ret project

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1 INTRODUCTION Elevators are used to move loads from one height to another without disturbing the load itself. The prime mover of an elevator can be given by an electric motor. Suspension systems driven by electric motors are the ideal choice for applications having minimal space and great heights because these systems do not require infrastructure to be built beneath the floor of the elevator and are limited in height only by the ability of the electric drive to overcome static forces such as gravity and dynamic forces such as friction and air drag. The physical model of elevator is analyzed and converted the physical model into mathematical equations to find the transfer function. The purpose to find the transfer function is that we can see the behavior of system theoretically using software and design the physical model accordingly. We can compare the theoretical results and practical results to improve response of elevator for the comfort passengers. Electronic control systems (we have used) for control of lift are composed of hardware components. Using Electronic a control system to dictate the position of an elevator’s elect ric drive increases the accuracy and precision with which the elevator system responds to position commands. DC motor is as simple as changing the magnitude of voltage applied to the motor’s armature circuit; to make the motor operate in the opposite direction the polarity of the supply voltage needs to only be reversed.. In our system, as box moves upward and reaching its top position it stops automatically by touching limiting switch then polarity reverses of motor to move lift downward and it stops again following same mechanism. Different Components used in Lift Control Mechanism Toggle Switch Limiting Switch Diode Power Supply Power Window Motor Bread board LED

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  • 1

    INTRODUCTION

    Elevators are used to move loads from one height to another without disturbing the load

    itself. The prime mover of an elevator can be given by an electric motor. Suspension systems

    driven by electric motors are the ideal choice for applications having minimal space and great

    heights because these systems do not require infrastructure to be built beneath the floor of the

    elevator and are limited in height only by the ability of the electric drive to overcome static

    forces such as gravity and dynamic forces such as friction and air drag.

    The physical model of elevator is analyzed and converted the physical model into

    mathematical equations to find the transfer function. The purpose to find the transfer function

    is that we can see the behavior of system theoretically using software and design the physical

    model accordingly. We can compare the theoretical results and practical results to improve

    response of elevator for the comfort passengers.

    Electronic control systems (we have used) for control of lift are composed of hardware

    components. Using Electronic a control system to dictate the position of an elevators electric

    drive increases the accuracy and precision with which the elevator system responds to

    position commands. DC motor is as simple as changing the magnitude of voltage applied to

    the motors armature circuit; to make the motor operate in the opposite direction the polarity

    of the supply voltage needs to only be reversed.. In our system, as box moves upward and

    reaching its top position it stops automatically by touching limiting switch then polarity

    reverses of motor to move lift downward and it stops again following same mechanism.

    Different Components used in Lift Control Mechanism

    Toggle Switch

    Limiting Switch

    Diode

    Power Supply

    Power Window Motor

    Bread board

    LED

  • 2

    Description of Components

    Toggle Switch:-

    Toggle Switches have a to and fro switching movement. The most familiar form of switch is

    a manually operated electromechanical device with one or more sets of electrical contacts,

    which are connected to external circuits. Each set of contacts can be in one of two states:

    either "closed" meaning the contacts are touching and electricity can flow between them, or

    "open", meaning the contacts are separated and the switch is non-conducting. The mechanism

    actuating the transition between these two states (open or closed) can be either a "toggle' (flip

    switch for continuous "on" or "off1') or "momentary" (push-for "on" or push- for "off

    1') type.

    Purpose of Toggle Switch in our project is to change the polarity of motor that is when it is

    pressed at one side it performs the switching action and give polarity to the motor so that it

    rotates clockwise. At center, toggle switch does not any current to the motor and when

    pressed at another side the motor rotates anticlockwise.

    Limit Switch: -

    A limit switch is an electromechanical device that consists of an actuator mechanically linked

    to a set of contacts. When an object comes into contact with the actuator, the device operates

    the contacts to make or break an electrical connection. As its name suggests, a limit switch

    regulates the operations of machines that are equipped with moving parts connected to a

    switching action mechanism. A wide range of industrial machinery uses limit switches to

    control the movement of devices performing on a production line, but these switches are also

    found in non-industrial applications, such as electric motor operation and garage door opener

    units. The switch also deactivates the motor as the door closes, preventing it from being

    pushed into the ground. A limit switch is typically composed of a series of electrical contacts

    coupled to an actuator that controls the mechanical device responsible for on and off

    functions.

  • 3

    Diode Symbol

    Diode:-

    In electronics, a diode is a two-terminal electronic component . it has low (ideally zero)

    resistance to current in one direction, and high (ideally infinite) resistance in the other. A

    semiconductor diode, the most common type today, is a crystalline piece of semiconductor

    material with a p-n junction connected to two electrical terminals.

    The most common function of a diode is to allow an electric current to pass in one direction

    (called the diode's forward direction), while blocking current in the opposite direction (the

    reverse direction).. This unidirectional behavior is called rectification, and is used to convert

    alternating current.

    The function of diode on our project is that to allow the current in one direction (close

    switch) and block the current in other direction (open switch) for control mechanism of

    Lift.

  • 4

    Power Supply:

    A power supply unit (PSU) converts mains AC to low-voltage regulated DC power. An AC

    powered unregulated power supply usually uses a transformer to convert the voltage from the

    wall outlet (mains) to a different, nowadays usually lower, voltage. If it is used to produce

    DC, a rectifier is used to convert alternating voltage to a pulsating direct voltage, followed by

    a filter, comprising one or more capacitors, resistors, and sometimes inductors, to filter out

    (smooth) most of the pulsation. For purposes such as charging batteries the ripple is not a

    problem, and the simplest unregulated mains-powered DC power supply circuit consists of a

    transformer driving a single diode in series with a resistor.

    The power window motor we have used required 12 V input DC voltage. For this purpose we

    used Power Window Motor:-

    Power window motor is DC motor which converts electrical energy into mechanical energy.

    The power window motor is used in vehicle, usually in car windows to lift the window glass

    up and down in vehicles. To operate this motor (to move the window glass), we press an

    automated button then the motor shaft rotates in clockwise direction. The glass is attached to

    shaft of the motor and as motor rotates clockwise the glass moves upward. When we press

    the button again, the motor rotates anticlockwise and glass moves downward. Same

    mechanism is used in the upward and downward movement of the cabin of the lift. When

    toggle switch is pressed at one side, motor rotates clockwise and when toggle switch is

    pressed towards other direction, the polarity of the motor changes and it rotates in

    anticlockwise direction.

  • 5

    Bread Board:-

    A breadboard is usually a construction base for prototyping of electronics. Because the solder

    less breadboard for electronics does not require soldering, it is reusable. This makes it easy to

    use for creating temporary prototypes and experimenting with circuit design.

    Light-Emitting Diode (LED):-

    A light-emitting diode (LED) is a two-lead semiconductor light source that resembles a basic PN-

    junction diode, except that an LED also emits light. Light emitting diode emits light when current is

    passed through the LED. The maximum voltage it can bear is 5V

  • 6

    Control Mechanism of lift:

    As we seen that the purpose of the toggle switch is to change the polarity of the motor, so for upward

    movement of the lift one positive end of the wire of the motor is connected to the positive end of the

    toggle switch and negative end is connected to limit switch. The other end of limit switch is

    connected to positive end of diode. The negative end of the diode is connected to the negative end of

    the toggle switch.

    When toggle switch is pressed at one side, the current flow from toggle switch through limit switch

    and diode. As the current flow through motor, it will rotate clockwise and life move upward, as the

    life strike to the limit switch, the circuit will break and motor will which will result in stopping of

    cabin.

    For downward movement of the lift, the positive end of the motor is connected to the positive end of

    the toggle switch as above and the negative end of the motor is connected to another limit switch

    which is attached at the elevator base. The other end of this limit switch is connected to the negative

    end of the diode and the positive end of the diode is connected to negative end of toggle switch. But

    important point is that as the toggle switch is pressed in the other direction, it will change the polarity

    automatically. Now the positive end of motor will become negative and negative end of motor will

    become positive. The motor will move downward, as it strikes the limit switch, the circuit will break

    and motor will stop. As the circuit break motor will stop which will result in stopping of cabin.

    As the cabin strike the limit switch, the circuit will break and current cannot flow through an other

    path because in this path a diode is connected at reverse polarity which will block the current.

    And other addition is made in the circuit, 2 LEDs are connected with reverse polarities to each other

    parallel to the motor. As LEDs conduct in only one direction so when motor move upward one LED

    will be ON and when motor moves downward other LED will be ON.

    Two resistances are connected in series and parallel to each LED to limit the value of voltage and

    current across LED. As it can bear 5V maximum voltage and we have used a 12V power supply as

    shown in the circuit:

  • 7

    Solar Panel:

    Solar panels generate free power from the sun by converting sunlight to electricity with no moving

    parts, zero emissions, and no maintenance. The solar panel, the first component of a electric solar

    energy system, is a collection of individual silicon cells that generate electricity from sunlight. The

    photons (light particles) produce an electrical current as they strike the surface of the thin silicon

    wafers. A single solar cell produces only about 1/2 (.5) of a volt. However, a typical 12 volt panel

    about 25 inches by 54 inches will contain 36 cells wired in series to produce about 17 volts peak

    output. If the solar panel can be configured for 24 volt output, there will be 72 cells so the two 12

    volt groups of 36 each can be wired in series, usually with a jumper, allowing the solar panel to

    output 24 volts. When under load (charging batteries for example), this voltage drops to 12 to 14

    volts (for a 12 volt configuration) resulting in 75 to 100 watts for a panel of this size.

    Multiple solar panels can be wired in parallel to increase current capacity (more power) and wired in

    series to increase voltage for 24, 48, or even higher voltage systems. The advantage of using a higher

    voltage output at the solar panels is that smaller wire sizes can be used to transfer the electric power

    from the solar panel array to the charge controller & batteries. Since copper has gone up

    considerably in the last few years, purchasing large copper wiring and cables is quite expensive.

    (that's why pennies are made of mostly zinc today).

    Crystalline-silicon module comprises 4 solar cells and has an aluminum frame and glass on the front.

  • 8

    The 3 Basic Types of Solar Panels

    Mono-crystalline Solar Panels:

    The most efficient and expensive solar panels are made with Mono crystalline cells. These solar cells

    use very pure silicon and involve a complicated crystal growth process. Long silicon rods are

    produced which are cut into slices of .2 to .4 mm thick discs or wafers which are then processed into

    individual cells that are wired together in the solar panel.

    Mono crystalline Solar Panel

    Polycrystalline Solar Panels:

    Often called Multi-crystalline, solar panels made with Polycrystalline cells are a little less expensive

    & slightly less efficient than Monocrystalline cells because the cells are not grown in single crystals

    but in a large block of many crystals. This is what gives them that striking shattered glass

    appearance. Like Monocrystalline cells, they are also then sliced into wafers to produce the

    individual cells that make up the solar panel.

    Polycystalline Solar Pannel

  • 9

    Amorphous Solar Panels:

    These are not really crystals, but a thin layer of silicon deposited on a base material such as metal or

    glass to create the solar panel. These Amorphous solar panels are much cheaper, but their energy

    efficiency is also much less so more square footage is required to produce the same amount of power

    as the Monocrystalline or Polycrystalline type of solar panel. Amorphous solar panels can even be

    made into long sheets of roofing material to cover large areas of a south facing roof surface.

    Amorphous Solar Panel

    The Power Inverter

    Unless you plan on using battery power for everything, you will need a Power Inverter. Since the

    majority of modern conveniences all run on 120 volts AC, the Power Inverter will be the heart of

    your Solar Energy System. It not only converts the low voltage DC to the 120 volts AC that runs

    most appliances, but also can charge the batteries if connected to the utility grid or a AC

    Generator as in the case of a totally independent stand-alone solar power system.

    Power Inverter

  • 10

    Square Wave Power Inverters:

    This is the least expensive and least desirable type. The square wave it produces is inefficient and is

    hard on many types of equipment. These inverters are usually fairly inexpensive, 500 watts or less,

    and use an automotive cigarette lighter plug-in. Don't even consider one of these types of power

    inverters for a home system

    Modified Sine Wave Power Inverters:

    This is probably the most popular and economical type of power inverter. It produces an AC

    waveform somewhere between a square wave and a pure sine wave. Modified Sine Wave inverters,

    sometimes called Quasi-Sine Wave inverters are not real expensive and work well in all but the most

    demanding applications and even most computers work well with a Modified Sine Wave inverter.

    However, there are exceptions. Some appliances that use motor speed controls or that use timers may

    not work quite right with a Modified Sine Wave inverter. And since more and more consumer

    products are using speed controls & timers, I would only recommend this type of inverter for smaller

    installations such as a camping cabin.

    True Sine Wave Power Inverters:

    A True Sine Wave power inverter produces the closest to a pure sine wave of all power inverters and

    in many cases produces cleaner power than the utility company itself. It will run practically any type

    of AC equipment and is also the most expensive. Many True Sine Wave power inverters are

    computer controlled and will automatically turn on and off as AC loads ask for service. I believe

    they are well worth the extra cost. True Sine Wave power inverter used and find that its automatic

    capabilities makes it seem more like Utility Company power. You just flick on a light switch (or

    whatever) and it works. When you turn off the light or the refrigerator kicks off for example, the

    power inverter shuts down to save battery power

    Graph of pure sine wave inverter

  • 11

    Charge Controller:

    A solar regulator is a small box consisting of solid state circuitry that is placed between a solar panel

    and a battery. Its function is to regulate the amount of charge coming from the panel that flows into

    the deep cycle battery bank in order to avoid the batteries being overcharged. A regulator can also

    provide a direct connection to appliances, while continuing to recharge the battery; i.e. you can run

    appliances directly from it, bypassing the battery bank; but the batteries will continue to be charged.

    Charge controller is basically used to charge solar batteries from Solar Panels. Solar panels normal

    give 15-17 volt, charge controller converts that to 12-14 volt and charges battery. Battery often need

    a higher voltage than it already have to charge the battery If you is using big solar panel system so it

    is better to have an advanced charge controller. That gives you complete statistics of how much volt

    and ampere it has charged battery.

    Benefits of CHARGE CONTROLLER:

    Charge controller prevents batteries to be over charged.

    Stops to charge when battery is fully charged.

    It will give longer life for battery.

    Advanced charge controllers also show you how much ampere is on batteries

    Charge controllers can automatic disconnect battery if it is going to be empty

    Maximum Power Point Tracking:

    The newer Maximum Power Point Tracking (MPPT) controllers are even better. They match

    the output of the solar panels to the battery voltage to insure maximum charge (amps). For

    example: even though your solar panel is rated at 100 watts, you won't get the full 100 watts

    unless the battery is at optimum voltage. The Power/Watts is always equal to Volts times

    Amps or P=E*I (see Ohm's law for more info). With a regular charge controller, if your

    batteries are low at say 12.4 volts, then your 100 watt solar panel rated at 6 amps at 16.5 volts

    (6 amps times 16.5 volts = 100 watts) will only charge at 6 amps times 12.4 volts or just 75

    watts. You just lost 25% of your capacity! The MPPT controller compensates for the lower

    battery voltage by delivering closer to 8 amps into the 12.4 volt battery maintaining the full

    power of the 100 watt solar panel! 100 watts = 12.4 volts times 8 amps = 100 (P=E*I).

  • 12

    Batteries:

    A battery is a device that converts chemical energy contained in its active materials directly

    into electrical energy by means of an electrochemical reaction. Batteries used in photovoltaic

    (PV) lighting systems must be rechargeable.

    Lead-acid batteries are the most common type of batteries used in PV systems, due to their

    wide availability in many sizes, their low cost, and their well understood performance

    characteristics. Lead-acid batteries are also commonly recycled.

    Most Common Types Of Lead-Acid Batteries

    The most common types of lead-acid batteries used in PV systems are,

    lead-antimony batteries,

    lead-calcium batteries,

    lead-antimony/lead-calcium hybrid batteries,

    Captive electrolyte lead-acid batteries, which include gelled batteries and absorbed glass mat

    (AGM) batteries. Nickel-cadmium cells are used in some applications, but their high initial

    cost limits their use.

    1. Wires And Cables:

    To connect the components of a Solar Energy System, use correct wire sizes to ensure low loss of

    energy and to prevent overheating and possible damage or even fire. If we use the proper size

    numbers for a 12 volt system we can achieve a 3% or less voltage drop.

    PV System Design Rules:

    1. Determining the total load current and operating time requirements in Ampere-hours

    2. Taking care of system losses and safety factors

    3. Determining the worst case (wintertime) Equivalent Sun Hours (ESH)

    4. Determining total solar array current requirements

    5. Determining optimum module arrangement for solar array.

    6. Determining battery size for recommended reserve time

  • 13

    Calculation for the Solar PV System Components for Solar Lift

    We have a 36 watt DC motor which draws 3 ampere current. We want to operate it solar PV

    system for complete 5 hours.

    Calculation of energy requirement:

    Considering peak hours = 7 hours

    Motor power = 36watt

    Energy consumed directly from solar panel for 7 hours = 36*7 = 252watt.hour

    Energy consumed directly from battery for 17 hours = 36*16 = 612watt.hour

    Let us assumed the loses in battery, wire, panel etc. is 7%

    Energy consumed in one day for overcoming loses = 86.4

    Total energy required in one day = 252+612+86.4 = 950.4 watt hour/day

    Solar Plate/Array Calculation:

    Solar peak hours = 7 hours

    Size for solar array = 950.4/7 = 135.77watt

    So we recommended 150 watt solar array having voltage equal to 12v, which is easily available in

    market

    Calculation for Battery:

    Normally depth of discharge (DOD) is taken 1 for its value equal to 50%

    Here we are considering the DOD = 80%

    So we take the factor DOD equal to 1.6

    Total watt hour per day for battery = 612 watt-hours/day

    Adding the losses equal to 10%

    Total watt hour per day for battery = 612+61.2 = 673.2

  • 14

    Now battery (Ah) = (673.2*(0.76*1.6))/12

    Battery (Ah) = 807.84/12 = 67.32 ampere-hour

    We recommend 70 Ah battery for 12 volts

    Calculation for MPPT charge controller:

    P = V*I

    P = solar array size = 150watt

    B = Battery voltage = 12 volts

    150watt = 12v*I

    I = 150/12 = 12.5 ampere

    It is recommended that we have to take account the special conditions in which solar arraying is

    producing more power as in ordinary conditions so we have to add 25% of I

    I = 12.5+3.125 = 15.625 Ampere

    Keeping in mind the safety factors

    We recommend that charge controller must be of 20 ampere capacity, we have only one array of 150

    watt having battery 12v, now by keeping in mind the open circuit of solar array use 12 volt charge

    controller

    Results:

    Total energy required per day = 950.4watt hour/day solar array = 150watt, 12V

    Battery=70Ah, 12

    Charge controller = 20 ampere, 12v

    Now considering solar peak hours = 6

    Lift run on battery = 2 hours

    Total working hours = 8hr/day

    Total energy required per day = 8*36 = 288Wh/day

  • 15

    Losses in battery, wire etc. = 10%

    Total energy required per day with considering losses = 361.8Wh/day

    Solar plate:-

    Peak hours = 6

    Size of solar array = 361.8/6 = 52.8W

    In market 60W plate is available, so we recommend 60W & 12 V solar plate.

    Battery:

    No. of days = 2hr = 0.25 days

    Total watt hours/day for battery = 36*2 = 72Wh/day + 5.76 Wh/day (losses) = 77.6 Wh/day

    Battery = 77.60.71.6/12 = 7.25 V

    Depth of discharge = 80% = 1.6

    We recommend battery = 10A.hr

    Hence battery is of 12V, A.hr

    Charge Controller:

    P = VI

    P = solar plate =60W

    Battery voltage = V =12volts

    I = P/V = 60/12 = 5Amp

    It is recommended that we have to take into account special conditions in which solar panel

    producing more power. Also keeping in mind the safety of charge controller, we have taken charge

    controller having capacity 10Amp and 12V.

  • 16

    Conclusion

    The PV system is successfully designed for a lift control mechanism. The calculation is done for 24

    hours as well as for eight hours. But in prototype we considered eight hours application to make it

    cost effective The system require 70Amp.hr and 12V Battery, 150 W solar plate and 20 amp and 12

    volt charge controller for 24-hours working. As actually we make it for eight working hours like

    office timing application. For this we require battery of 7Amp.hr, solar plate of 60W and charge

    controller 10amp and12 volt. The implementation of solar PV system on an elevator driven by a

    motor which is charge by solar plate with position control of elevator provide an illustrative example

    for those who wish to apply solar systems to drives various mechanical systems. Such renewable

    energy technology is important to minimize the energy crisis in Pakistan.

  • 17

    References

    www.wikipedia.com

    www.fordthesis.com

    http://en.wikipedia.org/wiki/Photovoltaic_system.

    http://www.energysavingtrust.org.uk/domestic/content/solar-panels

    http://www.moneysavingexpert.com/utilities/free-solar-panels.