Temperature Control And Maintenance Of Polyester X-Ray Coating Station

International Journal of Emerging Technology and Advanced Engineering

119

Temperature Control And Maintenance Of Polyester X-Ray

Coating Station

R.S.Kiruthika

, G.Saranya

1, 2 _{Faculty of Electronics & Communication Engineering, Dr. N.G.P. Institute of Technology, Coimbatore, India}

Abstract— The Aim of this paper is to design Embedded based system to replace the existing TRIAC based technology that is controlling the temperature for the coating station in HPF Polyester X-Ray plant. The most important component for the production of the X-ray in the coating station is the seasoned steel rod. The seasoned steel rod is a Cuban technology made, in order to meet the specified standards required for the X-ray film. The device must always maintain a constant temperature of 40 degree Celsius in order to obtain uniformity for the X-ray film. The existing TRIAC method is failing to maintain this particular requirement and thus it makes deformations to the steel rod. This is affecting the quality of the X–ray film manufactured. As a solution to this we had suggested the embedded system based temperature control for this plant which will be much more effective than the existing method. Along with this, we are also giving an alarm system, a fan for temperature control and an LCD display to make the system even more effective.

Keywords— HD44780 LCD controller, LM35 Sensor, PIC

Microcontroller, Polyester X-Ray Coating Station (PXCS), Optocoupler

I. INTRODUCTION

Hindustan Photo Films Manufacturing Company Limited is a Public Sector Undertaking under the department of Heavy Industry, incorporated in the year of 1960, with a mission to make India self-reliant in the field of Photo Sensitized goods. HPF is the only integrated manufacturer of Photo Sensitized goods in the whole of South East Asia. It is the only Company with the technology for manufacturer of Medical X-Ray, Graphic Arts and Black and White products of international standards. The manufacturing plant consist more than 60,000 motors and advanced Control Systems. One of the main parts in X-ray production unit is the coating station plant. The coating station of HPF is the plant which provides fine uniformity for the X-Ray film produced on the plant. For obtaining this uniformity X-Ray will be passed through the seasoned steel rod which works under a constant temperature of 40°C.The X-Ray film once passed through the rod having constant temperature makes the uniformity for the film. So it is very much essential to maintain the temperature in this particular station.

The industry so far had been satisfying this with a TRIAC based system which is now failing to function properly. So an idea was put forward for having an embedded system based temperature control system which could work more efficiently than the existing method.

Along with the temperature monitoring and controlling, special alarm system and cooling methods are also adopted for making the plant much safer and efficient.

II. PXCS’S TEMPERATURE CONTROL BLOCK DIAGRAM DESCRIPTION

Fig.1 Block Diagram of PXCS’s Temperature Controller

This embedded based system starts with temperature sensor LM35 which senses the temperature of the heating coil. The LM35 is directly connected to the microcontroller which will constantly monitor the difference in temperature and gives necessary output to control different devices. The microcontroller controls devices such as Heating coil, Fan, Buzzer and 16X2 LCD.

International Journal of Emerging Technology and Advanced Engineering

120 It is the combination of an LED and LDR circuit which provides suitable voltage when the LED is been lighted up by the microcontroller output. Three such opt couplers will give enough protection to the microcontroller, which is the most important part of the system.

For the proper operation of the devices such as heating coil, Fan and Buzzer, it requires sufficient voltage. Microcontroller alone cannot supply this voltage to the devices. So we need Relays for driving the devices and for switching these Relays, we are using Transistors. A 16X2 LCD is been used to display the temperature continuously so that a clear knowledge about the current temperature will be obtained.

A Fan is provided for cooling purpose when the temperature is above the Threshold limit and a Buzzer is fitted to provide alarms when the temperature crosses the maximum limit value.

III. PXCS’S TEMPERATURE CONTROL CIRCUIT DIAGRAM

 The Microcontroller PIC16F877A is used as the main part of the system. It is an 8-bit microcontroller and has 32 input/output ports.

 LM 35DZ is used as the temperature sensor for our project.

 The temperature sensor is directly connected to the AN7 channel of Port A.

 The respective port of the PIC is programmed so as to do the Analog to Digital conversion.

 Suitable Reference voltage is given to the AN5 channel of Port A.

 16X2 LCD display is interfaced to the PIC in Port D.

 Heater is connected to RB7 channel of Port B.

 Fan is connected to RB5 channel of Port B.

 Buzzer is connected to RB3 channel of Port B.

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121

 Output devices are connected to microcontroller using Optocoupler PC 817.

 Transistor BC548 is been used for doing the switching applications

 Relays provide suitable voltage for the output.

 We are using 12V DPST relays for driving the outputs.

 Regulated voltage supply of 5V & 12V is used for the circuit operations.

 5V supply is used for the working of PIC, LCD and Variac.

 12V supply is given for the operation of Relay.

 The 5V regulated supply is obtained from regulator IC 7805.

 The 12V regulated supply is obtained from regulator IC 7812.

 LED’s are provided in power supply units for the indication of power

IV. OPERATION

 LM35 sensor senses the temperature and sends the corresponding voltage signals to the PIC Microcontroller. The PIC will be programmed to do the A/D conversion internally. Thus the temperature of the environment is sensed and is compared with the limit values which we have already assigned.

 Limit value 1 = 40°C Limit value 2 = 40.5°C Limit value 3 = 41°C

 If the sensed temperature is below the Limit 1; Heater is switched ON.

 If the sensed value is between Limit 1 & Limit 2; Heater is switched OFF.

 If the sensed value is between Limit 2 & Limit 3: Fan is switched ON.

 If the sensed value is above Limit 3; Fan & Buzzer is made ON.

TABLE I

OUTPUT AT VARIOUS TEMPERATURES OF PXCS’S TEMPERATURE

CONTROLLER

Temperature Heater Fan Buzzer

0 - 40 Degrees ON OFF OFF 40 – 40.5 Degrees OFF OFF OFF 40.5 - 41 Degrees OFF ON OFF 41 > Degrees OFF ON ON

V. HARDWARE DESIGN

A. Power Supply Unit

The power supply unit consists of 12-0-12,2A Transformer, Bridge rectifier, Voltage regulator IC -7805, Capacitor-1000μf 25v.Transformer step down the input 230V supply into 12 volt and is then fed to the bridge circuit. It will convert the 12V AC into 12V DC supply. A 1000μf, 25V capacitor is provided for ripple reduction. An LED with 150ohm resistor is also connected with the circuit for the indication of power. This regulated 5V power supply is fed to PIC Microcontroller, LCD display, POT etc. A similar 12V regulated power supply is also made so as to provide necessary voltage for the working of relay. There we use the Voltage regulator IC-7812 instead of IC-7805.

B. IC Voltage Regulator

Voltage regulator comprises a class of widely used IC’s regulator IC outs which contains the circuit for reference source, comparator amplifier, control device, and overload protection all in a single IC. Although the central construction of the IC is somewhat different from that described for discrete voltage regulator circuit, the central operation is much the same IC.

A power supply can be built by using a transformer connected to the ac supply line to step the ac voltage to desired amplitude, then rectifying that ac voltage, filtering with a comparator RC filter, if desired, and finally regulating the dc voltage using IC regulator.

Example of monolithic regulators is 78xx/79xx series and 723 general purpose regulators. 78xx series are three terminal, positive fixed voltage regulators. In 78xx the last two numbers indicate the output voltage and the 7812 represent a 12v regulator. The third IC terminal is connected to ground. While the input voltage may vary over some permissible voltage range and the output load may vary over some acceptable range. The output voltage options available are 5, 6, 8, 10, 12, 18 and 24V.

VI. LM35 SENSOR

International Journal of Emerging Technology and Advanced Engineering

122 A. General Description

The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ˚ Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±0.25˚C at room temperature and ±0.75˚Cover a full −55 to +150˚C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 μA from its supply, it has very low self-heating, less than 0.1˚C in still air. The LM35 is rated to operate over a −55˚ to +150˚C temperature range, while the LM35C is rated for a −40˚ to +110˚C range (−10˚ with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.

B. Applications

The LM35 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or cemented to a surface and its temperature will be within about 0.01°C of the surface temperature. This presumes that the ambient air temperature is almost the same as the surface temperature; if the air temperature were much higher or lower than the surface temperature, the actual temperature of the LM35 die would be at an intermediate temperature between the surface temperature and the air temperature. This is especially true for the TO-92 plastic package, where the copper leads are the principal thermal path to carry heat into the device, so its temperature might be closer to the air temperature than to the surface temperature. To minimize this problem, be sure that the wiring to the LM35, as it leaves the device, is held at the same temperature as the surface of interest.

The easiest way to do this is to cover up these wires with a bead of epoxy which will insure that the leads and wires are all at the same temperature as the surface, and that the LM35 die’s temperature will not be affected by the air temperature.

The TO-46 metal package can also be soldered to a metal surface or pipe without damage. Of course, in that case the V− terminal of the circuit will be grounded to that metal. Alternatively, the LM35 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LM35 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold temperatures where condensation can occur. Printed-circuit coatings and varnishes such as Humiseal and epoxy paints or dips are often used to insure that moisture cannot corrode the LM35 or its connections. These devices are sometimes soldered to a small light-weight heat fin, to decrease the thermal time constant and speed up the response in slowly-moving air.

VII. MICRO CONTROLLER A. PIC Microcontroller

The microcontroller that has been used for this project is from PIC series. PIC microcontroller is the first RISC based microcontroller fabricated in CMOS (complementary metal oxide semiconductor) that uses separate bus for instruction and data allowing simultaneous access of program and data memory.

The main advantage of CMOS and RISC combination is low power consumption resulting in a very small chip size with a small pin count .The main advantage of CMOS is that it has immunity to noise than other fabrication techniques. Various microcontrollers offer different kinds of memories .EEPROM ,EPROM,FLASH etc. are some of the memories of which FLASH is the most recently developed . Technology that is used in PIC 16F877A is flash technology, so that the data is retained even when the power is switched off .Easy programming and erasing are other features of PIC 167877A.

International Journal of Emerging Technology and Advanced Engineering

123 B. Analog to Digital Converter (ADC)

There are two types of analog digital converter is present in this IC. We use 10-bit ADC. The ADC module can have up to eight analog inputs for a device. The analog input charges a sample and hold capacitor. The output of sample and hold capacitor is the input into the converter. The converter then generates a digital result of this analog level via successive approximation .The A/D conversion of the analog input signal results in a corresponding 10-bit digital number. The A/D module has high and low voltage reference input that is software selectable to some combinations of VDD, VSS and RA2 or RA3.The A/D module has four registers .These registers are

 A/D RESULT HIGH REGISTER (ADRESH)

 A/D RESULT LOW REGISTER (ADRESL)

 A/D CONTROL REGISTER 0 (ADCON0)

 A/D CONTROL REGISTER 1 (ADCON1) The Analog-to-Digital (A/D) Converter module has five inputs for the 28-pin devices and eight for the 40/44-pin devices. The conversion of an analog input signal results in a corresponding 10-bit digital number. The A/D module has high and low-voltage reference input that is software selectable to some combination of VDD, VSS, RA2 or RA3. The A/D converter has a unique feature of being able to operate while the device is in Sleep mode. To operate in Sleep, the A/D clock must be derived from the A/D’s internal RC oscillator.

C. Applications of Micro Controller

Micro controller are designed for use in sophisticated real time application such as

 Industrial control

 Instrumentation

 Intelligent computer peripherals

 They are used in industrial applications to control

 Motor

 Robotics

 Discrete and continuous process control

 In missile guidance and control

 In medical instrumentation

 Telecommunication

 Automobiles

 Driving an LCD

 For frequency measurements

 Period measurements

VIII. OPTOCOUPLER A. General Description

In electronics, an Opto-Isolator, also called an Optocoupler, Photocoupler, or optical isolator, is "an electronic device designed to transfer electrical signals by utilizing light waves to provide coupling with electrical isolation between its input and output". The main purpose of an Opto-Isolator is "to prevent high voltages or rapidly changing voltages on one side of the circuit from damaging components or distorting transmissions on the other side”. Commercially available Opto-Isolators withstand input-to-output voltages up to 10 kV] and voltage transients with speeds up to 10 kV/μs.

An Opto-Isolator contains a source (emitter) of light, almost always a near infrared light-emitting diode , that converts electrical input signal into light, a closed optical channel (also called dielectrically channel), and a photo sensor, which detects incoming light and either generates electric energy directly, or modulates electric current flowing from an external power supply. The sensor can be a photo resistor, a photodiode, a phototransistor, a silicon-controlled rectifier or a TRIAC. Because LEDs can sense light in addition to emitting it, construction of symmetrical, bidirectional Opto-Isolators is possible. An Optocoupled solid state relay contains a photodiode Opto-Isolator which drives a power switch, usually a complementary pair of MOSFETs. A slotted optical switch contains a source of light and a sensor, but its optical channel is open, allowing modulation of light by external objects obstructing the path of light or reflecting light into the sensor.

International Journal of Emerging Technology and Advanced Engineering

124 B. Applications

 Increasing switching speed

 Stabilizing output levels

 Elimination of induced voltage

 Elimination of input surges

 Application to high potential circuit

 To isolate one section of a circuit from another, each section having different signal voltage levels to ensure compatibility between them

IX. TRANSISTOR

A. BC 548

The BC548 is general purpose silicon, NPN, bipolar junction transistor. It is used for amplification and switching purposes. The current gain may vary between 110 and 800. The maximum DC current gain is 800. B. Applications

 Switching operation

 Amplify all aspects of a signal, voltage, current and power

 Optimized to add minimum distortion to the signal

 Optimized for high output power or efficiency (ratio of output power versus power drawn from the supply)

C. Advantages

The key advantages that have allowed transistors to replace their vacuum tube predecessors in most applications are

 Small size and minimal weight, allowing the development of miniaturized electronic devices.

 Highly automated manufacturing processes, resulting in low per-unit cost.

 Lower possible operating voltages, making transistors suitable for small, battery-powered applications.

 No warm-up period for cathode heaters required after power application.

 Lower power dissipation and generally greater energy efficiency.

 Higher reliability and greater physical ruggedness.

 Extremely long life. Some transistorized devices have been in service for more than 50 years.

 Complementary devices available, facilitating the design of complementary-symmetry circuits, something not possible with vacuum tubes.

 Insensitivity to mechanical shock and vibration, thus avoiding the problem of microphones in audio applications.

X. SPDT RELAY

Fig.4 SPDT Relay Connection Diagram

A. Operation

When an electric current is passed through the coil it generates a magnetic field that activates the armature and the consequent movement of the movable contact either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing.

International Journal of Emerging Technology and Advanced Engineering

125 Alternatively, a contact protection network consisting of a capacitor and resistor in series (Snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper "shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.

XI. LIQUID CRYSTAL DISPLAY

A. HD44780 LCD Controller

A 16×2 LCD based on HD44780 controller is used for displaying the temperature. The control lines EN, R/W and RS of the LCD module are connected to pins RA1, RA2 and RA3 of Port A of the microcontroller, respectively. The commands and the data to be displayed are sent to the LCD module in the nibble mode from Port D of the microcontroller. The higher four bits of the LCD (D4 through D7) are connected to the lower nibble of Port D (RD0 through RD3).

Hitachi HD44780 LCD controller is one of the most common dot matrix liquid crystal display (LCD) display controllers available. Hitachi developed the microcontroller specifically to drive alphanumeric LCD display with a simple interface that could be connected to a general purpose microcontroller or microprocessor. Many manufacturers of displays integrated the controller with their product making it the informal standard for this type of displays. The device can display ASCII characters, Japanese Kana characters, and some symbols in two 28 character lines. Using an extension driver, the device can display up to 80 characters.

The screens come in a small number of standard configurations. Common sizes are 8x1 (one row of eight characters), 16×2, 20×2 and 20×4. Larger custom sizes are made with 32, 40 and 80 characters and with 1, 2, 4 or 8 lines. The most commonly manufactured larger configuration is 40×4 characters, which requires two individually addressable HD44780 controllers with expansion chips as a single HD44780 chip can only address up to 80 characters. A common smaller size is 16×2, and this size is readily available as surplus stock for hobbyist and prototyping work

XII. ADVANTAGES

 Ease of installation

 Installation is cost effective

 Flexible and stable

 Modifications are easy

 Extensions are possible

 Real time monitoring

 Efficient control

 Add-on features can be done

 Zigbee module can be implemented for wireless monitoring purpose

 To control devices with respect to the temperature, We can make use of Radio control circuit

International Journal of Emerging Technology and Advanced Engineering

126 XIII. CONCLUSION

It is very much essential to have a real time monitoring, maintaining and alert system for the industry to run efficiently. We have developed a microcontroller based temperature control system that will ensure working environment of the plant in an effective manner. The promise of temperature control is easy to make, but hard to keep. Undergoing through different way of achieving our goal we had understood the working of several components, devices, materials and the difficulties which comes while implementing in real time scenario. We learned how new technologies could respond to the problems an industry usually faces.

ACKNOWLEDGEMENT

The authors would like to thank Dr. N.G.P. Institute of Technology, Coimbatore.

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[3] Milman. J and C. C. Halkiaus (1988) ’Integrated Electronics; Analog and Digital Circuits and Systems’, McGraw-Hill Education. [4] Raj Kamal (2003) ‘Embedded Systems’, Tata McGraw-Hill

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