report on design of automatic flame sensor testing

A VB based GUI for Flame Optic SimulatorAnupam Das

A REPORT

ON

“A VB BASED GUI FOR FLAME OPTIC SIMULATOR”

BY

Anupam Das2006P8PS212

B.E. (Hons.) Electronics & Instrumentation

Prepared in Partial Fulfillment of thePractice School – I Course No.

BITS C221/ BITS C231/ BITS C241

AT

Bharath Heavy Electricals Limited (BHEL), Tiruchirapalli

A Practice School – I Station of

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI

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JULY, 2008

ACKNOWLEDGEMENT

I would like to take this opportunity to express our heartfelt gratitude to all those persons who have helped me to spend the most fruitful time in BHEL, Trichy in an atmosphere of learning, wholesome knowledge and experience.

First and foremost we would like to thank the PS Division of BITS, Pilani for having in faith in me and appointing me in such a wonderful PS-I Station. Next I would like to thank our PS instructor Dr. P. Srinivasan for guiding me throughout my stay and providing me with valuable inputs regarding the plant and its units when no other BHEL personnel were ready to spare their valuable time for me in the face of the infrastructural change taking place.

The complete project would have been a mere pipedream without the guidance, help and support of my mentors Mr. A. Shanmugham, Senior Deputy General Manager, Controls & Instrumentation (FB), and Mr. K. Karthikeyan, Deputy Manager, Controls & Instrumentation (FB). They were instrumental in introducing me to the new aspect of communicating with electronic devices and devising them to suit our goals. Nevertheless their constant moral support was a boosting factor throughout.

Last but not the least; I would like to thank my friends who shared their knowledge with me any time and anywhere. They were always eager to help me with any kind of technical know – how relevant for my project. I would also like to thank all those known and unknown hands whose unparallel contribution can never be forgotten.

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BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCEPILANI (RAJASTHAN)Practice School Division

Station: Bharath Heavy Electricals Limited (BHEL) Centre: Tiruchirapalli

Duration: From 22nd May, 2008 To: 15th July, 2008

Date of Submission 14th July, 2008

Title of the Project: “A VB Based GUI for Flame Optic Simulator”

2006P8PS212 Anupam Das Electronics & Instrumentation

Name of expert: Mr. K. Karthikeyan Designation: Deputy Manager, C&I (FB)

Name of the PS Faculty: Dr. P. Srinivasan

Key Words: Flame, Optic, Simulator, RS-232, Serial Communication

Project Area: Controls & Instrumentation

Abstract: This project aims at developing an Integrated Visual Basic Application for interfacing a light source, light filter, light chopper and flame scanner, to simulate a real – time boiler furnace flame and, measure its intensity and flicker frequency via the scanner thus establishing the genuinity of the flame scanner as well. This is achieved by using serial communication principles and data transmission based on RS – 232 standard.

Signature of Student Signature of PS Faculty

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Table of Contents

Chapter No.

Chapter Page No.

1 Introduction 82 Basics of Serial Communication Used in the

Project10

2.1 What is Serial Communication? 102.2 The Serial Port Interface Standard 102.3 Connecting two devices with a Serial Cable 102.4 Serial Port Signals and Pin Assignments 112.5 Signal States 122.6 Data Pins 132.7 Control Pins 132.8 Serial Data Format 14

2.8.1 Byte Versus Values 152.8.2 Synchronous and Asynchronous Communication 152.8.3 How are the Bits Transmitted? 152.8.4 Start and Stop Bits 162.8.5 Data Bits 162.8.6 The Parity Bit 16

3 A Quick Peek into the Devices used for Simulating the Flame

18

3.1 The Light Source 183.1.1 Collimated Beam 193.1.2 Real Lenses 193.1.3 Spherical Aberrations 193.1.4 Chromatic Aberrations 193.1.5 Important Parts of the Source 19

3.2 Light Filter (Model No. 74041) 213.3 Light Chopper (Model No. MC1000A) 22

3.3.1 Input/ Output Specifications 233.3.2 Controller Front Panel Features 243.3.3 Optical Head 26

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4 Testing Procedure Involved 275 Simulation & Validation 28

5.1 How do the above mentioned devices simulate a real time boiler furnace flame?

28

5.2 Validating a Flame Scanner 296 Visual Basic Codes Involved 31

6.1 The MSComm Control of Visual Basic 316.2 “Welcome Page” 33

6.2.1 Code 336.3 “Details Page” 36

6.3.1 Code 366.4 “Test Page” 38

6.4.2 Code 387 Result 41

Bibliography 42

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Table of Figures & Tables

Figure Number Figure Details Page Number

1 DTE to DCE Connection 112 Null Modem Connection 113 DB9 Pin Configuration 124 Data & Control Signal 135 Serial Data Format 146 The QTH Light Source 187 Details of Light Source 208 Light Filter 219 Light Chopper 2210 Chopper Front Panel 2411 Chopper Mounting 2612 Flow of Light 2813 MSComm Control 3114 The Welcome Page 3315 The Details Page 3616 The Test Page 38

Table Number

Table Details Page Number

1 Serial Port Pin and Signal Assignment

12

2 Parity Types 173 Filter wheel Characteristics 214 Data Table of Flame Scanner 29

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1. Introduction

The flame generated due to firing of the fuel through the burners, is required to be monitored continuously to avoid accumulation of un-burnt fuel components in the furnace (which may lead to explosion). Suitable flame scanners are employed to monitor the flame.

In corner fired boiler furnaces, four flame scanners are installed at one level in the four corners of the furnace. Each flame scanner consists of a scanner head with fiber optic cable assembly. The scanner head housing contains an electronics module that converts the light transmitted from the furnace flame via a fiber optic light guide, to an electric current signal. The electric signal is further taken to a signal-processing module. Input from each flame scanner is divided into 2 components viz. one corresponding to intensity and the other corresponding to flicker frequency. Both signals are processed digitally in micro controller based equipment to compute intensity and flicker frequency parameters of the flame. The apparatus also has the facility for digital settings, indications and processing of other associated state of flame parameters. The apparatus also determines the required availability of the flame in the respective corners of the furnace.

In the currently available flame detectors, flame sensing is implemented through two characteristics namely intensity of the flame & flicker frequency of the flame.

In known flame scanner apparatus, several electronic modules are used to perform the signal processing and logic control functions. One module receives the electric signal from the light transducer (that views the flame) and transmits it for further signal processing. The signal processing modules typically perform intensity comparison check and flicker frequency comparison check for the flame signal with preset values for ascertaining the presence/absence of flame in the field of view.

A need exists for an integrated testing system for the flame scanner apparatus. The testing system will have to incorporate features to test the functionality of the flame scanner apparatus in such a manner as to

a) Ascertain the functionality of the scanner more accurately than the legacy systems.

b) Log the testing data for future reference & traceability.c) In case of a faulty apparatus, to clearly identify the nature of the fault present.d) Enunciate the nature of fault present for further corrective action.

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Other than the above-mentioned aspects, a need is felt for simplifying the testing procedure and reducing the tie it takes to conduct the functional test of a flame scanner apparatus.

The invented system for testing the flame scanner apparatus meets the above mentioned needs in a manner most suitable for use with any type of known flame scanner apparatus.

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2. Basics of Serial Communication Used in the Project

2.1 What Is Serial Communication?

Serial communication is the most common low-level protocol for communicating between two or more devices. Normally, one device is a computer, while the other device can be a modem, a printer, another computer, or a scientific instrument such as an oscilloscope or a function generator. As the name suggests, the serial port sends and receives bytes of information in a serial fashion - one bit at a time. These bytes are transmitted using either a binary (numerical) format or a text format.

2.2 The Serial Port Interface Standard

The serial port interface for connecting two devices is specified by the TIA/EIA-232C standard published by the Telecommunications Industry Association. The original serial port interface standard was given by RS-232, which stands for Recommended Standard number 232. The term "RS-232" is still in popular use, and is used in this guide when referring to a serial communication port that follows the TIA/EIA-232 standard. RS-232 defines these serial port characteristics:

The maximum bit transfer rate and cable length The names, electrical characteristics, and functions of signals The mechanical connections and pin assignments

Primary communication is accomplished using three pins: the Transmit Data pin, the Receive Data pin, and the Ground pin. Other pins are available for data flow control, but are not required. Other standards such as RS-485 define additional functionality such as higher bit transfer rates, longer cable lengths, and connections to as many as 256 devices.

2.3 Connecting Two Devices with a Serial Cable

The RS-232 standard defines the two devices connected with a serial cable as the Data Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE). This terminology reflects the RS-232 origin as a standard for communication between a computer terminal and a modem. Throughout this guide, your computer is considered a DTE, while peripheral devices such as modems and printers are considered DCE's. Note that many scientific instruments function as DTE's. Because RS-232 mainly involves connecting a DTE to a DCE, the pin assignments are defined

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such that straight-through cabling is used, where pin 1 is connected to pin 1, pin 2 is connected to pin 2, and so on. A DTE to DCE serial connection using the transmit data (TD) pin and the receive data (RD) pin is shown below.

Figure 1 DTE to DCE Connection

If you connect two DTE's or two DCE's using a straight serial cable, then the TD pin on each device are connected to each other, and the RD pin on each device are connected to each other. Therefore, to connect two like devices, you must use a null modem cable. As shown below, null modem cables cross the transmit and receive lines in the cable.

Figure 2 Null Modem Function

2.4 Serial Port Signals and Pin Assignments

Serial ports consist of two signal types: data signals and control signals. To support these signal types, as well as the signal ground, the RS-232 standard defines a 25-pin connection. However, most PC's and UNIX platforms use a 9-pin connection. In fact, only three pins are required for serial port communications: one for receiving data, one for transmitting data, and one for the signal ground. The pin assignment scheme for a 9-pin male connector on a DTE is given below.

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Figure 3 DB9 Pin Configuration

The pins and signals associated with the 9-pin connector are described below.

Pin Label Signal Name Signal Type1 CD Carrier Detect Control2 RD Receive Data Data3 TD Transmit Data Data4 DTR Data Terminal Ready Control5 GND Signal Ground Ground6 DSR Data Set Ready Control7 RTS Request To Send Control8 CTS Clear To Send Control9 RI Ring Indicator Control

Table 1 Serial Port Pin and Signal Assignments

The term "data set" is synonymous with "modem" or "device," while the term "data terminal" is synonymous with "computer."

2.5 Signal States

Signals can be in either an active state or an inactive state. An active state corresponds to the binary value 1, while an inactive state corresponds to the binary value 0. An active signal state is often described as logic 1, on, true, or a mark. An inactive signal state is often described as logic 0, off, false, or a space. For data signals, the "on" state occurs when the received signal voltage is more negative than -3 volts, while the "off" state occurs for voltages more positive than 3 volts. For control signals, the "on" state occurs when the received signal voltage is more positive than 3 volts, while the "off" state occurs for voltages more negative than -3 volts. The voltage between -3 volts and +3 volts is considered a transition region, and the signal state is undefined. To bring the signal to the "on" state, the controlling device un-asserts (or lowers) the value for data pins and asserts (or raises) the value for control pins. Conversely, to bring the signal to the "off" state, the controlling device asserts the value for data pins and un-asserts the value for control pins. The "on" and "off" states for a data signal and for a control signal are shown below.

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Figure 4 Data & Control Signal

2.6 Data Pins

Most serial port devices support full-duplex communication meaning that they can send and receive data at the same time. Therefore, separate pins are used for transmitting and receiving data. For these devices, the TD, RD, and GND pins are used. However, some types of serial port devices support only one-way or half-duplex communications. For these devices, only the TD and GND pins are used. In this guide, it is assumed that a full-duplex serial port is connected to your device. The TD pin carries data transmitted by a DTE to a DCE. The RD pin carries data that is received by a DTE from a DCE.

2.7 Control Pins

9-pin serial ports provide several control pins that: Signal the presence of connected devices Control the flow of data

The control pins include RTS and CTS, DTR and DSR, CD, and RI.The RTS and CTS Pins. The RTS and CTS pins are used to signal whether the devices are ready to send or receive data. This type of data flow control - called hardware handshaking - is used to prevent data loss during transmission. When enabled for both the DTE and DCE, hardware handshaking using RTS and CTS follows these steps:

The DTE asserts the RTS pin to instruct the DCE that it is ready to receive data.

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The DCE asserts the CTS pin indicating that it is clear to send data over the TD pin. If data can no longer be sent, the CTS pin is unasserted.

The data is transmitted to the DTE over the TD pin. If data can no longer be accepted, the RTS pin is unasserted by the DTE and the data transmission is stopped.

The DTR and DSR Pins. Many devices use the DSR and DTR pins to signal if they are connected and powered. Signaling the presence of connected devices using DTR and DSR follows these steps:

The DTE asserts the DTR pin to request that the DCE connect to the communication line.

The DCE asserts the DSR pin to indicate it's connected. DCE un-asserts the DSR pin when it's disconnected from the communication

line.The DTR and DSR pins were originally designed to provide an alternative method of hardware handshaking. However, the RTS and CTS pins are usually used in this way, and not the DSR and DTR pins. However, you should refer to your device documentation to determine its specific pin behavior.

The CD and RI Pins. The CD and RI pins are typically used to indicate the presence of certain signals during modem-modem connections. CD is used by a modem to signal that it has made a connection with another modem, or has detected a carrier tone. CD is asserted when the DCE is receiving a signal of a suitable frequency. CD is unasserted if the DCE is not receiving a suitable signal. RI is used to indicate the presence of an audible ringing signal. RI is asserted when the DCE is receiving a ringing signal. RI is unasserted when the DCE is not receiving a ringing signal (for example, it's between rings).

2.8 Serial Data Format

The serial data format includes one start bit, between five and eight data bits, and one stop bit. A parity bit and an additional stop bit might be included in the format as well. The diagram below illustrates the serial data format.

Figure 5 Serial Data Format

The format for serial port data is often expressed using the following notation “number of data bits - parity type - number of stop bits”. For example, “8-N-1” is

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interpreted as eight data bits, no parity bit, and one stop bit, while 7-E-2 is interpreted as seven data bits, even parity, and two stop bits. The data bits are often referred to as a character because these bits usually represent an ASCII character. The remaining bits are called framing bits because they frame the data bits.

2.8.1 Bytes versus Values

The collection of bits that comprise the serial data format is called a byte. At first, this term might seem inaccurate because a byte is 8 bits and the serial data format can range between 7 bits and 12 bits. However, when serial data is stored on your computer, the framing bits are stripped away, and only the data bits are retained. Moreover, eight data bits are always used regardless of the number of data bits specified for transmission, with the unused bits assigned a value of 0. When reading or writing data you might need to specify a value, which can consist of one or more bytes. For example, if you read one value from a device using the int32 format, then that value consists of four bytes.

2.8.2 Synchronous and Asynchronous Communication

The RS-232 standard supports two types of communication protocols: synchronous and asynchronous. Using the synchronous protocol, all transmitted bits are synchronized to a common clock signal. The two devices initially synchronize themselves to each other, and then continually send characters to stay synchronized. Even when actual data is not really being sent, a constant flow of bits allows each device to know where the other is at any given time. That is, each bit that is sent is either actual data or an idle character. Synchronous communications allows faster data transfer rates than asynchronous methods, because additional bits to mark the beginning and end of each data byte are not required. Using the asynchronous protocol, each device uses its own internal clock resulting in bytes that are transferred at arbitrary times. So, instead of using time as a way to synchronize the bits, the data format is used. In particular, the data transmission is synchronized using the start bit of the word, while one or more stop bits indicate the end of the word. The requirement to send these additional bits causes asynchronous communications to be slightly slower than synchronous. However, it has the advantage that the processor does not have to deal with the additional idle characters. Most serial ports operate asynchronously.

2.8.3 How Are the Bits Transmitted?

By definition, serial data is transmitted one bit at a time. The order in which the bits are transmitted is given below:

The start bit is transmitted with a value of 0.

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The data bits are transmitted. The first data bit corresponds to the least significant bit (LSB), while the last data bit corresponds to the most significant bit (MSB).

The parity bit (if defined) is transmitted. One or two stop bits are transmitted, each with a value of 1.

The number of bits transferred per second is given by the baud rate. The transferred bits include the start bit, the data bits, the parity bit (if defined), and the stop bits.

2.8.4 Start and Stop Bits

As described in Synchronous and Asynchronous Communication, most serial ports operate asynchronously. This means that the transmitted byte must be identified by start and stop bits. The start bit indicates when the data byte is about to begin and the stop bit(s) indicates when the data byte has been transferred. The process of identifying bytes with the serial data format follows these steps:

When a serial port pin is idle (not transmitting data), then it is in an "on" state. When data is about to be transmitted, the serial port pin switches to an "off"

state due to the start bit. The serial port pin switches back to an "on" state due to the stop bit(s). This

indicates the end of the byte.

2.8.5 Data Bits

The data bits transferred through a serial port might represent device commands, sensor readings, error messages, and so on. The data can be transferred as either binary data or ASCII data. Most serial ports use between five and eight data bits. Binary data is typically transmitted as eight bits. Text-based data is transmitted as either seven bits or eight bits. If the data is based on the ASCII character set, then a minimum of seven bits is required because there are 27 or 128 distinct characters. If an eighth bit is used, it must have a value of 0. If the data is based on the extended ASCII character set, then eight bits must be used because there are 28 or 256 distinct characters.

2.8.6 The Parity Bit

The parity bit provides simple error (parity) checking for the transmitted data. The types of parity checking are given below.

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Parity Type DescriptionEven The data bits plus the parity bit result in an even number of

1's.Mark The parity bit is always 1.Odd The data bits plus the parity bit result in an odd number of 1's.Space The parity bit is always 0.

Table 2 Parity Types

Mark and space parity checking are seldom used because they offer minimal error detection. You might choose to not use parity checking at all. The parity checking process follows these steps:

The transmitting device sets the parity bit to 0 or to 1 depending on the data bit values and the type of parity checking selected.

The receiving device checks if the parity bit is consistent with the transmitted data. If it is, then the data bits are accepted. If it is not, then an error is returned.

For example, suppose the data bits 01110001 are transmitted to your computer. If even parity is selected, then the parity bit is set to 0 by the transmitting device to produce an even number of 1's. If odd parity is selected, then the parity bit is set to 1 by the transmitting device to produce an odd number of 1's.

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3. A Quick Peek into the Devices Used for Simulating the Flame

3.1 The Light Source

Figure 6 The QTH Light Source

These lamps were designed for efficient production of light by the usage of 300 W Quartz – Tungsten Filament Bulb and set of special lenses. The lenses are designed for efficient collection of light from the filament. By moving the focusing lever, we can move the position of the condenser lenses to produce a diverging beam, “collimated beam” or to re-image the filament. The lenses in these housing are designed for collimation rather than imaging. The lens shape and orientation are selected to minimize lens induced distortion (aberration) when the lenses are close to the position which produces a collimated beam (the collimating position). When you use them for imaging, there are 2 penalties

Lens aberrations increases Light collection is reduced

For imaging, the lens is moved further from the filament and so gathers less of the light emitted by filament within its aperture. The lens operates at a high F/#.

If we need to image the filament close to the lamp housing, or equivalently, produce a small image of the filament, then it is more efficient to use the condenser in the collimating position and use a secondary focusing lens to create the image.

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3.1.1 Collimated Beam

The usual concept of a collimated beam is a parallel cylinder of light. If the intensity is same anywhere across a section of the cylinder, the beam is uniform. Some residual divergence in the limit governed by the laws of diffraction and they usually have non – uniform, though sometimes known, intensity distributions.

3.1.2 Real Lenses

The condenser lenses are intended for efficient light collection from the filament. They operate at low F/#S. As a result, the single element F/0.85 & F/1 lenses suffer from severe spherical aberrations. All lenses perform best while collimating the light from the source.

3.1.3 Spherical Aberrations

Light rays at the ends of a lens converge. This is called Spherical Aberration. In general, spherical aberration is decreased by dividing the refraction as equally as possible between as many surfaces as possible.

3.1.4 Chromatic Aberration

This term describes the variation of focal length with colour. This variation is due to the change in the lens index of refraction (n) with wavelength. As the wavelength increases, lens index decreases & focal length increases.

3.1.5 Important Parts of the Source

Lamp and Reflector Adjustments Lamp cooling (Built – in – fan) Safety & monitoring features Elapsed Time Indicator (ETI) – 6 digit LCD Meter Mounting screws Housings with condensing lens

Note: For lamps running at 50 W or less, fan is not required.

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Figure 7 Details of Light Source

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3.2 Light Filter (Model No. 74041)

Figure 8 Light Filter

It is also known as the Light Intensity Variation device. It is a six position motorized filter wheel system. The wheel holds upto six 1.0 inch (2.54 cms) diameter filters/other optical components. The filter wheel can be remotely controlled, by a PC using either IEEE – 488 (GPIB) or RS – 232 interfaces, or manually, via control box front panel. The six filters available are:

Filter Wheel No. Kind of Light Transmitted1 (Opaque)2 UV Light3 IR Light4 20% Visible Light5 60% Visible Light6 80% Visible Light

Table 3 Filter Wheel Characteristics

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3.3 Light Chopper (Model No. MC1000A)

Figure 9 Light Chopper

It is also known as the Light Frequency Variation device. The MC1000A Optical Chopper is a precision instrument utilizing advanced features to meet the most demanding approach. The MC1000A uses a phased – lock loop (PLL) motor speed control design to precisely lock the chopping speed and phase to a reference signal. An internal, crystal stabilized frequency synthesizer provides an accurate and stable reference frequency for ultra – low long term frequency drift.

Unlike conventional, open-loop speed control designs, the PLL speed control circuit also allows the MC1000A chopper to be synchronized to external reference signals, including other MC1000A choppers and reference sources such as DSP lock-in amplifiers.

For more advanced measurements, the MC1000A can lock to a harmonic, sub – harmonic, or fractional – harmonic of an external reference frequency. A second PLL circuit is used to multiply the external reference up to the 15th harmonic. This multiplier is followed by a digital divider to divide the reference down to the 15 th sub – harmonic. By combining both the frequency multiplication and division together, a fractional harmonic can be obtained.

The MC1000A also supports 2-frequency chopping from a single chopper blade. A special blade is available with 7 outer slots and 5 inner slots. This slot combination

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allows a single beam to be split and individually modulated for ratio metric experiments. Other applications include pump-probe experiments where the pump beam is modulated at the outer frequency while modulating a probe beam at the inner frequency. The MC1000A provides the sum and difference frequencies of the 2-frequency blade for accurate lock-in detection of the frequency-mixed response.

A high quality, Swiss-made, rare earth magnet DC motor and a photo-etched chopper optical wheel drive the precision. The compact optical head has a wide base for extra stability. The base is slotted for two ¼-20 mounting screws on 2” centers. The interface cable uses standard RJ-45 modular connectors for easy setup.

The MC1000A controller includes a large, 4-digit, easy to read LED display for monitoring the chopper frequency. All of the operating modes are accessible from streamlined, front panel push-button controls. Multiple user setups can be easily saved and recalled from non-volatile memory. An RS-232 serial interface is included as a standard feature for remote interfacing the MC1000A to other equipment.

3.3.1Input/Output Specifications

Ext. Input Compatibility: TTL/CMOS Ext. Input Voltage Range: 0 – 5V Input High > 2V Input Low <0.8V Ext. Input Impedance: 200Ω Ref Out Compatibility: TTL/CMOS Ref Out Voltage Range: 0 – 5V typ. Ref Out Impedance: 200Ω Min Load Impedance: 500Ω Ref Out Signals: Chopping Blade, Synthesizer, Sum and Diff Frequencies Ref Out Selection: ‘Mode’ Keypad selection or RS232 command ‘O’

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3.3.2 Controller Front Panel Features

Figure 10 Chopper Front Panel

1) FREQ DOWN / ENTER Key - This key is used to decrease the chopping frequency when operating in the internal reference mode. It is also used for as an enter key when setting the various operating parameters.

2) 4-Digit LED Display (to display operating frequency and user messages) 3) EXT IN ENABLE Key - Pressing this key toggles the MC1000 between the

internal and external reference mode. 4) EXT IN LED – This LED will illuminate when the External Input is enabled. 5) EXT REF IN - the external reference signal is connected to this input BNC

(TTL / CMOS logic level). 6) REF OUTPUT - the reference output signal selected by the REF SELECT

mode (CMOS logic level). 7) SAVE SETUP - When this LED is lit, the user can save the current

configuration to one of five setups. Use the FREQ UP / CYCLE key to select the setup number and press the FREQ DOWN / ENTER to save the setup to that number. Note: the setup number will wrap around back to 1 after it reaches 5 when pressing the FREQ UP / CYCLE key.

8) RECALL SETUP - In this mode, the user can recall one of the five user setups. Select the setup number with the FREQ UP / CYCLE key and press the FREQ DOWN / ENTER to restore the saved configuration.

9) SET D - This mode allows the user to select a sub-harmonic of the external reference input. The external reference frequency will be divided by this value and used to synchronize the chopper blade. The sub-harmonic can be used with

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the harmonic multiplier, N, to create fractional harmonics (i.e. chopper frequency, fchopper = REFEXT * N / D). Note: The Harmonic, N, and sub-harmonic, D, are only available when using the external reference input and a single frequency chopping blade (i.e. 10, 15, or 30 slot blade).

10) SET N - This mode allows the user to select a harmonic of the external reference input. The external reference frequency will be multiplied by this value and used to synchronize the chopper blade. The harmonic multiplier can be used with the sub-harmonic divider, D, to create fractional harmonics (i.e. chopper frequency, fchopper = REFEXT * N / D).

11) REF SELECT - This LED indicates the REF OUT signal mode. Pressing the ‘▲’ or ‘▼’ keys selects the ‘REF OUTPUT” signal from a number of sources depending on the operating mode selected.

Operating Mode Available sync sources Internal Reference Mode: OUT, SYN External Reference: OUT 2-Frequency Blade: OUT, SYN, SUM, DIFF Where: OUT = chopper wheel frequency (for the 2-frequency blade, the outer blade frequency) SYN = the internal frequency synthesizer (or the harmonic generator for the external mode) SUM = sum frequency for the 2 frequency blade DIFF = difference frequency for the 2 frequency blade

12) MODE - Pressing this key cycles through the various input modes (REF SELECT, SET N, SET D, RECALL and SAVE). The LED above the legend indicates the currently active mode. Note: the available input modes are dependent on the operating state (i.e. the SET N and SET D are not active when operating in the internal reference mode).

13) POWER button - Press in to power the MC1000 on. 14) FREQ UP / CYCLE Key - This key is used to increase the chopping

frequency when operating in the internal reference mode. It is also used for cycling through input options for other operating modes.

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3.3.3 Optical Head

Figure 11 Chopper Mounting

1) Precision Chopper Blade (available in 2,10, 15, 30 or 60 slots, and a 7:5 2-frequency)

2) 1/16” Hex Mounting Screws and lock washers (qty 3) 3) Photo-interrupter Speed Sensor 4) Blade Hub 5) Modular Interface Connector 6) Mounting Base

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4. Testing Procedure Involved

The complete aim of the project was to incorporate the following test steps in the Visual Basic based Graphical User Interface (GUI).

Step – I: Initialize the Scanner Test Program Step – II: Fit the Scanner head on the test-mount , Connect the RS232

terminals to PC Step – III: Note the project name & scanner code in the PC Step – IV: Select type of test configuration in the selection window as follows

a) Filter wheel Window1) UV Filter2) IR Filter3) 60% Visible Filter4) 80% Visible Filter5) 20 % Visible Filter

b) Select flicker wheel frequency on the RPM controller display between 20 Hz – 1000 Hz.

Step – V: Click ‘Test start’ after selecting test configuration Step – VI: The source controller turns ON the illuminating lamp source Step – VII: The filter controller turns the intensity filter to the set value Step – IX: The flicker controller runs the flicker wheel to the set frequency Step – X: After two minutes acknowledge the ‘Test complete’ message in PC Step – XI: Repeat the procedure from step 2 if any other scanners are required

to be tested. Step – XII: After the end of testing all the scanners, click “print report” for

printing the report of scanner test performed.

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5. Simulation & Validation

5.1 How do the above mentioned devices simulate a real time boiler furnace flame?

The complete operation of these devices can be easily understood by the following flow diagram of light:

Figure 12 Flow of Light

The light emanating from the filament of the Light Source comprises of various kinds of light, like UV, IR, and Visible Light etc. This is similar to a furnace flame as a flame in a furnace would have IR light emanated from the red – hot charred coal, visible light from the flame being produced out of it and UV light too along with the visible light.

This light is allowed to pass through a sequence of light filters in the motorized filter wheel system which allows only a particular kind of light to pass through them at a time. Thus we can isolate the various “intensities” of light from the mixture of light falling on the filter wheel.

The boiler flame has a characteristic feature known as the “Flicker Frequency” which is nothing but the vibrating effect of the flames. This frequency of vibration varies according to the portion of the flame being monitored. The portion of the flame near

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the coal has least flicker frequency whereas high above it has very high flicker frequency. This effect is introduced in the light coming from the filter using the Light Chopper which chops the light in several planes according to the frequency set by the user thus mimicking the flicker of the real – time boiler furnace flame.

The light coming out of the Light Chopper is a complete imitation of the boiler furnace flame. This simulated light is allowed to fall on to the flame scanner.

5.2 Validating a Flame Scanner

The flame scanner is an assembly of flame sensor, fiber optic cable to transmit the light signal to a transducer which converts it into an electric signal. The signal is sent to a signal processing module which processes the intensity and the flicker frequency of the light and sends back the control panel with a set of data. This data is generally in the form of bytes of information. 2 bytes of data comprise of a particular kind of information which is sent to a designated area in the memory (Registers with particular address sequence). This data sequence is as follows:

Address Contents40001 Intensity Corner 140002 Pull in Corner 140003 Pull Out Corner140004 Flicker Coal Corner 140005 Flicker Oil S1 Corner140006 Actual Freq1 Corner140007 Actual Freq2 Corner140008 Coal Flame Corner140009 Oil Flame Corner140010 Intensity Corner 240011 Pull in Corner 240012 Pull Out Corner240013 Flicker Coal Corner 240014 Flicker Oil S1 Corner240015 Actual Freq1 Corner240016 Actual Freq2 Corner240017 Coal Flame Corner240018 Oil Flame Corner240019 Intensity Corner 340020 Pull in Corner 340021 Pull Out Corner340022 Flicker Coal Corner 340023 Flicker Oil S1 Corner3

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40024 Actual Freq1 Corner340025 Actual Freq2 Corner340026 Coal Flame Corner340027 Oil Flame Corner340028 Intensity Corner 440029 Pull in Corner 440030 Pull Out Corner440031 Flicker Coal Corner 440032 Flicker Oil S1 Corner440033 Actual Freq1 Corner440034 Actual Freq2 Corner440035 Coal Flame Corner440036 Oil Flame Corner440037 System Fault40038 Flame On40039 Slave Packet Count40040 Firmware Version Numbers

Table 4 Data Table of Flame Scanner

If the flame intensity and flicker frequency sensed by the flame scanner matches with the ones set by the user during simulation, then the scanner is said to be in “perfect working condition”.

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6. Visual Basic Codes Involved

The complete application involves the following steps: The welcome page which introduces the user to the testing sequence. The welcome page allows the user to understand the procedure as directed and

also allows him to know the specific connections that have to be made before starting the test procedure.

The details page, which follows the welcome page, asks the user to fill in the project number and the scanner code to be logged in for future reference and generating the test results in a desired fashion.

The user is then taken to the test scanner page where he is asked to set the chopper frequency and then the user just needs to click test start button.

The system first initializes by starting the light source, the chopper at the set frequency and the filter wheel at its default value.

After the initialization of the system is complete, the scanner is set to start collecting the data for a complete period of 2 mins. Each 20 sec interval within this 2 min is for rotating the filter wheel by one filter segment. Hence; the scanner gets to collect 20 secs of each kind of intensity of light source.

After the period of 2 min the data collection stops and so do the simulating devices.

The user is then asked to either continue further by testing other flame scanners or he is allowed to exit the application.

If some kind of error occurs during the initialization of the system stage then the application is halted till the user rectifies the specified error in the displayed device and restarts the test.

6.1 The MSComm Control of Visual Basic

Figure 13 MSComm Control

This component of VB helps in serial communication processes. It was thus used to establish communication with the three simulating components and the flame scanner with the PC via serial ports of a “Serial Multiplexer Card” installed in the PC. This

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card helped in communicating with the flame scanner and the simulating devices simultaneously via a single dedicated PC.Following were the properties of the MSComm control used in the project:

For Light Source: Com Port – 3 Settings – “9600, 8, N, 1” Rthreshold – 1 Sthreshold – 1 MSCommName – CommLight

For Light Filter: Com Port – 4 Settings – “9600, 8, N, 1” Rthreshold – 1 Sthreshold – 1 MSCommName – CommFilter

For Light Chopper: Com Port – 5 Settings – “19200, 8, N, 1” Rthreshold – 1 Sthreshold – 1 MSCommName – CommChopper

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6.2 “Welcome Page”

Figure 14 the Welcome Page

Components Required: Standard Form 4 Command Buttons 1 Text Box 1 Label 2 Timer Controls

6.2.1 Code

Dim lol As Boolean

Private Sub ABOUT_Click()Text1.Text = "THIS APPLICATION IS DEVISED TO ASCERTAIN THE FUNCTIONALITY OF THE SCANNER MORE ACCURATELY THAN THE LEGACY SYSTEMS." & vbCrLfText1.Text = Text1.Text & "IT IS HIGHLY USER FRIENDLY AND COMPATIBLE FOR USE ON SYSTEMS WITH WINDOWS 98/NT/XP/VISTA."End Sub

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Private Sub FINISH_Click()chk = MsgBox("DO YOU WANT TO END THE APPLICATION?", vbYesNo, "VERIFY")If chk = vbYes ThenEndEnd IfEnd Sub

Private Sub Form_Load()Text1.Text = ""Timer1.Enabled = TrueEnd Sub

Private Sub HELP_Click()Text1.Text = "Fit the Scanner head on the testmount.Connect the RS232 terminals to PC." & vbCrLfText1.Text = Text1.Text & "1)CommPort3 - Light Source." & vbCrLfText1.Text = Text1.Text & "2)CommPort4 - Filter Wheel." & vbCrLfText1.Text = Text1.Text & "3)CommPort5 - Optical Chopper" & vbCrLfText1.Text = Text1.Text & "4)CommPort6 - Flame Scanner" & vbCrLfEnd Sub

Private Sub PROCEED_Click()WELCOME.HideDETAILS.ShowEnd Sub

Private Sub Timer1_Timer()If Text1.Width <= 6855 ThenText1.Width = Text1.Width + 45ElsePROCEED.Enabled = TrueHELP.Enabled = TrueABOUT.Enabled = TrueFINISH.Enabled = TrueTimer1.Enabled = FalseEnd IfEnd Sub

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Private Sub Timer2_Timer()If lol ThenLabel1.BackColor = &H404000Label1.ForeColor = &HFFFFC0ElseLabel1.BackColor = &HFFFFC0Label1.ForeColor = &H404000End Iflol = Not lolEnd Sub

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6.3 “Details” Page

Figure 15 the Details Page

Components Required: 1 Frame 2 Label Boxes 2 Text Boxes 3 Command Buttons

6.3.1 Code

Private Sub BACK_Click()Me.HideWELCOME.ShowEnd Sub

Private Sub NEXT_Click()If Text1.Text = "" Or Text2.Text = "" ThenMsgBox "PLEASE ENTER DETAILS!"ElseMe.Hide

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TEST.Show If TEST.CommLight.PortOpen = False Then TEST.CommLight.PortOpen = True End If If TEST.CommFilter.PortOpen = False Then TEST.CommFilter.PortOpen = True End If If TEST.CommChopper.PortOpen = False Then TEST.CommChopper.PortOpen = True End IfEnd IfEnd Sub

Private Sub SAVE_Click()If Text1.Text = "" Or Text2.Text = "" ThenMsgBox "PLEASE ENTER DETAILS!"Elseproject = Text1.Textcode = Text2.TextText1.Locked = TrueText2.Locked = TrueOn Error GoTo filerrorOpen "C:\Documents and Settings\All Users\Desktop\Records.xls" For Append As #1temp = project & " " & code & vbCrLfPrint #1, , tempClose #1MsgBox "Data Saved."SAVE.Enabled = FalseExit Subfilerror:MsgBox "Error in updating records."End IfEnd Sub

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6.4 “Test” Page

Figure 16 Test Page

Components Required: 4 MSComm Controls 4 Timer Controls 3 Command Buttons 2 Progress Bars 2 Label Boxes

6.4.1 Code

Dim j As Integer

Private Sub Command1_Click()j = 1Timer3.Enabled = TrueCommand1.Visible = FalseCommChopper.Output = "R"CommFilter.Output = "FILTER 1" & vbCrLf

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CommLight.Output = "START" & vbCrLfEnd Sub

Private Sub Command3_Click()If CommChopper.PortOpen = True ThenCommChopper.PortOpen = FalseEnd IfIf CommFilter.PortOpen = True ThenCommFilter.PortOpen = FalseEnd IfIf CommLight.PortOpen = True ThenCommLight.PortOpen = FalseEnd Ifchk = MsgBox("Do You Want To Test More Scanners? ", vbYesNo, "Enquiry")If chk = vbYes ThenDETAILS.ShowMe.HideCommand1.Visible = TrueCommand2.Visible = FalseCommand3.Visible = FalseDETAILS.Text1.Locked = FalseDETAILS.Text2.Locked = FalseDETAILS.Text1.Text = ""DETAILS.Text2.Text = ""DETAILS.SAVE.Enabled = TrueElseEndEnd IfEnd Sub

Private Sub Command4_Click()Dim BUFFER As StringCommChopper.Output = "R"CommChopper.Output = "E"Do DoEvents BUFFER = BUFFER & CommChopper.InputLoop Until InStr(BUFFER, "r)")MsgBox BUFFERBUFFER = ""CommChopper.InBufferCount = 0End Sub

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Private Sub Timer1_Timer()If ProgressBar1.Value < ProgressBar1.Max ThenProgressBar1.Value = ProgressBar1.Value + 1Elsetemp = MsgBox("DATA PROCESSING COMPLETE!!", vbExclamation, "FINISH")Command2.Visible = TrueCommand3.Visible = TrueProgressBar1.Visible = FalseProgressBar1.Value = 0Label1.Visible = FalseCommChopper.Output = "R"CommLight.Output = "STOP" & vbCrLfCommFilter.Output = "FILTER 1" & vbCrLfTimer2.Enabled = FalseTimer1.Enabled = FalseEnd IfEnd Sub

Private Sub Timer2_Timer()Dim OUTBUFF As StringSelect Case jCase 2OUTBUFF = "FILTER 2" & Chr$(10)CommFilter.Output = OUTBUFFCase 3OUTBUFF = "FILTER 3" & Chr$(10)CommFilter.Output = OUTBUFFCase 4OUTBUFF = "FILTER 4" & Chr$(10)CommFilter.Output = OUTBUFFCase 5OUTBUFF = "FILTER 5" & Chr$(10)CommFilter.Output = OUTBUFFCase 6OUTBUFF = "FILTER 6" & Chr$(10)CommFilter.Output = OUTBUFFCase Is > 6CommFilter.Output = "FILTER 1" & vbCrLfTimer2.Enabled = FalseEnd Selectj = j + 1

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End Sub

7. Result

The three major components of simulation were successfully interfaced with the PC. They were also successfully programmed using serial communication principles using RS – 232 standard. The programming for varying the Optical Chopper frequency took quite a long time, but ultimately it could be successfully done using the PC. In the final page, all the three devices were simultaneously manipulated at one time. Moreover, the system was partially automated to allow minimum user involvement thus reducing the possibilities of manual errors. Due to some unavoidable circumstances and conditions the scanner head could not be completely interfaced with the PC and thus its testing procedure wasn’t complete. This also led to the incomplete coding of the final form – “Test Form”. Apart from this sole technical glitch, the project was completely in operating condition for the rest of the devices.

The learning part of the project was a highly fruitful one. Many aspects of data communication, including serial communication, were of high importance. Understanding of these concepts would definitely enable one to handle any kind of electronic devices and communicate with them remotely.

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Bibliography

- Data Communication and Networking – Behrouz A. Forouzan- Manuals Of Light Source, Light Filter, Light Chopper- Electronic Devices and Circuit Theory – Robert L. Boylestad &

Louis Nasheslsky- MATLAB Help Files- MSDN Help Library of Visual Basic 6.0

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report on design of automatic flame sensor testing

Technology

light chopper model

flow of light

serial cable

serial port pin

light filter219light

flame optic simulator

light filter model

basics of serial communication