Multifunctional Elevator Driven by Solar Energy

CHAPTER-1

INTRODUCTION

 Elevators have been built throughout history but the first modern passenger elevators were developed no more than about 150 years ago. Steam and hydraulic elevators had already been introduced by 1852, when Elisha Otis made one of the most important elevator inventions, the clutch, which prevented the elevator from falling. Following this, in 1857, the first passenger elevator was installed in the store of E. Haughwout&Company, New York.

 The development of elevator technology was fast. With the advent of modern high-rise buildings, more elevator history than in any other single location was made in 1889, when the 321-meter-high Eiffel Tower was built for the Universal Exposition in Paris. In the Eiffel Tower, hydraulic double-deck elevators operated between ground level and the second platform. Between the second and third platforms two cars counterbalancing each other handled the traffic. The early hydraulic and steam-driven elevators functioned with pressurized water, which was either taken from the city water pipes or provided by steam engines. The elevator car was connected to a long piston that moved up when water was pumped into a cylinder, and came down when water was released by a hydraulic valve. In 1880 Werner von Siemens introduced the utilization of electric power. Soon after, the geared or gearlesstractionelectricelevators started to replace the hydraulic elevators. The development of electric elevators added impetus to high-rise construction. The fastest elevators today move at about 10 meters per second.

            Due to modernization, the elevator system has become a part and parcel of life as high-rise buildings is a common sight. High-rise building will not be realizable without the implementation of elevators. Elevators play an important part of our daily lives. But almost all elevators worldwide, more than 99% they are in use today are designed to carry the people in vertical direction.

            Only few elevators designed for special purposes can move in different directions, the hidden technology involved in these elevators is not popular, there by this project work is taken up to high light this technology. To prove the concept practically, a proto type module is constructed using simple technology for the live demonstration.

The main objective of the project is to develop a hardware prototype and software to simulate the multi-functional elevator system, which is quite useful for the people for crossing the railway tracks at railway stations and for crossing the busy Roads. 89C51 microcontroller is used as control system of the elevator. The software of the elevator system is to control the overall elevator system and its algorithm. As for the hardware prototype, it is used to simulate the elevator system with three motors to control the movement and motion of the elevator in vertical and horizontal directions. Push buttons to act as input requests from passengers of the elevator from one side to other end. Limit switches are used and they are arranged at various points of mechanical structure to identify the position of the elevator. The detailed description is provided in following chapters.

It's a new method that is more predictable, more reliable, more product friendly and less maintenance prone than conventional elevators. The mechanical transmission section designed with lubricated bearing type sliding channels moves the elevator smoothly. Quite simply, it will perform the duty that other screw elevators won't.

Definition of an Elevator: An elevator is a device, generally used for vertical transportation of passengers or freight to different floors or levels, as in a building or a mine. The term elevator generally denotes a unit with automatic safety devices; the very earliest units were called hoists. Elevators consist of a platform or car traveling in vertical guides in a shaft or hoist way, with related hoisting and lowering mechanisms and a source of power. The development of the modern elevator profoundly affected both architecture and the mode of development of cities by making many-storied buildings practical.

            Nowadays elevators primarily consist of a shaft in which the car (also known as cab) moves up and down. In “traction” elevators the car is pulled up with the help of steel ropes, which roll over the surface of a grooved pulley. The load of the car is normally balanced with a counterweight.

            An elevator is a transport device used to move goods or people vertically. The name comes from the action it performs ‘to elevate’. Elevators are also popularly known as lifts in many countries. An elevator is a platform, which is either pulled up or pushed down by mechanical means.

            When elevators first came into civilization, they were powered by animals, water, or even humans. In 1853, American inventor Elisha Otis showed the world a safe machine powered elevator. He demonstrated to the public the break system he had made that would stop the elevator car if a cable broke. Although his demonstration was considered successful, in the beginning, only men were allowed on elevators due to safety concerns.

            The Otis Company started manufacturing elevators in 1861 that were steam powered. The electric elevator came into use towards the end of the 19th century. German inventor Werner von Siemens in 1880 built the first one. To this day, elevators are electric. Many improvements have been made to the elevator specifically in concern to speed and safety. Today’s elevators can travel up to 25 mph and some can even hold up to 60 people! With skyscrapers growing taller each year, elevators will have to keep up.

            The following are the two important tips for general elevators, which travels in vertical direction only.

• The Rule of Efficiency: The elevator will stop at any floor on which a person has ‘called’ it. So if we started on floor 10 and wanted to go to floor 3 and someone on floor 7 was also going down… the elevator will stop on floor 7 to let them in.


• Elevator Kindness: Elevators generally won’t change direction until they’ve finished dropping everyone off. So, if we started on floor 10 and wanted to go to floor 3, the elevator will not start going up until it has gone all the way to floor 3.

            The multifunctional elevator designed here is quite different, the advantages and applications are plenty when compared with simple vertical elevator, here this elevator, after carrying the persons up to certain height, and it will act as a person conveyor. Means the same carrier is also used to carry the people in horizontal direction also, there by it can be called as horizontal people mover.

            The entire system is designed to operate at 12 V DC; the required power source is derived from solar panel, the idea of using solar energy is to utilize non–conventional energy resources effectively.

            The heart of the project work is microcontroller unit; it is designed with 89C51 ATMEL chip. These days there is no such electronic or electrical device that functions without microcontroller; we are living in the Embedded World surrounded with many embedded products designed with much variety of microcontroller chips produced by different companies. Our daily life largely depends on the proper functioning of these gadgets. Television, Radio, CD player, Washing Machine, Microwave Oven and many more house hold gadgets, and Card readers, Access Controllers, Palm devices of our work space enable us to do many of our tasks very effectively. Apart from all these, many controllers embedded in our car, which take care of many car operations to make it as fully automated.

            The ATMEL 89C51 is an 8 bit controller, the internal Architecture is similar to the 8031 core. The most popular and used architecture is Intel’s 8031. Market acceptance of this particular family has driven many semiconductor manufacturers to develop something new based on this particular architecture. The 8031 contains variety of configurations; Even after 25 years of existence, semiconductor manufacturers still come out with some kind of device using this 8031 core.

1.1 Hydraulic Versus Electric Elevators

1.1.1 Hydraulic Elevators

            In the late 1870s Otis Brothers introduced their "safe, simple, economical 'hydraulic elevator. In matters of safety, utility, and economy, the hydraulic elevator quickly proved itself superior to steam elevators. Furthermore, the Otis company advertised that its hydraulic elevators were superior to the competition in safety, smoothness and noiselessness of motion, speed, economy of operation, and durability.

The Otis Standard Hydraulic Elevator could be adapted for use in hotels, publicbuildings, stores, office buildings, flats, private houses, warehouses, and factories.The Otis Standard Hydraulic Elevator operated by water pressure from streetmains, from a tank in an upper story, a tank on the roof, or a pressure tank in thebasement. If the pressure came from municipal waterworks, no skilled attendant wasneeded; otherwise someone needed to maintain the pressure tank in the basement orthe steam pump or gas engine used to raise water from a discharge tank in the basementto the supply tank above. Gravity provided the pressure for water taken fromthe supply tank. The water under pressure went into a bored cylinder, and thereinacted upon a solid piston, which, via ropes and gears, drove the car. In other words, the Otis Standard was a rope-geared hydraulic elevator.

1.1.2 Electric Elevators

            Thomas Edison had demonstrated the practicality of electric power in 1882, throughthe successful operation of his Pearl Street Central Station in New York City. Electricitythere after gradually altered the elevator industry that had relied upon steamengines and hydraulic motors. The direct-drive electric elevator took advantage of the increasing availability of electricity in a manner similar to the hydraulic elevator moving into cities with municipal waterworks. Compared to hydraulic motors and steam engines, the electric motor was compact and efficient. Still, the earliest electric elevators were not seen as competition for hydraulic elevators, but as "a valuable adjunct adapted to small buildings, where space is limited, and where the cost of operation of a hydraulic plant would be abnormally high."

            Most early electric elevators used worm gearing to turn a drum,which limited the height of the lift, because the gearing was not suitable for highspeeds and the drums did not hold enough rope for high rises. Hydraulic elevatorstherefore remained popular in commercial and public buildings.

            In the matter of control, electric elevators rendered possible the elimination of the hand rope used in nearly all hydraulic elevators. Yet the hand rope manipulated manually or via a wheel or lever.

 Chapter-2

History

            The history of elevator is very long, however the safety elevator, which was equipped with safety gear, appeared in 1854. In Japan, the first elevator appeared in 1890 and present elevator companies started elevator manufacturing around in 1933. The history of motor drive system, the history of machine-room-less elevator and the research subjects of elevator system technology are described. The history of Electric motor drives and control equipments have progressed significantly by the application of power electronics and microelectronics from 1970 to 1990.

            As the history of elevator system including mechanical equipment, electrical equipment and their system configuration, we focused the history of machine-room-less elevator started from around 1990. The feature of this elevator is space-saving. The machine-room-less elevator has begun from the home elevator and the linear-motor elevator. By deregulation, the machine-room-less elevator appeared in 1998, and now most standard elevators replaced with the machine-room-less elevators. Utilization of the permanent-magnet electric motor contributed for the miniaturization of the traction machine, and noise reduction.

            Elevators basically work on the principle of the pulley. Though the modern day elevator installed in millions of buildings around the world are only 150 years old, the history of elevators can be traced two centuries back. In fact, ancient Egyptians used lifts to transport the heavy blocks of stone during the construction of the pyramids however the effort to hoist the blocks was of human nature.

One of the first mentions of an elevator like device is found in the works of a Roman architect, Vitruvius, who reported that the great Greek Archimedes built a rough structure like the lift in 236 BC. In late 1700’s at the insistence of the Czar, Ivan Kulibin designed an elevator with screw lifting mechanism for the Winter Palace of Saint Petersburg. Henry Waterman, an American, invented the modern day lift in 1850. But his intention was to use it for only for transporting goods.

However his accomplishment was eclipsed only three years later when Elisha Otis unveiled his design of the elevator at the New York World’s Fair in 1853. This design was revolutionary considering it was the first of its kind which would prevent the fall of the cab in the event the hoisting cable snapped. A safety device would was immediately engaged in such a scenario. Even today’s elevators have the same design in principle.

The first elevators were operated by steam power to turn the cable drums and the first Otis elevator was installed at 488 Broadway in New York. In 1871 the hydraulic elevators made their debut using water pressure as a source of power. Later it was realized that the best source of power would be electricity and the first electric elevator was built by Werner von siemens in 1880.

Today, Otis is the world’s largest elevator manufacturing company. The control system on early elevators required manual inputs to decide the speed of the lift and opening and closing the doors. In 1970’s solid state electronic controls became an essential of any elevators.

Chapter-3

Over view

      

3.1 Elevator safety

            Elevators are characterized as being extremely safe. Their safety record of moving millions of passengers every day, with extremely low rate of incident, is unsurpassed by any other vehicle system. Even so, fatalities due to malfunction have been known to occur on occasion. A certain number of passengers do die every year in elevator-related incidents. In 1998, in the United States, it was reported that of the estimated 120 billion rides per year in the approximately 600,000 elevators in the U.S., 10,000 people wound up in the emergency room because of elevator-related accidents.

            Past problems with hydraulic elevators meant those built prior to a code change in 1972 were subject to possible catastrophic failure. The code had previously required only single-bottom hydraulic cylinders. In the event of a cylinder breach, an uncontrolled fall of the elevator might result. Because it is impossible to verify the system completely without a pressurized casing (as described below), it is necessary to remove the piston to inspect it. The cost of removing the piston is such that it makes no economic sense to re-install the old cylinder; therefore it is necessary to replace the cylinder and install a new piston. Another solution to protect against a cylinder blowout is to install a "life jacket." This is a device which, in the event of an excessive downward speed, clamps onto the cylinder and stops the car. This device is also known as a Rupture Valve in some parts of the world.

            In addition to the safety concerns for older hydraulic elevators, there is risk of leaking hydraulic oil into the aquifer and causing potential environmental contamination. This has led to the introduction of PVC liners (casings) around hydraulic cylinders which can be monitored for integrity.

            In the past decade, recent innovations in inverted hydraulic jacks have eliminated the costly process of drilling the ground to install a borehole jack. This also eliminates the threat of corrosion to the system and increases safety.

            On traction lifts there is a device called a "Safety Gear" that is fitted to the bottom of the lift car frame. This device connects to another device commonly known as a "Overspeed Governor." There is a separate rope from the main lifting ropes that connects the safety gear to the overspeed governor. The Overspeed Governor usually has a pulley which the safety rope runs on. The overspeed governor usually has an arm type latch. If the device spins too quickly, the arm is forced out from the middle of the unit by centrifugal force. This locksthe pulley, which stops the rope. Once the rope stops and the car is still moving down, the rope pulls up on the safety gear causing a wedge type friction roller or a solid plate to clamp very tightly on the lift running guides. This causes the lift to stop suddenly ("instantaneous" safety gear) or in a progressive slowing motion ("progressive" safety gear). There are many different versions of these but they all work in the same way.

3.2 Uses of elevators

3.2.1Passenger service

            A passenger lift is designed to move people between a building's floors. Passenger elevators capacity is related to the available floor space. Generally passenger elevators are available in capacities from 1,000 to 6,000 lb (455 to 2,727 kg) in 500 lb (230 kg) increments. Generally passenger elevators in buildings eight floors or less are hydraulic or electric, which can reach speeds up to 200 ft/min (1.0 m/s) hydraulic and up to 500 ft/min electric. In buildings up to ten floors, electric & gearless elevators are likely to have speeds up to 500 ft/min (2.5 m/s), and above ten floors speeds begin at 500 ft/min (2.5 m/s) up to 2000ft/min (10 m/s).

            Sometimes passenger elevators are used as a city transport along with funiculars. For example, there is a 3-station underground public elevator in Yalta, Ukraine, which takes passengers from the top of a hill above the Black Sea on which hotels are perched, to a tunnel located on the beach below.

3.2.2Types of passenger elevators

            The former World Trade Center's twin towers used sky-lobbies, located on the 44th and 78th floors of each tower. Passenger elevators may be specialized for the service they perform, including: Hospital emergency (Code blue), front and rear entrances, double Decker, and other uses. Cars may be ornate in their interior appearance, may have audio visual advertising, and may be provided with specialized recorded voice instructions.

            An express elevator does not serve all floors. For example, it moves between the ground floor and a skylobby, or it moves from the ground floor or a skylobby to a range of floors, skipping floors in between. These are especially popular in eastern Asia.

3.2.3 Entrapment

            All elevators are required to have communication connection to an outside 24 hour emergency service, automatic recall capability in a fire emergency, and special access for fire fighters' use in a fire. Elevators should not be used by the public if there is a fire in or around the building, and as such numerous building codes require signs near the elevator to state as much. However, emergency evacuations in some countries do allow the use of special 'fire elevators'.

3.2.4 Capacity

            Residential elevators may be small enough to only accommodate one person while some are large enough for more than a dozen. Wheelchair, or platform lifts, a specialized type of elevator designed to move a wheelchair 6 ft (1.8 m) or less, often can accommodate just one person in a wheelchair at a time with a maximum load of 1000 lb (455 kg).

3.2.5 Freight elevators

            A freight elevator (or goods lift) is an elevator designed to carry goods, rather than passengers. Freight elevators are often exempt from some code requirements and from some of the requirements for fire service. However, new installations would likely be required to comply with these requirements.

            Freight elevators are generally required to display a written notice in the car that the use by passengers is prohibited, though certain freight elevators allow dual use through the use of an inconspicuous riser. Freight elevators are typically larger and capable of carrying heavier loads than a passenger elevator, generally from 2,300 to 4,500 kg. Freight elevators may have manually operated doors, and often has rugged interior finishes to prevent damage while loading and unloading. Although hydraulic freight elevators exist, electric elevators are more energy efficient for the work of freight lifting.

            Stage and Orchestra lifts are specialized lifts for use in the performing arts, and are often exempt from some requirements. Local jurisdictions may govern their use, installation and testing, however they are often left out of local code enforcement provisions due to their infrequent installation.

3.2.6 Vehicle elevators

            Vehicular elevators are used within buildings with limited space (in lieu of ramps) to move cars into the parking garage. Geared hydraulic chains (not unlike bicycle chains) generate lift for the platform and there are no counterweights. To accommodate building designs and improve accessibility, the platform may rotate so that the driver always drives forward instead of in reverse.

3.2.7 Boat elevators

            In some smaller canals, boats and small ships can pass between different levels of a canal with a boat lift rather than through a canal lock.

3.2.8 Aircraft elevators

            On aircraft carriers, elevators carry aircraft between the flight deck and the hangar deck for operations or repairs. These elevators are designed for much greater capacity than any other elevator ever built, up to 200,000 pounds of aircraft and equipment. Smaller elevators lift munitions to the flight deck from magazines deep inside the ship.

3.2.9 Paternoster

            A special type of elevator is the paternoster, a constantly moving chain of boxes. A similar concept moves only a small platform, which the rider mounts while using a handhold and was once seen in multi-story industrial plants.

3.2.10 Material handling belts and belt elevators

            A different kind of elevator is used to transport material. It generally consists of an inclined plane on which a conveyor belt runs. The conveyor often includes partitions to prevent the material from sliding backwards. These elevators are often used in industrial and agricultural applications. When such mechanisms (or spiral screws or pneumatic transport) are used to elevate grain for storage in large vertical silos, the entire structure is called a grain elevator.

            There have occasionally been lift belts for humans; these typically have steps about every seven feet along the length of the belt, which moves vertically, so that the passenger can stand on one step and hold on to the one above. These belts are sometimes used, for example, to carry the employees of parking garages, but are considered too dangerous for public use.

3.3 Types of elevator hoist mechanisms

            In general, there are three means of moving an elevator:

3.3.1 TRACTION ELEVATORS

• Geared and gearless traction elevators

            Geared Traction machines are driven by AC or DC electric motors. Geared machines use worm gears to control mechanical movement of elevator cars by "rolling" steel hoist ropes over a drive sheave which is attached to a gearbox driven by a high speed motor. These machines are generally the best option for basement or overhead traction use for speeds up to 500 ft/min (2.5 m/s).

            Gearless Traction machines are low speed (low RPM), high torque electric motors powered either by AC or DC. In this case, the drive sheave is directly attached to the end of the motor. Gearless traction elevators can reach speeds of up to 2,000 ft/min, or even higher. A brake is mounted between the motor and drive sheave (or gearbox) to hold the elevator stationary at a floor. This brake is usually an external drum type and is actuated by spring force and held open electrically; a power failure will cause the brake to engage and prevent the elevator from falling (see inherent safety and safety engineering).

            In each case, cables are attached to a hitch plate on top of the cab or may be "underslung" below a cab, and then looped over the drive sheave to a counterweight attached to the opposite end of the cables which reduces the amount of power needed to move the cab. The counterweight is located in the hoist-way and rides a separate rail system; as the car goes up, the counterweight goes down, and vice versa. This action is powered by the traction machine which is directed by the controller, typically a relay logic or computerized device that directs starting, acceleration, deceleration and stopping of the elevator cab. The weight of the counterweight is typically equal to the weight of the elevator cab plus 40-50% of the capacity of the elevator. The grooves in the drive sheave are specially designed to prevent the cables from slipping. "Traction" is provided to the ropes by the grip of the grooves in the sheave, thereby the name. As the ropes age and the traction grooves wear, some traction is lost and the ropes must be replaced and the sheave repaired or replaced.

Elevators with more than 100' of travel have a system called compensation. This is a separate set of cables or a chain attached to the bottom of the counterweight and the bottom of the elevator cab. This makes it easier to control the elevator, as it compensates for the differing weight of cable between the hoist and the cab. If the elevator cab is at the top of the hoist-way, there is a short length of hoist cable above the car and a long length of compensating cable below the car and vice versa for the counterweight. If the compensation system uses cables, there will be an additional sheave in the pit below the elevator, to guide the cables. If the compensation system uses chains, the chain is guided by a bar mounted between the counterweight rails.

3.3.2 HYDRAULIC ELEVATORS

            In hydraulic elevator systems, emergency power will lower the elevators to the lowest landing and open the doors to allow passengers to exit. The doors then close after an adjustable time period and the car remains unusable until reset, usually by cycling the elevator main power switch. Typically, due to the high current draw when starting the pump motor, hydraulic elevators aren't run using standard emergency power systems. Buildings like hospitals and nursing homes usually size their emergency generators to accommodate this draw. However, the increasing use of current limiting motor starters, commonly known as "Soft-Start" contactors, avoid much of this problem and the current draw of the pump motor is less of a limiting concern.

            The main components of the hydraulic elevator are elevator car, the control system, piston, cylinder, tank (reservoir), pump and valve. The hydraulic elevator utilizes a hydraulic ram which is a piston that is mounted inside a hollow cylinder. The hydraulic ram is driven in and out of a hollow cylinder by the pressure of hydraulic fluid. The cylinder is connected to the pumping system that consists of the pump and valve which is connected to the reservoir. For the elevator car to move up, the valve will be closed for the fluid to flow to the cylinder and hence lifting the elevator car. When the elevator reaches the correct level (storey), the pump will be turn off (the control system will then sends signal to the motor to gradually turn off the pump) this will cause the fluid to stay in the cylinder hence the elevator car will stay in the same position.( note that in this case, the valve is still closed) The elevator car will move downward when the control system sends a signal to the valve. The valve will be opened and this will allow the fluid to flow out from the cylinder to the reservoir. The elevator car push down the piston and the elevator car will descend.

            The advantage of the hydraulic elevator is that it is easy to generate more energy to lift the elevator car. The disadvantages of the hydraulic elevator are the size of the components of the elevator and efficiency of the elevator. The component size of the hydraulic elevator is relatively big and much effort needs to be put into implementing the system. Hydraulic elevator is not as efficient as the roped elevator due to more energy is required to push the elevator car up and there is no way to store the energy hence energy will be wasted in this case. Refer to figure 2.1 for the diagram of a hydraulic elevator.

• Conventional Hydraulic elevators were first developed by Dover Elevator (now ThyssenKrupp Elevator). They are quite common for low and medium rise buildings (2-8 floors), attain speeds of up to 200 feet/minute (1.0 m/s), and use a hydraulically powered plunger to push the elevator upwards. On some, the hydraulic piston (plunger) consists of telescoping concentric tubes, allowing a shallow tube to contain the mechanism below the lowest floor. On others, the piston requires a deeper hole below the bottom landing, usually with a PVC casing (also known as a caisson) for protection.
• Roped hydraulic elevators use a combination of ropes and hydraulics.
• Twin post hydraulic provides higher travel with no underground hole.
• Holeless hydraulic elevators do not require holes to be dug for the hydraulic cylinder. In most designs, the cab is lifted by a pair of hydraulic jacks, one on each side of the elevator.

3.3.3 ROPED ELEVATORS

            The main components of a simple roped elevator are elevator car, traction steel rope, motor, sheave and counterweight.

            The traction steel rope is connected to the elevator car and looped around a sheave. The sheave is a pulley system, when the sheave rotates, the rope will move. The motor is connected to the sheave.

            To move the elevator upwards, the motor will move in one direction, having been connected to the sheave, the sheave will rotate and hence the traction steel rope will move causing the elevator car will to move. To move the elevator car downwards, the motor will move in the other direction and the sheave will lower the elevator. A counterweight is connected to the elevator car with the rope. The counterweight is to balance the elevator car and is usually the weight of the elevator car when it’s 40% full. To ensure safety of the elevator, the elevator uses multiple ropes connected with the elevator car. In an event if the rope that holds the elevator car and counterweight snap, other ropes will help hold the elevator car in place. There are also other safety measures such as inbuilt safeties that prevent the elevator car from moving too fast.

            The mechanism behind the roped elevator design will be used as a mechanical benchmark model for the implementation phase of the project

3.3.4 CLIMBING ELEVATOR

            A climbing elevator is a self-ascending elevator with its own propulsion. The propulsion can be done by an electric or a combustion engine. Climbing elevators are used in guyed masts or towers, in order to make easy access to parts of these constructions, such as flight safety lamps for maintenance. An example would be the Moonlight towers in Austin, Texas, where the elevator holds only one person and equipment for maintenance.

3.3.5Controlling elevators

            North American Elevator Buttons made by Dover/ThyssenKrupp (with no thirteenth floor): A modern elevator has buttons to allow passengers to select the desired floor.

A typical modern passenger elevator will have:

• Space to stand in, guardrails, seating cushion (luxury)
• Electric fans or air conditioning units to enhance circulation and comfort.


• Call buttons to choose a floor. Some of these may be key switches (to control access). In some elevators, certain floors are inaccessible unless one swipes a security card or enters a passcode (or both). In the United States and other countries, call button text and icons are raised to allow blind users to operate the elevator; many have Braille text besides.
• A set of doors kept locked on each floor to prevent unintentional access into the elevator shaft by the unsuspecting indidual. The door is unlocked and opened by a machine sitting on the roof, which also drives the doors that travel with the car. Door controls are provided to close immediately or reopen the doors. Objects in the path of the moving doors will either be detected by sensors or physically activate a switch that reopens the doors. Otherwise, the doors will close after a preset time.
• A stop switch (not allowed under British regulations) to halt the elevator while in motion and often used to hold an elevator open while freight is loaded. Keeping an elevator stopped for too long may trigger an alarm. Often, this will be a key switch.
• An alarm button or switch, which passengers can use to signal that they have been trapped in the elevator.

Some elevators may have one or more of the following:

• An elevator telephone, which can be used (in addition to the alarm) by a trapped passenger to call for help.
• Hold button: This button delays the door closing timer, useful for loading freight and hospital beds.
• Call Cancellation: A destination floor may be deselected by double clicking.
• Keycard reading devices that restrict elevator use to those holding valid RFID cards, magnetic stripes, or even hotel room keys.
• A second or more set of doors that can serve different floor plans. For example, in an elevated crosswalk setup, the front doors may open on the street level, and the rear doors open on the crosswalk level.

            Other controls, which are generally inaccessible to the public (either because they are key switches, or because they are kept behind a locked panel, include:

• Fireman's Service, Phase II key switch
• Switch to enable or disable the elevator.
• An inspector's switch, which places the elevator in inspection mode (this may be situated on top of the elevator)
• Manual up/down controls for elevator technicians, to be used in inspection mode, for example.
• An independent service/Exclusive Mode will prevent the car from answering to hall calls and only arrive the selected floors in the panel. The door should stay open while parked on a floor. This mode may be used for temporarily transporting goods.
• Buttons used by elevator attendants to start the elevator (intead of holding the door open) or bypass certain floors.

Controls in early elevators

Manual pushbutton elevator controls.

• Some older freight elevators are controlled by switches operated by pulling on adjacent ropes. Safety interlocks ensure that the inner and outer doors are closed before the elevator is allowed to move.
• Early elevators had no automatic landing positioning. Elevators were operated by elevator operators using a motor controller. The controller was contained within a cylindrical container about the size and shape of a cake container and this was operated via a projecting handle. This allowed some control over the energy supplied to the motor (located at the top of the elevator shaft or beside the bottom of the elevator shaft) and so enabled the elevator to be accurately positioned — if the operator was sufficiently skilled. More typically the operator would have to "jog" the control to get the elevator reasonably close to the landing point and then direct the outgoing and incoming passengers to "watch the step". After stopping at the landing the operator would open the door/doors. Some slightly later lifts though, had door(s) that could be operated by the same control (so when the lever is moved in the desired direction, between the idle and motion points there are a trigger to close the doors. When the handle is moved to idle, the doors open again.) This sort of arrangement was used sometimes in subway stations. Manually operated elevators were generally refitted or the cabs replaced by automatic equipment by the 1950s. The major exception is freight elevators which today are just as common to be manually operated or have automatic operation, and even when equipped with automatic controls, they are often operated by an attendant to ensure efficiency.
• Early automatic elevators used relays as logic gates to control them, which began to be replaced by microprocessors from the late 1980s.
• Large buildings with multiple elevators of this type would also have an elevator dispatcher stationed in the lobby to direct passengers and to signal the operator to leave with the use of a mechanical "cricket" noisemaker.
• Some elevators still in operation have pushbutton manual controls.

3.3.6 EXTERNAL CONTROLS

            Elevators are typically controlled from the outside by up and down buttons at each stop. When pressed at a certain floor, the elevator arrives to pick up more passengers. If the said elevator is currently serving traffic in a certain direction, it will only answer hall calls in the same direction unless there are no more calls beyond that floor.

            In a group of two or more elevators, the call buttons may be linked to a central dispatch computer, such that they illuminate and cancel together. This is done to ensure that only one car is called at one time.

            Key switches may be installed on the ground floor so that the elevator can be remotely switched on or off from the outside.

            In sky lobby elevator systems, one would select the intended destination floor (in lieu of pressing "up") and be notified which elevator is to serve that request.

3.4 FLOOR NUMBERING

3.4.1 THE ELEVATOR ALGORITHM

            The elevator algorithm, a simple algorithm by which a single elevator can decide where to stop, is summarized as follows:

• Continue traveling in the same direction while there are remaining requests in that same direction.
• If there are no further requests in that direction, then stop and become idle, or change direction if there are requests in the opposite direction.

            The elevator algorithm has found an application in computer operating systems as an algorithm for scheduling hard disk requests. Modern elevators use more complex heuristic algorithms to decide which request to service next.

3.4.2 COMPUTER DISPATCHED

            Efficiencies of multiple elevators installed in an office building may increase if a central dispatcher is used to group passengers going to the same floor to the same elevator. In the industry, this is known as the 'Destination floor control system'. In buildings with these computer-dispatched elevator system, passengers key in their destination floor in a central dispatch panel located at the building lobby. The dispatch panel will then tell the passenger which elevator to use. Inside the elevator there is no call button to push (or the buttons are there but they cannot be pushed, they only indicate stopping floors). The system was first pioneered by Schindler Elevator as the Miconic 10. Manufacturers of such systems claim that average traveling time can be reduced by up to 30%. There are some problems with the system, though. Sometimes, one person enters the destination for a large group of people going to the same floor. The dispatching algorithm is usually unable to completely cater for the variation, and late comers may find the elevator they are assigned to is already full. Also, occasionally, one person may press the floor multiple times. This is common with up/down buttons when people believe this to hurry elevators. However, this will make the computer think multiple people are waiting and will allocate empty cars to serve this one person.

3.5 Special operating modes

3.5.1 Anti-Crime Protection (ACP)

            Anti-Crime Protection force each car to stop at a pre-defined landing and open its doors. This allows a security guard or a receptionist at the landing to visually inspect the passengers. The car stops at this landing as it passes to serve further demand.

3.5.2 Up peak (MIT)

            During Up Peak mode (also called Moderate Incoming Traffic), elevator cars in a group are recalled to the lobby to provide expeditious service to passengers arriving at the building, most typically in the morning as people arrive for work or at the conclusion of a lunch-time period. Elevators are dispatched one-by-one when they reach a pre-determined passenger load, or when they have had their doors opened for a certain period of time. The next elevator to be dispatched usually has its hall lantern or a "this car leaving next" sign illuminated to encourage passengers to make maximum use of the available elevator system capacity.

            The commencement of Up Peak may be triggered by a time clock, by the departure of a certain number of fully loaded cars leaving the lobby within a given time period, or by a switch manually operated by a building attendant.

3.5.3 Down peak

            During Down Peak mode, elevator cars in a group are sent away from the lobby towards the highest floor served, after which they commence running down the floors in response to hall calls placed by passengers wishing to leave the building. This allows the elevator system to provide maximum passenger handling capacity for people leaving the building. The commencement of Down peak may be triggered by a time clock, by the arrival of a certain number of fully loaded cars at the lobby within a given time period, or by a switch manually operated by a building attendant.

3.5.4 Sabbath service (SHO)

            In areas with large populations of observant Jews, one may find a "Sabbath elevator". In this mode, an elevator will stop automatically at every floor, allowing people to step on and off without having to press any buttons. This prevents violation of the Sabbath prohibition against operating electrical devices when Sabbath is in effect for those who observe this ritual.[9]

3.5.5 Independent service (ISC)

            Independent service is a special service mode found on most elevators. It is activated by a key switch either inside the elevator itself or on a centralized control panel in the lobby. When an elevator is placed on independent service, it will no longer respond to hall calls. (In a bank of elevators, traffic would be rerouted to the other elevators, while in a single elevator; the hall buttons will be disabled). The elevator will remain parked on a floor with its doors open until a floor is selected and the door close button is held until the elevator starts to travel. Independent service is useful when transporting large goods or moving groups of people between certain floors.

3.5.6 Inspection service (INS)

            Inspection service is designed to provide access to the hoistway and car top for inspection and maintenance purposes by qualified elevator mechanics. It is first activated by a key switch on the car operating panel usually labelled 'Inspection', 'Car Top', 'Access Enable' or 'HWENAB'. When this switch is activated the elevator will come to a stop if moving, car calls will be cancelled (and the buttons disabled), and hall calls will be assigned to other elevator cars in the group (or cancelled in a single elevator configuration). The elevator can now only be moved by the corresponding 'Access' key switches, usually located at the top-most (to access the top of the car) and bottom-most (to access the elevator pit) landings. The access key switches will bypass the door lock circuit for the floor it is located on and allow the car to move at reduced inspection speed with the hoistway door open. This speed can range from anywhere up to 60% of normal operating speed on most controllers, and is usually defined by local safety codes.

            Elevators have a car top inspection station that allows the car to be operated by a mechanic in order to move it through the hoistway. Generally, there are three buttons - UP, RUN, and DOWN. Both the RUN and a direction button must be held to move the car in that direction, and the elevator will stop moving once one of the buttons is no longer being pressed for safety reasons. The inspection station is usually also equipped with a light, alarm button and stop switch.

3.5.7 Fire service mode (EFS)

            Depending on the location of the elevator, fire service code will vary state to state and country to country. Fire service is usually split up into two modes. Phase One and Phase Two are separate modes that the elevator can go into. Phase one mode is activated by a corresponding smoke sensor or heat sensor in the building. Once an alarm has been activated, the elevator will automatically go into phase one. The elevator will wait an amount of time, then proceed to go into nudging mode to tell everyone the elevator is leaving the floor. Once the elevator has left the floor, depending on where the alarm was set off, the elevator will go to the Fire Recall Floor. However, if the alarm was activated on the fire recall floor the elevator will have an alternate floor to recall to. When the elevator is recalled, it proceeds to the recall floor and stops with its doors open. The elevator will no longer respond to calls or move in any direction. Located on the fire recall floor is a fire service key switch. The fire service key switch has the ability to turn fire service off, turn fire service on or to bypass fire service. The only way to return the elevator to normal service is to switch it to bypass after the alarms have reset.

            Phase two mode can only be activated by a key switch located inside the elevator on the centralized control panel. This mode was created for firefighters so that they may rescue people from a burning building. The phase two key switch located on the COP has three positions: off, on, and hold. By turning phase two on, the firefighter enables the car to move. However, like independent service mode, the car will not respond to a car call unless the firefighter manually pushes and holds the door close button. Once the elevator gets to the desired floor it will not open its doors unless the firefighter holds the door open button.

            This is in case the floor is burning and the firefighter can feel the heat and knows not to open the door. The firefighter must hold door open until the door is completely opened. If for any reason the firefighter wishes to leave the elevator, they will use the hold position on the key switch to make sure the elevator remains at that floor. If the firefighter wishes to return to the recall floor, they simply turn the key off and close the doors.

3.5.8 Medical emergency/'Code Blue' service (EHS)

            Commonly found in hospitals, Code Blue service allows an elevator to be summoned to any floor for use in an emergency situation. Each floor will have a 'Code Blue' recall key switch, and when activated, the elevator system will immediately select the elevator car that can respond the fastest, regardless of direction of travel and passenger load. Passengers inside the elevator will be notified with an alarm and indicator light to exit the elevator when the doors open.

            Once the elevator arrives at the floor, it will park with its doors open and the car buttons will be disabled to prevent a passenger from taking control of the elevator. Medical personnel must then activate the Code Blue key switch inside the car, select their floor and close the doors with the door close button. The elevator will then travel non-stop to the selected floor, and will remain in Code Blue service until switched off in the car. Some hospital elevators will feature a 'hold' position on the Code Blue key switch (similar to fire service) which allows the elevator to remain at a floor locked out of service until Code Blue is deactivated.

3.5.9 Emergency power operation (EPR)

            Many elevator installations now feature emergency power systems which allow elevator use in blackout situations and prevent people from becoming trapped in elevators.

3.5.10 Traction elevators

            When power is lost in a traction elevator system, all elevators will initially come to a halt. One by one, each car in the group will return to the lobby floor, open its doors and shut down.

            People in the remaining elevators may see an indicator light or hear a voice announcement informing them that the elevator will return to the lobby shortly. Once all cars have successfully returned, the system will then automatically select one or more cars to be used for normal operations and these cars will return to service. The car(s) selected to run under emergency power can be manually overridden by a key or strip switch in the lobby. In order to help prevent entrapment, when the system detects that it is running low on power, it will bring the running cars to the lobby or nearest floor, open the doors and shut down.

3.6 Elevator convenience features

            Elevators may feature talking devices as an accessibility aid for the blind. In addition to floor arrival notifications, the computer announces the direction of travel, and notifies the passengers before the doors are to close.

            In addition to the call buttons, elevators usually have floor indicators (often illuminated by LED) and direction lanterns. The former are almost universal in cab interiors with more than two stops and may be found outside the elevators as well on one or more of the floors. Floor indicators can consist of a dial with a rotating needle, but the most common types are those with successively illuminated floor indications or LCDs. Likewise, a change of floors or an arrival at floors is indicated by a sound, depending on the elevator.

            Direction lanterns are also found both inside and outside elevator cars, but they should always be visible from outside because their primary purpose is to help people decide whether or not to get on the elevator. If somebody waiting for the elevator is going up but a car comes first indicating that it is going down, then the person may decide not to get on the elevator. If the person waits, then one will still stop going up. Direction indicators are sometimes etched with arrows or shaped like arrows and/or use the convention that one that lights up red means "down" and green means "up". Since the color convention is often undermined or overrided by systems that do not invoke it, it is usually used only in conjunction with other differentiating factors.

            An example of a place whose elevators use only the color convention to differentiate between directions is the Museum of Contemporary Art in Chicago, where a single circle can be made to light up green for "up" and red for "down." Sometimes directions must be inferred by the position of the indicators relative to one another.

            In addition to lanterns, most elevators make a chime to indicate if the elevator is going up or down either before or after the doors open, usually in conjunction with the lanterns lighting up. Universally, one chime is for up, two is for down, and none indicates an elevator that is 'free'.

            Observatory service elevators often convey other facts of interest, including elevator speed, stopwatch, and current position (altitude), as with the case for Taipei 101's service elevators.

3.7 Standards

            The mechanical, electrical and design of elevators are dictated according to various standards (aka elevator codes), which may typically be international, national, state, regional or city based. Where once many standards were prescriptive, specifying exact criteria which must be complied with, there has been a shift towards more performance-based standards where the onus falls on the designer to ensure that the elevator meets or exceeds the standard.

Some of the national elevator standards include:

• Australia – AS1735
• Canada – CAN/CSA B44
• Europe – EN 81 series (EN 81-1, EN 81-2, EN 81-28, EN 81-70, EN 12015, EN 12016, EN 13015, etc.)
• USA – ASME A17

            Because an elevator is part of a building, it must also comply with standards relating to earthquake resilience, fire standards, electrical wiring rules and so forth. The American National Elevator Standards Group (ANESG) sets an elevator weight standard to be 2200 lbs. Additional requirements relating to access by disabled persons may be mandated by laws or regulations such as the Americans with Disabilities Act

Chapter-4

DESIGN

4.1 Block Diagram

            The block diagram belongs to the project work is shown above and explained in brief, this project work “Multi Functional Elevator Driven by solar Energy” is basically aimed for crossing the busy roads of main cities and national high way roads where there is no chance for the public to cross these roads because of continuous flowing traffic. The same system also can be utilized at railway stations for crossing the railway tracks. The innovative concept involved in the system is to utilize non-conventional energy resource, there by these kinds of elevators can be constructed at rural areas across the high ways, where availability of conventional power supply is critical. The other main advantage of using non-conventional energy resource is to minimize the Burdon over conventional energy supplied by the Govt.

            In the present day traffic, due to population growth and urbanization, Globalization the traffic leading to cities are increasing day by day at a fast rapid growth. Hence the roads are becoming day by day over crowded; people are frightened to cross the roads, if any body dared, leading to accidents. In order to overcome this problem, this project work is taken up, which carries people to other end of the road safely. Otherwise, means if this kind of system is not existed, than manual traffic control has to be incorporated at busy centres (where people are intended to cross the road) and it needs a continuous, dedicated manpower is required and also it should cater 24 hours a day, 365 days a year, which calls for not only financial burden but also the human fatigue element cannot be avoided. Thus lot of re-search took place in this direction to evolve a suitable solution such that it should takes care all the above problems. Hence, considering all the above situations this project work gives better result and better investment and take care the needs of society. It also satisfies the Human living environments.

            To function the circuit in all weather conditions and all atmosphere conditions a battery-based solar panel, which produces a 12V DC voltage is adopted for the design of this project work.  During night timings and the days when sunlight is not available, the 12V battery will be take care the operation of the circuit.  Whenever sunlight comes provision will made in the project work such that the sunlight will charge solar panel which in turn charges the battery so that the functionality of the circuit will be all the times without any interruption.

            In this regard selection of solar panels and battery is important, always higher rating batteries and panels must be preferred for un-interruption operation.  

            For the purpose of demonstration, a small-scale model consisting of three DC motors of built in reduction gear mechanism are chosen for mechanical transmission section. The advantage of using reduction gear mechanism motor is that the motor speed will be decreased and torque will be increased, there by a small motor can drive heavy loads.

            Total three push buttons are used in this project work for the accessibility of user, one push button is installed inside the container and the other two push buttons are installed at either side of the mechanism. Initially when the machine is in idle condition, the door of elevator remains in open condition, whenever any person wants use the elevator to cross the road or rail track, he/she will enter inside the cab and depresses the push button, by which the elevator door will be closed automatically and it will be traveled vertically up to certain distance, after that immediately the elevator direction will be changed and traveled in horizontal direction up to certain distance, from there again the same cab travels in vertical direction in down wards to reach the ground level. After reaching the elevator to other side, the cab door will be opened automatically. The other two switches installed at either side of the mechanism, in other words either side of the road, provides a facility to the user such that irrespective of cab’s position, it can be brought to the user side automatically. For example, if the sides are denoted as ‘A’ and ‘B’, and a person stood at ‘A’ side, where as the elevator remains at ‘B’ side, in such condition the person who stood at ‘A’ side has to depress the push button arranged at his side, by which the elevator process begins right from closing the door and traveling all the way, finally it reaches to the user end automatically. Similarly other side person also will have this facility.

            As described in the block diagram, limit switches block is designed with six lever switches, and these switches are arranged at various points of the mechanism to control the mechanical transmission section at various levels. To sense weather the door of a cab is opened or closed, two limit switches are arranged at either side of the door.

            If the door remains in open condition, one switch remains in activated condition, otherwise the other switch will be in activated condition. The outputs of these two switches are fed to microcontroller, by which it can understand the condition of the door, like wise all the switches outputs are fed to this controller for identifying the cab condition. Two switches are arranged at either side of the mechanism, which are activated automatically while traveling the cab horizontally. Similarly for vertical movement also two switches are arranged for identifying the cab weather it is in ground level or upper level. Depending up on the cab position, these lever switches are operated automatically, and based on the information produced by these switches, the controller controls the motors independently.

            To control the three motors independently in both the directions (forward and reverse movements), six relays are used and they are interfaced with microcontroller through their drive circuits. Depending up on the signals generated by the push buttons and lever switches, the controller controls the motors through relay contacts. Each motor is driven through two relays, one relay for forward direction and the other relay for reverse direction. The motors used in this project work are DC motors; the polarity is changed through relay contacts. If the correct polarity is maintained, then the motor rotates in clock wise direction, similarly if the polarity is reversed, the motor rotates in anti-clock wise direction. The door control motor installed over the cab, when it rotates in forward direction, the door is opened, and similarly when it rotates in reverse direction, the door is closed.

            Whenever the microcontroller port output is high to energize the relay, the transistor 547 becomes on with the help of +12V power supply through the coil of the relay and there by the relay becomes on. This contact of the relay is used to energize the corresponding motor. To provide a visual indication an LED is also provided along with the coil of the relay so that whenever relay energizes its LED also gets energized.

Microcontroller: Microcontroller based machine is designed to cater the input requirements for cab position detection circuit designed with limit switches and push buttons, output requirements for controlling the motors through relays to create mechanical transmission of the cab in horizontal and vertical directions.  

            Micro-controller unit is constructed with ATMEL 89C51 Micro-controller chip.  The ATMEL AT89C51 is a low power, higher performance CMOS 8-bit microcomputer with 4K bytes of flash programmable and erasable read only memory (PEROM).  Its high-density non-volatile memory compatible with standard MCS-51 instruction set makes it a powerful controller that provides highly flexible and cost effective solution to control applications.

            Micro-controller works according to the program written in it. Most micro controllers today are based on the Harvard architecture, which clearly defined the four basic components required for an embedded system. These include a CPU core, memory for the program (ROM or Flash memory), memory for data (RAM), one or more timers (customizable ones and watchdog timers), as well as I/O lines to communicate with external peripherals and complementary resources — all this in a single integrated circuit. A microcontroller differs from a general-purpose CPU chip in that the former generally is quite easy to make into a working computer, with a minimum of external support chips. The idea is that the microcontroller will be placed in the device to control, hooked up to power and any information it needs, and that's that.

            A traditional microprocessor won't allow you to do this. It requires all of these tasks to be handled by other chips. For example, some number of RAM memory chips must be added. The amount of memory provided is more flexible in the traditional approach, but at least a few external memory chips must be provided, and additionally requires that many connections must be made to pass the data back and forth to them.

           

            For instance, a typical microcontroller will have a built in clock generator and a small amount of RAM and ROM (or EPROM or EEPROM), meaning that to make it work, all that is needed is some control software and a timing crystal (though some even have internal RC clocks). Micro controllers will also usually have a variety of input/output devices, such as analog-to-digital converters, timers, UARTs or specialized serial communications interfaces like I²C, Serial Peripheral Interface and Controller Area Network. Often these integrated devices can be controlled by specialized processor instructions.

            Originally, micro controllers were only programmed in assembly language, or later in C code. Recent micro controllers integrated with on-chip debug circuit accessed by In-circuit emulator via JTAG (Joint Text Action Group) enables a programmer to debug the software of an embedded system with a debugger.

            More recently, however, some micro controllers have begun to include a built-in high-level programming language interpreter for greater ease of use. BASIC is a common choice, and is used in the popular BASIC Stamp MCUs (Master Control Unit). Micro controllers trade away speed and flexibility to gain ease of equipment design and low cost. There's only so much room on the chip to include functionality, so for every I/O device or memory increase the microcontroller includes, some other circuitry has to be removed. Finally, it must be mentioned that some microcontroller architectures are available from many different vendors in so many varieties that they could rightly belong to a category of their own. Chief among these are the 8051 family.

4.2 CIRCUIT DESCRIPTION

            The circuit description as per the main circuit diagram provided at the end of this chapter is as follows:

LIMIT SWITCHES: The limit switches used in this project work are having long levers and are intended to limit the mechanical transmission at particular prescribed position.

            For example, to limit the movement of cab in vertical direction, two limit switches are arranged over the mechanism for sensing the cab position at upper and lower levels. The lower level is nothing but ground level, whenever the cab reaches to the ground level, the lower level switch lever is operated, there by switch is activated. When the switch is activated the contact gets closed, and a logic zero signal is generated for the microcontroller.

            The entire mechanical transmission section is designed with 6 limit switches, one end of all the switches are shorted together and terminated to the power supply ground (also called as circuit ground). In fact these are one pole and two way switches, there by normally open and normally closed contacts are available for the convenient of circuit design. Here normally open contacts are selected; means when the switch is activated, normally open contact gets closed and due to the switch one end is terminated to the ground, logic zero is generated for the controller chip. All the switches poles are interfaced with microcontroller at its input lines. Each in put is connected with a pull-up resistor of 10K, there by all the six inputs of microcontroller remains at logic high state. Whenever any switch is activated, that particular input will become zero. Now all the six limit switches are arranged at mechanism at six different locations for identifying the cab position at six different locations.

            Relays and their Driving Sequence: Pin numbers 21 to 26 of microcontroller are used to drive the six relays independently. These pins are belongs to port 2, and these lines are treated as output lines. Each output is used to conduct a low power switching transistor, whenever any out put is energized, that particular transistor is conducted, which in turn energizes the relay. Here BC 547 general purpose switching transistor is used, this is a NPN transistor and its emitter is connected to ground. The relay used here is a single changing over contact relay, and working voltage of the relay is 12V DC, means when the coil is energized through 12V DC relay will be activated. One end of the relay coil is connected to +12V DC source and the other end is connected to ground through transistor collector. When the transistor is conducted, the emitter collector junction is closed and supply is provided to relay coil. These relays are energized and de-energized depending up on the input data that is obtained from limit switches and push buttons.

            The push button which is mounted inside the cab is treated as one of the in put command signal to the microcontroller, whenever this button is depressed, the controller energizes relay – 2, where as relay – 1 remains in de-energized condition. In this sequence the supply connected to the relay coil is reversed, motor +Vcc is connected to the ground through relay – 1 contact, because this relay remains in off condition and motor positive is connected to ground through its normally closed contact. Since relay – 2 is in on condition, normally open contact gets closed and motor negative is connected to +Vcc. In this concept polarity is reversed and motor rotates in anti-clock wise, by which the cab door will be closed automatically.

            Once the cab door is closed, it remains in closed condition until it reaches to the other end. When the cab is reached to the ground level of other end, the corresponding limit switch arranged below the cab will be activated automatically; this is another input command signal to the microcontroller, by which the controller energizes relay – 1, and relay – 2 remains in off condition. In this logic the polarity is maintained by connecting the motor positive to +Vcc and motor negative to ground through relay contacts, there by motor rotates in clock wise, which in turn the cab door will be opened to allow the people out from the cab. Like wise depending up on the other input commands fed through the remaining four limit switches, corresponding relays are controlled and based on the supply sequence, the remaining two motors drives the cab in horizontal and vertical directions.

            The three motors used to control the movement of the cab are denoted as motors ‘A’ ‘B’ & ‘C’, they are similar motors, motor ‘A’ is used to control the cab door, motor ‘B’ is used to drive the cab in vertical direction, and motor ‘C’ is used to drive the cab in horizontal direction.

Microcontroller unit: The microcontroller unit is designed with ATMEL 89C51 chip, this is belongs 8051 family and it is an 8 – bit controller. Eight bit controllers are the most popular controllers in use today. These chips are proven to be a very useful word size for many tasks. This chip is capable of 256 decimal values (1/4 % resolution), the one byte data word is sufficient for many control and monitoring applications.

            In addition, most low cost RAM and ROM memories store one byte per memory location for easy interfacing to an 8 bit controller. One indication of the popularity of eight bit microcontrollers is the fact that some 44 manufacturers produce over 600 models based on the 8051 architecture alone. This controller can be called as a true computer on a chip; the design incorporates all of the features found in a computer like CPU, ALU, ROM, RAM, serial and parallel input/output ports, counters, clock, etc. This controller can be used as a general purpose device, which can read data, perform limited calculations depending up on the program prepared for it, and control the other devices interfaced with this controller. The prime use of a microcontroller is to control the operation of a machine using a fixed program that is stored in ROM and that does not change over the life time of the system.  

            Here limit switches and push buttons are interfaced with micro-controller at its input side, by activating these devices command signals are generated for the controller; these are called set of instructions. These instructions are used to move code and data from internal memory to the ALU. These instructions in the form of above devices are coupled with pins to the IC package; these pins are programmable, means capable of having several different functions depending up on the program prepared for it. The microcontroller is concerned with getting data from and to its own pins; the architecture and instruction set are optimized to handle data in bit, byte, and word size.

The 89C51 architecture consists the following features:

• Eight bit CPU with registers A and B
• Eight bit program status word (PSW)
• Sixteen bit program counter (PC) and data pointer (DPTR)
• Eight bit stack pointer (SP)
• Internal ROM (4K)
• Internal RAM of 128 bytes
• Four register banks, each containing eight registers
• Sixteen bytes which may be addressed at the bit level
• Eight bytes of general purpose data memory
• Thirty two I/O pins arranged as four eight bit ports
• Two 16 bit timer/counters
• Full duplex serial data receiver/transmitter (SBUF)
• Control registers
• Two external and three internal interrupt sources
• Oscillator and clock circuits.

Oscillator & clock: An external crystal of 12 MHz is connected between pins 18 and 19 of microcontroller, the internal oscillator of 89C51 chip generates the clock pulses and by connecting quartz crystal and 33pf capacitors externally, a stable frequency of 12 MHz is generated by which all internal operations are synchronized. The crystal frequency is the basic internal clock frequency of the microcontroller. The manufacturer of the chip specifies the frequency rating, if the frequency is less than the specified, the data stored in the chip will be lost. The crystal oscillator generates a pulse train and the clock frequency establishes the smallest interval of time within the microcontroller, called the pulse. The smallest interval of time to accomplish any simple instruction, however, is the machine cycle.

Internal memory: A functioning computer must have memory for program code bytes, commonly in ROM, and RAM memory for variable data that can be altered as the program runs. The 8051 series chips have internal RAM and ROM memory for these functions. Additional memory can be added externally using suitable devices like EEPROM.

4.3 POWER SOURCE DESCRIPTION

            The main power source to drive the entire machine is derived from solar panel, for this purpose 12V, 0.6 Amps output panel is selected. Here high efficiency solar cells configured in series and parallel configuration to generate required voltage and current panel is utilized. The solar cells are called as photo-voltaic cells, which converts ultra violet energy in to electrical energy. The ultra violet energy delivered from the Sun will be strong at noon; especially in summer the Sun is very "strong" by Martian standards because of the season. During this time the solar panel generates maximum energy, the peak power will be always more, other then specified by the manufacturer. The panels used here can produce about 7.2 watts peak, or about 43 watt-hours total per day. In other words, the Sun is bright enough to activate the solar panels for only about six hours per Martian day. The power produced from the solar panel is utilized to drive DC motors and other electronic circuitry including microcontroller unit, the excess energy produced by the panel is used to charge the battery.

            As described in previous chapters, the entire machine is designed to operate at 12V DC, there by here in addition to the solar panel, a heavy duty rechargeable battery of 12V and 7.5 AH (Ampere Hour) is used as a back-up source, which drives entire machine in absence of Sun. The DC motors used in this project work consumes 150 milli amps each, and other circuitry including relays & microcontroller will consume around 150 milli amps, there by total consumption of the system is 300 milliamps approximately. Though the machine utilizes three DC motors, always any one motor will be in the running condition; there by the prototype module will not consume more than 300 ma, i.e. 0.3 amp. Since huge rating lead acid battery is used where as the machine consumes less power, the battery can take care of the machine for long time. The battery back-up time = battery rating / consumed energy = 7.5 / 0.3 = 25. Means the battery can with stand up to 25 hours continuously without solar power.

            The solar panel selected for the purpose can deliver a maximum voltage of 18V during under the bright sun, when a 600 ma load connected across the panel output terminals, the voltage may fall down to 12V. Means at 12V the panel can supply 600 ma current, as the sun intensity decreases current output also decreases. Average current can be taken as 500 ma, means the panel rating can be defined as, 12 X 0.5A (500 ma) = 6 watts. When the machine is working completely based on solar energy, it consumes only 300 ma, the excess energy produced by the panel, i.e. 200 ma can be used to charge the battery. During the idle condition, the complete out put of the panel can be utilized to charge the battery, in this condition the battery is charged with 0.5A current. At this rate, the battery charging time = battery rating / charging current = 7.5 AH / 0.5 A = 15 hours. To charge the battery in less time, higher rating solar panels can be utilized.

            To define how long the machine has to run without solar power, it is purely depends up on the capacity of the battery and Solar panels. The DC motors selected to drive the mechanical transmission section operates at 12V DC, hence output of the battery or solar panel can be used to drive these motors directly. The control circuit designed with microcontroller required a stable supply of + 5V DC, here using a positive voltage regulator of LM7805, constant supply of +5 V is generated, though the battery voltage or solar panel voltage varies +/_ 30 %, the output of the regulator remains constant.

 Chapter-5

Construction

5.1 Mechanical Constructions

            This project comes under the subject of mechatronics, generally electro mechanical machines are called as mechatronics. Mechatronics has been defined as the synergistic integration of mechanical devices, electronics and software. Mechatronics is viewed as encompassing topic ranging from embedded microprocessor control of “intelligent” products, to robotics and manufacturing automation. It is associated particularly with the enhancement of products, machinery and processes with electronics and computers.

            Mechatronics has allowed entirely new classes of machinery to be created. The addition of some inexpensive electronics and a simple computer or microcontroller can radically change the functionality of a machine. Mechatronics combine mechanical engineering, electronics and computing. It is unabling  technology of computer automated manufacturing through the use of robots and automated machine tools. Mechatronics may be concerned individual machines such as robots, or manufacturing system automated in their entirely. Mechatronics engineers use computers and other digital control systems to control industrial process. They bring electronic, materialand mechanical science together with robotics, manufacturing and packaging techniques to create diverse range of products. These range from everyday products such as washing machine, camera, photocopier and antilock car brakes, to miniaturized substitutes for human organ, to powerful and precise computer controlled machine tools used in manufacturing. This course was the first of its kind in Australia, and is in high demand by local and overseas students.

            Now coming to the project work, here complete mechanical transmission section is designed with three DC motors, the function of each motor differs from one to other. With the help of one motor mounted on the cab, the cab door mechanism is controlled such that the door can be opened or closed. Here sliding type of door is designed, due to the lack of resources for initial door mechanism such as proper rollers, the design of the door mechanism has changed to utilize materials that are available, the following is the picture of cab and its slided door mechanism constructed with MS (mild steel) plates, 1 mm thick MS plate is selected for the purpose, and it is cut in to the different sizes and welded in to a box shape.

            The above diagram shows the new door mechanism with the intended position of the motor and the plastic door guide as well as the gear on the motor. A small geared wheel or toothed wheel is directly coupled to the motor shaft, this wheel is aligned with plastic door guide. Since the motor rotates in both the directions, the elevator door can be opened or closed. The DC motor used here is a 30 RPM, since the motor speed is very less, the door is moved slowly. The movement of door is control by the rotation of the DC motor. The door movement is controlled with two limit switches, these limit switches are arranged over the cab, while opening the door, the motor rotates in forward direction and the door is moved towards left side, after moving certain distance, the door mechanism activates the limit switch by activating its lever. there by the door movement is stopped. Similarly while closing the door, and to stop the movement ofthe door after closing, another limit switch is arranged over the cab mechanism at its right side.The door which moves in between the sliding channels arranged inside the box, is attached to the plastic strip (plastic door guide). Upon reaching the desired level, to make the elevator door open, signal will be given for the motor to rotate. When the motor shaft rotates, the plastic strip with the trigger bar will move until it touches latch of the micro-switch, this will then create an input to stop the motor.

            After staying open for a few seconds, the motor will be controlled to move again in the other direction. This motion will be the closing and opening door movement. A program will be added to the main program for the motion of the elevator door. For more clarity about the toothed wheel that is coupled directly to the DC motor shaft, DC motor arrangement over the cab, the plastic strip alignment with wheel,etc.  is shown in the following diagram.

            In the above diagram a simple box made out of acrylic sheets is shown. it is in unfinished condition, and it is not attached to the main structure, and also it doesn’t contain limit switches. Only to have clarity about the sliding door mechanism, this picture is shown here.

The following is the diagram of limit switch

            The limit switch shown above is having long lever, like this six limit switches are used, and they are arranged at six different posotions of the mechanical structure to control the movement of mechanical transmission section. The motion of the motor in the form mechanical movement, if it touches to the lever, than the switch is activated and generates a logic low signal for the microcontroller. based on this signals produced by the all six limit switches, the microcontroller controls the mechanical movements of entire machine.

            During vertical movement of the elevator, one limit switch is arranged at top side of the mechanical structure, while the elevator travelling in vertical direction towards up, this switch is controlling the movement of elevator. Means, whenever the mechanism lifts the elevator up to certain extent, this switch is operated, there by the elevator stops at certain fixed height and travels in horizontal direction to reach other end of the road. likewise with the help of these limit switches/lever switches, the horizontal and vertical movements of the elevator are controlled effectively.

            The following is the picture shows the elevator and its driving mechanism in vertical direction.

                                           

            In the above diagram, with the help of a second motor mounted at top side ofthe mechanism, the elevator is lifted up and pulled down through the vertical mechanical transmission section designed with sliding channels. Here the motor is mounted over a small metal plate and this plate along with the motor is coupled to the sliding channels. The geared wheel coupled to the motor shaft is aligned with a chain firmly, now this chain is mounted to the mechanical structure in vertical direction. Depending up on the movement of the motor rotation, the motor itself moves in up down directions along with chain. Here elevator is also fixed with the sliding channels, thereby it also moves up and down along with the motor.

            Here in this page, the complete structure of the elevator along with its drive circuit designed with microcontroller is shown. The drive circuit and its power source through high power battery is mounted over the wooden plank, and this plank is fixed over the mechanical structure. The solar panel that drives the machine and charges the battery is not shown in the picture.

            The third DC motor shown at the top left side of the mechanism is used to drive the elevator in horizontal direction. This motor is also mounted over the vertical moving section, which moves along with another chain system mounted over the structure in horizontal direction.

5.2 89C51 microcontroller

Description

            The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.

The 89C51 architecture consists the following features:

• Eight bit CPU with registers A and B
• Eight bit program status word (PSW)
• Sixteen bit program counter (PC) and data pointer (DPTR)      
• Eight bit stack pointer (SP)
• Internal ROM (4K)
• Internal RAM of 128 bytes
• Four register banks, each containing eight registers
• Sixteen bytes which may be addressed at the bit level
• Eight bytes of general purpose data memory
• Thirty two I/O pins arranged as four eight bit ports
• Two 16 bit timer/counters
• Full duplex serial data receiver/transmitter (SBUF)
• Control registers
• Two external and three internal interrupt sources
• Oscillator and clock circuits.

Oscillator & clock: An external crystal of 12 MHz is connected between pins 18 and 19 of microcontroller, the internal oscillator of 89C51 chip generates the clock pulses and by connecting quartz crystal and 33pf capacitors externally, a stable frequency of 12 MHz is generated by which all internal operations are synchronized. The crystal frequency is the basic internal clock frequency of the microcontroller. The manufacturer of the chip specifies the frequency rating, if the frequency is less than the specified, the data stored in the chip will be lost. The crystal oscillator generates a pulse train and the clock frequency establishes the smallest interval of time within the microcontroller, called the pulse. The smallest interval of time to accomplish any simple instruction, however, is the machine cycle.

Internal memory: A functioning computer must have memory for program code bytes, commonly in ROM, and RAM memory for variable data that can be altered as the program runs. The 8051 series chips have internal RAM and ROM memory for these functions. Additional memory can be added externally using suitable devices like EEPROM.

5.3 Solar Energy

            The main power source to drive the entire machine is derived from solar panel, for this purpose 12V, 0.6 Amps output panel is selected. Here high efficiency solar cells configured in series and parallel configuration to generate required voltage and current panel is utilized. The solar cells are called as photo-voltaic cells, which converts ultra violet energy in to electrical energy. The ultra violet energy delivered from the Sun will be strong at noon; especially in summer the Sun is very "strong" by Martian standards because of the season. During this time the solar panel generates maximum energy, the peak power will be always more, other then specified by the manufacturer. The panels used here can produce about 7.2 watts peak, or about 43 watt-hours total per day. In other words, the Sun is bright enough to activate the solar panels for only about six hours per Martian day. The power produced from the solar panel is utilized to drive DC motors and other electronic circuitry including microcontroller unit, the excess energy produced by the panel is used to charge the battery.

            The solar panel selected for the purpose can deliver a maximum voltage of 18V during under the bright sun, when a 600 ma load connected across the panel output terminals, the voltage may fall down to 12V. Means at 12V the panel can supply 600 ma current, as the sun intensity decreases current output also decreases. Average current can be taken as 500 ma, means the panel rating can be defined as, 12 X 0.5A (500 ma) = 6 watts. When the machine is working completely based on solar energy, it consumes only 300 ma, the excess energy produced by the panel, i.e. 200 ma can be used to charge the battery. During the idle condition, the complete out put of the panel can be utilized to charge the battery, in this condition the battery is charged with 0.5A current. At this rate, the battery charging time = battery rating / charging current = 7.5 AH / 0.5 A = 15 hours. To charge the battery in less time, higher rating solar panels can be utilized.

            To define how long the machine has to run without solar power, it is purely depends up on the capacity of the battery and Solar panels. The DC motors selected to drive the mechanical transmission section operates at 12V DC, hence output of the battery or solar panel can be used to drive these motors directly. The control circuit designed with microcontroller required a stable supply of + 5V DC, here using a positive voltage regulator of LM7805, constant supply of +5 V is generated, though the battery voltage or solar panel voltage varies +/_ 30 %, the output of the regulator remains constant.

5.4 Motors and their details

            Permanent magnet DC motor responds to both voltage and current. The steady state voltage across a motor determines the motor’s running speed, and the current through its armature windings determines the torque. Apply a voltage and the motor will start running in one direction; reverse the polarity and the direction will be reversed. If you apply a load to the motor shaft, it will draw more current, if the power supply does not able to provide enough current, the voltage will drop and the speed of the motor will be reduced. However, if the power supply can maintain voltage while supplying the current, the motor will run at the same speed.

            In general, you can control the speed by applying the appropriate voltage, while torque is controlled by current. In most cases, DC motors are powered up by using fixed DC power supply, therefore; it is more efficient to use a chopping circuit.

            Consider what happens when a voltage applied to a motor’s windings is rapidly turned ON and OFF in such a way that the frequency of the pulses produced remains constant, but the width of the ON pulse is varied. This is known as Pulse Width Modulation (PWM). Current only flows through the motor during the ON portion of the PWM waveform. If the frequency of the PWM input is high enough, the mechanical inertia of the motor cannot react to the ripple wave; instead, the motor behaves as if the current were the DC average of the ripple wave. Therefore, by changing the width of pulse, we can control the motor speed.

            At the most basic level, electric motors exist to convert electrical energy into mechanical energy. This is done by way of two interacting magnetic fields -- one stationary, and another attached to a part that can move. A number of types of electric motors exist, but most BEAM bots use DC motors in some form or another. DC motors have the potential for very high torque capabilities (although this is generally a function of the physical size of the motor), are easy to miniaturize, and can be "throttled" via adjusting their supply voltage. DC motors are also not only the simplest, but the oldest electric motors.

            The basic principles of electromagnetic induction were discovered in the early 1800's by Oersted, Gauss, and Faraday. By 1820, Hans Christian Oersted and Andre Marie Ampere had discovered that an electric current produces a magnetic field. The next 15 years saw a flurry of cross-Atlantic experimentation and innovation, leading finally to a simple DC rotary motor. A number of men were involved in the work, so proper credit for the first DC motor is really a function of just how broadly you choose to define the word "motor

Principles of operation

            In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current  in the conductor, and to the strength of the external magnetic field.

            As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.

            Let's start by looking at a simple 2-pole DC electric motor (here dark black represents a magnet or winding with a "North" polarization, while light colour represents a magnet or winding with a "South" polarization).

            Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator, field magnet’s, and brushes. In most common DC motors, the external magnetic field is produced by high-strength permanent magnets. The stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. The above diagram shows a common motor layout -- with the rotor inside the stator (field) magnets.

           

            The geometry of the brushes, commutator contacts, and rotor windings are such that when power is applied, the polarities of the energized winding and the stator magnet(s) are misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets.

            As the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the next winding. Given our example two-pole motor, the rotation reverses the direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic field, driving it to continue rotating.

            In real life, though, DC motors will always have more than two poles (three is a very common number). In particular, this avoids "dead spots" in the commutator. You can imagine how with our example two-pole motor, if the rotor is exactly at the middle of its rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a moment where the commutator shorts out the power supply (i.e., both brushes touch both commutator contacts simultaneously). This would be bad for the power supply, waste energy, and damage motor components as well. Yet another disadvantage of such a simple motor is that it would exhibit a high amount of torque "ripple" (the amount of torque it could produce is cyclic with the position of the rotor).

5.5 Relays

The electromagnetic relay, one of mankind’s first electrical device, was used practically in telegraphy as early as 1850. The modern relay, properly applied, is one of the most simple, effective and dependable component available. In the majority of instances, it can achieve better reliability at lesser cost than an equivalent solid-state complex type of relay.

The term ‘relay’ was used for the first time to describe an invention made by Samuel Morse in 1836. The device invented by Morse was a “Telegraph Amplifying Electromagnetic Device” which enabled a small current flowing in a coil to switch on a large current in another circuit and thus helped in “relay” of signals.

                

A relay is a device that opens or closes an auxiliary circuit under some predetermined condition in the main circuit. The object of a relay is generally to act as a sort of electric magnifier, that is to say, it enables a comparatively weak current to bring into operation a much stronger current. It also provides complete electrical isolation between the controlling circuit and the controlled circuit.

Relays are widely used in industry. Railroads, pipelines and heavy-duty signaling operations have relied for many years to handle their automatic and remote control problems. Most of the traffic control signals on our streets use relays. Telephone, telegraph and telemetry systems depend on relays to provide circuit selection and switching. Complete automatic and many semi-automatic control processes in industrial plants use relays extensively. In computer circuit, relays can be arranged to provide mathematical functions and to count. In short, relays are used to perform a wide variety of tasks in electrical and electronics engineering activities.

Though relays are simple devices, they are rarely fully understood by electronic equipment designers because there are so many varieties.   They have been developed to meet a wide range of requirements. A relay, when used properly under good climatic conditions, can have a very long life. Under other conditions, it can give considerable trouble.

The relays used in this project work are electromagnetic relays. The electromagnetic relay is basically a switch (or a combination of switches) operated by the magnetic force generated by a current flowing through a coil.  Essentially, it consists of four parts an electromagnet comprising a coil and a magnetic circuit, a movable armature, a set of contacts, and a frame to mount all these components. However, very wide ranges of relays have been developed to meet the requirements of the industry.

This relay is nothing but a switch, which operates electro-magnetically. It opens or closes a circuit when current through the coil is started or stopped.  When the coil is energized armature is attracted by the electromagnet and the contacts are closed. That is how the power is applied to the signals (indicators).

The construction of the typical relay contains a code surrounded by a coil of copper wire. The core is mounted on a metal frame. The movable part of the relay is called armature. When a voltage is applied to the coil terminals, the current flowing through the coil produces a magnetic field in the core.  In other words, the core acts as an electromagnet and attracts the metal armature.

When the armature is attracted to the core, the magnetic path is from the core through armature, through the frame, and back to the core. On removing the voltage the spring attached to the armature returns the armature to its original position. In this position, there is a small air-gap in the magnetic path. Hence, more power is needed to pull in the armature than that needed to keep it held in the attracted position.

The relay contacts and the terminals are mounted on an insulated board. When no current flows through the relay coil, the contact arm, or pole as it is called, mounted on the armature, touches the “top” contact.   When the coil is energized by flow of current, the armature along with the contact arm assembly moves downwards so that the contact arm touches the “bottom” contact.

When an electric current is flowing through a relay coil, it is said to be energized, and when the current flow stops, the relay is said to be de-energized.  They have a set of parallel contacts, which are all pulled in when the electromagnet pulls in the armature. On being energized, whether a relay makes contact(s) or breaks them depends on the design of contact arrangements. Though the contacts are open or close simultaneously, the sequence of operation cannot be guaranteed in this of construction.  To have a definite switching sequence, stacked contacts are used.

5.6 Relay Characteristics

A relay is a device that opens or closes an auxiliary circuit under predetermined condition in the main circuit. The object of a relay is generally to act as a sort of electrical magnifier; that is to say, it enables a comparatively weak current to bring into operation a much stronger current. It also provides complete electrical isolation between the controlling circuit and the controlled circuit.

Relays are extensively used in electronics, electrical engineering and many other fields. A wide variety of relays have been developed to meet the varied requirements of industry. There are relays that are sensitive to conditions of voltage, current, temperature, frequency, or some combination of these conditions. The basic working of an electromagnetic relay is easy to understand. However, in order to select a relay to perform a particular function efficiently and that too for a long time requires knowledge of relay characteristics and that of the circuits in which the relay is used.

Chapter-6

DATA SHEET OF 89C51

Features

·        Compatible with MCS-51™ Products

·        4K Bytes of In-System Reprogrammable Flash Memory

·        Endurance: 1,000 Write/Erase Cycles

·        Fully Static Operation: 0 Hz to 24 MHz

·        Three-level Program Memory Lock

·        128 x 8-bit Internal RAM

·        32 Programmable I/O Lines

·        Two 16-bit Timer/Counters

·        Six Interrupt Sources

·        Programmable Serial Channel

·        Low-power Idle and Power-down Modes

 

Description

            The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density non-volatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional non-volatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.

 

  

Chapter-7

Cost Estimation

The following components which are used in this project are as follows:

Sl. No.	Particulars	Quantity	Price
1	89C51Microcontroller	1	150.00
2	Reduction Dc motor	3	450.00
3	Solar panel	1	1200.00
4	Relays	6	240.00
5	Limit switches	3	50.00
6	12v Battery	1	800.00
7	Push buttons	3	10.00
8	Regulators	1	800.00
9	Fabrication	-	1300.00
Grand Total			5000.00

     

Chapter-8

CONCLUSIONS

            The current work shows the development of basic module of bench type prototype of multifunctional elevator. The technology can be successfully applied in the industries or day to day life applications. “Multifunctional Elevator”. While designing and developing the prototype module lot of problems are faced, and a systematic step-by-step approach is followed to rectify the problems one after another. We have given lot of importance for the mechanical structure; for this purpose lot of literature review related to the electromechanical structures are referred, and a good looking robust mechanical structure is designed. All electronic hardware including mechanical transmission section is mounted to this structure. Heavy duty battery is also accommodated over the structure, whereas the Solar panel is to be kept outside to capture the Sun energy, it is not mounted over the structure. Three small DC motors with built in reduction gear mechanism are used to drive entire machine to perform multiple tasks.

            The future scope of this work which is economical in nature can be applied in India, for various applications such as multistoried buildings as well as for rail or road crossings.

REFERENCES

[1]        Shigeru Abe, Eiki Watanabe, History of elevators and related research

[2]        Tai sukkim,  Moving elevators cell system in indoor buildings, IEEE Transactions on vehicular technology, vol. 49, 5^th September 2000

[3]        Anne Millbrooke, Hydraulic versus Electric elevators

[4]        William McBride and MiroslavDjukic, Experimental evaluation of OLDS Elevator concept

[5]        T. Mori,  Mechatronics, yasakawa internal  trademark application memo, 12 july 1969

[6]        marjaliisasiilkonen, planning and control models for elevators in high rise buildings

[7]        J.S.Rao and R.V. Dukkipati, Mechanism and Machine theory, new age international , 1992

[8]        Joseph J Carr, Electronic circuit guidebook, vol. 1, 1997

[9]        Mitchel E Schultz, Grobs basic electronis, Mc graw Hill 2011

[10]      G.D.RAI, solar energy utilization, khanna publisher, Delhi         

[11]      Kenneth J. Ayala, 8051Microcontroller architecture, programming and applications