. Transverse noise is any noise or waveform deformation that is efficaciously superimposed on the entrance AC wave form. and this is coupled through the transformer along with the wanted signal – the brinies. Common manner noise is any noise signal that is common to both the active ( hot ) and impersonal brinies leads. This is non coupled through the transformer magnetically. but capacitively. The higher the electrical capacity between primary and secondary twists. the more common manner noise will acquire through to the amplifier. The much loved toroidal transformer is much worse than conventional “EI” ( Ee-Eye ) lamination transformers in this regard because of the big inter-winding electrical capacity. An electrostatic shield will assist. but these are uncommon in mass produced toroidal transformers.
The conventional transformer is normally better. and by utilizing side-by-side twists alternatively of the more common ( and cheaper ) homocentric twists. common manner noise can be reduced by an order of magnitude. Input mains filters can take either signifier of high frequence noise constituent to some grade. and big spikes can be removed utilizing Metal Oxide Varistors ( MOVs ) that efficaciously short circuit the noise pulsation. cut downing it to a degree that is ( hopefully ) unhearable. Contrary to the beliefs of some. there is no Panacea for noise. and it is best attacked in the equipment. instead than the now popular ( but chiefly misconceived ) impression that an expensive brinies lead will bring around all. 3. 1. 3 Rectifiers:
The 2nd block of the power supply is the rectifier block. The most common rectifiers are …
• Full Wave Bridge
• Full Wave
• Dual Full Wave ( Full Wave Centre Tap )
The full moving ridge electromotive force doubler is still common in valve amplifier circuits and for preamp supplies.
The Full Wave Bridge Rectifier
The span rectifier is the most normally used rectifier circuit for the undermentioned grounds: [ 1 ] No Centre – tapped transformer is required.
[ 2 ] The span rectifier produces about dual the end product electromotive force as a full moving ridge C-T transformer rectifier utilizing the same secondary electromotive force
Fig 3. 1. 3. 1
Basic Circuit Operation
During the positive half rhythm. both D1 and D3 are frontward biased. At the same clip. both D2 and D4 are rearward biased. Note the way of current flow through the burden. On the negative half rhythm. D2 and D4 are frontward biased and D1 and D3 are rearward biased. Again note that way of current through the burden is in the same way although the secondary twist mutual opposition has reversed.
In a span rectifier the rectifying tubes may be of variable types like 1N4001. 1N4002. 1N4003. 1N4004. 1N4005. 1N4006. 1N4007 etc…… . can be used. But we use 1N4007 because it can with stand up to 1kv.
3. 14 Regulators:
Fixed electromotive force regulated
Very many devices need good regulated power. The most typical attack used electronics devices is to utilize a transformers that work straight from the domestic electricity supply at 60 Hz ( in the U. S. A. 50 Hz in some other states ) and this is followed by rectifier + regulator circuitry that uses additive ordinance. In this type of regulator a transistor. or a particular IC. is used as a series resistance whose value of opposition is controlled so as to keep the end product electromotive force changeless despite fluctuations in burden. This work good. is rather simple to do. but is rather inefficient as a batch of power is wasted as heat ( otiose heat is define by expression: bead electromotive force over regulator ( Vs ) * current taken ( in amperes ) = power loss ( in Watts ) ) . Linear ordinance works really good in low power applications where some lost heat is no job ( in higher power applications switched more power supplies are today preferred because of less otiose power ) . Here we use 7812 regulator and it supplies 12v to the accountant.
3. 1. 5 Filters
In order to obtain DC electromotive force of 0 Hz. we have to utilize a low base on balls filter ( LPF ) . So that capacitive filter circuit is used where a capacitance is connected at the rectifier end product & A ; District of Columbia is obtained across it. The filtered wave form is basically a dc electromotive force with negligible ripplings & A ; it is finally fed to the burden.
3. 2 Micro accountant
Features: • Compatible with MCS-51® Merchandises
• 8K Bytes of In-System Programmable ( ISP ) Flash Memory– Endurance: 1000 Write/Erase Cycles • 4. 0V to 5. 5V Operating Scope
• Fully Inactive Operation: 0 Hz to 33 MHz
• Three-level Program Memory Lock
• 256 ten 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Beginnings
• Full Duplex UART Serial Channel
• Low-power Idle and Power-down Modes
• Interrupt Recovery from Power-down Mode
• Watchdog Timer
• Dual Data Pointer
• Power-off Flag
3. 2. 1 Description:
The AT89S52 is a low-power. high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured utilizing Atmel’s high-density nonvolatilizable memory engineering and is compatible with the industry- criterion 80C51 direction set and pinout. The on-chip Flash allows the plan memory to be reprogrammed in-system or by a conventional nonvolatilizable memory coder. By uniting a various 8-bit CPU with in-system programmable Flash on a massive bit. the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-efficient solution to many embedded control applications. The AT89S52 provides the following standard characteristics: 8K bytes of Flash. 256 bytes of RAM. 32 I/O lines. Watchdog timer. two information arrows. three 16-bit timer/counters. a six-vector two-level interrupt architecture. a full semidetached house consecutive port. on-chip oscillator. and clock circuitry. In add-on. the AT89S52 is designed with inactive logic for operation down to zero frequence and supports two package selectable power salvaging manners. The Idle Mode stops the CPU while leting the RAM. timer/counters. consecutive port. and interrupt system to go on working. The Power-down manner saves the RAM contents but freezes the oscillator. disenabling all other bit maps until the following interrupt or hardware reset.