SCADA BASED MONITORING AND CONTROLLING USING ZIGBEE

SCADA BASED MONITORING AND CONTROLLING USING ZIGBEE

ABSTRACT

Almost all the Industrial Data Acquisition and control systems today use connection oriented concepts for interfaces. However, the variety of physical shapes and functional commands that each cable or wire based system has also raises numerous problems: the difficulties in locating the particular area affected by the industrial parameter, the complexity in operation of the system, the maintenance issue and so on. The control of sensitive industrial parameters by using SCADA-based wireless technology has gained significant industry and academic attention lately for the usability benefits and convenience that it offers users. The control of the temperature of a room containing chemicals and toxic gases the existing research has failed to provide a flexible solution for controlling such conditions by connection oriented systems.

They have used cables and bulky equipment which require large amount of space, high degree of the maintenance and are easily detoriated by moisture and excessive heat.

Additionally, the Data acquisition and control techniques used so far have imposed considerable computational burden and have not provided a consistent and accurate results expected by the employees and their industries.

Keywords- SCADA, Zigbee, Monitoring, Controlling.

INTRODUCTION

Data Acquisition and Control Systems have gained much larger importance in the Industrial field because of the rapid Technological advancement and Security reasons. Whether it is an Industrial workshop, Defence go-down or experimental lab of the power plant accurate monitoring of the parameters is the need of the day. It could be the temperature, humidity, gas or light detecting sensor waiting for our command to provide us with information about the measured parameter of the particular area where they are installed. Advantage of the system is that the engineer or worker not only can obtain accurate data about the industrial parameters in remote area, but also there is no need to be physical present over there. The amount of computation required to process the data detected by sensors is much greater than that of the mechanical devices. Many of those approaches have been implemented to focus in detection of the single parameter such as temperature, gas, humidity or light by dedicating the entire system to only one parameter.

 

FIG. 1 Block Diagram of Transmitter

TRANSMITTER

The Temperature sensor LM-35 is used for detecting the physical parameter temperature of the particular device or the place where the product is stored or manufactured. It produces an output voltage which is proportional to Celsius temperature. It is a three pin device out of which the middle pin is used to measure the output voltage. It transmits the data to microcontroller. The Light Dependent Resistor (LDR) are used in places where there is need to control the Intensity and level of light especially for protecting photo films and frames. An LDR is made of semiconductor material. It has a high resistance because the vast majority of the electrons are locked into the crystal lattice and unable to move. Therefore in this state there is a high LDR resistance. As light falls on the semiconductor, the light photons are absorbed by the semiconductor lattice and some of their energy is transferred to the electrons. This gives some of them sufficient energy to break free from the crystal lattice so that they can then conduct electricity. This results in a lowering of the resistance of the semiconductor and hence the overall LDR resistance. This data is given to  microcontroller.

The GAS sensor MQ-6 can be used both in home and industry. It has a very high sensitivity to gases such asLPG, Iso-Butane, Propane. Sensor is composed of micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel net. The enveloped MQ-6 have 6 pin , 4 of them are used to fetch signals, and other 2 are used for providing heating current. The most important objective of Infrared sensor is the Intrusion detection. This circuit uses an infrared (IR) beam system to transmit the infrared signal that is of 38 to40 KHz signal when interrupted by any device it will sounds an alarm and simultaneously it will be given to the microcontroller for further process. When the beam is broken a relay is tripped which can be used to sound a bell or alarm. Distances over 25 yards (8 to 10 meters) can be monitored. Humidity sensor HSY-220 is mostly used in places where there is need to control the humidity such as food preservation industries, clothing etc. This capacitive atmospheric humidity sensor consists of a non-conductive foil, which is covered on both sides with a layer of gold. The dielectric constant of the foil changes as a function of the relative humidity of the ambient atmosphere and, accordingly, the capacitance value of the sensor is a measure for relative humidity.PIC-Microcontroller 16F877A is a 40-pin IC. It consists of five ports and built in A-D converter. Microcontroller converts the analog signals to digital signals and then gives it to the Zig-bee Transmitter via Zig-bee Interface. This is the monitoring function of the project in the transmitter section. The controlling function comes into picture when the obtained value crosses the set parameter value of the sensors. Then the Microcontroller commands the Relay driver (ULN 2803) to operate the respective device in accordance. Zig-bee is a technological standard created for control and sensor networks. It operates in personal area networks (PAN’s) and device-to-device networks. In the transmitter section the Zig-bee transmitter is interfaced with the Microcontroller by using MAX232. All the data collected by the sensors is given to Zig-bee transmitter via Microcontroller for wireless transmission. IT transmits the data in the form of packets and reduces the cost of wiring and cables. In accordance with the industrial purposes it provides a very good alternative. The relay ULN 2803 is an Integrated circuit chip with a high voltage/high current Darlington transistor array. It takes signals from TTL, CMOS, PMOS which operate at low voltages and currents. It is a relay of sorts for itself, switching on or off higher signal on the opposite side.

RECEIVER

 

Fig.2 Block Diagram of Receiver

The receiver circuitry of the project is quite simple. The data transmitted by the Zig-bee Transmitter is received by the Zig-bee receiver. This data is then given to PIC Microcontroller via Zig-bee interfacing. The data is then displayed on the LCD screen. If the parameter value crosses certain range of limit then controlling action is performed by the controller. Initially it performs the operation of alarming the Buzzer. The Buzzer alarm makes the operator alert. Buzzer or beeper is a signalling device, usually electronic, typically used in automobiles, household appliances such as a microwave oven, or game shows. It most commonly consists of a number of switches or sensors connected to a control unit that determines if and which button was pushed or a preset time has lapsed, and usually illuminates a light on the appropriate button or control panel, and sounds a warning in the form of a continuous or intermittent buzzing or beeping sound. The word "buzzer" comes from the rasping noise that buzzers made when they were electromechanical devices, operated from stepped-down AC line voltage at 50 or 60 cycles. LCD is used to display the numerical values of the parameters which are detected by the sensors. LCD creates images on a flat surface by shining light through a combination of liquid crystals and polarized glass. The technology differs from CRT because a CRT uses a beam of electrons projected through a large glass tube to create images. The topologies according to which the Zig-bee can be connected are star, cluster tree, mesh etc. The devices which are connected to Zig-bee can be Full Function Devices (FFD’s) or Reduced Function Devices (RFD’s).

Zig-bee operation takes place in two states: Active, Sleep. Active state is used for receiving the data and Zig-bee is in sleep mode when the data reception does not take place.

SOFTWARE DESCRIPTION

The Pic-Basic Pro Compiler is the easiest way to program the fast and powerful Microchip Technology PIC-micro microcontrollers. Pic-Basic Pro converts BASIC programs into files that can be programmed directly into a PIC-micro MCU.

The Pic-Basic Pro Compiler features: BASIC commands, direct and library routine access to pins on PORTA, C, D, E, as well as PORTB, arrays, real IF..THEN..ELSE and interrupt processing in BASIC. The Pic-Basic Pro Compiler gives direct access to all of the PIC-micro MCU registers - I/O ports, A/D converters, hardware serial ports, etc. - easily and in BASIC. It automatically takes care of the page boundaries and RAM banks. It even includes built-in commands to control intelligent LCD modules. The Pic-Basic Pro Compiler instruction set is upward compatible with the BASIC Stamp II and Pro uses BS2 syntax. Programs can be compiled and programmed directly into a PIC-micro MCU, eliminating the need for a BASIC Stamp module. These programs execute much faster and may be longer than their Stamp equivalents. They may also be protected so no one can copy code. The Pic-Basic Pro Compiler is a DOS command line application (it also works in Windows) and runs on PC compatibles. It can create programs for any of Microchip's PIC-micro microcontrollers and works with most PICmicro

MCU programmers, including our EPIC Plus PICmicro Programmer.

The Pic-Basic Pro Compiler can also be used inside Microchip's MPLAB IDE. This allows programs to be edited and simulated within Windows. More information is on the MPLAB page.

Pic-Basic Pro Compiler now has limited support for the 12-bit core microcontrollers and BASIC source-level debugging. If maximum compatibility is need with the BASIC Stamp I, or would like to save a little money, or just don't need all the extra features in PicBasic Pro, please take a look at standard PicBasic Compiler.

APPLICATIONS

(a)Electric Power Generation, Transmission and Distribution

(b) Water and Sewage

(c) Buildings, Facilities and Environments

(d) Mass transit

(e) Manufacturing and Traffic signals

(f) Being an automated system less manpower is required

RESULT AND CONCLUSION

The importance of monitoring and controlling Industrial parameters lies in building efficient SCADA based wireless technology. Its applications range from providing security through intrusion detection to measuring important parameters such as Temperature, Light Intesity etc. Given the amount of literature on the problem of Data Acquisition and control and the promising recognition rates reported, one would be led to believe that the problem is nearly solved. Sadly this is not so. A main problem hampering most approaches is that they rely on several underlying assumptions that may be suitable in a controlled lab setting but do not generalize to arbitrary settings.

Several common assumptions include assuming absence of dust particles in the atmosphere of the room and ambient lighting conditions. In addition, recognition results presented in the literature are based on each author’s own collection of data, making comparisons of approaches impossible and also raising suspicion on the general applicability. To ameliorate these problems there is a need for the establishment of a standard database for the evaluation and comparison of techniques. SCADA-based wireless technology has gained significant academic and commercial interest lately with the goal of allowing workers and engineers to control sensitive industrial parameters with Zigbee modules. We are presenting an intelligent gesture interface for reliably commanding sensors and relays through a user-defined language.

FUTURE SCOPE

Data can be sent in a bi-directional way. The ultimate goal of this project is to develop a technology to aid in the further development of bi-directional communication between a PC and a remote robot. A user should be able to send data in a full duplex mode i.e. transmit and receive simultaneously. Data can be broadcasted. Broadcasted data can be sent which will enable data to reach multiple recipients. We can use SCADA to manage any kind of equipment. Typically, SCADA systems are used to automate complex industrial processes where human control is impractical systems where there are more control factors, and more fast-moving control factors, than human beings can comfortably manage.

REFERENCES

(1)IEEE Recommended Practice for Data Communications Between Remote Terminal Units and Intelligent Electronic Devices in a Substation, IEEE Std 1379-2000(Revision of IEEE Std 1379- 1997),21 September 2000

(2)Chan, E.-K., Ebenhoh, H., The implantation and evolution of a SCADA system for a large distribution network, Power Systems, IEEE Transactions on, Volume:7, Issue:1, Feb.1992

(3)Aung Naing Myint, “Design and Application of SCADA Based Control System for Filling Process (Interfacing and Monitoring)”, MTU, Mandalay, Myanmar, November 2007.

(4)Prof. James Trevelyan, “SCADA System Development-Design Study”, Dept. of Mechanical & Mat. Engineering, the University of Western Australia, June 2000.

(5)Michael P. Ward, An Architectural Framework For Describing Supervisory Control And Data Acquisition (SCADA) Systems, by Publishing Monterey, California, September 2004.

(6)Microchip Technology, ”PIC 16F87X DATA sheet 28/40-pin 8-bit CMOS FLASH Microcontrollers”, in USA,2001. Available:http://www.microcontroller.com/catalog/database.

(7)Gareth Talamini, Operator Interface Design for Industrial Control, Submitted for the degree of Bachelor of Engineering (honours) In the division of Electrical and Electronic Engineering, October 2004.

(8)Thomas L. Floyd, Electronic Devices Volume 2, Fourth Edition, Printed by Prentice-Hall Inc, A Simon and Schuster Company, New Jersey,1996

(9)Controlling of large Data Acquisition System using an Industrial SCADA system using Stefan Koestner,Member,IEEE,on behalf of the LHCb Online Group

PATIENT MONITORING SYSTEM USING GSM TECHNOLOGY

PATIENT MONITORING SYSTEM USING GSM TECHNOLOGY

ABSTRACT

In this fast pace of life, it is difficult for people to be constantly available for their near ones who might need them while they are suffering from a disease or physical disorder. So also constant monitoring of the patient’s body parameters such as temperature, pulse rate, sugar level etc. becomes difficult. Hence to remove human error and to lessen the burden of monitoring patient’s health from doctor’s head, this paper presents the methodology for monitoring patients remotely using GSM network and Very Large Scale Integration (VLSI) technology. Patient monitoring systems measure physiological characteristics either continuously or at regular intervals of time.

Keywords :[GSM network ,Patient Monitoring System, VLSI]

INTRODUCTION

Recently, the health care sensors are playing a vital role in hospitals. The patient monitoring systems is one of the major improvements because of its advanced technology. So we are here, just connecting the temperature sensor and heartbeat sensor so that simultaneously we can monitor the patient’s condition and hence ruling out the use of the thermometer and other devices to check the condition of the patient. This project describes the design of a simple, microcontroller based heart rate & body temperature measuring device with LCD output. Heart rate of the subject is measured from the index finger using IRD (Infra Red Device sensors and the rate is then averaged and displayed on a text based LCD). Also Saline Level is measured continuously for different levels.

The device alarms when the heart beat & the body temperature exceed the provided threshold value. This threshold value is defined by the programmer at the time of programming the microcontroller. The threshold value given for the project is as 20 to 120 pulses per minute for heart beat indication & 18°C to 38°C for temperature.

This information i.e. the Heart Rate & the Body Temperature and saline level is then transmitted wirelessly to the doctor which in not in the vicinity of the patient through GSM technique. The sensors measure the information and transmit it through GSM Modem on the same frequency as on which cell phones work.

 

Figure 1: [Block Diagram]

 

Figure 2: [Schematic Diagram]

ELEMENTS OF PMS

1.LM35 Temperature Sensor

The LM35 series are precision integrated-circuit LM35 temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 sensor 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 sensor does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C over 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 sensor 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 sensor is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.

 

Figure 3.Temperature sensor

TABLE 1. Specifications

 

HEARTBEAT SENSOR

The sensor consists of a super bright red LED and light detector. The LED needs to be super bright as the maximum light must pass spread in finger and detected by detector. Now, when the heart pumps a pulse of blood through the blood vessels, the finger becomes slightly more opaque and so less light reached the detector. With each heart pulse the detector signal varies. This variation is converted to electrical pulse. This signal is amplified through an amplifier which outputs analog voltage between 0 to +5V logic level signal. It works on the principle of light modulation by blood flow through finger at each pulse.

 

Figure 4:Heart Rate Sensor

TABLE 2. Specifications

 

Output:

 

Applications of Heartbeat sensor

Ø Digital Heart Rate monitor

Ø Patient Monitoring System

Ø Bio-Feedback control of robotics and Applications

MAX232

The MAX 232 is a dual RS-232 receiver/transmitter that meets all EAI RS232c specifications whole using only a +5v power supply. It has 2 onboard charge pump voltage converter which generate +10v and -10v power supplies from a single 5v power supply. It has four level translators, two of which are RS232 transmitters that converter TTL\CMOS input levels into +9V RS232 outputs. The other two level translators are RS232 receiver that converts RS232 inputs to 5V. TTL\CMOS output level. It is a serial communicating device it is used to is the convert TTL Logic (Transistor Transistor Logic) to CMOS (Complementary Metal-Oxide Semiconductor) Logic.

The MAX232 device is a dual driver/receiver that includes a capacitive voltage generator to supply EIA-232 voltage levels from a single 5-V supply. Each receiver converts EIA-232 inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V and a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into EIA-232 levels. The MAX232 is characterized for operation from 0°C to 70°C. The MAX232I is characterized for operation from –40°C to 85°C.

Features of MAX 232

Ø Operates With Single 5-V Power Supply

Ø Two Drivers and Two Receivers

Ø ±30-V Input Levels

Ø Low Supply Current 8 mA Typical

Ø Designed to be Interchangeable With

Ø Maxim MAX232

Ø Battery-Powered Systems

555 Timer

555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation:

Monostable and stable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in stable mode the frequency & duty cycle are controlled by two external resistors and a capacitor. 555 is very commonly used for generating time delays and pulses.

Features of 555

Ø Direct replacement for SE555/NE555

Ø Timing from microseconds through hours

Ø Operates in both stable and monostable modes

Ø Adjustable duty cycle

Ø Output can source or sink 200 Ma

Ø Output and supply TTL compatible

Ø Temperature stability better than 0.005% per °C

Ø Normally on and normally off output

Ø Available in 8-pin MSOP package

555 Applications

Ø Precision timing

Ø Pulse generation

Ø Sequential timing

Ø Time delay generation

Ø Pulse width modulation

Ø Pulse position modulation

Ø Linear ramp generator 

GSM module

GSM module is used to establish communication between a computer and a GSM system. GSM module consists of a GSM modem assembled together with power supply circuit and communication interfaces (like RS- 232, USB, etc) for computer. GSM MODEM is a class of wireless MODEM devices that are designed for communication of a computer with the GSM network. It requires a SIM (Subscriber Identity Module) card just like mobile phones to activate communication with the network. Also they have IMEI (International Mobile Equipment Identity) number similar to mobile phones for their identification. A GSM MODEM can perform the following operations:

1. Receive, send or delete SMS messages in a SIM.

2. Read, add, search phonebook entries of the SIM.

3. Make, Receive, or reject a voice call.

GSM module features

Ø E-GSM 900/1800 MHz and GSM 1800/1900 with GSM Phase 2 / 2+

Ø Output Power Class 4 (2W) at GSM 850/900 MHz and Class 1 (1W) at GSM 1800/1900 MHz

Ø Control via AT commands (ITU, GSM, GPRS and manufacturer supplementary)

Ø Supply Voltage range: 3.22 V - 4.2 V, nominal: 3.8 V

Ø Power consumption: Idle mode: <1.8mA, speech mode: 200 mA (average)

Ø Dimensions (mm): 3 x 20 x 20 and weight (g): 3.2 (including shielding)

The GSM module offers the advantages as below

·         Ultra small size (22x22x3 mm), lightweight (3.2 g) and easy to integrate

·         Low power consumption

·         R&TTE type approval plus CE, GCF, FCC, PTCRB, IC

·         Full RS232 on CMOS level with flow control (RX, TX, CTS, RTS, CTS, DTR, DSR, DCD, RI)

·         Embedded TCP/IP Stack UDP/IP Stack , Embedded FTP and SMTP Client High performance on low price

CONCLUSION

This paper reviews the product Patient Monitoring System Using GSM which is innovated to enable remote monitoring of patients.

The key objective of developing patient monitoring systems is to reduce health care costs by reducing emergency room and physician office visits, hospitalizations, and diagnostic testing procedures. Many new wireless transmission protocols and echnologies adapt easily to new applications. Some technologies and protocols most applicable to RPM include:

·         Bluetooth

·         Zigbee

·         Mobile phone protocols (GSM, CDMA, EVDO and EDGE)

·         WiFi

·         WiMax

·         Radio frequency identification (RFID)

REFERENCES

(1) R.S.Sedha, Applied Electronics, S.Chand &company Ltd.

(2)Muhammad Ali Mazidi, Details of 8051 microcontroller & Embedded systems, Pearson education & www.8051projects.net

(3)William Kleitz, Hardware & Software of 8051 microcontroller, Pearson Education.

(4)H.S.Kalshi,Electronics Instrumentation, Tata Mc Grawhill.

(5)David E.Simon, Programming in embedded ‘C’, Pearson Education.

(6)D.Roy Chodhary, Shile B.Jani, Linear integrated circuits.

(7) www.datasheet4u.com

(8) www.Alldatasheet.co

DESIGN, IMPLEMENTATION AND PERFORMANCE STUDY OF PROGRAMMABLE AUTOMATIC VOLTAGE REGULATOR

DESIGN, IMPLEMENTATION AND PERFORMANCE STUDY OF PROGRAMMABLE AUTOMATIC VOLTAGE REGULATOR

ABSTRACT

This paper proposes the design and implementation of a Programmable Automatic Voltage Regulator (PAVR) with higher precision, appropriate hysteresis and defense of anomaly. Current systems available locally lack precision and suffer the problem of oscillating between two output voltage and hence creating surge at the output which can damage valuable electronics. To avoid these, the stabilization of power voltage, minimization of output wave rate and unchangeable power-voltage to the instruments are needed while the load changes. That requires the maintenance of stable voltage and rapid reaction against the sudden change of input voltage and load. This paper defines the shortcomings and introduces a new system in the tolerable and substantial stable of 220V with '4.5% output accuracy for any deviation of input supply voltage within 100V-340V. To control the whole system automatically a microcontroller is used with some protection devices where to detect fault and the circuit implementation in this system are simple and flexible than conventional analog control circuitry. A simulation for both circuit and program has been accomplished for establishing better performance.

Keywords: Programmable Automatic Voltage Regulator (PAVR), Hysteresis, Microcontroller, Protection, Simulation.

INTRODUCTION

AC power supply by Power Development Board (PDB) in Bangladesh is subjected to variation from time to time. Moreover in rural areas supply voltage remains lower than specified most of the times. This poses a considerable threat to the sophisticated electronic devices. For that reason, many important electric machine or electric equipments may destroy. Power quality related problems, in particular voltage sags, surge and brownouts have a major negative impact on industrial productivity. This appears to be true for both industrialized as well as developing nations. So ensuring the input voltage to remain in a tolerable pre-specified limit has become a necessity in rural as well as some urban areas. In order to save these we need to use the Automatic Voltage Regulator.

An AVR is an electronic device that automatically regulates a variation of input voltage at a certain desired level to load. The voltage of main power supply may be affected by various troubling physical factors, so that special regulating equipment is required to keep the voltage steady. In replace of AVR, Programmable AVR is more flexible, easy to modify and the best for good precision and hysteresis. The existing systems like servo-stabilizers, CVTs, Ferro resonant regulators, thyristor ac regulators, tap changers and the electronic regulators are the available means for voltage regulator. Here the performances of existing commercially available technologies are compared by this system regarding response, faults handling, precision, efficiency and other important parameters. It is essential that the supply ac voltage is needed to operate automatically due to the interconnections among the systems in modern age. The electronic control circuit may be utilized to get the desired output which is very simple, flexible, reliable and cost effective.

AVR mainly functions to measure and regulate the input voltage for producing the stable output and to provide the Protection against sag, surge, spike, impulse, notch, brown out, over voltage, under voltage, over current and hysteresis to the sophisticated equipments and machineries. In this system, the whole operations are implemented by a microcontroller. Microcontroller here performs all actions in accordance with the program maintaining proper precision and hysteresis as we desire and the undesired input transitions are handled by the AC protection devices. The whole proposed design is illustrated in the following block diagram (Figure-1).

 

Figure-1: Block diagram of PAVR

A multi-tapped transformer with input supply and switches connected in primary and in secondary respectively to obtain regulated and stabilized output voltage at the load side is used. Here microcontroller plays the important role to decide and hence to control the switches through which secondary tap carries the power from input to load with a steady voltage. This system also provides the protection against surge, spike, lightning, overvoltage and excess current by adding AC breaker (MCB), Automatic Voltage Switcher (AVS) [25] in the Input line. In the upcoming sections the designing procedure with simulations, programming, the control operation of microcontroller and performance analysis will be discussed.

DESIGNING PROCEDURE AND DISCUSSION

Description of Circuit Design

As the designing commitment which is to stabilize automatically a large range (100V- 340V) variation of input voltage at a normal prescribed level output voltage (Table-1) with a great precision. For this the voltage regulation of input supply is designed which is regulated automatically in such a way that when the input voltage varies, the output voltage will remain stable at a constant value. To achieve this, a microcontroller has been programmed is such a way that when the dc input to microcontroller varies in accordance with the variation of input voltage, microcontroller will operate the suitable switch to get a regulated output from desired transformer tap. Table-1 represents the designing configuration of the multi-tapped transformer.

Firstly, the microcontroller compares a converted variable DC voltage which is found by stepped down the ac supply voltage with the range, which is shown in Table-2 and is set in the memory of the microcontroller. The voltage range for the program has been chosen in such different manner for letting switches functioned to select the different taps for getting desired output of around 220V AC (Table-2). Thus the stable output voltage occurs at the output of this designed regulation system for any short of variation of input voltage automatically. The whole schematic of the PAVR is shown in Figure-2 and Figure-3.

 

Figure-2: Schematic diagram of PAVR (Part-1)

 

Figure-3: Schematic diagram of PAVR (Part-2)

Simulation Procedure

To determine the accurate level of voltage for designing of switching and making the microcontroller program this circuit has been simulated using PSPICE Simulator. The operation of switching of PAVR at different level of input voltage is observed as well. Here, for input supply voltage of 130V, the switching operation is shown graphically in

Figure-4 where the switch under PB0 and Q0 is “ON”. At any input voltage within 100V- 340V, one and only one switch is activated at a time as defined in the program.

 

Figure-4: Simulation for 130V Input

Flowchart description

The microcontroller program of the PAVR is designed and functioned, as the following flowchart (Figure-5), to measure the received DC voltage and then to compare with the prescribed range stored in the microcontroller memory and finally to obtain a decision for the output. In the flowchart, it is also shown that when the received DC input is out of the range (i.e. above 5V and below 1V), microcontroller will operate “No Operation (NOP)”. That means, the PAVR will remain “OFF” during excess high and low voltage AC supply to protect the devices and equipments from damaging. Here the increasing and decreasing of DC input voltage are given orderly to maintain the hysteresis properly.

 

Figure-5: Flowchart for the program of microcontroller operation

Description of Program Operation

The program that was designed for the PAVR has been simulated using PIC Simulator IDE software [28]. PIC Simulator IDE is a basic complier, assembler, disassembler and debugger for microchip family PICmicro. Firstly, the microcontroller has to be selected to load the program. Then the simulation has to be run. The sequences of operation have to be executed as follows.

Option>Select Microcontroller

Tools>Assembler

File>open/PAVR.asm

Tools>Assemble & Load

Simulation>Start

Tools>Microcontroller View

Tools>8×LED Board

The overview of simulation is presented by Figure-6 with PIC Simulator IDE interface. In this figure, the PORTB0 is displayed as ON when the input voltage is in the range of 1.0V-1.5V (2Ch-0Fh).

 

Figure-6: The simulation interface of PIC Simulator IDE with output Display

Description of Microcontroller Operation

A PIC16F876A CMOS FLASH-based 8-bit microcontroller (Figure-7) is used to control the whole system which is more reliable, simple and flexible than conventional analog control circuitry. It features especially Self-reprogrammable under software control, 2 I/O pins & 3 I/O ports, 256 bytes of EEPROM data memory, 2 Comparators, 5 channels of 10-bit Analog-to-Digital (A/D) converter, Programmable code protection, Power-saving Sleep mode, Selectable oscillator options and In-Circuit Debug via two pins.

 

Figure-7: Pin diagram of PIC16F876A Microcontroller with program placing.

An assembly language program is loaded in the microcontroller memory (Figure-7) that configures the A/D module, comparator module and I/O ports, and sets different registers of the memory with the different range of digital code (Table-3). In the program the registers are assigned by any arbitrary names to make the program more readable.

Here port-A is used as input port and port-B as output port. Firstly, microcontroller receives the DC input corresponding to supply AC input from stepped-down transformer at RA1 of PORTA. And then it is compared with the ranges that are set in the memory of microcontroller in the form of code via an A/D converter and a comparator. After that it makes anyone of the output pins (RB0-RB7) of PORTB HIGH corresponding to the range, as mentioned in Table-2, which in turn activates a respective switch to get the regulated output from the transformer. Here a constant voltage level is maintained although the input voltage level goes high than the constant desired level (Table-4). To sense this change, the microcontroller periodically checks terminal voltage and compares this with defined reference voltage levels. For designing purpose the reference voltage and code as a range has been calculated to corresponding pins of PORTB. This is shown in Table-2 and Table-3.

Table-1: (For the Design of Multi-tapped Transformer) Output Voltage Range corresponding to Input Range and Transformation Ratio at different Taps at Normal Input Voltage of 220V

Table-2: Selection of output pins, Switches and Transformer Taps for the prescribed input DC voltage range corresponding to input AC supply voltage range.

Table-3: Hexadecimal Value of digital code equivalent to prescribed DC voltage range corresponding to AC input and PAVR output voltage.

Table-4: Experimented Analog DC input for ADC of Microcontroller and Regulated AC Output Voltage for typical AC Input Supply

PERFORMANCE ANALYSIS

This system has been experimented practically after designing. Here for some typical AC input voltage supply, the regulated output approximate to desired level is found that is shown in Table-4. From this table, it is clearly revealed that this PAVR is able to regulate any variation of input voltage of a system within 100V-340V at a stable range of 210V- 230V and also to defend the system from damage due to extreme decrease and increase in AC supply voltage which is out of the range of 100V-340V. In Figures below present some performance curves of PAVR. Figure-8 shows the desired response curve of PAVR which is produced from the desired output voltage (210V-230V) for any input supply voltage within range of 100V-340V. In Figure-9, a typical input-output voltage characteristics curve of PAVR is put on view of the regulated output voltage that is near about 220V AC (Data in Table-4).

The Figure-10 exhibits a practical input-output voltage characteristics of PAVR for random supply. In this response curve, it confirms the design requisition of a stable output in range of 210V-230V as the regulation of any change in AC supply voltage within 100V- 340V, and the protection any system from spoiling due to low voltage i.e. below 100V and high voltage i.e. above 340V. A hysteresis curve, given in Figure-11, shows the hysteresis behavior of PAVR during the operation of switches at the transition of different ranges of input supply voltage. It is needed to maintain properly to prevent the frequent vacillation of switching between “ON” and “OFF”.

 

Figure-8: Desired Response Curve of PAVR

 

Figure-9: Typical Input-Output Voltage Charactesistics of PAVR

 

Figure-10: Practical Input-Output Voltage Characteristics of PAVR for Random Supply

 

 Figure-11: Hyteresis Curve

CONCLUSION

It is clear that, from above design and discussion, and the comparison shown in Table-5 with some other common existing AVR systems, my proposed proprietary PAVR performs better than any other existing systems. Because it is mainly programmable that can be programmed as the demand maintaining proper precision and sufficient hysteresis over a wide range of input variation. Here the protection against the excessive high and low voltage and current is confirmed which is crucial for the sophisticated electrical and electronic equipments. It is mentionable that the PAVR is very much cheap than other systems because of having microcontroller in place of discrete electronic components and simple protection units. Therefore, the circuit design and implementation are very much easy, flexible and the efficiency of this system is good enough as well. According to market comparison study, the commercially available AVR has a three to four step stabilization of the input variable voltage where the output becomes a big changing stable value within a prescribed range that is not an absolute design to get an output precised. For this reason in my research the way has been adopt to make the system for getting the precision output within in a large variation of input is the design of the main transformer having a many number of taps in the secondary winding side of the transformer maintaining a small turn difference between two adjacent taps. PAVR is applied to all electrical and electronics equipments especially in communications and precision instruments of manufactories.

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