To PRINT Boiler Automation of Temperature, Water Level Monitoring & Control System Using PLC

8/7/2019 To PRINT Boiler Automation of Temperature, Water Level Monitoring & Control System Using PLC

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ABSTRACT

A Boiler or steam generator is employed wherever a source of system is required.

A boiler incorporates a firebox or furnace in order to burn the fuel and generate

heat; The heat is initially transferred to water to make steam; this produces

saturated steam at ebullition temperature. Higher the furnace temperature, faster

the steam production. The saturated steam thus produced can then either be used

immediately to produce power via a turbine and alternator, or else may be further

superheated to a higher temperature; This notably reduces suspended water content

making a given volume of steam produce more work.

In this paper, we propose the parameters like the temperature of the steam, the

level of water, control of feed water pump, Pressure of the steam has to be

measured and critically monitored for reliable and safe operation of the generation

unit. This kind of operation with critical importance can be carried out efficiently

and implemented employing Programmable Logic Controller (PLC).Experimental

results are presented.

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LIST OF TABLES

Table No. Name of Table Page No.

3.1 Definition Of Sensor 10

Level sensor

Pressure sensor

Temperature sensor

3.2 Features of sensor 12

Level sensor

Pressure sensor

Temperature sensor

4.1 DIFFERENT SECTIONS OF THE PROJECT: 20

Boiler Section

Controlling Section

Water Supply Section

Power Supply Section

4.2 STAGES OF PROJECT DESIGN 21

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LIST OF FIGURES

Figure No. Name of the Figure Page no.

1.1 Overall Block Diagram 06

3.1 PIR sensors 114.1 Microcontroller 14

4.2 40 lead PDIP 17

4.3 Internal Block Diagram 18

4.4 ADC 26

4.5 ADC (interfacing with 28

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1. INTRODUCTION

Programmable Logic Controls can provide the right solution at the right time.Using the PLC can extend your performance gains across the business with, theonly integrated control and information platform that runs discrete, motion, drives,

process and safety control, assuring the different automation technologies worktogether. While using PLC the entire manufacturing cycle will be simple andpower full technology.

In this system we have to measure load with the help of CT (in case of AC/DCMotor) or PT (in case of Steam Turbine/ Hydraulic drive) & water is measure byThe Water Flow Meter & all above input are feed to PLC. Controller is calculatingwith input & set point. On the controllers output Control valve will be operating &you will find the actual result as per you get.

In this project the water level of the boiler tank is monitored with the aid of ananalog interface with the Programmable logic controller (PLC).The level is thencontrolled by controlling the feed water input which is affected on a DC motor.The temperature in the same way is measured using a temperature sensor and themeasured analog value is interfaced with the PLC. The response given by the PLCto control the temperature is carried out by controlling the induction heater. Thecontrol action required to stabilize the temperature and the level within the safelimits can be effectively optimized by using Programmable Logic Controller(PLC).Thus the boiler management system is designed in this project using PLC.

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1.1 BLOCK DIAGRAM:

Figure 1.1 Overall Block Diagram.

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PressureSensor

ProgrammableLogic Controller

Liquid Level

Sensor

TemperatureSensor

Buzzer

PowerSupply

PowerSupply

DC Motor


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2. VOLATILE ORGANIC COMPOUNDS

2.1 DEFINITION

Volatile organic compounds (VOCs) refer to organic chemical compounds whichhave significant vapor pressures and which can affect the environment and humanhealth. VOCs are numerous, varied, and ubiquitous. Although VOCs include bothman-made and naturally occurring chemical compounds, it is the anthropogenicVOCs that are regulated, especially for indoors where concentrations can behighest. VOCs are typically not acutely toxic but have chronic effects. Because theconcentrations are usually low and the symptoms slow to develop, analysis of

VOCs and their effects is a demanding area.

2.2 Biologically derived VOCsThe majority of VOCs arise from plants. An estimated 1150 Tg C/yr (Tg = 1012

grams) are produced annually by plants, the main constituent being isoprene. Thisvalue excludes biogenic methane. Anthropogenic (human produced) emissions areabout 10% of the biological level. One indication of this flux is the strong odoremitted by many plants. The emissions are affected by a variety of factors, such as

temperature, which determines rates of volatilization and growth, and sunlight,which determines rates of biosynthesis. Emission occurs almost exclusively fromthe leaves, the stomata in particular. A major class of VOCs are terpenes, such asmyrcene. Providing a sense of scale, a forest 62,000 km2 in area (the U.S. state ofPennsylvania) is estimated to emit 3,400,000 kilograms of terpenes on a typicalAugust day during the growing season. Induction of genes producing volatileorganic compounds and subsequent increase in volatile terpenes has been achievedin maize using (Z)-3-Hexen-1-ol and other plant hormones.

2.3 Health risks

Respiratory, allergic, or immune effects in infants or children are associated withman-made VOCs and other indoor or outdoor air pollutants.

Some VOCs, such as styrene and limonene, can react with nitrogen oxides or withozone to produce new oxidation products and secondary aerosols, which can cause

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sensory irritation symptoms. Unspecified VOCs are important in the creation ofsmog.

Health effects include:

Eye, nose, and throat irritation; headaches, loss of coordination, nausea;damage to liver, kidney, and central nervous system. Some organics cancause cancer in animals; some are suspected or known to cause cancer inhumans. Key signs or symptoms associated with exposure to VOCs includeconjunctival irritation, nose and throat discomfort, headache, allergic skinreaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis,epistaxis, fatigue, dizziness.The ability of organic chemicals to cause health effects varies greatly fromthose that are highly toxic, to those with no known health effect. As with

other pollutants, the extent and nature of the health effect will depend onmany factors including level of exposure and length of time exposed. Eyeand respiratory tract irritation, headaches, dizziness, visual disorders, andmemory impairment are among the immediate symptoms that some peoplehave experienced soon after exposure to some organics. At present, notmuch is known about what health effects occur from the levels of organicsusually found in homes. Many organic compounds are known to causecancer in animals; some are suspected of causing, or are known to cause,cancer in humans.

2.4 VOCs Sensors

VOCs in the environment or certain atmospheres can be detected based in different

principles and interactions between the organic compounds and the sensor

components. There are electronic devices that can detect ppm concentrations

despite the non-selectivity. Others can predict with reasonable accuracy the

molecular structure of the volatile organic compounds in the environment orenclosed atmospheres and could be used as accurate monitors of the Chemical

Fingerprint and further as health monitoring devices.

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3 PIR SENSOR

3.1 General Description

The PIR (Passive Infra-Red) Sensor is a pyroelectric device that detectsmotion by measuring changes in the infrared levels emitted by surrounding objects.This motion can be detected by checking for a high signal on a single I/O pin.

3.2 Features

Single bit output Small size makes it easy to conceal Compatible with all Parallax microcontrollers

3.3 Application Ideas

Alarm Systems Halloween Props

Robotics

3.4 Theory of Operation

Pyroelectric devices, such as the PIR sensor, have elements made of a crystallinematerial that generates an electric charge when exposed to infrared radiation. Thechanges in the amount of infrared striking the element change the voltagesgenerated, which are measured by an on-board amplifier. The device contains aspecial filter called a Fresnel lens, which focuses the infrared signals onto the

element. As the ambient infrared signals change rapidly, the on-board amplifiertrips the output to indicate motion.

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3.5 Pin Definitions and Ratings

Pin Name Function

- GND Connects to Ground or Vss

+ V+ Connects to +5 VDCor Vdd

OUT Output Connects to an I/O pin

set to INPUT modeTable 3.1 pin def. & ratings of PIR sensor.

3.6 Connecting and Testing

Connect the 3-pin header to your circuit so that the minus (-) pin connects toground or Vss, the plus (+) pin connects to +5 volts or Vdd and the OUT pinconnects to your microcontrollers I/O pin. One easy way to do this would be touse a standard servo/LCD extension cable, available separately from Parallax

(#805-00002). This cable makes it easy to plug sensor into the servo headers onour Board Of Education or Professional Development Board. If you use the BoardOf Education, be sure the servo voltage jumper (located between the 2 servoheader blocks) is in the Vdd position, not Vin. If you do not have this jumper onyour board you should manually connect to Vdd through the breadboard.

You may also plug the sensor directly into the edge of the breadboard and connectthe signals from there. Remember the position of the pins when you plug thesensor into the breadboard.

Once the sensor warms up (settles) the output will remain low until there is motion,at which time the output will swing high for a couple of seconds, then return low.If motion continues the output will cycle in this manner until the sensors line ofsight of still again.

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3.7 Calibration

The PIR Sensor requires a warm-up time in order to function properly. This isdue to the settling time involved in learning its environment. This could beanywhere from 10-60 seconds. During this time there should be as little motion aspossible in the sensors field of view.

3.8 Sensitivity

The PIR Sensor has a range of approximately 20 feet. This can vary withenvironmental conditions. The sensor is designed to adjust to slowly changing

conditions that would happen normally as the day progresses and theenvironmental conditions change, but responds by toggling its output when suddenchanges occur, such as when there is motion

PIR SENSOR

Figure 3.1 PIR sensors

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FEATURES:-

S.NO. PARAMETER VALUE

1 Power source 220-240V/AC,100-130V/AC

2 Rated load 100W(max.)

3 Detection distance 8m(max.


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4 HARDWARE REQUIREMENTS

Microcontroller

PIR

ADC

Buzzer

PC

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4.1 MICROCONTROLLER:-

Figure 4.1 Microcontroller interfacing with the sub-components.

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AT89s52 Microcontroller:

Features:

Compatible with MCS-51 Products 8K Bytes of In-System Programmable (ISP) Flash

Memory

Endurance: 1000 Write/Erase Cycles 4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Full Duplex UART Serial Channel

Low-power Idle and Power-down Modes

Interrupt Recovery from Power-down Mode

Watchdog Timer

Dual Data Pointer

Power-off Flag

Fast Programming Time

Flexible ISP Programming (Byte and Page Mode) Green (Pb/Halide-free) Packaging Option

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Figure 4.2 Pin Diagram for 40-lead PDIP Microcontroller.

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Figure 4.3 Architecture of Microcontroller.

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Pin Description

VCC Supply voltage.

GND Ground.

Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. Asan output port, each pin can sink eight TTL inputs. When1s are written to port 0 pins, the pins can be used ashigh-impedance inputs. Port 0 can also be configured to

be the multiplexed low-order address/data bus duringaccesses to external program and data memory. In thismode, P0 has internal pull-ups. Port 0 also receives thecode bytes during Flash programming and outputs thecode bytes during program verification. External pull-ups are required during program verification.

Port 1

Port 1 is an 8-bit bidirectional I/O port with internalpull-ups. The Port 1 output buffers can sink/source fourTTL inputs. When 1s are written to Port 1 pins, they arepulled high by the inter-nal pull-ups and can be used asinputs. As inputs, Port 1 pins that are externally beingpulled low will source current (IIL) because of the internalpull-ups. In addition, P1.0 and P1.1 can be configured tobe the timer/counter 2 external count input (P1.0/T2) andthe timer/counter 2 trigger input (P1.1/T2EX),respectively, as shown in the following table. Port 1 alsoreceives the low-order address bytes during Flashprogramming and verification.

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System Programming) P1.7 SCK (used for In-SystemProgramming)

Port 3

Port 3 is an 8-bit bidirectional I/O port with internalpull-ups. The Port 3 output buffers can sink/source fourTTL inputs. When 1s are written to Port 3 pins, they are

pulled high by the internal pull-ups and can be used asinputs. As inputs, Port 3 pins that are externally beingpulled low will source current (IIL) because of the pull-ups. Port 3 receives some control signals for Flashprogramming and verification. Port 3 also serves thefunctions of various special features of the AT89S52, asshown in the following table.

Table 4.2 Alternate Functions of Port 3 of Microcontroller.

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RST

Reset input. A high on this pin for two machinecycles while the oscillator is running resets the device.

This pin drives high for 98 oscillator periods after theWatchdog times out. The DISRTO bit in SFR AUXR(address 8EH) can be used to disable this feature. In thedefault state of bit DISRTO, the RESET HIGH out feature isenabled.

ALE/PROG

Address Latch Enable (ALE) is an output pulse forlatching the low byte of the address during accesses toexternal memory. This pin is also the program pulse input(PROG) during Flash programming. In normal operation,ALE is emitted at a constant rate of 1/6 the oscillatorfrequency and may be used for external timing or

clocking purposes. Note, however, that one ALE pulse isskipped during each access to external data memory. Ifdesired, ALE operation can be disabled by setting bit 0 ofSFR location 8EH. With the bit set, ALE is active onlyduring a MOVX or MOVC instruction. Otherwise, the pin isweakly pulled high. Setting the ALE-disable bit has noeffect if the microcontroller is in external execution mode.

PSEN

Program Store Enable (PSEN) is the read strobe toexternal program memory. When the AT89S52 isexecuting code from external program memory, PSEN isactivated twice each machine cycle, except that two

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PSEN activations are skipped during each access toexternal data memory.

EA/VPP

External Access Enable. EA must be strapped to GNDin order to enable the device to fetch code from externalprogram memory locations starting at 0000H up toFFFFH. Note, however, that if lock bit 1 is programmed,EA will be internally latched on reset. EA should bestrapped to VCC for internal program executions. This pinalso receives the 12-volt programming enable voltage

(VPP) during Flash programming.

XTAL1

Input to the inverting oscillator amplifier and inputto the internal clock operating circuit.

XTAL2

Output from the inverting , oscillator amplifier.

Memory Organization

MCS-51 devices have a separate address space for

Program and Data Memory. Up to 64K bytes each ofexternal Program and Data Memory can be addressed.

Program Memory

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If the EA pin is connected to GND, all programfetches are directed to external memory. On theAT89S52, if EA is connected to VCC, program fetches toaddresses 0000H through 1FFFH are directed to internal

memory and fetches to addresses 2000H through FFFFHare to external memory.

Data Memory

The AT89S52 implements 256 bytes of on-chip RAM.The upper 128 bytes occupy a parallel address space tothe Special Function Registers. This means that the upper

128 bytes have the same addresses as the SFR space butare physically separate from SFR space. When aninstruction accesses an internal location above address7FH, the address mode used in the instruction specifieswhether the CPU accesses the upper 128 bytes of RAM orthe SFR space. Instructions which use direct addressingaccess the SFR space. For example, the following directaddressing instruction accesses the SFR at location 0A0H

(which is P2). MOV 0A0H, #data Instructions that useindirect addressing access the upper 128 bytes of RAM.For example, the following indirect addressing instruction,where R0 contains 0A0H, accesses the data byte ataddress 0A0H, rather than P2 (whose address is 0A0H).MOV @R0, #data Note that stack operations areexamples of indirect addressing, so the upper 128 bytesof data RAM are available as stack space.

Watchdog Timer (One-time Enabled with Reset-out)

The WDT is intended as a recovery method insituations where the CPU may be subjected to softwareupsets. The WDT consists of a 14-bit counter and the

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Watchdog Timer Reset (WDTRST) SFR. The WDT isdefaulted to disable from exiting reset. To enable theWDT, a user must write 01EH and 0E1H in sequence tothe WDTRST register (SFR location 0A6H). When the WDT

is enabled, it will increment every machine cycle whilethe oscillator is running. The WDT timeout period isdependent on the external clock frequency. There is noway to disable the WDT except through reset (eitherhardware reset or WDT overflow reset). When WDT over-flows, it will drive an output RESET HIGH pulse at the RSTpin.

Using the WDT

To enable the WDT, a user must write 01EH and0E1H in sequence to the WDTRST register (SFR location0A6H). When the WDT is enabled, the user needs toservice it by writing 01EH and 0E1H to WDTRST to avoida WDT overflow. The 14-bit counter overflows when itreaches 16383 (3FFFH), and this will reset the device.

When the WDT is enabled, it will increment everymachine cycle while the oscillator is running. This meansthe user must reset the WDT at least every 16383machine cycles. To reset the WDT the user must write01EH and 0E1H to WDTRST. WDTRST is a write-onlyregister. The WDT counter cannot be read or written.When WDT overflows, it will generate an output RESETpulse at the RST pin. The RESET pulse duration is

98xTOSC, where TOSC = 1/FOSC. To make the best useof the WDT, it should be serviced in those sections ofcode that will periodically be executed within the timerequired to prevent a WDT reset.

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WDT during Power-down and Idle

In Power-down mode the oscillator stops, whichmeans the WDT also stops. While in Power-down mode,the user does not need to service the WDT. There are twomethods of exiting Power-down mode: by a hardwarereset or via a level-activated external interrupt which isenabled prior to entering Power-down mode. When

Power-down is exited with hardware reset, servicing theWDT should occur as it normally does whenever theAT89S52 is reset. Exiting Power-down with an interrupt issignificantly different. The interrupt is held low longenough for the oscillator to stabilize. When the interruptis brought high, the interrupt is serviced. To prevent theWDT from resetting the device while the interrupt pin isheld low, the WDT is not started until the interrupt is

pulled high. It is suggested that the WDT be reset duringthe interrupt service for the interrupt used to exit Power-down mode. To ensure that the WDT does not overflowwithin a few states of exiting Power-down, it is best toreset the WDT just before entering Power-down mode.Before going into the IDLE mode, the WDIDLE bit in SFRAUXR is used to determine whether the WDT continues tocount if enabled. The WDT keeps counting during IDLE

(WDIDLE bit = 0) as the default state. To prevent theWDT from resetting the AT89S52 while in IDLE mode, theuser should always set up a timer that will periodicallyexit IDLE, service the WDT, and reenter IDLE mode. WithWDIDLE bit enabled, the WDT will stop to count in IDLEmode and resumes the count upon exit from IDLE.

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4.2 ADC

Figure 4.4 Interfacing ADC with other components of the system.

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ADC 0808/0809:

General Description

The ADC0808, ADC0809 data acquisition componentis a monolithic CMOS device with an 8-bit analog-to-digital converter, 8-channel multiplexer andmicroprocessor compatible control logic. The 8-bit A/Dconverter uses successive approximation as theconversion technique. The converter features a highimpedance chopper stabilized comparator, a 256Rvoltage divider with analog switch tree and a successive

approximation register. The 8-channel multiplexer candirectly access any of 8-single-ended analog signals. Thedevice eliminates the need for external zero and full-scaleadjustments. Easy interfacing to microprocessors isprovided by the latched and decoded multiplexer addressinputs and latched TTL TRI-STATE outputs. The designof the ADC0808, ADC0809 has been optimized byincorporating the most desirable aspects of several A/D

conversion techniques. The ADC0808, ADC0809 offershigh speed, high accuracy, minimal temperaturedependence, excellent long-term accuracy andrepeatability, and consumes minimal power. Thesefeatures make this device ideally suited to applicationsfrom process and machine control to consumer andautomotive applications. For 16-channel multiplexer withcommon output (sample/hold port) see ADC0816 data

sheet. (See AN-247 for more information.)

Features

Easy interface to all microprocessors

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Figure 4.5 ADC Block Diagram.

Pin Diagram:

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Figure 4.6 Pin Diagram for ADC.

Functional Description:

Multiplexer:

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The device contains an 8-channel single-endedanalog signal multiplexer. A particular input channel isselected by using the address decoder. Table 1 shows the

input states for the address lines to select any channel.The address is latched into the decoder on the low-to-high transition of the address latch enable signal.

Table 4.3 Channel Selection for 8-channel MUX.

4.3 BUZZER

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Figure 4.7 Buzzer.

A buzzer or beeper (BUZZERS)is a signaling device, usually electronic,typically used in automobiles, household appliances such as a microwave oven, orgame shows. It most commonly consists of a number of switches or sensorsconnected to a control unit that determines if and which button was pushed or apreset time has lapsed, and usually illuminates a light on the appropriate button orcontrol panel, and sounds a warning in the form of a continuous or intermittentbuzzing or beeping sound. Initially this device was based on an electromechanicalsystem which was identical to an electric bell without the metal gong (whichmakes the ringing noise). Often these units were anchored to a wall or ceiling andused the ceiling or wall as a sounding board. Another implementation with someAC-connected devices was to implement a circuit to make the AC current into anoise loud enough to drive a loudspeaker and hook this circuit up to a cheap 8-ohmspeaker. Nowadays, it is more popular to use a ceramic-based piezoelectricsounder which makes a high-pitched tone. Usually these were hooked up to"driver" circuits which varied the pitch of the sound or pulsed the sound on and off.

Features Rated Frequency: 3,100Hz Operating Voltage: 3 - 20Vdc Current Consumption: 14mA @ 12Vdc Sound Pressure Level (30cm): 73dB @ 12Vdc

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http://www.innovision.us/Buzzers.htmhttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Microwave_ovenhttp://en.wikipedia.org/wiki/Game_showhttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Electric_bellhttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Microwave_ovenhttp://en.wikipedia.org/wiki/Game_showhttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Electric_bellhttp://en.wikipedia.org/wiki/Piezoelectrichttp://www.innovision.us/Buzzers.htm


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King State Buzzer - KPE-200 Dimensions: 22.5mm Diameter, 19mm High, 29mm between mounting holes

4.4 Voltage Regulator:

Figure 4.8 Voltage Regulator.Features:

Output Current up to 1A Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V Thermal Overload Protection Short Circuit Protection Output Transistor Safe Operating Area Protection

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Figure 4.9 Internal Block Diagram for Voltage Regulator.

Description:

The KA78XX/KA78XXA series of three-terminalpositive regulator are available in the TO-220/D-PAKpackage and with several fixed output voltages, makingthem useful in a wide range of applications. Each typeemploys internal current limiting, thermal shut down andsafe operating area protection, making it essentiallyindestructible. If adequate heat sinking is provided, theycan deliver over 1A output current. Although designed

primarily as fixed voltage regulators, these devices canbe used with external components to obtain adjustablevoltages and currents.

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constant circuit is added to discharge all the capacitors

quickly. To ensure the power supply a LED is connected

for indication purpose.

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OVERALL CIRCUIT DIAGRAM

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5 MARKOV MODEL OF DIGITAL APPROXIMATION

Once the wavelet coefficients are obtained ,a MM basedclassification procedure, similar to theone in [7], is carried outfor VOC gas leak detection. There are three types of events to beclassified: a walking person a gas leak and a no-activity event.Two three-state Markov models are used to model a VOC gas

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leak and a walking person. In the training step, two thresholdvalues are defined in the wavelet domain for each model, T1 < 0and T2 > 0.Since the wavelet signal is a zero mean signal, T2 =

T1.The same threshold values are used in each model. Let thethree states be S0, S1 and S2. States of wavelet coefficients aredefined as follows:

if (w[k] < T1)then state S0else if (T1 < w[k] < T2)then state S1

elsestate S2 is attained accordinglyend

Thresholds are defined such that the wavelet coefficientsof theno-activity event remain in state S1. The system is instate S1 aslong as there is not any significant activity in theviewing range

of the PIR sensor. Therefore, although thereare three events tobe classified, only two Markov models are used, one for awalking person and the other for a gasleak as shown in Figure 5.No-activity event is detected bycontrolling whether the systemremains in S1 or not.During the training phase, only the state transition probabilitiespa(i, j) and pb(i, j) are estimated for each model.During the

classification process, we only use two models Corresponding tothe VOC gas leak and walking person eventsas the systemmostly remains in state S1 when there is no activity,The statetransition probability, p(1, 1), is very close to1 and others areclose to 0. To decide the class affiliation ofa test signal, statevector and the corresponding number of

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Fig. 5.1 Markov models and state transition definitions for (a)VOC gas leak and (b) walking person classes

Transitions of the signal are determined. Let C be the statesequence of the test signal and tij be the number of transitionsFrom i th state to j th state. Then the probabilities forThe state sequence Cof belonging to gas leak and walkingpersonclasses are computed as follows:Pa,b(C) =Li=1pa,b(Ci+1|Ci) =2i=02j=0(pa,b(i, j))tij , (1)where L is the length of the state sequence Cof the test signal.During the classification phase, the state sequence of the

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test signal Cis divided into windows of length 25 and eachwindow is fed into the gas leak and the walking personmodels. The model yielding the highest probability is

determined and monitored at the end of each 4 seconds period,as the result of the analysis of PIR sensor data. To avoidmultiplications during classification, we use Eq. 2 instead ofEq.1.Pa,b(C) =2i=2j=0tij log10(pa,b(i, j)) (2)

Log values are obtained from a look-up table. The decisionAlgorithm is as follows:

ifPa(C) > Pb(C)Then the test window is affiliated with the gas leak classElseThe window is affiliated with the walking person classEndifptest(1, 1) > 0.8

The test window is affiliated to the no-activity classEnd

6 SOFTWARE REQUIREMENTS

1. EMBEDDED C2. Lab VEIW

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6.1 INTRODUCTION

The C programming language is perhaps the most popular programming language

for programming embedded systems.

Most C programmers are spoiled because they program in environments where notonly is there a standard library implementation, but there are frequently a numberof other libraries available for use. The cold fact is, that in embedded systems,there rarely are many of the libraries that programmers have grown used to, butoccasionally an embedded system might not have a complete standard library, ifthere is a standard library at all. Few embedded systems have capability fordynamic linking, so if standard library functions are to be available at all, theyoften need to be directly linked into the executable. Oftentimes, because of space

concerns, it is not possible to link in an entire library file, and programmers areoften forced to "brew their own" standard c library implementations if they want touse them at all. While some libraries are bulky and not well suited for use onmicrocontrollers, many development systems still include the standard librarieswhich are the most common for C programmers.

C remains a very popular language for micro-controller developers due to the codeefficiency and reduced overhead and development time. C offers low-level controland is considered more readable than assembly. Many free C compilers areavailable for a wide variety of development platforms. The compilers are part of an

IDEs with ICD support, breakpoints, single-stepping and an assembly window.The performance of C compilers has improved considerably in recent years, andthey are claimed to be more or less as good as assembly, depending on who youask. Most tools now offer options for customizing the compiler optimization.Additionally, using C increases portability, since C code can be compiled fordifferent types of processors.

EXAMPLE:

An example of using C to change a bit is below

Clearing Bits

PORTH &= 0xF5; // Changes bits 1 and 3 to zeros using C

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PORTH &= ~0x0A; // Same as above but using inverting the bit mask - easier to see which bitsare cleared

Setting Bits

PORTH |= 0x0A; // Set bits 1 and 3 to one using the OR

In assembly this would be

Clearing Bits

BCLR PORTH,$0A ;Changes bits 1 and 3 to zeros using 68HC12 ASM

Setting Bits

BSET PORTH,$0A ;Changes bits 1 and 3 to ones using 68HC12 ASM

Bit Fields

Bit fields are a topic that few C programmers have any experience with, although it

has been a standardized part of the language for some time now. Bit fields allow

the programmer to access memory in unaligned sections, or even insections smaller than a byte. Let us create an example:

struct _bitfield {flagA : 1;flagB : 1;nybbA : 4;byteA : 8;

}

The colon separates the name of the field from its size in bits, not bytes. Suddenly

it becomes very important to know what numbers can fit inside fields of what

length. For instance, the flagA and flagB fields are both 1 bit, so they can only hold

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boolean values (1 or 0). the nybbA field can hold 4 bits, for a maximum value of

15 (one hexadecimal digit).

fields in a bitfield can be addressed exactly like regular structures. For instance, thefollowing statements are all valid:

struct _bitfield field;field.flagA = 1;field.flagB = 0;field.nybbA = 0x0A;field.byteA = 255;

The individual fields in a bit field do not take storage types, because you aremanually defining how many bits each field takes. I wish that's how Richie had

done it. However, I'm pretty sure that:Each bit fieldrequires a storage type such

as "unsigned". However, the fields in a bitfield may be qualified with the

keywords "signed" or "unsigned", although "signed" is implied, if neither is

specified.

If a 1-bit field is marked as signed, it has values of +1 and 0

It is important to note that different compilers may order the fields differently in a

bitfield, so the programmer should never attempt to access the bitfield as an integerobject. Without trial and error testing on your individual compiler, it is impossible

to know what order the fields in your bitfield will be in.

Also bitfields are aligned, like any other data object on agiven machine, to a certain boundary.

C COMPILERS FOR EMBEDDED SYSTEMS

Perhaps the biggest difference between C compilers for embedded systems and C

compilers for desktop computers is the distinction between the "platform" and the

"target". The "platform" is where the C compiler runs -- perhaps a laptop running

Linux or a desktop running Windows. The "target" is where the executable code

generated by the C compiler will run -- the CPU in the embedded system, often

without any underlying operating system.

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The GCC compiler is the most popular C compiler for embedded systems. GCC

was originally developed for 32-bit Princeton architecture CPUs. So it was

relatively easily ported to target ARM core microcontrollers such as XScale and

Atmel AT91RM9200; Atmel AVR32 AP7 family; MIPS core microcontrollerssuch as the Microchip PIC32; and Freescale 68k/ColdFire processors.

The people who write compilers have also (with more difficulty) ported GCC to

target the Texas Instruments MSP430 16-bit MCUs; the Microchip PIC24 and

dsPIC 16-bit Microcontrollers; the 8-bit Atmel AVR microcontrollers; the 8-bit

Freescale 68HC11 microcontrollers.

Other microcontrollers are very different from a 32-bit Princeton architecture CPU.

Many compiler writers have decided it would be better to develop an independent

C compiler rather than try to force the round peg of GCC into the square hole of 8-

bit Harvard architecture microcontroller targets:

SDCC - Small Device C Compiler for the Intel 8051, Maxim 80DS390, Zilog Z80,

Motorola 68HC08, Microchip PIC16, Microchip

There are some highly respected companies that sell commercial C compilers. You

can find such a commercial C compiler for practically every microcontroller,

including the above-listed microcontrollers. Popular microcontrollers not already

listed (i.e., microcontrollers for which the only known C compiler is a commercial

C compiler) include the Cypress M8C MCUs; Microchip PIC10 and Microchip

PIC12 MCUs; etc

SPECIAL FEATURES:

The C language is standardized, and there are a certain number of operators

available that everybody knows and loves. However, many microprocessors have

capabilities that are either beyond what C can do, or are faster than the way C does

it. For instance, the 8051 and PIC microcontrollers both have assembly instructionsfor setting and checking individual bits in a byte. C can affect bits individually

using clunky structures known as "bit fields", but bit field implementations are

rarely as fast as the bit-at-a-time operations on some microprocessors.

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Bit Fields

Bit fields are a topic that few C programmers have any experience with, although it

has been a standardized part of the language for some time now. Bit fields allow

the programmer to access memory in unaligned sections, or even in

sections smaller than a byte. Let us create an example:

struct _bitfield {flagA : 1;flagB : 1;nybbA : 4;byteA : 8;

}

The colon separates the name of the field from its size in bits, not bytes. Suddenly

it becomes very important to know what numbers can fit inside fields of what

length. For instance, the flagA and flagB fields are both 1 bit, so they can only hold

boolean values (1 or 0). the nybbA field can hold 4 bits, for a maximum value of

15 (one hexadecimal digit).

fields in a bitfield can be addressed exactly like regular structures. For instance, the

following statements are all valid:

struct _bitfield field;field.flagA = 1;field.flagB = 0;field.nybbA = 0x0A;field.byteA = 255;

The individual fields in a bit field do not take storage types, because you are

manually defining how many bits each field takes. I wish that's how Richie had

done it. However, I'm pretty sure that:Each bit fieldrequires a storage type such

as "unsigned". However, the fields in a bitfield may be qualified with thekeywords "signed" or "unsigned", although "signed" is implied, if neither is

specified.

If a 1-bit field is marked as signed, it has values of +1 and 0 .It is important to note

that different compilers may order the fields differently in a bitfield, so the

programmer should never attempt to access the bitfield as an integer object.

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Without trial and error testing on your individual compiler, it is impossible to

know what order the fields in your bitfield will be in.

Also bitfields are aligned, like any other data object on a given machine, to a

certain boundary.

const

A "const" in a variable declaration is a promise by the programmer who wrote it

that the program will not alter the variable's value.

There are 2 slightly different reasons "const" is used in embedded systems.

One reason is the same as in desktop applications:

Often a structure, array, or string is passed to a function using a pointer. When thatargument is described as "const", such as when a header file says

void print_string( char const * the_string );

, it is a promise by the programmer who wrote that function that the function will

not modify any items in the structure, array, or string. (If that header file is

properly #included in the file that implements that function, then the compiler will

check that promise when that implementation is compiled, and give an error if that

promise is violated).

On a desktop application, such a program would compile to exactly the same

executable if all the "const" declarations were deleted from the source code -- but

then the compiler would not check the promises.

When some other programmer has an important piece of data he wants to pass tothat function, he can be sure simply by reading the header file that that functionwill not modify those items. Without that "const", he would either have to gothrough the source code of the function implementation to make sure his data isn't

modified (and worry about the possibility that the next update to thatimplementation might modify that data), or else make a temporary copy of the datato pass to that function, keeping the original version unmodified.

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6.2 LabVIEW

Lab VIEW is a program development application, much like various commercial Cor BASIC development systems, or National Instruments LabWindows.However,Lab VIEW is different from those applications in one important respect. Otherprogramming systems use text-basedlanguages to create lines of code,while LabVIEW uses a Graphical programming language , to create programs in blockdiagram form.You can use Lab VIEW with little programming experience. Lab VIEW usesterminology, icons, and ideas familiar to scientists and engineers and relies ongraphical symbols rather than textual language to describe programming actions.Lab VIEW has extensive libraries of functions and subroutines for mostprogramming tasks. For Windows, Macintosh, and Sun, Lab VIEW containsapplication specific libraries for data acquisition and VXI instrument control. LabVIEW also contains application-specific libraries for GPIB and serial instrumentcontrol, data analysis, data presentation, and data storage.LabVIEW includesconventional program development tools, so you can set breakpoints, animateprogram execution to see how data passes through the program, andSingle-step through the program to make debugging and program development

easier.

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WORKING OF LabVIEW

Lab VIEW includes libraries of functions and development tools designedspecifically for instrument control. For Windows, Macintosh, and Sun, Lab VIEWalso contains libraries of functions and development tools for data acquisition. LabVIEW programs are called virtual instruments (Vis)because their appearance andoperation imitate actual instruments. However, they are analogous to functionsfrom conventional language programs. VIs have both an interactive user interfaceand a source code equivalent, and accept parameters from higher-level Visitedfollowing are descriptions of these three VI features

VIs contains an interactive user interface, which is called the front Panel,because it simulates the panel of a physical instrument. The front panel cancontain knobs, push buttons, graphs, and other controls and indicators. Youinput data using a keyboard and mouse, and then view the results on thecomputer screen.

VIs receives instructions from a block diagram, which you construct in G.The block diagram supplies a pictorial solution to a programming problem.The block diagram contains the source code for the VI.

VIs use a hierarchical and modular structure. You can use them as top-levelprograms, or as subprograms within other programs or subprograms. A VI

within another VI is called a subVI.The icon and connector pane of a VIwork like a graphical parameter list so that other VIs can pass data to it as asubVI.

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Virtual InstrumentsLab VIEW programs are called virtual instruments (VIs). VIs has three main parts:the frontpanel, the block diagram, and the icon/connector.OBJECTIVE

To open, examine, and operate a Vi and to familiarize yourself with the basicconcepts of a virtual instrument.

LabVIEW Programs Are Called Virtual Instruments(VIs):-

Front Panel

Controls = Inputs

Indicators = Outputs

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Block Diagram

Accompanyingprogramfor front panel Componentswired together

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VI Block Diagram

BlockDiagram

Toolbar

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OPERATION ON VIs.Creating a VI

Front Panel Window

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Block Diagram Window


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Control Indicator Terminals


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txs(huns+0x30);tens=((value1/10)%10);txs(tens+0x30);

ones=(value1%10);txs(ones+0x30);}

void adata(unsigned int adcout){

unsigned char val=0;val=val|(adcout&0x80)>>7;val=val|(adcout&0x40)>>5;

val=val|(adcout&0x20)>>3;val=val|(adcout&0x10)>>1;val=val|(adcout&0x8)


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{relay1=relay2=0;serialint();

while(1){while(RI==0){A1=0;B1=0;C1=0;delay(50);txs('P');adata(adcout);

delay(100);

A1=1;B1=0;C1=0;delay(50);txs('Q');adata(adcout);delay(100);

}switch(SBUF)

{case 'B': relay1=1;RI=0;break;case 'C': relay2=1;RI=0;break;case 'D': relay1=0;RI=0;break;case 'E': relay2=0;RI=0;break;

}}}

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2)Vision3 Build LogProject:C:\Documents and Settings\Embedded02\Desktop\BACK

UP\Atmel Pgm\ADC+Serial\AJENT.uv2Project File Date: 11/20/2010

Output:

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7 EXPERIMENTAL RESULTS

The detection range of the PIR sensor is 5 meters, but in ourexperiments we record VOC gas leak and walking personsequences at a distance of up to 3 meters because we use thePIR sensor without the Fresnel lens on it. As a result, after3 meters the strength of the PIR output signal decreases andthe sensor is not able to respond to the changes. We used abottled gas which contains a mixture of butane and propanegases, in ratios of %70 and %30, respectively. We recorded

the VOC gas leak signal by releasing gas vapor from thecontainer when it is 10 cm, 1 meter and 3 meters away from theSensor. We first started recording the background and then Startthe VOC gas leak without entering the viewing range of thesensor. In 4 of 32 gas leak experiments, we used a 1 meter longpipe between the sensor and the bottled gas to have controlledexperiments making sure that the sensor signal is due

to the gas vapor. Since the PIR sensor also reacts to the ordinarymotion ofhot bodies, we recorded signals due to a personwalking in the viewing range of the PIR sensor on a straight linewhich is tangent to a circle with a radius of 1, 2 and 3 metersand the sensor being at the center. We also record waving armmovements at distances of 1, 2 and 3 meters to the sensor.We use the threshold values, (T1 = T2 = 10) to estimatethe reference transition probabilities. Threshold valuesare greater than 2.5 of the background signal. The statesequence is divided into windows of lengths 25, each coveringa time frame of 4 seconds. At the end of each time frame, theresult of the analysis is monitored. If two consequent framesare analyzed as gas leak, we trigger an alarm. Moreover,

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if the probability of a transition from S1 to S1, ptest(1, 1),is greater than 0.8, we decide that there is no-activity. Theresults for the MM analysis are presented in Table 1.

OurTable 1. Classification resultsfor 32 VOC gas leak and 50non-gas test sequences. The systemtriggers an alarm when a VOC gas leak is detected in theviewing range of the PIR sensor.Test Seq. # of Test # of False # of Missed # ofSequences Alarms Leaks Detect.Gas Leak 32 - 2 30Non-Gas 50 5 - -method successfully detects VOC gas leak for

30 of the 32gas leak test sequences. The two missed leaksbelong to cases that are at a distance greater than 3 meters to thesensor. The strength of the output signal of the PIR sensordecreases for the leaks far away from the sensor and they areanalyzed as a no-activity event. Our system triggers a falsealarm for 5 of 50 non-gas test sequences. Three of them belongto the walking person and two of them belong to the arm waving

experiments. If a person is at a distance of up to 1m, we do notencounter any false alarms. However, when the person is faraway, the strength of the sensor output signal decreases, as aresult walking event may be confused as a gas leak. Therefore,the range of our VOC sensor is 1 meter and it can be placedfacing valves and other possible leak locations. We also carriedout experiments with different sensors.For example, a ME-O2electrochemical gas sensor has a response time of about 30seconds , a MQ-4 gas sensor has a response time longer than 5minutes and a hydrogen selective gas sensor described in has aresponse time of 50 seconds. On the other hand, we can detect agas leak with a PIR sensor at 8 seconds.

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8 CONCLUSION

In our project, we proposed andimplemented a novel and cost efficient method for VOC gasdetection by using a PIR sensor. We used the fact that the sensorhas spectral response in the infrared part of the spectrumintersecting with the absorption bands of butane and propanegases. Gas vapor spread out gradually, whereas the IR radiationpropagation is very rapid. Therefore, unlike conventional

detectors, infrared sensor has fast response time.

Markov models (MM) which are tailoredfor VOC gas detection are used and they process the wavelettransformed sensor data. The algorithm is computationallyefficient and it can be implemented using a low-cost digitalsignal processor.

In future, steps to increase the range of PIRsensor can be worked upon. Better understanding of simulationsoftware like LABVIEW would help in effectivetroubleshooting in real time applications.

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REFERENCES

[1] J. G. Crowder, S. D. Smith, A. Vass, and J. Keddie, Mid-infrared Semiconductor

Optoelectronics, chapter Infrared Methods for Gas Detection,pp. 595613, Springer Berlin / Heidelberg, 2006.

[2] Cambridge Sensotec, Gas analysis methods, http://pdf.directindustry.com/pdf/cambridgesensotec/gasdetectionmethod-explained/14678-44117-42.html, Accessed at May 2009.[3] D.D. Lee and D.S. Lee, Environmental gas sensors,Sensors Journalize, vol. 1, no. 3, pp. 214224, Oct 2001.[4] Figaro Engineering Inc., Tgs 2610 - for the detection of lpgas, .

[5] E. Bakker and M. Telting-Diaz, Electrochemical sensors,Anal. Chem., vol. 74, 2002.[6] N. Aschen brenner, Laser diode measures carbon monoxide

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traces,http://w1.siemens.com/innovation/en/news_events/ct_pressemitteilungen/index/e_research_news/2009/e_22_resnews_091htm, Accessed at May 2009.

[7] B.U. Toreyin, E.B. Soyer, O. Urfalioglu, and A.E. Cetin,Flame Detection System Based on Wavelet Analysis of PIRSensor Signals with an HMM Decision Mechanism, in 16thEuropean Signal Processing Conference (EUSIPCO 2008),2008.

[8] Yuan Y. Tan, Wavelet Theory and Its Application to Pattern

Recognition (Machine Perception & Artificial Intelligence),World Scientific Publishing Company.[9] E. Bala and A.E. Cetin, Computationally efficient waveletaffine invariant.functions for shape recognition, vol. 26, no. 8,2004.[10] Hanwei Electronics, ME-O2 Electrochemical Gas Sensor,http://www.diytrade.com/china/4/products/5010173/O2_electroc

hemical_gas_sensors.html, Accessed at May 2009.[11] Hanwei Electronics, Technical Data MQ4 Gas Sensor,http://www.hwsensor.com/English/PDF/sensor/MQ-4.pdf,Accessed at May 2009.[12] Woosuck Shin, Masahiko Matsumiya, Noriya Izu, andNorimitsu Murayama,Hydrogen-selective thermoelectric gassensor, Sensors and Actuators B: Chemical, vol. 93, no. 1-3,pp. 304 308, 2003, Proceedings of the Ninth InternationalMeeting on Chemical Sensors.

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