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 SectionControlling SectionWater Supply SectionPower 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 11 4.1 Microcontroller 14

4.2 40 lead PDIP 17

4.3 Internal Block Diagram 18

4.4 ADC 26

4.5 ADC (interfacing with 28 Microcontroller) Block Diagram

4.6 ADC (pin diagram) 29

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4.7 Buzzer 31

4.8,4.9 Voltage Regulator 33

4.11 Power Supply 34

LIST OF SYMBOLS

PLC Programmable Logic ControllerCPU Central Processing Unit

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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, the only integrated control and information platform that runs discrete, motion, drives, process and safety control, assuring the different automation technologies work together. While using PLC the entire manufacturing cycle will be simple and power full technology.

In this system we have to measure load with the help of CT (in case of AC/DC Motor) or PT (in case of Steam Turbine/ Hydraulic drive) & water is measure by The Water Flow Meter & all above input are feed to PLC. Controller is calculating with input & set point. On the controller’s 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 an analog interface with the Programmable logic controller (PLC).The level is then controlled 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 the measured analog value is interfaced with the PLC. The response given by the PLC to control the temperature is carried out by controlling the induction heater. The control action required to stabilize the temperature and the level within the safe limits 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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Pressure Sensor

Programmable Logic Controller

Liquid Level Sensor

Temperature Sensor

BuzzerPower Supply

Power Supply

DC Motor

1.1 BLOCK DIAGRAM:

Figure 1.1 Overall Block Diagram.

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2. VOLATILE ORGANIC COMPOUNDS

2.1 DEFINITION

Volatile organic compounds (VOCs) refer to organic chemical compounds which have significant vapor pressures and which can affect the environment and human health. VOCs are numerous, varied, and ubiquitous. Although VOCs include both man-made and naturally occurring chemical compounds, it is the anthropogenic VOCs that are regulated, especially for indoors where concentrations can be highest. VOCs are typically not acutely toxic but have chronic effects. Because the concentrations 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. This value excludes biogenic methane. Anthropogenic (human produced) emissions are about 10% of the biological level. One indication of this flux is the strong odor emitted 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 from the leaves, the stomata in particular. A major class of VOCs are terpenes, such as myrcene. Providing a sense of scale, a forest 62,000 km2 in area (the U.S. state of Pennsylvania) is estimated to emit 3,400,000 kilograms of terpenes on a typical August day during the growing season. Induction of genes producing volatile organic compounds and subsequent increase in volatile terpenes has been achieved in 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 with man-made VOCs and other indoor or outdoor air pollutants.

Some VOCs, such as styrene and limonene, can react with nitrogen oxides or with ozone to produce new oxidation products and secondary aerosols, which can cause sensory irritation symptoms. Unspecified VOCs are important in the creation of smog.

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Health effects include:

Eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis, epistaxis, fatigue, dizziness.The ability of organic chemicals to cause health effects varies greatly from those 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 on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer 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 or enclosed 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 detects motion 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 crystalline material that generates an electric charge when exposed to infrared radiation. The changes in the amount of infrared striking the element change the voltages generated, which are measured by an on-board amplifier. The device contains a special filter called a Fresnel lens, which focuses the infrared signals onto the element. As the ambient infrared signals change rapidly, the on-board amplifier trips 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 VDC or Vdd

OUT Output Connects to an I/O pin set to INPUT mode

Table 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 to ground or Vss, the plus (+) pin connects to +5 volts or Vdd and the OUT pin connects to your microcontroller’s I/O pin. One easy way to do this would be to use a standard servo/LCD extension cable, available separately from Parallax(#805-00002). This cable makes it easy to plug sensor into the servo headers on our Board Of Education or Professional Development Board. If you use the Board Of Education, be sure the servo voltage jumper (located between the 2 servo header blocks) is in the Vdd position, not Vin. If you do not have this jumper on your board you should manually connect to Vdd through the breadboard.

You may also plug the sensor directly into the edge of the breadboard and connect the signals from there. Remember the position of the pins when you plug the sensor 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 of sight of still again.

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3.7 Calibration

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

3.8 Sensitivity

The PIR Sensor has a range of approximately 20 feet. This can vary with environmental conditions. The sensor is designed to adjust to slowly changing conditions that would happen normally as the day progresses and the environmental 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 VALUE1 Power source 220-240V/AC,100-

130V/AC2 Rated load 100W(max.)3 Detection distance 8m(max.<24)4 Detection range 100°/360°5 Ambient light <2Lux-daylight6 Duration time 5-480S7 Power frequency 50-60Hz8 Switch function auto / off / on

Table 3.2 Features of PIR sensor.

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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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Description:

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the Indus-try-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory pro-grammer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM con-tents but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset.

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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. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs. Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory. In this mode, P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming and outputs the code 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 internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the inter-nal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1 also receives the low-order address bytes during Flash programming and verification.

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Table 4.1 Alternate Functions of Port 1 of Microcontroller.

Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. Port Pin Alternate Functions P1.0 T2 (external count input to Timer/Counter 2), clock-out P1.1 T2EX (Timer/Counter 2

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capture/reload trigger and direction control) P1.5 MOSI (used for In-System Programming) P1.6 MISO (used for In-System Programming) P1.7 SCK (used for In-System Programming)

Port 3

Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull-ups. Port 3 receives some control signals for Flash programming and verification. Port 3 also serves the functions of various special features of the AT89S52, as shown in the following table.

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Table 4.2 Alternate Functions of Port 3 of Microcontroller.

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. This pin drives high for 98 oscillator periods after the Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is enabled.

ALE/PROG

Address Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external 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 oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.

PSEN

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Program Store Enable (PSEN) is the read strobe to external program memory. When the AT89S52 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming.

XTAL1

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

XTAL2

Output from the inverting , oscillator amplifier.

Memory Organization

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MCS-51 devices have a separate address space for Program and Data Memory. Up to 64K bytes each of external Program and Data Memory can be addressed.

Program Memory

If the EA pin is connected to GND, all program fetches are directed to external memory. On the AT89S52, if EA is connected to VCC, program fetches to addresses 0000H through 1FFFH are directed to internal memory and fetches to addresses 2000H through FFFFH are to external memory.

Data Memory

The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a parallel address space to the Special Function Registers. This means that the upper 128 bytes have the same addresses as the SFR space but are physically separate from SFR space. When an instruction accesses an internal location above address 7FH, the address mode used in the instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space. Instructions which use direct addressing access the SFR space. For example, the following direct addressing instruction accesses the SFR at location 0A0H (which is P2). MOV 0A0H, #data Instructions that use indirect addressing access the upper 128 bytes of RAM. For example, the following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte at address 0A0H, rather than P2 (whose address is 0A0H). MOV @R0, #data Note that stack operations are examples of indirect

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addressing, so the upper 128 bytes of data RAM are available as stack space.

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

The WDT is intended as a recovery method in situations where the CPU may be subjected to software upsets. The WDT consists of a 14-bit counter and the Watchdog Timer Reset (WDTRST) SFR. The WDT is defaulted to disable from exiting reset. To enable the WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location 0A6H). When the WDT is enabled, it will increment every machine cycle while the oscillator is running. The WDT timeout period is dependent on the external clock frequency. There is no way to disable the WDT except through reset (either hardware reset or WDT overflow reset). When WDT over-flows, it will drive an output RESET HIGH pulse at the RST pin.

Using the WDT

To enable the WDT, a user must write 01EH and 0E1H in sequence to the WDTRST register (SFR location 0A6H). When the WDT is enabled, the user needs to service it by writing 01EH and 0E1H to WDTRST to avoid a WDT overflow. The 14-bit counter overflows when it reaches 16383 (3FFFH), and this will reset the device. When the WDT is enabled, it will increment every machine cycle while the oscillator is running. This means the user must reset the WDT at least every 16383 machine cycles. To reset the WDT the user must write 01EH and 0E1H to WDTRST. WDTRST is a write-only register. The WDT counter cannot be read or written.

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When WDT overflows, it will generate an output RESET pulse at the RST pin. The RESET pulse duration is 98xTOSC, where TOSC = 1/FOSC. To make the best use of the WDT, it should be serviced in those sections of code that will periodically be executed within the time required to prevent a WDT reset.

WDT during Power-down and Idle

In Power-down mode the oscillator stops, which means the WDT also stops. While in Power-down mode, the user does not need to service the WDT. There are two methods of exiting Power-down mode: by a hardware reset or via a level-activated external interrupt which is enabled prior to entering Power-down mode. When Power-down is exited with hardware reset, servicing the WDT should occur as it normally does whenever the AT89S52 is reset. Exiting Power-down with an interrupt is significantly different. The interrupt is held low long enough for the oscillator to stabilize. When the interrupt is brought high, the interrupt is serviced. To prevent the WDT from resetting the device while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high. It is suggested that the WDT be reset during the interrupt service for the interrupt used to exit Power-down mode. To ensure that the WDT does not overflow within a few states of exiting Power-down, it is best to reset the WDT just before entering Power-down mode. Before going into the

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IDLE mode, the WDIDLE bit in SFR AUXR is used to determine whether the WDT continues to count if enabled. The WDT keeps counting during IDLE (WDIDLE bit = 0) as the default state. To prevent the WDT from resetting the AT89S52 while in IDLE mode, the user should always set up a timer that will periodically exit IDLE, service the WDT, and reenter IDLE mode. With WDIDLE bit enabled, the WDT will stop to count in IDLE mode 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 component is a monolithic CMOS device with an 8-bit analog-to-digital converter, 8-channel multiplexer and microprocessor compatible control logic. The 8-bit A/D converter uses successive approximation as the conversion technique. The converter features a high impedance chopper stabilized comparator, a 256R voltage divider with analog switch tree and a successive approximation register. The 8-channel multiplexer can directly access any of 8-single-ended analog signals. The device eliminates the need for external zero and full-scale adjustments. Easy interfacing to microprocessors is provided by the latched and decoded multiplexer address inputs and latched TTL TRI-STATE® outputs. The design of the ADC0808, ADC0809 has been optimized by incorporating the most desirable aspects of several A/D conversion techniques. The ADC0808, ADC0809 offers high speed, high accuracy, minimal temperature dependence, excellent long-term accuracy and repeatability, and consumes minimal power. These features make this device ideally suited to applications from process and machine control to consumer and automotive applications. For 16-channel multiplexer with common output (sample/hold port) see ADC0816 data sheet. (See AN-247 for more information.)

Features

Easy interface to all microprocessors

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Operates ratio metrically or with 5 VDC or analog span

Adjusted voltage reference No zero or full-scale adjust required 8-channel multiplexer with address logic 0V to 5V input range with single 5V power supply Outputs meet TTL voltage level specifications Standard hermetic or molded 28-pin DIP package 28-pin molded chip carrier package ADC0808 equivalent to MM74C949 ADC0809 equivalent to MM74C949-1

Key Specifications

Resolution 8 Bits Total Unadjusted Error ±1⁄2 LSB and ±1 LSB Single Supply 5 VDC Low Power 15 mW Conversion Time 100 μs

Block Diagram:

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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:

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Multiplexer:

The device contains an 8-channel single-ended analog signal multiplexer. A particular input channel is selected 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, or game shows. It most commonly consists of a number of switches or sensors connected to a control unit that determines if and which button was pushed or a preset time has lapsed, and usually illuminates a light on the appropriate button or control panel, and sounds a warning in the form of a continuous or intermittent buzzing or beeping sound. Initially this device was based on an electromechanical system which was identical to an electric bell without the metal gong (which makes the ringing noise). Often these units were anchored to a wall or ceiling and used the ceiling or wall as a sounding board. Another implementation with some AC-connected devices was to implement a circuit to make the AC current into a noise loud enough to drive a loudspeaker and hook this circuit up to a cheap 8-ohm speaker. Nowadays, it is more popular to use a ceramic-based piezoelectric sounder 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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• 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-terminal positive regulator are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.

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4.5 POWER SUPPLY:

Power supply is a reference to a source of electrical

power. A device or system that supplies electrical or

other types of energy to an output load or group of loads

is called a power supply unit or PSU. The term is most

commonly applied to electrical energy supplies, less

often to mechanical ones, and rarely to others.

A 230v, 50Hz Single phase AC power supply is given

to a step down transformer to get 12v supply. This

voltage is converted to DC voltage using a Bridge

Rectifier. The converted pulsating DC voltage is filtered

by a 2200uf capacitor and then given to 7805 voltage

regulator to obtain constant 5v supply. This 5v supply is

given to all the components in the circuit. A RC time

constant circuit is added to discharge all the capacitors

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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 based classification procedure, similar to theone in [7], is carried out for VOC gas leak detection. There are three types of events to be classified: a walking person a gas leak and a no-activity event. Two three-state Markov models are used to model a VOC gas leak and a walking person. In the training step, two threshold values are defined in the wavelet domain for each model, T1 < 0 and 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 are defined as follows:

if (w[k] < T1)then state S0else if (T1 < w[k] < T2)then state S1elsestate S2 is attained accordinglyend

Thresholds are defined such that the wavelet coefficientsof the no-activity event remain in state S1. The system is instate S1 as long as there is not any significant activity in theviewing range of the PIR sensor. Therefore, although thereare three events to be classified, only two Markov models are used, one for a walking person and the other for a gasleak as shown in Figure 5. No-activity event is detected bycontrolling whether the system remains in S1 or not.During the training phase, only the state transition probabilities

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pa(i, j) and pb(i, j) are estimated for each model.During the classification process, we only use two models Corresponding to the VOC gas leak and walking person eventsas the system mostly remains in state S1 when there is no activity,The state transition probability, p(1, 1), is very close to1 and others are close to 0. To decide the class affiliation ofa test signal, state vector and the corresponding number of

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

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Transitions of the signal are determined. Let C be the state sequence of the test signal and tij be the number of transitionsFrom i − th state to j − th state. Then the probabilities forThe state sequence C of belonging to ’gas leak’ and ’walkingperson’classes 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 C of the test signal.During the classification phase, the state sequence of thetest signal C is divided into windows of length 25 and eachwindow is fed into the ’gas leak’ and the ’walking person’models. 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 avoid multiplications during classification, we use Eq. 2 instead of Eq.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:

if Pa(C) > Pb(C)Then the test window is affiliated with the ’gas leak’ classElseThe window is affiliated with the ’walking person’ classEndif ptest(1, 1) > 0.8The test window is affiliated to the ’no-activity’ classEnd

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6 SOFTWARE REQUIREMENTS

1. EMBEDDED C2. Lab VEIW

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6.1 INTRODUCTIONThe 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 not only is there a standard library implementation, but there are frequently a number of 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, but occasionally an embedded system might not have a complete standard library, if there is a standard library at all. Few embedded systems have capability for dynamic linking, so if standard library functions are to be available at all, they often 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 are often forced to "brew their own" standard c library implementations if they want to use them at all. While some libraries are bulky and not well suited for use on microcontrollers, many development systems still include the standard libraries which are the most common for C programmers.

C remains a very popular language for micro-controller developers due to the code efficiency and reduced overhead and development time. C offers low-level control and is considered more readable than assembly. Many free C compilers are available 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, and they are claimed to be more or less as good as assembly, depending on who you ask. Most tools now offer options for customizing the compiler optimization. Additionally, using C increases portability, since C code can be compiled for different 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 PORTH &= ~0x0A; // Same as above but using inverting the bit mask - easier to see which bits are cleared

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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 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:

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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 field requires 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 integer object. 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.

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.

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

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Atmel AT91RM9200; Atmel AVR32 AP7 family; MIPS core microcontrollers such 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 instructions for 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.

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:

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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 field requires 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 integer object. 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.

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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 that argument 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 to that function, he can be sure simply by reading the header file that that function will not modify those items. Without that "const", he would either have to go through 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 that implementation might modify that data), or else make a temporary copy of the data to 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 C or BASIC development systems, or National Instruments LabWindows.However, Lab VIEW is different from those applications in one important respect. Other programming systems use text-based languages to create lines of code,while Lab VIEW uses a Graphical programming language , to create programs in block diagram form.You can use Lab VIEW with little programming experience. Lab VIEW uses terminology, icons, and ideas familiar to scientists and engineers and relies on graphical symbols rather than textual language to describe programming actions.Lab VIEW has extensive libraries of functions and subroutines for most programming tasks. For Windows, Macintosh, and Sun, Lab VIEW contains application specific libraries for data acquisition and VXI instrument control. Lab VIEW also contains application-specific libraries for GPIB and serial instrument control, data analysis, data presentation, and data storage.LabVIEW includes conventional program development tools, so you can set breakpoints, animate program 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 designed specifically for instrument control. For Windows, Macintosh, and Sun, Lab VIEW also contains libraries of functions and development tools for data acquisition. Lab VIEW programs are called virtual instruments (Vis)because their appearance and operation imitate actual instruments. However, they are analogous to functions from conventional language programs. VIs have both an interactive user interface and a source code equivalent, and accept parameters from higher-level Visited following 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 can contain knobs, push buttons, graphs, and other controls and indicators. You input data using a keyboard and mouse, and then view the results on the computer 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-level programs, or as subprograms within other programs or subprograms. A VI within another VI is called a subVI.The icon and connector pane of a VI work like a graphical parameter list so that other VIs can pass data to it as a subVI.

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Virtual InstrumentsLab VIEW programs are called virtual instruments (VIs). VIs has three main parts: the front panel, the block diagram, and the icon/connector.OBJECTIVETo open, examine, and operate a Vi and to familiarize yourself with the basic concepts of a virtual instrument.

LabVIEW Programs Are Called Virtual Instruments(VIs):-

Front Panel Controls = Inputs Indicators = Outputs

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Block DiagramAccompanying“program”for front panel Components“wired” together

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OPERATION ON VIs.

Creating a VIFront Panel Window

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Block Diagram Window

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Control Indicator Terminals

6.3 PROGRAM USED

#include<reg51.h>sfr adcout=0xa0;sbit A1=P1^0;sbit B1=P1^1;sbit C1=P1^2;sbit relay1=P1^3;sbit relay2=P1^4;void delay(unsigned char value2);void adata(unsigned int);unsigned char a,b,c,d;void serialint(){SCON=0x50;TMOD=0X20; TH1=0XFD;TR1=1;}void txs(unsigned char kk) { TI=0; SBUF=kk; while(TI==0); TI=0; } void conv(unsigned int value1) { unsigned int huns,tens,ones; huns=(value1/100);

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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)<<1; val=val|(adcout&0x4)<<3; val=val|(adcout&0x2)<<5; val=val|(adcout&0x1)<<7; conv(val); }

void delay(unsigned char value2){int i,j;for(i=0;i<=value2;i++){for(j=0;j<=1000;j++){}}}

void main()

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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)<html><body><pre><h1>µVision3 Build Log</h1><h2>Project:</h2>C:\Documents and Settings\Embedded02\Desktop\BACK UP\Atmel Pgm\ADC+Serial\AJENT.uv2Project File Date: 11/20/2010

<h2>Output:</h2>

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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 person sequences 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 recordedthe VOC gas leak signal by releasing gas vapor from the container when it is 10 cm, 1 meter and 3 meters away from theSensor. We first started recording the background and then Start the VOC gas leak without entering the viewing range of the sensor. In 4 of 32 gas leak experiments, we used a 1 meter long pipe between the sensor and the bottled gas to have controlled experiments making sure that the sensor signal is dueto the gas vapor. Since the PIR sensor also reacts to the ordinary motion ofhot bodies, we recorded signals due to a person walking in the viewing range of the PIR sensor on a straight line which is tangent to a circle with a radius of 1, 2 and 3 meters and 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 2.5σ of the background signal. The state sequence 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 results for 32 VOC gas leak and 50non-gas test sequences. The system triggers an alarm when a VOC gas leak is detected in the viewing 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 leaks belong to cases that are at a distance greater than 3 meters to the sensor. The strength of the output signal of the PIR sensor decreases for the leaks far away from the sensor and they are analyzed as a no-activity event. Our system triggers a false alarm for 5 of 50 non-gas test sequences. Three of them belong to 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 not encounter any false alarms. However, when the person is far away, the strength of the sensor output signal decreases, as a result walking event may be confused as a gas leak. Therefore, the range of our VOC sensor is 1 meter and it can be placed facing valves and other possible leak locations. We also carried out experiments with different sensors. For example, a ME-O2 electrochemical gas sensor has a response time of about 30 seconds , a MQ-4 gas sensor has a response time longer than 5 minutes and a hydrogen selective gas sensor described in has a response time of 50 seconds. On the other hand, we can detect a gas leak with a PIR sensor at 8 seconds.

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8 CONCLUSION

In our project, we proposed and implemented a novel and cost efficient method for VOC gas detection by using a PIR sensor. We used the fact that the sensor has spectral response in the infrared part of the spectrum intersecting with the absorption bands of butane and propane gases. Gas vapor spread out gradually, whereas the IR radiation propagation is very rapid. Therefore, unlike conventional detectors, infrared sensor has fast response time. Markov models (MM) which are tailored for VOC gas detection are used and they process the wavelet transformed sensor data. The algorithm is computationally efficient and it can be implemented using a low-cost digital signal processor.

In future, steps to increase the range of PIR sensor can be worked upon. Better understanding of simulation software like LABVIEW would help in effective troubleshooting in real time applications.

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REFERENCES

[1] J. G. Crowder, S. D. Smith, A. Vass, and J. Keddie, Mid-infrared SemiconductorOptoelectronics, chapter Infrared Methods for Gas Detection,pp. 595–613, 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. 214–224, Oct 2001.[4] Figaro Engineering Inc., “Tgs 2610 - for the detection of lp gas,” .[5] E. Bakker and M. Telting-Diaz, “Electrochemical sensors,” Anal. Chem., vol. 74, 2002.[6] N. Aschen brenner, “Laser diode measures carbon monoxidetraces,http://w1.siemens.com/innovation/en/news_events/ct_pressemitteilungen/index/e_research_news/2009/e_22_resnews_091htm, Accessed at May 2009.

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[7] B.U. T¨oreyin, E.B. Soyer, O. Urfalioglu, and A.E. Cetin, “Flame Detection System Based on Wavelet Analysis of PIR Sensor Signals with an HMM Decision Mechanism,” in 16th European 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 wavelet affine 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_electrochemical_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, and Norimitsu Murayama,“Hydrogen-selective thermoelectric gas sensor,” Sensors and Actuators B: Chemical, vol. 93, no. 1-3, pp. 304 – 308, 2003, Proceedings of the Ninth International Meeting on Chemical Sensors.

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