Car Park Space Management

7/28/2019 Car Park Space Management

1/52

CHAPTER ONE

INTRODUCTION

1.0 PREAMBLE

It is very common to have huge crowds in places like mega shopping

malls and stadiums during peak periods. In shopping malls, discounts

and season sales offered by merchants can attract thousands of

customers to come during the sale periods. Most of the customers

travel to the shopping malls with their own vehicles and it is not

surprising to see that car parks are always full during these periods.

However, research into drivers' behavior when trying to park their cars

indicated that this does not seem to stop many drivers from queuing at

their favourite car park for significant periods (Percival and Sedgwick,

2002). New generation information services have been proposed or

developed to replace traditional "Full/Spaces" sign at the entrance.

These come in the form of parking information via mobile phones,

personal digital assistants (PDAs), RDS-TMC, navigation systems and

Urban Traffic Management and Control (UTMC) (Percival and Sedgwick,

2002). Parking guidance system such as the one developed at

Shinjuku, Japan (Kurogo, et al., 1995) and Tapiola, Finland (Ristola,

1992) are examples of systems developed to guide drivers in finding

vacant car parks.

There are mainly four categories of car park guidance systems using

different technologies:

Counter-based,

Wired sensor-based,

1


2/52

Wireless sensor-based and

Image-based categories.

Counter-based systems use sensors to count the number of vehicles

entering and exit a car park area. This can be gate-arm counters and

induction loop detectors located at the entrances and exits (Ristola,

1992). This system can give information on the total number of vacant

lots in a closed car park area, but does not help much in guiding the

driver to the exact location of the vacant lots; typical display of this

system is as shown in fig.1.

Fig.1: Display system of Car park Capacity

1.1 PROJECT MOTIVATION

In large parking areas such as those at mega shopping malls or

stadiums, drivers always have difficulty to find vacant car park lots

especially during peak periods or when the parking lots are almost full.

A solution to reduce the drivers searching time for vacant car-park lots

will greatly save time, reduce cost and improve the traffic flow in the

car park areas. In this project a system will be designed and developed

to acquire car park occupancy information. Motivation for developing

this system is to provide a cost effective means using sensors on each

gate of a parking lot.

2


3/52

The need to reduce or eliminate the problems associated with the pneumatic or manual operation

of valves by humans has been the drive for this project. More so, ways of improving the control

efficiency of equipments and systems provided the concept of the micro-processor based control

valve. Control is better achieved with lesser human interference.

This project is aimed at the following:-

To design a valve that can be remotely and efficiently controlled in the plant.

Prevention of local operators from undertaking simultaneous operation (SIMOP).

To increase operational accuracy.

To prevent local operators from hazardous fluids.

To increase efficiency, safety, profitability and ecology

Ultimately the time, quality and cost of production is optimized.

1.2 LITERATURE REVIEW

In a world of ever growing demand for high quality and quantity of goods, there is a great need

for the constant upgrade of production processes to meet this surge in demand. This explains the

technological advancement achieved in the last couple of years in the field of control engineering

which not only enhances quality but also ensures reliability of the processes once control

parameters are acquired correctly.

Control of process variables (e.g. flow, pressure, level e.t.c.) was done manually in the past,

where operators have to manually operate the valve in the field. This posed a lot of challenges

3


4/52

such as health issues (hazardous plants), human error, slow response time, e.t.c. Though this

method served the purpose then but it was not effective.

These challenges prompted the invention of pneumatic control systems which uses air and

mechanical levers to operate the valves. It was recorded as a tremendous achievement in the field

of control. Moving ahead, the hydraulic system was developed which uses oil instead of air in its

operation. Hydraulic system helped overcome the problem of low power, slower response,

leakages e.t.c. that the pneumatic system had. Still the need for increased response, accuracy and

remote control was evident. A breakthrough was made with the electronic control system which

filled in all the need. This uses electronic circuits to send signals to the final control element

(valve). The advent of microprocessors in electronics technology made it more precise, faster

and easier to achieve control objectives. (www.wikipedia.com)

Dr. Fred .O. (5), a process engineer in the refining industry, in his paper titled The role of

control in Process engineering highlighted the need to fully incorporate advancement achieved

in the electronic field into the control of process. He also mentioned the merits of this method of

control process.

Engr. Benson Ihua (3), in 1999 designed and constructed a pneumatic control valve as his final

year project. This involves the use of a compressor to compress the air, then through a filter to

clean the air and finally to a regulator to determine the pressure that is delivered to the valve.

In 2005, Abideen (4) designed and constructed a motorized valve using a toggle switch to

operate a motor coupled to a valve via a gear system. This was done manually.

A project was presented in the Michigan science fare (6) involving the use of a PIC programmed

to drive a crankshaft in both clockwise and anticlockwise direction. This project converted

rotational motion to translational motion. A servo motor was used to achieve the bi-directional

motion.

4


5/52

Several contributions have been listed in the world of control engineering ranging from

improvement in speed and response time to reduction in size, all geared towards enhancing the

quality of control methodology implemented.

This project uses a programmed microprocessor to remotely drive an electric motor coupled to a

valve assembly via a gear system. More so, sensors (reed switches) send position signal to the

microprocessor as a feedback input.

1.3 PROBLEM DEFINITION AND METHODOLOGY

Maintaining a high level of operational stability amidst the constantly changing process variables

has posed a great challenge to many industries. Control of these process variables can be

implemented by a valve. Manual operation of valves by humans in the past has not made this

implementation any easier. Human factors such as emotions, attitude and time lag between

request and response contribute to the control errors generated during operational procedures. In

this project, electronic control options are considered which reduces the problems encountered in

manual operations.

This project was implemented on the following design methodology;

* PIC Controller

* Sensor

* Amplifier

* Motor

* Valve

* Control switches

5


6/52

Each of these design stages defines the integral functions that the project hopes to achieve.

1.4 PROJECT OUTLINE

The project is outlined in five (5) chapters. Chapter one (1) gives an introduction to the project,

chapter two (2) gives a theoretical background of various components used. Chapter three (3)

deals with the general design procedures employed in the implementation of the system

including the decisions made in material and component selection. The construction and testing

was carried out in chapter four (4), chapter five (5) gives the conclusion and recommendation for

future work.

6


7/52

CHAPTER TWO

THEORETICAL BACKGROUND

2.0 INTRODUCTION

This project bothers on a couple of engineering principles and applies many other techniques

ranging from Electrical Electronics Engineering to Mechanical Engineering. The overall

principle that explains the entirety of this project work can be said to be the concept of control

engineering. Basically the control of any system can be achieved in two different ways, closed-

loop or open-loop. First, there is need to explain what a control loop is in relation to process

control.

A control loop is a set or an arrangement of interconnected equipments or processes that accepts

an input, acts on it and produces an output. The input and outputs depends on the type of control

system used (pneumatic-air, electronic-current, hydraulic-oil e.t.c.). The control loop can be well

explained with an example

CLOSED-LOOP CONTROL

Consider a scenario where a certain flow rate is to be maintained in a process. A control valve

controls the flow rate in this system. In a closed loop, the controller receives its input from the

process (present flow rate) and compares the value with the set point (desired flow rate) and

generates an error signal. Then sends it to the final control element (control valve) in order to

change the flow rate. This continues until the prevailing flow rate is same with the desired flow

7


8/52

rate. It is illustrated in the diagram below. (Tony Kuphaldt, Lessons in industrial instrumentation

,version 1.12 2010)

Fig 2.1: A block diagram of a closed loop control

It can be deduced that the output is fed back to the control; this is why its also called a feedback

control. Closed loop is designed to achieve and maintain the desired process condition by

comparing the set point to the present condition and produce an error signal to correct the offset

in the process.

OPEN-LOOP CONTROL

A common domestic application that illustrates open loop control is a washing machine. The

system is pre-set and operates on a time basis, going through cycles of wash, rinse and spin as

programmed. In this case, the control action is the manual operator assessing the size and

dirtiness of the load and setting the machine accordingly. The machine does not measure the

output signal, which is the cleanliness of the clothes, so the accuracy of the process, or success of

the wash, will depend on the calibration of the system. Illustrated by the diagram below. (Tony

Kuphaldt, Lessons in industrial instrumentation ,version 1.12 2010)

8

Controll

er

Final

Control

Element

Feedback

Element

Inpu

t

Outpu

t


9/52

Fig2.2: A block diagram of an open loop control

This project employs the open-loop control. This is not to state that the open-loop control is the

best scheme; as a matter of fact the closed loop serves for greater efficiency in terms of control.

For the purpose of this work, the open loop is sufficient to serve.

2.1 Component Description

Below is the brief explanation of the individual components used in this project work.

2.1.1 Control Valve

A control valve is a valve with a pneumatic, hydraulic, electric or other externally powered

actuator that automatically, fully or partially opens or closes the valve to a position dictated by

signals transmitted from controlling instruments.

Globe valves are frequently used for control applications because of their suitability for throttling

flow. Whilst a wide variety of valve types exist, this document will concentrate on those which

are most widely used in the automatic control of commercial and industrial fluids. These include

valve types which have linear and rotary spindle movement. Linear types include globe valves

and slide valves.

9

Controll

er

Final

ControlElement

Inpu

t

Outpu

t


10/52

Rotary types include ball valves, butterfly valves, plug valves and their variants.

Globe and the ease with which they can be given a specific 'characteristic', relating valve

opening to flow. Two typical globe valve types are shown in Figure below. An actuator coupled

to the valve spindle would provide valve movement. (Emerson Process Management, Control

valve system, fourth edition, 2005)

Fig.2.3 Two differently shaped globe valves

The major constituent parts of globe valves are:

The body.

The bonnet.

The valve seat and valve plug, or trim.

The valve spindle (which connects to the actuator).

10


11/52

The sealing arrangement between the valve stem and the bonnet.

Fig 2.4 is a diagrammatic representation of a single seat two-port globe valve. In this case the

fluid flow is pushing against the valve plug and tending to keep the plug off the valve seat.

Fig.2.4 Flow through a single seat, two-port globe valve

The difference in pressure upstream (P1) and downstream (P2) of the valve, against which the

valve must close, is known as the differential pressure (DP). The maximum differential pressure

against which a valve can close will depend upon the size and type of valve and the actuator

operating it. ((Emerson Process Management, Control valve system, fourth edition, 2005)

In broad terms, the force required from the actuator may be determined using Equation below

11


12/52

Valve Sizing

Over sizing of valves sometimes occurs when trying to optimize process performance through a

reduction of process variability. This results from using line-size valves, especially with high-

capacity rotary valves, as well as the conservative addition of multiple safety factors at different

stages in the process design.

Over sizing the valve hurts process variability in two ways. First, the oversized valve puts too

much gain in the valve, leaving less flexibility in adjusting the controller. Best performance

results when most loop gain comes from the controller. If the valve is oversized, making it more

likely to operate in or near this region, this high gain can likely mean that the controller gain will

need to be reduced to avoid instability problems with the loop. This, of course, will mean a

penalty of increased process variability. The second way oversized valves hurt process

variability is that an oversized valve is likely to operate more frequently at lower valve openings

where seal friction can be greater, particularly in rotary valves. Because an oversized valve

produces a disproportionately large flow change for a given increment of valve travel, this

phenomenon can greatly exaggerate the process variability associated with dead band due to

friction. Regardless of its actual inherent valve characteristic, a severely oversized valve tends to

act more like a quick opening valve, which results in high installed process gain in the lower lift

regions. In addition, when the valve is oversized, the valve tends to reach system capacity at

relatively low travel.

Process control studies show that, for some industries, the majority of valves currently in

process control loops are oversized for the application. While it might seem counterintuitive, it

often makes economic sense to select a control valve for present conditions and then replace the

valve when conditions change. When selecting a valve, it is important to consider the valve style,

12


13/52

inherent characteristic, and valve size that will provide the broadest possible control range for the

application. (Emerson Process Management, Control valve system, fourth edition, 2005)

2.1.2 MICROCONTROLLER

A microcontroller is a computer control system on a single chip. It has many electronic circuits

built into it, which can decode written instructions and convert them to electrical signals. The

microcontroller will then step through these instructions and execute them one by one.

Microcontrollers are now changing electronics design. Instead of hard wiring number of logic

gates together to perform some functions we now use instructions to wire the gates

electronically. The list of these instructions given to the microcontroller is called a program.

Fig.2.5 A block diagram of the basic microcontroller system

The input components would consist of digital devices such as switches, push buttons,

pressure mats, float switches, keypads, radio receivers etc and analogue censors such as

light dependent resistors, thermistors, gas sensors, pressure sensors etc.

The control unit is the microcontroller. The microcontroller will monitor the inputs and as

a result the program would turn outputs on and off. The microcontroller stores the

program in its memory and executes the instructions under the control of the clock

circuit.

13

INPUT CONTROL OUTPUT


14/52

The output devices would be made up from LEDs, buzzers, motors, alphanumeric

displays, radio transmitters, 7-segment displays, heaters, fans, etc.

Types of Microcontroller

There are basically two types of microcontrollers, flash and One Time Programmable Devices

(OTP). The flash devices can be programmed in the programmer whereas OTP devices once

programmed cannot be reprogrammed.

All OTP devices, however, do have a windowed variety, which enables them to be erased under

ultraviolet light in about 15 minutes, so that they can be reprogrammed. The windowed devices

have a suffix JW to distinguish them from the others.

Using the Microcontroller

In order to use the microcontroller in a circuit there are basically two areas one need to

understand.

How to connect the microcontroller to the hardware

How to write and program the code into the microcontroller

Microcontroller Hardware

The hardware that the microcontroller needs to function is as shown below. The crystal and the

capacitors connected to pin 15 and 16 of the 16F684 produce the clock pulses that are required to

step the microcontroller through the program and provide the timing pulses. The 0.1F capacitor

is placed as close to the chip as possible between 5V and 0V. Its role is to divert (filter) any

electrical noise on the 5V power supply line to 0V, thus bypassing the microcontroller. ( L.A.

Bryan & E.A. Bryan, Programmable Controller theory and implementation, second edition,

1997)

14


15/52

2.1.3 7805, VOLTAGE REGULATOR CIRCUIT

Probably, the most common power supply connection for the microcontroller is a three terminal

voltage regulator IC, the 7805. The connection for this is shown below;

Fig 2.6: 7805 block diagram

The supply voltage, Vin, to the 7805 can be anything from 7V to 10V. The output voltage will be

a fixed 5V and can supply currents up to 1amp. (Linear regulator,www.wikipedia.com, 2009).

2.1.4 DIODES

Diode is one of the basic solid-state components and there are many types, each with its own

characteristics and applications. The various diodes types are easily identified by name, circuit

application and schematic symbols.

A diode is a two-way terminal device that acts as a one-way conductor. The most basic type of

diode is the pn-junction diode, which is a pn-junction with a lead connected to each of the

semiconductor materials. When forward biased, the diode will conduct, but revere biased, the

diodes voltage will drop to nearly zero. The schematic symbol for the pn-junction diode as well

as the biasing is shown below. n-type material is called the cathode and p-type material is called

the anode. (John Bird, Electrical & Electronic Principles & Technology, 2ndedition,98)

15

7805

Vin

5v
http://www.wikipedia.com/http://www.wikipedia.com/http://www.wikipedia.com/http://www.wikipedia.com/


16/52

Fig 2.7: Circuit explanation of a diode

Light Emitting Diode

Light emitting diodes are semiconductor display devices. Since there is no filament that would

cause excessive heating, they are very reliable, durable and long lasting. They are inexpensive,

easily interfaced to circuits and do not require high voltage. The light is emitted when a

conduction electron and hole recombine. This recombination requires that, the energy possessed

by the unbound free electron is enough to be transferred to another state. (John Bird, Electrical

& Electronic Principles & Technology, 2ndedition,98)

16

Anode

P-type

Cathode

N-type

Symbol for a diode

P N

i

d v

d(a) A forward biased pn-junction

P N

v

d

i

d

Depletion

layer

(b) A reverse biased pn-junction


17/52

Fig 2.8: Symbol of LED

2.1.5 BIPOLAR JUNCTION TRANSISTOR

Most common transistor are BJTs (Bipolar Junction Transistor). Basically the word transistor is

as a result of the combination:

Transfer + Resistance = Transistor

It consist of two back to back junctions manufactured in a single piece of semiconductor crystal.

These two junctions give rise to three regions called, Emitter, Base and collector.

As shown in figure below, whereby a particular material of semi conductor is sandwiched in

between two semi conductor materials of the same type. Fig(a) shows a layer of p-type material

sandwiched between two p-type materials. This is called a PNP transistor.

The Emitter, base and collector are provided with terminals that are labelled as E, B, and C. The

two junctions are , Emitter- Base (E/B) junction and collector- Base junction (C/B). The

symbols employed for PNP and NPN are also shown with figure (a) and (b) respectively. The

arrowhead is normally used to denote the emitter and in each case, its direction indicates the

conventional direction of current flow. For a PNP transistor, arrowhead points from emitter to

base (and also with respect to collector). For NPN transistor, it points from Base to Emitter

meaning that the base (and collector) is positive with respect to the emitter.

Various Parts of a transistor

Emitter

17

Ano

deCatho

deLight Emitting Diode

Symbol


18/52

It is the most heavily doped then any of the other regions because its main function is to supply

majority charge carriers (either electrons or holes) to the base.

Base

It forms the middle section of the transistor. It is very thin (10-6m) as compared to either the

emitter, or collector and it is lightly doped.

Collector

Its main function (as the name implies) is to collect/ receive majority charge carriers coming

from the emitter and passing through the base, In most transistor, collector region is made

physically larger than the emitter region because, It has to dissipate much greater power.

Transistor as a signal amplifier

The voltage applied between the emitter and collector is fixed and relatively high, while the

voltage between the emitter and the base is low and variable (It is the incoming signal) When

there is no base voltage, the resistance from the emitter to the collector is high, and no current

flows. A small voltage across the base to the emitter however the resistance and allows a large

output to flow from emitter to the collector. (John Bird, Electrical & Electronic Principles &

Technology, 2nd edition,98)

18


19/52

Fig 2.9: Symbol of a BJT

2.1.6 DC POWER SUPPLY

Most the electronic device and power circuit require a dc source for their operation. Dry cells

and batteries are one form of dc source. They have the advantage of being portable and ripple

free. However, their voltages are low; they need frequent replacement and are expensive as

compared to conventional dc power supplies. Since the most convenient and economical source

of power is the domestic ac supply. It is advantageous to convert this alternating voltage

(usually, 220Vrms) to Dc voltage (usually smaller in value). This process of converting ac

voltage into dc voltage is called rectification and is accomplished with the help of a;

(i) Rectifier

(ii) Filter

(iii) Voltage regulator circuit

These element put together constitute dc power supply

19


20/52

A typical dc power supply consists of five stages

-Transformer

-Rectifier

-Filter

-voltage regulator

-voltage Divider

Transformer;

Its job is either to step up or (mostly) step-down the ac supply voltage to suit the requirement of

the solid-state electronic devices and circuits fed by the dc power supply. It also provides

isolation from the supply line, an important safety consideration.

Rectifier;

It is a circuit which employs one or more diodes to convert ac voltage into pulsating dc voltage.

Filter

The function of this circuit element is to remove the fluctuations or pulsations (called ripples)

present in the output voltage supplied by the rectifier, of course , no filter can in practice give an

output voltage as ripple- free as that of a dc battery but it approaches so closely that the power

supply performs as well.

Voltage regulator

Its main function is to keep the terminal voltage of the dc supply constant even when

(a) ac input voltage to the transformer varies (deviations from 0V are common); or

20


21/52

(b) The load varies

Usually, Zener diodes and transistors are used for voltage regulation purposes. (John Bird,

Electrical & Electronic Principles & Technology, 2ndedition,98)

Voltage Divider

Its function is to provide different dc-voltages needed by different electronic circuits. It consists

of a number of resistors connected in series across the output terminals of the voltage regulator

Obviously it eliminates the necessity of providing separate dc power supplies to different

electronic circuit working on different dc levels

Figure 2.10: A typical DC supply

Due to low-cost fabrication technique, many commercial integrated- circuit (IC) regulators are

available since the past few decades. These include fairly simple, fixed- voltage types of high

quality precision regulators. These IC regulators have much improved performance as compared

to those made from discrete components. They have a number of unique build- in features such

21

TRANSFO

RMER

RECTIFIER FILTER VOLTAGE

REGULAT

VOLTAGE

DIVIDERDC

AC INPUT


22/52

as current limiting, self protection against over temperature, remote control operation over a

wide range of input voltages and feedback current limiting.

Types of IC voltage regulators

-Fixed positive linear voltage regulators

-Fixed negative linear voltage regulators

Adjusted positive linear voltages regulator and

Adjusted negative linear voltage regulators

For the sake of this report, I am going to limit myself to the fixed positive linear voltage

regulators. (Newnes Power Engineering Series, Power Electronic Control in Electrical system,

2002)

Fixed positive linear voltage Regulators

There are many IC regulators available in the market that produces a fixed positive output

voltage. But 7800 series of IC regulators is representative of three terminal devices that are

available with several fixed positive output voltages making them useful in a wide range of

applications. Figure (2.9a) below shows a standard configuration of a fixed positive voltage IC

regulator of 7800 series. It should be noted that it has three terminals labelled as input, output

and ground. The last two digits (marked xx) in the part number designate the output voltage. For

example, IC 7805 is a +5V regulator .Similarly IC 7812 is a +12V regulator and Ic 7815 is a

+15v regulator. The capacitor (typically 0.33F) is required only if the power supply filter is

located more than 3 inches from the IC regulator. The capacitor acts

basically as a line filter to improve transient response.

22


23/52


24/52

designed gears and flat-toothed sectors, be employed to transform reciprocating motion into

rotating motion, and vice versa.

Gear system has been used in the motion field to vary the speed of a particular object. The

variation in the speed depends on the number of teeth on the meshing surfaces and the

diameter/radius of the driven part. Gears were used to also transfer rotational motion to the valve

spindle. (Gear systems, www.howstuffworks.com, 2000)

Fig 2.12: A gear wheel assembly

2.1.9 ELECTRIC MOTOR

Electric motors are devices that convert electrical energy to mechanical energy by the interaction

between magnetic field set up in the stator and rotor windings. It operates on the principle of

electromagnetism. It explains that, if a current is passed through a conductor located in a

magnetic field, the field exerts a mechanical force on it.

24
http://www.howstuffworks.com/http://www.howstuffworks.com/


25/52

The electric motor has several classifications, but of interest is the type of supply voltage used i.e

Direct current (DC motor) and Alternating current (AC motor). For a DC motor; when current is

passed through the armature of a DC motor, a torque is generated by magnetic reaction, and the

armature revolves.

The speed at which a DC motor operates depends on the strength of the magnetic field acting on

the armature, as well as on the armature current. The stronger the field, the slower is the rate of

rotation needed to generate a back voltage large enough to counteract the applied voltage. For

this reason the speed of DC motors can be controlled by varying the field current. (How a dc

motor works, www.howstuffworks.com, 2005).

Fig 2.13: Electric motor make up diagram

CHAPTER THREE

DESIGN PROCEDURES

25


26/52

3.0 INTRODUCTION

This chapter entails the different design considerations made in the selection of materials

and the implementation of the project structure. Also describing the factors that

influenced the decisions taken with respect to the limitations encountered. The project

structure diagram and the circuit diagram are contained and explained herein. Moreover,

it also discusses how the microcontroller (PIC 16F84) was interfaced with the circuit

board.

In this write-up, each of the components is briefly described and later, the main principles

of operation of the project is now discussed in details.

3.1 DESIGN METHODOLOGY

Fig 3.1: Block diagram of the project outline.

Control Switch: is a switch used in this case for uttering the position of the valve

26

Sensor

PIC

Controller

Amplifier Motor

Valve

Stem

Valve

Body

Control

Input

Switch


27/52

PIC Controller: is a programmable integrated circuit controller that processes the instruction

from the control switch to either open more or close more.

Sensor: the sensor senses the current position of the valve stem

Amplifier: the output commend signal from the PIC controller is further amplified so that the

motor gets enough power to effect the command.

Motor: is an induction meter that implements the command to turn.

Valve stem: is the part of the valve that transmit motion

Valve body: The main pressure boundary of the valve that also provides the pipe connecting

ends, the fluid flow passage way, and supports the seating surfaces and the valve closure

member.

The project was implemented on the structure illustrated by the block diagram above.

Components were selected to achieve the purpose intended. It is pertinent to note at this point

that this project is a prototype, therefore size is not fully considered.

3.2 SENSOR

The general definition of a sensor is a device capable of detecting and responding to physical

stimuli such as movement, light or heat etc. The design requires a sensor that can detect circular

motion. The sensor is the eye of the PIC by providing the PIC with signals indicating the

number of revolution made by the valve spindle.

A set of reed switches were selected to implement this. As described earlier in the previous

chapter, reed switch close its contact when placed in the vicinity of a magnetic field.

27


28/52

Fig 3.2: Gear wheel showing reed switch position

As seen in the diagram above, the reed switches were placed at the four quadrants of the gear

circumference and a magnet placed on the gear surface. So as the gear rotates, the magnet rotates

with it; making and breaking the contacts of the reed switches as it moves along. This making

and breaking of contacts is sent to the PIC as counting pulses.

3.3 PIC CONTROLLER

This is a programmable integrated circuit that receives input from sensors, processes it and

compares it with the resident program and then sends out appropriate output signal in response to

the input. In order to choose a microcontroller for a particular control system let us first of all

consider the block diagram of the microcontroller system which is as shown below;

28

Reed

switch

Magnet

Gea

r

INPUT CONTOROL OUTPUT

The basic microcontroller


29/52

- The input components would consist of digital devices such as switches, push buttons,

pressure mats, float switches, keypads, radio receivers etc and analogue censors such as

light dependent resistors, thermistors, gas sensors, pressure sensors etc.

- The control unit is the microcontroller. The microcontroller will monitor the inputs and as a

result the program would turn outputs on and off. The microcontroller stores the program in

its memory and executes the instructions under the control of the clock circuit.

- The output devices would be made up from LEDs, buzzers, motors, alphanumeric displays,

radio transmitters, 7-segment displays, heaters, fans, etc.

The next consideration would be what size of program memory storage is required.

The clock frequency determines the speed at which instructions are executed. This is important if

any lengthy calculations are being undertaken. The higher the clock frequency the quicker the

micro will finish one task and start another.

Other considerations are the number of interrupts and timer circuits required, and how much data

EEPROM if any is needed.

After due consideration, PIC16F628A controller was selected as suitable to implement the

controller function. The description of this PIC has been detailed in the previous chapter.

(Newnes Power Engineering Series, Power Electronic Control in Electrical system, 2002)

3.4 AMPLIFIER

An amplifier in the electronic application is a circuit that increases the magnitude of some of the

features of a signal i.e. current, voltage, power etc. Electronic amplifiers find applications where

the input level (current, voltage, power etc) is not up to the level required. So a boost is needed to

29


30/52

achieve the input level. For the purpose of this project, the amplification is needed because the

PIC output is not enough to drive the electric motor.

The amplification circuit consist of transistors (TIP41, TIP42, BC557, BC548), resistors and

capacitors. The values of these circuit components were carefully selected to produce an output

that can drive the motor conveniently.

More so, the PIC also needs a voltage transformation because its input voltage is 2.2v to 5.5v

DC. This is necessary because the voltage supply is an unregulated 220v AC. So the power

supply circuit is considered to convert the unregulated 220v AC to a regulated 5v DC voltage for

the use of the PIC. (Newnes Power Engineering Series, Power Electronic Control in Electrical

system, 2002)

3.5 CONTROL INPUT SWITCH

These are toggle switches that when depressed closes a contact and sends signal in form of

pulses to the PIC. This helps for the selection of the desired position of the valve from fully

closed (0%), 25%, 50%, 75%, and fully open (100%). The switch was selected for its durability

and good temporal contact switching.

3.6 VALVE ASSEMBLY

The implementation of the valve assembly was achieved with a number of components. First is

the valve body which houses the valve internals. The selection of this part of the assembly is

very important because it determines the effectiveness of flow control. The plunger should be

able to handle throttling and shut off without wear. It should also be able to handle the pressure,

flow, and temperature it will be subjected to. Next is the valve stem which consist of spindle

30


31/52


32/52

Table 3.2 TRANSISTOR RATING

Transistor VCBO VCEO VEBO IC hfe Tj

TIP42 -40v -40v -5v -6A 75 150oC

TIP41 40v 40v 5v 6A 75 150oC

BC557 -80v -65v -5v -

100mA

80

0

150oC

3.9 CIRCUIT DESCRIPTION

32


33/52

Fig. 3.3: Circuit Diagram

The individual circuit components have been explained in the previous chapter. So the circuit

will be explained as a functional block.

33


34/52

As contained in the programme of the PIC, switching on the power will reset the system by

sending an output to the motor to close the valve. Depressing any of the switch sends a

discriminate input pulse to the PIC, the PIC then acts on the input according to the program. In

response to the input, the micro controller reads the present position of the valve using a

magnetic sensor, it will now use this to determine the extent the valve stem is to travel and

whether the dc motor will turn clockwise or anti-clockwise to achieve the request from the

operator.

3.10 Process Control Terminology

Actuator: A pneumatic, hydraulic, or electrically powered device that supplies force and motion

to open or close a valve.

Actuator Assembly: An actuator, including all the pertinent accessories that make it a complete

operating unit.

Capacity (Valve): The rate of flow through a valve under stated conditions.

Closed Loop: The interconnection of process control components such that information

regarding the process variable is continuously fed back to the controller set point to provide

continuous, automatic corrections to the process variable.

Controller: A device that operates automatically by use of some established algorithm to

regulate a controlled variable. The controller input receives information about the status of the

process variable and then provides an appropriate output signal to the final control element.

Control Valve Assembly: Includes all components normally mounted on the valve: the valve

body assembly, actuator, positioner, air sets, transducers, limit switches, etc.

34


35/52

Dead Band: The range through which an input signal can be varied, upon reversal of direction,

without initiating an observable change in the output signal. Dead band is the name given to a

general phenomenon that can apply to any device. For the valve assembly, the controller output

(CO) is the input to the valve assembly and the process variable (PV) is the output When the

term Dead Band is used, it is essential that both the input and output variables are identified, and

that any tests to measure dead band be under fully loaded conditions. Dead band is typically

expressed as a percent of the input span.

Dead Time: The time interval (Td) in which no response of the system is detected following a

small step input. It is measured from the time the step input is initiated to the first detectable

response of the system being tested. Dead Time can apply to a valve assembly or to the entire

process.

Final Control Element: The device that implements the control strategy determined by the

output of the controller. While the final control element can be a damper, a variable speed drive

pump, or an on-off switching device, the most common final control element in the process

control industries is the control valve assembly. The control valve manipulates a flowing fluid,

such as gasses, steam, water, or chemical compounds, to compensate for the load disturbance and

keep the regulated process variable as close as possible to the desired set point.

Hysteresis: The maximum difference in output value for any single input value during a

calibration cycle, excluding errors due to dead band.

Inherent Characteristic: The relationship between the flow coefficient and the closure member

(disk) travel as it is moved from the closed position to rated travel with constant pressure drop

across the valve. Typically these characteristics are plotted on a curve where the horizontal axis

is labeled in percent travel and the vertical axis is labeled as percent flow (or Cv). Because valve

flow is a function of both the valve travel and the pressure drop across the valve, conducting

flow characteristic tests at a constant pressure drop provides a systematic way of comparing one

35


36/52

valve characteristic design to another. Typical valve characteristics conducted in this manner are

named Linear, Equal-Percentage, and Quick Opening.

Installed Characteristic: The relationship between the flow rate and the closure member (disk)

travel as it is moved from the closed position to rated travel as the pressure drop across the valve

is influenced by the varying process conditions.

I/P: Shorthand for current-to-pressure (I-to-P). Typically applied to input transducer modules.

Linearity: The closeness to which a curve relating to two variables approximates a straight line.

(Linearity also means that the same straight line will apply for both upscale and downscale

directions. Thus, dead band as defined above, would typically be considered a non-linearity.)

Linear Characteristic: An inherent flow characteristic that can be represented by a straight line

on a rectangular plot of flow coefficient (Cv) versus rated travel. Therefore equal increments of

travel provide equal increments of flow coefficient, Cv.

Loop Gain: The combined gain of all the components in the loop when viewed in series around

the loop. Sometimes referred to as open-loop gain. It must be clearly specified whether referring

to the static loop gain or the dynamic loop gain at some frequency.

Open Loop: The condition where the interconnection of process control components is

interrupted such that information from the process variable is no longer fed back to the controller

set point so that corrections to the process variable are no longer provided. This is typically

accomplished by placing the controller in the manual operating position.

Packing: A part of the valve assembly used to seal against leakage around the valve disk or

stem.

Positioner: A position controller (servomechanism) that is mechanically connected to a moving

part of a final control element or its actuator and that automatically adjusts its output to the

actuator to maintain a desired position in proportion to the input signal.

36


37/52

Process: All the combined elements in the control loop, except the controller. The process

typically includes the control valve assembly, the pressure vessel or heat exchanger that is being

controlled, as well as sensors, pumps, and transmitters.

Process Gain: The ratio of the change in the controlled process variable to a corresponding

change in the output of the controller.

Process Variability: A precise statistical measure of how tightly the process is being controlled

about the set point. Process variability is defined in percent as typically (2s/m), where m is the

set point or mean value of the measured process variable and s is the standard deviation of the

process variable.

Response Time: Usually measured by a parameter that includes both dead time and time

constant. When applied to the valve, it includes the entire valve assembly.

Sensor: A device that senses the value of the process variable and provides a corresponding

output signal to a transmitter. The sensor can be an integral part of the transmitter, or it may be a

separate component.

Set Point: A reference value representing the desired value of the process variable being

controlled.

Sizing (Valve): A systematic procedure designed to ensure the correct valve capacity for a set of

specified process conditions.

Transmitter: A device that senses the value of the process variable and transmits a

corresponding output signal to the controller for comparison with the set point.

Travel: The movement of the closure member from the closed position to an intermediate or

rated full open position.

Trim: The internal components of a valve that modulate the flow of the controlled fluid.

Bonnet: The portion of the valve that contains the packing box and stems seal and can guide the

stem. It provides the principal opening to the body cavity for assembly of internal parts or it can

37


38/52

be an integral part of the valve body. It can also provide for the attachment of the actuator to the

Valve body.

Typical bonnets are bolted, threaded, welded, pressure-seals, or integral with the body. (This

term is often used in referring to the bonnet and its included packing parts. More properly, this

group of component parts should be called the bonnet assembly.)

Packing Box (Assembly): The part of the bonnet assembly used to seal against leakage around

the closure member stem. Included in the complete packing box assembly are various

combinations of some or all of the following component parts: packing, packing follower,

packing nut, lantern ring, packing spring, packing flange, packing flange studs or bolts, packing

Flange nuts, packing ring, packing wiper ring, felt wiper ring, Belleville springs, and anti-

extrusion ring.

Plug: A term frequently used to refer to the closure member.

Port: The flow control orifice of a control valve.

Seat: The area of contact between the closure member and its mating surface that establishes

valve shut-off.

Static Unbalance: The net force produced on the valve stem by the fluid pressure acting on the

closure member and stem with the fluid at rest and with stated pressure conditions.

Stem Connector: The device that connects the actuator stem to the valve stem.

Valve Body: The main pressure boundary of the valve that also provides the pipe connecting

ends, the fluid flow passageway, and supports the seating surfaces and the valve closure member.

Among the most common valve body constructions are: a) single-ported valve bodies having one

port and one valve plug; b) double-ported valve bodies having two ports and one valve plug; c)

two-way valve bodies having two flow connections, one inlet and one outlet; d) three-way valve

bodies having three flow connections, two of which can be inlets with one outlet (for converging

or mixing flows), or one inlet and two outlets (for diverging or diverting flows). The term valve

body, or even just body, frequently is used in referring to the valve body together with its bonnet

38


39/52

assembly and included trim parts. More properly, this group of components should be called the

Valve body assembly.

Yoke: The structure that rigidly connects the actuator power unit to the valve.

Clearance Flow: That flow below the minimum controllable flow with the closure member not

seated.

Double-Acting Actuator: An actuator in which power is supplied in either direction.

Fail-Safe: A characteristic of a valve and its actuator, which upon loss of actuating energy

supply, will cause a valve closure member to be fully closed, fully open, or remain in the last

position, whichever position is defined as necessary to protect the process. Fail-safe action can

involve the use of auxiliary controls connected to the actuator.

Flow Characteristic: Relationship between flow through the valve and percent rated travel as

the latter is varied from 0 to 100 percent. This term should always be designated as either

inherent flow characteristic or installed flow characteristic.

Inherent Flow Characteristic: The relationship between the flow rate and the closure member

travel as it is moved from the closed position to rated travel with constant pressure drop across

the valve.

Installed Flow Characteristic: The relationship between the flow rate and the closure member

travel as it is moved from the closed position to rated travel as the pressure drop across the valve

is influenced by the varying process conditions.

Vena Contracta: The portion of a flow stream where fluid velocity is at its maximum and fluid

static pressure and the cross-sectional area are at their minimum. In a control valve, the vena

contracta normally occurs just downstream of the actual physical restriction.

Controller: A device that operates automatically to regulate a controlled variable.

Feedback Signal: The return signal that results from a measurement of the directly controlled

variable. For a control valve with a positioner, the return signal is usually a mechanical

indication of closure member stem position that is fed back into the positioner.

39


40/52

Hunting: An undesirable oscillation of appreciable magnitude, prolonged after external stimuli

disappear. Sometimes called cycling or limit cycle, hunting is evidence of operation at or near

the stability limit. In control valve applications, hunting would appear as an oscillation in the

loading pressure to the actuator caused by instability in the control system or the valve

positioner.

Repeatability: The closeness of agreement among a number of consecutive measurements of the

output for the same value of the input under the same operating conditions, approaching from the

same direction, for full range traverses. It is usually measured as a non-repeatability and

expressed as repeatability in percent of span.

Sensitivity: The ratio of the change in output magnitude to the change of the input that causes it

after the steady-state has been reached.

Signal: A physical variable, one or more parameters of which carry information about another

variable the signal represents. (Broiles Tega, Basic Instrumentation handbook, U.S.A., 2006)

40


41/52

CHAPTER 4

CONSTRUCTION AND TESTING

4.0 INTRODUCTION

The focus of this chapter will be on the precaution observed, construction details, performance

evaluation, testing and results obtained during the course of the construction of this project.

4.1 PRECAUTIONS

During the construction of this project, various precautionary measures were observed to ensure

the safety of both the personnel and the components. Some of these precaution are listed below.

Ensure proper electrical isolation is done before terminating any point.

When drilling, cutting and bending, the work has to be fastened on a vice.

Before testing or using any component, its capacity (voltage, current, power) is

confirmed.

During soldering of component on the board, a good temperature is maintained in order

to prevent the damage of any of the temperature sensitive components, ICs and

transistors.

Finally, the workshop was well ventilated and rid of hazards.

4.2 CONSTRUCTION

Individual functional blocks were constructed separately and then coupled together. This method

enhanced the overall efficiency of the project work because it made testing and fault isolation

easier and accurate.

The circuit was first produced and tested in a circuit maker before transferring the circuit onto a

bread board. The components were soldered correctly as shown in the circuit diagram. The

41


42/52

outputs of the circuit were terminated out using single 0.5mm signal cable. The circuit was

screwed on the casing of the project.

The electric motor was mounted on a support/base constructed using Perspex glass. It was firmly

screwed to the base to prevent any external movement as a result of vibration. More so, the valve

assembly was adequately supported to avoid any vibration.

It is important to note that vibration is not totally eradicated by firm support but reduced.

Ensuring a proper meshing of the gear wheels is a necessary part for effective motion transfer.

Firm connections using nuts were made at the drive and driven ends of the gear wheels. By this

no wobbling was observed.

Supports were also constructed for the reed switches suspended at the top of the valve spindle. A

magnet was glued to the surface of the gear wheel attached to the valve spindle. So that when it

rotates, the magnet passes each reed switch.

A frame was constructed to serve the purpose of a casing and a general support for all the

interconnected functional blocks. This was achieved using a Perspex glass.

4.3 PERFORMANCE EVALUATION & TESTING.

42


43/52

Numerous test were conducted first on the individual functional blocks and then an overall

performance evaluation was deduced. Detailed below are the tests carried out.

Test on the power supply unit

Test on the servo motor

Test on the reed switch sensors

Test on the amplifier circuit

Test on the control switches

Test on the PIC

Test on the PIC for output voltage of 5v

Test on transformer

Test on the power supply unit

By design the power supply unit is to supply the circuit with two levels of voltage, these are; a 5v

regulated voltage and 12v unregulated voltage. After construction, the circuit was tested with a

220v AC supply which is stepped down to 12v. A 5v regulated voltage and 12v unregulated

voltage was produced respectively at the outputs. Power supply unit was confirmed ok.

Test on the servo motor

The servo motor is a 12v operated motor. A 12v supply was injected to the terminals of the

motor and it was tested for servo action by interchanging the input at the terminal. At the first

connection ( + -), the motor ran in the clockwise direction. When input was reversed (- +), the

motor rotated in the anti-clockwise direction. Test was successful.

Test on the reed switch sensors.

The reed switch sensors are magnetic switches i.e they operate

under the influence of a magnet . An ohmmeter was connected at the terminal of the reed switch

to test for continuity. At start (without a magnet), the switch was not continuous (open). When a

43


44/52

magnet was moved to the vicinity of the reed switch, it became continuous (close). This verifies

that the reed switch responds as appropriately expected.

Test on the amplifier circuit

The amplifier circuit is meant to amplify the signal coming from the PIC to a working signal to

be able to provide enough power to power the motor. A 5v supply was connected at the terminals

of the amplifier circuit and the output was also connected to the motor. When connections were

established, the electric motor coupled to the valve operated smoothly. Test ok.

Test on the control switches

Test on control switches was successful, however one failed and was replaced. It was tested for

continuity at depressed state.

Test on the PIC

Test on the PIC was done using a programming software in a computer and it confirms that the

PIC was okay with no memory problems. The memory was cleared and a simulation program

was used to check the functionality of the PIC. Few adjustment were made to the program and

the test on the PIC was ok. The input voltage test was successful as 5v was seen using an

Avometre.

Test on transformer

Test for shorting and expected voltage at the secondary of the transformer was successful. 220v

ac was connected to the primary terminal and a 24v ac was read at the secondary side of the

transformer using an Avometre.

4.4 DISCUSSION OF RESULTS

From above, it is obvious that the test result is okay however among the result obtained only one

control switch failed it test, when sort to replace it, was no longer available in the market so an

44


45/52

improvised one was gotten, tested and installed. After assemble of the entire constructed work, it

was tested and was found successful.

Below is the table of the test carried out and the result obtained from the various component of

the project.

Table 1:Test and result table

4.5 COST EVALUATION

The cost of components and construction is tabulated below.

45

S/N COMPONENT TEST CARRIED OUT RESULT

1 Power supply Tested with a 220v AC supplyProduced a regulated 5v and

unregulated 12v DC signal

2 Servo MotorTested with a 12v DC voltage and

input interchanged

Rotated clockwise with

normal input but anti-

clockwise with reversed

input

3 Reed Switch Tested for continuity with a magnet

contact open in the absence

of the magnet but closes inthe presence of a magnet

4 Amplifier circuitTested with a 5v input and connected

to the terminal of the motor

The motor rotated

appropriately

5 Control Switch Tested for continuity

Contact closed when

depressed but open when

otherwise

6 PICTested for program error and

memory status

Program ran successfully and

5v output verified


46/52

Table 2: Cost estimation

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.0 INTRODUCTION

46

S/N COMPONENT QTY PRICE

1 PIC 16F628 1

2 Resistors 15

3 Capacitors 9

4 IC 7805 1

5 Transistors 10

6 Transformer 17 Diodes 3

8 Flip switch 1

9 Reed switches 4

10 Push buttons 5

11 Oscillator 1

12 Electric motor 1

13 Gear wheels 4

14 Perspex glass 1 yard

15 Slide valve 1

16Screws, nuts and bolts

TOTAL

1500

200

300200

1000

300100

20

400

250

100

200

100

700

500

200

6870


47/52

This chapter states the aim and significance, limitations, conclusion and

recommendations of this project work.

5.1 APPLICATION

The project was carried out because of the great importance of a

electronically actuated control valve in the petrochemical industry and the

need to design an intrinsically safe final control element so as to meet the

marketing challenges

5.2 LIMITATIONS

Like every other work project, this project was not without constraints that

posed challenges to the optimum actualisation of the design structure. The

motor movement was not properly detected by the reed switch due to

vibration during operation, there by sending an incorrect position of the PIC.

This leads to error. After several operation, Slip is experienced in the motor

belt leading to non response of the valve. Gears jamming cause jerking and

non response. This is due to inability to reduce vibration.

5.3 CONCLUSION

This project Design and construction of a microprocessor based remote

control valve for industrial application is a step towards the enhancement of

control processes in industries. It describes a small loop which when

implemented on a large scale will improve the control system. This project

has not only achieved its aim but has also provided room for advancement if

the limitations are corrected and recommendations implemented.

5.2 RECOMMENDATION

47


48/52

This project is controlled with the use of switch by the operator in a control

room but a fully automated version can be achieved if valve is controlled

based on the set point from a controlled variable. More so, it would be a

great improvement if a display module is incorporated as a read out for the

position of the valve.

48


49/52

APPENDIX

TMR0 EQU 01HPORTA EQU 05H

TRISAEQU 85H

PORTB EQU 06H

TRISBEQU 86H

STATUS EQU 03HOPT EQU 81H

INTCON EQU 0BHSTATE EQU 10H

TIMER EQU 11H

COUNTER1 EQU 12HCOUNTER2 EQU 13H

LIST P=16F84

ORG 0

NOPNOP

NOPGOTO START

INT

BCF INTCON,2

DECFSZ COUNTER1,FRETFIE

INCF COUNTER2,F

BTFSSCOUNTER2,4RETFIE

BSF TIMER,0

RETFIE

CLEARCLRF TMR0

CLRF COUNTER1

CLRF COUNTER2CLRF TIMER

RETURN

OFFCALL CLEAR

CLRF STATE

OFF1

MOVLW 0X40

MOVWF PORTBBTFSC TIMER,0

GOTO OFF2BTFSSPORTA,1

CALL CLEAR

BTFSSPORTA,2CALL CLEAR

BTFSSPORTA,3

CALL CLEARGOTO OFF1

OFF2

49


50/52

CLRF PORTB

RETURN

ONGENMOVLW 0X20

MOVWF PORTB

ONGEN1

BTFSC PORTA,1

GOTO ONGEN1ONGEN2

BTFSC PORTA,0GOTO ONGEN2

CLRF PORTB

RETURNOFFGEN

MOVLW 0X40

MOVWF PORTB

OFFGEN1BTFSC PORTA,3

GOTO OFFGEN1OFFGEN2

BTFSC PORTA,0

GOTO OFFGEN2

CLRF PORTBRETURN

ONE

MOVFSTATE,WBTFSC STATUS,2

GOTO ONE1

MOVFSTATE,W

SUBLW 0X02BTFSC STATUS,2

GOTO ONE3

MOVFSTATE,WSUBLW 0X03

BTFSC STATUS,2

GOTO ONE4MOVFSTATE,W

SUBLW 0X04

BTFSC STATUS,2

GOTO ONE5

RETURNONE1

MOVLW 0X01MOVWF STATE

CALL ONGEN

GOTO ONGENONE3

MOVLW 0X01

MOVWF STATECALL OFFGEN

GOTO OFFGEN

50


51/52

ONE4

MOVLW 0X01


CALL OFFGEN

CALL OFFGEN

GOTO OFFGEN

ONE5MOVLW 0X01


CALL OFFGEN

CALL OFFGENCALL OFFGEN

CALL OFFGEN

GOTO OFFGEN

STARTBANKSEL TRISB

MOVLW 0X1FMOVWF TRISBCLRF OPT

BANKSEL PORTA

CLRF PORTACLRF PORTB

MOVLW 0XA0

MOVWF INTCONCALL OFF

REDO

BTFSSPORTB,0

NOPBTFSSPORTB,1

CALL ONE

BTFSSPORTB,2NOP

BTFSSPORTB,3

NOPBTFSSPORTB,4

NOP

GOTO REDO

END

51


52/52

REFERENCES

(1) Tony Kuphaldt: Lessons in Industrial Instrumentation, Version 1.12, 2010

(2) Emerson Process Management, Control Valve Handbook, fourth edition, U.S.A., 2005

(3) Newnes Power Engineering Series, Power Electronic Control in Electrical System,

Oxford, 2002

(4) Oladigbolu Abideen, Design and construction of a motorized valve, B.Eng (Electrical)

University of Ibadan, Ibadan, 2005.

(5) Dr. Fred .O., The role of control in process engineering, Asian Oil Journal, 2003.

(6) Michigan Science Fare, Design and construction of a PIC controlled crankshaft, 2005.

(7) http://www.howstuffworks.com

(8) http://www.wikipedia.com

Car Park Space Management

Documents

Transcript of Car Park Space Management