Chapter 3. Automation

Transcription

1 Chapter 3 Automation 3.1 INTRODUCTION Automation Systems are very essential for most modern industries.they play a very significant job in the integration of machines into a self-governing system. However, these systems achieve better performance compared to manual systems, in terms of power, accuracy and operating speed. The automation sector has constantly shown progress starting from age old days of data acquisition from register level programming, point to point communication through wired links, virtual instrumentation, Ethernet, industrial networks and the GSM (Ramamurthy et al 2007). The recent advancement in microcontroller based embedded system has paved way to develop systems for specific applications. The advantage of these systems is, it helps in continuous monitoring and control over the process at remote locations through social network like the GSM. Sensors are used to monitor the process and the need for a wireless sensor based control adds advantage in reduction of cost, power management in the system.many applications have been successfully implemented in systems like safety, monitoring, control and maintenance. ( Wynn 2003). The proposed work develops an embedded system with plug and play capability. The important features of the design provides a need to update the sensor parameters being monitored. It is divided into two main components the hardware interface which consists of combination of sensors, microcontrollers, relay circuit, GSM, resistive, capacitive elements to provide the necessary protection to the hardware. The sensor signals parameters monitored and their functions resides on the microcontroller of the hardware interface. The software interface provides the system integration framework. The machinery fabricated in this study is to : Automate the conveyor in developing wound dressing material in sheet form. To automate the process of drying the sheets. 66

2 3.2 FUNCTIONAL BLOCK DIAGRAM AND DESCRIPTION The functional block diagram of the entire system is shown in the Fig.3.1. The sensing unit consists of sensors like the moisture sensor module (SEN92355P), ph sensor module, IR sensor module (IR-TR-10),Touch Screen input from graphics LCD to display the measured parameters for local display, Atmega32 microcontroller, ARM Cortex M3 Controller, GSM MODEM (SIM 900A), Mobile Phone, Line driver and a relay. Fig.3.1. The Functional Block Diagram of the Entire System. Sensing unit is used for monitoring the process parameters and provide the required control for the process. The description of the modules used in the system is explained below Moisture sensor module (SEN92355P) The moisture sensor is used to detect the moisture of the sample.the module used is shown in the Fig

3 Fig.3.2. Moisture Sensor Module (SEN92355P). Source- Seed Studio Principle of operation The sensor used in the moisture sensor is of resistive type. The circuit inside the sensor is shown in the schematic shown in the Fig.3.3.The principle of operation of the sensor is, the resistance changes with the amount of water present in the sample in which the sensor is inserted. The moisture sensor has three pins Vcc, GND and analog pin A0. Fig.3.3. Circuit Diagram of the Moisture Sensor. Source- Seed Studio Specifications of moisture sensor The minimum and maximum values of the voltage, current and output and their respective units are summarized in the Table

4 Table 3.1. Specification of the moisture sensor (SEN92355P) Item Condition Min Max Unit Voltage V Current 0 35 ma Output Sensor in dry soil Sensor in humid Sensor in water ph Sensor The degree of acidity or basicity of a solution is measured by ph. It is also the measurement of the hydrogen ion concentration, [H+]. The value of ph ranges from 0 to 14pH as shown by the ph scale and is illustrated in Fig.3.4.Values below 7 ph are termed as acidic and those above 7 ph are termed as basic. 7 ph is the center of the measurement scale and regarded neither as acidic or basic and is called neutral ph. This definition of ph was introduced in 1909 by the Danish biochemist, Soren Peter Lauritz Sorensen and mathematically expressed as: ph = - log [H + ]. Where, [H + ] is the hydrogen ion concentration in mol/l. Fig ph scale 69

5 Working principle of the ph sensor The loop of a ph measurement consists of three components namely the ph sensor, temperature sensor, preamplifier and an analyzer or transmitter. The ph sensor includes a measuring electrode and a reference electrode, This loop has a battery with two terminals the positive terminal is the measuring electrode and the negative terminal is the reference electrode. The measuring electrode is sensitive to the hydrogen ion and develops a voltage directly related to the hydrogen ion concentration of the solution. A stable potential is provided by the reference electrode against the measuring electrode and is compared. When it is immersed in the solution, there is no change in the reference electrode potential with the change in hydrogen ion concentration. The solution in the reference electrode also makes contact with the sample solution and the measuring electrode through a junction, completing the circuit. The output of the measuring electrode changes with temperature though the ph is maintained, therefore a temperature sensor is used to correct this change in output. This process is accomplished by the analyzer or in the software. Signal conditioning is provided by the preamplifier. The function of a preamplifier is it takes a high-impedance ph electrode signal and converts to a low impedance signal which is accepted by the analyzer or transmitter. The function of a preamplifier is it strengthens and stabilizes the signal, making it less vulnerable to electrical noise. The sensor displays the electrical signal which is commonly done in a 120/240 V ac powered analyzer or in a 24 V dc loop powered transmitter. In addition calibration of the sensor, configuration of the outputs, alarms and control of ph is carried out by the analyzer or transmitter which is a man machine interface. The modern day ph sensors can be easily interfaced with the microcontrollers giving more flexibility for the user to display the output to the local user and also display it to the remote user. The ph sensor selected for this study was procured 70

6 from atlas scientific (Fig 3.5). The advantage of the sensor is it can be easily interfaced with the Arduino microcontroller. Fig 3.5 ph sensor and the Arduino microcontroller Signal conditioning circuit of the ph sensor The internal schematic of the signal conditioning circuit in a ph sensor is shown in the Fig 3.6 It consist of LED, resistors and transistors. The function of the circuit is it takes a signal of high-impedance and converts it into a low impedance signal which can be accepted by the transmitter or analyzer. Fig.3.6. Circuit Diagram of the ph Sensor. 71

7 Fig.3.7 illustrates the interfacing if the ph sensor with the Arduino microcontroller. It can be seen from the figure that the probe (ie, the BNC Connector) has three terminals namely the Input, Ground and VCC. Input is the signal from the sensor. To provide the supply for the circuit, the VCC is used. It ranges from 3.3v to 5.5v. It has a separate ground pin for the entire circuit. The Tx pin represents the transmitter pin which is connected to the receiver pin of the microcontroller and the Rx pin is the receiver pin which is connected to the transmitter pin of the microcontroller. This type of connection establishes a communication between the microcontroller and the sensor device. Fig Interfacing of the ph sensor with the microcontroller. Source-Atlas Scientific IR Sensor Working principle The working principle of the IR sensor is, when the Infrared (IR) light leaves an IR LED, it reflects on an object. This reflected light travels back to an IR receiver. The IR receiver detects the presence of an object. This is illustrated in Fig

8 IR receiver IR light reflected off object IR LED IR light from LED Fig.3.8. Working Principle of the IR Sensor. The IR sensor module selected for the study is the IR-TR-10 and shown in Fig 3.9. This module consists of an IR Transmitter, receiver, a LED, supply for the module ie, VCC and Ground pin shown in Fig 3.9. Fig.3.9. IR Sensor Module IR-TR-10. Table 3.2. The Specifications of the sensor and its labeled parts are shown in the Table 3.2. Specification of labeled parts Label Function Label Function A Signal indicator LED E VCC(+) [operating range: +4V to +6V] B IR transmitter F GND C IR Sensor G Output signal (s) D Preset 73

9 The features of the device include: 5V powered, low current consumption, less than 10mA. 3 pin interface namely Signal, GND and 5V. Small LED as indicator for detection status. Obstacle detection up to 8cm. Adjustable sensing range (2cm 8cm) Single bit output. Compatible with all types of microcontroller Relay module A relay is a switch which can be electrically and mechanically operated. It consist of an electromagnet and a set of contacts. The electromagnet aids in the switching mechanism of the relay. Relays are used in places where a low power signal is used to control a circuit. Relays are also called contactors used for high end applications which require high power to be driven by electric motors. These types of relay uses a single signal to control number of circuits. Relays are intended for two basic operations. The low voltage application and the other for a high voltage application. The low voltage application is used to reduce the noise of the whole circuit while high voltage applications are used to reduce a phenomenon called arcing Working principle of a relay Fig.3.10 (a) shows the internal diagram of the relay. It consists of an iron core surrounded by a control coil. The power source is given to the electromagnet through a control switch and through contacts to the load. When current starts flowing through the control coil, the electromagnet starts energizing and intensifies the magnetic field. The upper contact arm starts attracting to the lower fixed arm and thus closes the contacts causing a short circuit for the power to the load. On the other hand, if the relay is already de-energized the contacts closes and thus moves oppositely to make an open circuit. As soon as the coil current is off, the movable 74

10 armature is returned by a force back to its initial position. This force is almost equal to half the strength of the magnetic force. This force is mainly provided by two factors namely the spring and the gravity. Fig.3.10 (a). Internal diagram of the Relay. The present day components are available in the market as modules. In this study the relay module selected is a 4 channel 5V module as shown in the Fig 3.10 (b). Fig 3.10 (b). Relay Module Line driver The ULN2003 is a monolithic high voltage and high current Darlington transistor arrays. It consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode clamp diode for switching inductive loads. The collector-current rating of a single Darlington pair is 500mA. To provide higher 75

11 current capability these Darlington pairs may be paralleled. Applications include relay drivers, hammer drivers, lamp drivers, display drivers, line drivers, and logic buffers.. The ULN2003 module is illustrated in Fig Fig ULN2003 Module Touch screen graphic liquid crystal display A touch screen is an input device which is compatible with all PC systems. It can be widely used in computing applications Working principle of a touch screen The touch screen consists of a touch sensor, a controller, and a software driver.. A touch sensor consists of a glass panel with a touch responsive surface. The touch sensor is placed on a display screen so that the responsive area of the panel covers the viewable area of the video screen. The sensor generally has an electrical current or signal going through it. The touching the screen causes a voltage or a signal change. This voltage change determines the location of the touch to the screen. The controller is a small PC card that connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into an information that a PC can understand. The controller is usually installed inside the monitor for integrated monitors or is housed in a plastic case for external touch addons/ overlays. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port (PC or Macintosh). Software driver is a software update for the PC system that allows the touch screen and computer to work together. It tells the computer's operating system how to interpret the touch event information that is sent 76

12 from the controller. Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screen the same as clicking the mouse at the same location on the screen. This allows the touch screen to work with existing software and allows new applications to be developed without the need for touch screen specific programming. The touch screen graphic LCD used in the study is 16X4 display and shown in the Fig Fig Touch Screen Graphic LCD Microcontroller The microcontrollers used in the study is based on Arduino. Arduino is an open-source platform based on a simple Input/output board, and provides a development environment for writing the Arduino software. Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other outputs. The designs based on Arduino can be stand-alone, or can communicate with software running on the computer (e.g. Flash Processing, Max MSP).It is widely used owing to its flexibility. It supports many digital and analog inputs, SPI and serial interfaces, digital and PWM outputs. It is easy to use, connects to computer via USB and communicates using standard serial protocol, runs in standalone mode and as interface connected to 77

13 PC/Macintosh computers. The Arduino interfacing with Software can transmit or receive data via a serial channel, thereby any other device with serial capabilities can communicate with an Arduino irrespective of the program/ programming language driving the other device. Either the Arduino's main serial port can be used. Native serial capabilities are not available in some programs (like Flash). They can still communicate with Arduino through an intermediary which, like a translator, enables them to talk to each other. Microcontrollers used in this study are ATMEGA32 microcontroller. Arduino based ARM Cortex M3 Controller ATMEGA32 microcontroller ATmega32 is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. The Pin configuration of ATMEGA32 Microcontroller shown in the Fig Fig Pin configuration of ATMEGA32 Microcontroller. 78

14 It is a 40 pin IC, Dual-in-line package (DIP) with pins dedicated for serial communication, power supply and ground. The other pins include the transmitter (TXD), receiver (RXD), Interrupts, pins for timers and data handling etc. The important features of the microcontroller are listed as under. 32Kbytes of In-System Programmable Flash. Program memory with Read-While-Write capabilities. 1024bytes EEPROM. 2Kbyte SRAM. 32 general purpose I/O lines. 32 general purpose working registers. JTAG interface. On-chip debugging support and programming. Timer/Counters with compare modes. Internal and External Interrupts. Serial programmable USART. Two-wire Serial Interface. 8-channel, 10-bit ADC. Watchdog Timer with Internal Oscillator. SPI serial port. Power saving modes Arduino based Arm Cortex M3 microcontroller The other microcontroller used in the study is the Arduino based ARM cortex M3 microcontroller shown in the Fig

15 Fig 3.14 Arduino based ARM Cortex M3 Processor. The Arduino Due is a 32 bit processor (Atmel SAM3X8E ARM Cortex M3 MCU) with improved standard functionalities and new features. The features of the processor are 54 Digital input/output pins. 2 Analog inputs with 12 bit resolution 4 UARTs (Hardware serial port) 2 Digital to Analog Converter (DAC) 84 MHz crystal oscillator. 2 USB connections Power Jack. JTag header. Reset Button Global System for Mobile Communication (GSM) GSM the most widely used network around the globe (Gu and Peng 2010). The GSM is a dedicated modem which accepts a SIM card. Similar to a cellular phone it operates on a subscriber s mobile number over a network. Basically, it is a cell phone without display.sim300 is a tri-band GSM/GPRS engine that works on EGSM900MHz, DCS1800MHz and PCS1900MHz frequencies. It is RS232 logic 80

16 level compatible, i.e., it takes -3v to -15v as logic high and +3v to +15v as logic low.max232 is used to convert TTL into RS232 logic level converter used between the microcontroller and the GSM board. SIM300 is compatible to almost all the space requirement depending on the application used, such as Smart phone, PDA phone and other mobile devices. The physical interface to the mobile application is made through a 60 pin board-to-board connector, which provides all hardware interfaces between the module and customers boards. The SIM300 is designed with power saving technique, the current consumption is as low as 2.5mA in SLEEP mode. It is also integrated with the TCP/IP protocol, Extended TCP/IP. For data transfer applications, AT commands are developed to use the TCP/IP protocol easily. Fig 3.15 is the GSM MODEM implemented in this work. Fig GSM MODEM Features of GSM Single supply voltage 3.2V - 4.5V Typical power consumption in SLEEP Mode: 2.5mA. SIM300 tri-band MT,MO,CB, text and PDU mode, SMS storage: SIM card Supported SIM Card: 1.8V, 3V. 81

17 3.2.9 Mobile phone A mobile phone is also known as a wireless phone, cell phone, or cellular telephone. It is a portable radio telephone which serves as a powerful tool for worldwide communication. Presently these mobile phone are readily available owing to its low cost. The other advantage include are the capability of sending commands to operate parameters in industry, long distances communication without wires. The communication is established with the nearby base station connected to the main phone network. As the cell phone moves around and if it is far away from the cell it is connected to, that cell sends a message to another cell to tell the new cell to take over the call. This is called a hand off and the call continues with the new cell the phone is connected to. The hand off is done carefully and so well that the user will usually never even know that the call was transferred to another cell Max 232 level converters The present day microprocessors and microcontrollers are not compatible with RS232. A need for a line driver or voltage converter to convert RS232 signals to TTL voltage levels is necessary. This is accomplished by the MAX232 converter The MAX232 converter converts RS232 voltage levels to TTL voltage levels and vice versa. The advantage it uses a +5v power source, which is the same as the source voltage for the microcontroller Personal computer A Personal computer is a programmable machine that receives input, stores and manipulates data, and provides output in a useful format. A personal computer may be a desktop computer, a laptop, a tablet PC, or a handheld PC. The most common microprocessors in personal computers are x86-compatible CPUs. Software applications for personal computers include word processing, spread sheets, data bases, Web browsers and clients, games, and special-purpose software applications. Modern personal computers often have high-speed or dial-up 82

18 connections to the Internet allowing access to the World Wide Web and a wide range of other resources. Personal computers may be connected to a local area network (LAN), either by a cable or through a wireless connection. The data logging is achieved continuously by the ARDUINO DUE processor to the personal Computer via the MAX232. This data is received by the software running on the PC Temperature sensor Fig Temperature Sensor The working principle of the temperature sensor is as there is a rise in temperature, the resistance value of the sensor decreases. The temperature sensor uses a thermistor which returns the ambient temperature in the form of a resistance value, which alters the supply voltage Vcc (5V). It converts the voltage value measured by an analog input pin to a temperature. The operating range of the temperature sensor is -40 to 125 degrees Celsius, with an accuracy of ±1.5ºC shown in Fig (Nizar et al 2006) has presented the electronic system to control temperature via short message service (SMS). 3.3 HARDWARE IMPLEMENTATION AND DESCRIPTION The system implementation is divided into 2 modules. Module 1 explains the interfacing of the sensors and graphic LCD with ATMEGA32 microcontroller for display of the information to the local user. The sensors sense the parameters of the sample paste and gives an output corresponding to moisture, ph and temperature values. This signal is taken into ATMEGA32 microcontroller through analog input 83

19 channel/pin. It is digitized using the in- built ADC of the ATMEGA32 and displays the parameters in the touch screen display. This system has a provision to carry out further analysis by storing the information in the personal computer. Fig 3.17 illustrates the circuit diagram for the various sensors and the graphic display connected to the ATMEGA 32 microcontroller. Fig Circuit diagram of Interfacing sensors and Graphic LCD display with ATMEGA32 Microcontroller It can be seen from the above figure that an external crystal X1 is connected to provide the clock source for the microcontroller. The resistors and capacitors are used to filter the noise in the circuit. A 5V supply voltage is provided since it provides the operating voltage for all digital circuits. The circuit implementation and the prototype developed is shown in the Fig

20 Fig Prototype of the implementation of the hardware. Fig 3.18 illustrates the sensors interfaced with the Atmega 32 microcontroller board with relay circuit, graphic LCD and power supply circuit. Module 2 illustrates the connection of the ARM Cortex with conveyor and dryer arrangement as shown in the Fig.3.19.This module is designed mainly for thinning the sheets and improve the drying time of the sheet. To meet the design specification,three IR sensors are interfaced with the analog pins of the ARM CORTEX processor to detect the presence of the sample paste.the output pins of the processor are connected the conveyor and the dryer through the ULN2003A driver.this driver supplies the necessary 12V to drive the conveyor. Both the modules are integrated into a single system by connecting the controllers through SPI interface. 85

21 Fig Circuit diagram of Interfacing of Conveyors, Dryers, IR Sensors and GSM Module with the ARDUINO DUE ARM CORTEX Processor. Fig Prototype of the working system interfacing of GSM, sensors and relay circuit with the ARM processor. The proposed system can help operator s to monitor the measured moisture, ph and temperature values remotely through his/her mobile by issuing a string of commands to GSM MODEM and in turn to the processor. 86

22 3.4 SOFTWARE DEVELOPMENT The software for the system is developed using Embedded C. The Flow chart depicting the monitoring and control of the integrated system is shown in the Fig.3.21.In the following flowchart, the program flow proceeds with initializing the serial ports, sensors and the display values. The next step is the initialization of the threshold values for the sensors and simultaneously provides the option for the user to select the number of samples. After the initialization, the sensor values are displayed in the graphic LCD. Following this the presence of the paste on the conveyor I is checked by the change in the IR values from the IR sensor mounted on roller1.if the sample is detected only then the conveyor moves in the forward direction otherwise the conveyor does not move even though the power is ON. After detection of the sample the conveyor starts moving in the forward direction. The paste passes through the roller to form sheets. The sheets after passing through 3mm and 2mm roller is sensed by the IR sensor mounted on roller 3.The change in the threshold values reverses the direction of the conveyor and the sheet is again subjected through the 2mm and 3mm roller. This method of subjecting the sheet back and forth effectively reduces the moisture present in the sheet. The optimum value for sheet formation is estimated to be 5 times. After the 5 th iteration the sheet is transferred to conveyor 2 for drying under the dryers. In the drying unit is mounted the IR sensor 3.This sensor detects the presence of the sheet. Only if this condition is true the dryers are switched ON.The threshold for the dryer arrangement is fixed to be 35 ο C which is monitored by the temperature sensor. If it goes above this temperature the blowers are turned off and the drying process of the sheet continues until the moisture sensor reads 0 ο C.The blowers go off based on the moisture values and this completes the process of drying. The samples completed are checked with the samples entered initially. If the condition is true the process stops and the notification is sent to the operator s mobile. If the condition is not satisfied the system resumes to start the formation of a new sheet. 87

23 Fig Flow Chart of the Monitoring and Control Process. 88

24 3.5 AUTOMATION OF THE CONVEYOR The design requirement for the automation of the conveyor is the removal of moisture from the paste. The sheet is subjected to pass through the rollers repeatedly. In the hardware module two infrared sensors are mounted on top of Roller 1 and Roller 3.These sensors are connected to the relay module and interfaced with the ARM cortex microcontroller. The purpose of these sensors is when the wet sheet is processed through roller 1 and moves out of roller 2, the IR sensor mounted on roller 3 senses the wet sheet, activates the relay module, signals the microcontroller to reverse the direction of the conveyor. The conveyor reverses the direction and the sheet again passes through roller 2 and when moves out of roller 1, the IR sensor mounted on top of roller 1 detects the sheet triggers the relay and the microcontroller again reverses the direction of the conveyor.the firmware for the process is discussed in the earlier section. This method of subjecting the sheet repeatedly through the rollers, effectively reduces the moisture content of the sheet and further thinning of the sheet. 3.6 AUTOMATION OF THE DRYER ARRANGEMENT The hardware module for the dryer arrangement consists of an infrared sensor module, temperature sensor module and a moisture sensor module. All these sensors are interfaced with the ARM Cortex microcontroller. The dryers used to dry the collagen sheets are the normal blow dryers. To the dryer is connected a temperature sensor. This sensor is used to monitor the temperature of the dryer. The software control for the dryer system is as discussed above is that the material to be dried is within a temperature range of C. If the temperature exceeds the set range, the temperature sensor transfers the information to the microcontroller triggers the relay module and disconnects the dryer from the drying process. It automatically resumes its operation after the desired temperature range is reached thus avoiding the overheating of the collagen sheet material. The IR sensor module used in the dryer arrangement to primarily detect the presence of the sheet in the tray 89

25 for drying for the blowers to switch ON. If the sheet is not detected it does not switch on the dryers. The software module for this arrangement is discussed earlier. 3.7 RESULTS AND DISCUSSIONS The hardware module for interfacing with the machinery and automate the production of wound dressing material in sheet form is developed. The process begins by loading the paste in the hopper. The moisture sensor, temperature sensor and ph sensor mounted inside the hopper sense the moisture, temperature and ph of the sample paste and the output is displayed in the graphic LCD display as shown in Fig Fig.3.22 Display of Temperature, Moisture and ph from the sensors When the motor is switched ON, the conveyor starts moving and the paste is allowed to pass through the rollers. All the 3 rollers are adjusted manually for 3mm, 2mm and 1mm thickness of the output. when the paste passes through roller 1, there is a elongation in length to form a wet sheet with a thickness of 3mm.During this process approximately 10% of the water present is drained and collected in the drain tray. The sheet further goes through Roller 2 which gives an output thickness of 2mm. At the output of Roller 2, further approximately 20% of moisture content is eliminated in the wet sheet. The infrared sensor mounted on Roller 3 senses the wet sheet and reverses the direction of the conveyor. This method of repeatedly 90

26 subjecting the wet sheet through rollers removes the moisture to approximately 60%. The number of iterations we have adopted for the conveyor to reverses its direction is 5 iterations. Fig.3.23 illustrates the mounting of the Infrared sensors over roller1 and roller 3. a b Fig Infrared sensors mounted on a, Roller 3 b, Roller 1. The wet sheet finally moves through Roller 3 to produce an output of 1mm thickness with a moisture content of only 10%.The time taken for the removal of water content and formation of 1mm thickness of wet sheet is approximately 6 minutes. The length of the wet sheet formed is 30cm in length and this sheet is transferred to conveyor II and placed in a steel rack for drying. The Infrared sensor attached to the dryer senses the wet sheet in the steel rack, triggers the dryer to start the drying process. The wet sheet is dried over the dryer. The interfacing circuit for the dryer arrangement is shown in Fig

27 Fig Interfacing circuit for the dryer arrangement. After completion of the sheet formation process the operator is notified in his mobile phone with the various information about the samples completed and time taken for completion of the process shown in Fig Fig Notification to the operator through mobile phone 92

28 Drying Time(Hrs) A series of experiments were conducted to study the effect of drying the sheet with the new method usig the dryers. The plot of Number of Iterations Vs Drying Time are illustrated in the Fig 3.26, Fig. 3.27, Fig and Fig Fig.3.26.Illustrates the plot of drying time of the sheet with the number of iterations when the sheet is subjected only through a 3mm roller. 6.2 B No.of Iterations Fig Plot of Number of iterations Vs drying time when sheet is subjected through a 3mm roller Fig Illustrates the plot of drying time of the sheet with the number of iterations when the sheet is subjected through a 3mm and 2mm roller. 93

29 Drying Time (Hrs) Drying Time (Hrs) B No of Iteration Fig Plot of Number of iterations Vs drying time when sheet is subjected through 3mm and 2mm roller Fig Illustrates the plot of drying time of the sheet with the number of iterations when the sheet is subjected through a 3mm and 2mm roller. 4.1 B No of Iteration Fig Plot of Number of iterations Vs drying time when sheet is subjected through a 3mm roller 94

30 Drying Time ( Hrs) Fig Illustrates the plot of drying time of the sheet with the number of iterations when the sheet is subjected through a 3mm and 2mm roller back and forth. B No of iteration Fig Plot of Number of iterations Vs drying time when sheet is subjected through 3mm and 2mm roller back and forth It can be inferred from the above graphs that there is good improvement in the drying time of the sheets when the new method of drying with the dryers is adopted. The outcome of the sheets dried by this method exhibits satisfactory results compared to the earlier development of the sheets discussed in chapter 2. The optimum iteration for sheet development was arrived in our earlier result by subjecting the sheet back and forth under the 3mm and 2mm for 5 iterations and the plot related to this as illustrated in the Fig.3.30 shows the final sheet that is dried with a drying time of 70 minutes.thus automation of wound dressing material preparation gives advantages such as to develop sheets which can be mass produced during natural calamities, cost in production of the sheet and improved drying time of the sheet. 95

31 Fig Sheet developed from the automated machinery. 96