PC-based Transient Voltage Fluctuation Probing ...

PC-based Transient Voltage Fluctuation Probing System M.Z. Ahsan

Military Institute of Science and Technology, Mirpur Cantonment, Mirpur-12, Dhaka-1216, Bangladesh Abstract PC-based Transient Voltage Fluctuation Probing system is a comprehensive PC-based system to probe transient voltage fluctuations “on and no load” conditions of generators, fitted on board ships and aircrafts in particular. The major parts of its external circuitry are ADC0809 data acquisition component, 74LS373 latch and ULN2803 driver. The ADC 0809 component is used to input the analog signals from external machines/generators to the computer via printer port (LPT1). With adequate sensors and minor modifications of circuitry, this system can be realized as power monitoring and control system (PMCS). The interfacing software of this system is written in VB scripts. The mastery of this project will help the students to understand the basics on interfacing software, about the extended use of LPT1 port and the conversion of signals from analog to digital and digital to analog. Key word: ADC; TVFPS; PMCS; Interfacing Software, VB scripts 1.

Introduction

PC-based Transient Voltage Fluctuation Probing System (PC-based TVFPS) is a comprehensive PC-based system, designed for probing the transient fluctuations of voltage under “on and no load” conditions of the generator, fitted on board ships, aircraft and also installed in factory using sophisticate equipment and machineries. Fluctuations in voltage can be read out directly from the inbuilt voltmeter integrated with the PC-based TVFPS. A real-time graph presents the same over time and the readings are automatically recorded in a database at the backend. The database can be used for further analysis to evaluate the performance of the generator. Generator can be switched on/off from PC Console. Despite, the system has expandability touse suitable sensors via 8-channels from the PC and the parameters like fuel level, over heat, water level, excitation current and so on of generator can be monitored and controlled using suitable sensors and additional small and less expensive circuitry from the PC Console. Thus, the system may be realized as PC-based power monitoring and control system (PC-based PMCS). The functional blockof this system is IBM-PC and an analog to digital converter (ADC). IBM-PC’s parallel port (LPT1 – printer port) has been used to access bi-directionally from PC to ADC and ADC to PC through 25-way female D-type connector using specially developed interfacing software, written in VB. Spatiality of this PC-based system is the usage of 8-pins as in and out the corresponding signal. This spatiality facilitates the system to monitor and control 8 generators from the same control panel by a single operator, which manifest that the system is cost effective. Moreover, individually this PC-based system can be used as the probe for testing the transient fluctuations of voltage output of a generator during procurement as a separate unit. Keeping the above in view, the objective of this paper is to draw attention of the concerns for further enhancement of this system using its expandability features by providing comprehensive idea on PC-based TVFPS. 2.

Background

The background of this project is date back, which came out from the practical experiences of serving on board war ships. Usually, war ships are fitted with many sophisticated communication, navigational and fire control systems. These systems are to keep always running mode while the ships are at sea in operation by the 1 - 4 generators depending upon the class and type of ships. The stated systems are prone to damage for transient fluctuations of voltage beyond the tolerable limit. Generators, fitted with the ship are sophisticated and different from those are used for domestic and other normal usage and therefore more expensive. So these generators must maintain certain international standards.

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Accordingly, the generated voltage of these generators should have transient fluctuation within tolerable limit, which is usually 5 ~ 10% of rated values as specified in their technical details. As such, there is a necessity to probe tolerance limit of transient fluctuations under “on and no load” conditions. This is more important during the procurement of such new generator while the ship needs to replace the generator, which is beyond economic repair (BER). However, in the mean time, Diesel Generator Monitoring System (DGMS) has been developed and already commercially available with some features to detect abnormal behavior of the generator set, which indicates fault and exhibits the same by the alarm system. Fuel rack position, excitation current etc monitoring facilities are also integrated with this system for easy maintenance under marine automation project. Recently, on line generator monitoring system has been developed to monitor generated power, fuel level, battery voltage, run-hour using gateway devices, sensors and smart devices to facilitate generator set maintenance.But these systems donot have the feature to probe the voltage fluctuations for the protection of the systems run by the generator power. In view of the above, PC-based TVFPS has been indigenously designed under a project work and successfully experimented in the laboratory as a prototype. 3.

Utilities The utilities in usage of this PC-based TVFPS are as follows: o

Probing the fluctuations of voltage output under “on and no load” conditions of the generator.

o

Continual display of graph in the PC Console with thechanges in voltage output occurred within one second.

o

Continual recording of data in a database kept at the back end.

o

Provide the scope of further analysis using those data as and when required.

o

With minor modification of interfacing software and adding small circuitry using suitable sensors and corresponding calibrated dial in the PC console, the expected utilities of this system may be as under:  The fuel level, drinking water level, battery voltage, over heat condition, excitation current and similar other parameters may be monitored from the PC-Console of this system,  Whichultimate to facilitate proper and effective maintenance of the fitted generator locally. 

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By thus, the PC-based TVFPS helps to protect other sophisticated systems fitted on board ship from accidental damages.

Benefits The benefits, obtained from this PC-based TVFPS may be as under: o o o o o o

Standard performance of Generator may be ensured Probability of accidental damage may be reduced. Aid to procurement for maintaining international as standard as a probe. Reduced cost compared to any other microcontroller based similar system. With temperature sensor, this system may be realized as temperature monitoring and control system for laboratory usage because of its expandability features. With pressure sensor, this system may be realized as pressure monitoring system for lube oil pressure of ships and aircraft because of its expandability features.

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5.

Project Description

5.1.

Inside the Printer Port

5.1,1

Pin Configuration

The printer port (LPT1) is the most popular port for interfacing the external circuitry to the PC. The hardware of LPT1 consists of three ports, namely data port, status port and control port. In total, LPT1 has 12 digital outputs and 5 digital inputs. The number of pins of LPT1 is 25. These pins are the access of this port LPT1:     labeled.

8 output pins accessed via the data port. 5 input pins (one inverted) accessed via the status port. 4 output pins (three inverted) accessed via the control port. The remaining 8 pins are usually kept grounded.

Figure-1 shows a 25-way female D-type connector, wherein data pins, status pins and control pins are

Figure-1: Pin Configuration of LPT1 (Printer) Port 5.1.2.

Addressing the Port

The parallel port is integrated on to the mother boards, upon which its configuration is changed. However, the most commonly used parallel port is LPT1. The base address 378h in hexadecimal and 888 in decimal are normally assign it. When the computer is first turned on, BIOS will determine this base address. The base address, usually called the data port or data register, is simply used for output port’s data line (pin-2 to pin-9) as shown in table-1. The status register and control register are addressed by the base address +1 and base address +2 respective as demonstrated in the table-1.

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Table-1: The port pin configuration Address

Name

Read/Write

Bit No

Base+0 (888)

Data Port

Read/Write

Base+1 (89)

Status Port

Read only

Base+2 (890)

Control Port

Read/Write

Bit-7 = D7 Bit-6 = D6 Bit-5 = D5 Bit-4 = D4 Bit-3 = D3 Bit-2 = D2 Bit-1 = D1 Bit-0 = D0 Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0

5.2.

Hardware

5.2.1

Block Concept

Decimal Value of respective pin 128 64 32 16 8 4 2 1 128 64 32 16 8 4 128 64 32 16 8 4 2 1

Pin No 9 8 7 6 5 4 3 2 25 11 10 12 13 15 21 20 19 18 17 16 14 1

Figure-2 shows the block diagram of PC-based TVFPS. The generator voltage output, converted to dc at rated value of ADC, is connected to the input terminal of the ADC to convert it into 8-bit digital output. The 8-bit digital output is fed to the printer port (LPT1) through D-type connector, where 8-bit data port is used to input the signal to the PC. Data pins are used here as input pins by the indigenously developed interfacing software. Again data pin-2, pin-3 and pin-4 are used to send address of the ADC to select one of the 8 input terminals as channel-1, channel-2, channel-3, channel-4, channel-5, channel-6, channel-7 and channel-8. So, 8 sensors can be connected to these terminals of ADC. For one purpose, only one channel (terminal) has been used. Furthermore, 8- data pins are used to switch on the generator/external circuit by sending 1,2,3,4, 8, 16, 32, 64 and 128 for 1000 millisecond only and then resetting the data pins. Control pin-18 has been used to make data pins as input pins. Control pins 1 and 14 have been used to latch address to the ADC.

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Figure-2: Block diagram 5.2.2.

Circuital Details

Based on the block concept of this system, the detail circuit has been designed, whose schematic diagram is depicted in figure-3. The major parts are ADC0809 data acquisition component, 74LS373 latch and ULN2803 driver. The ADC 0809 component is used to input the analog signals from external machines/generators to the computer via printer port (LPT1). The latch is used for switching on the machines/generators from the computer by sending digital signal via the same LPT1 of the computer. The driver is used to operate the switching units of the machines/generators.

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Figure-3: Schematic circuit diagram The ADC0809 is the heart of this circuit. It is monolithic CMOS device with 8-bit analog-to-digital converter, 8-channel multiplexer and microprocessor compatible control logic. The 8-bit A/D converter uses successive approximation as the conversion technique. In its function, a particular input channel is selected by using the address decoder. Table-2 shows the input state for address lines to select any channel. The address is latched into the decoder on the low-to-high transition of the address latch enable signal.

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Table-2: Truth table for selecting the analog channel by address line Selected Analog Channel IN0 – Pin - 26 IN1 – Pin – 27 IN2 – Pin – 28 IN3 – Pin – 01 IN4 – Pin – 02 IN5 – Pin – 03 IN6 – Pin – 04 IN7 – Pin – 05 Note: L – logic 0 and H – logic 1

Address Line B-Pin-24 L L H H L L H H

C-Pin – 23 L L L L H H H H

A-Pin-25 L H L H L H L H

The heart of this single chip data acquisition system is its 8-bit analog-to-digital converter. The converter is designed to give fast, accurate, and repeatable conversion over a wide range of temperatures. The converter is partitioned into 3 major sections; the 265R ladder network, the successive approximation register, and the comparator. The converter’s digital outputs are positive true. 5.3.

Interface Software

5.3.1.

Features

Win95 dll file has been used to call and out the LPT1 port here in this interfacing software (Control software). Microsoft Access has been used for holding the real-time dataset. This software has been written in VB scripts. An active X-control has been created to present the real-time graph, which is being updated in each second, where in X-axis is taken as time and Y-axis as the voltage reading. Specialty is that the variance provision has been catered to reject the data out of this range and to keep in the database. Printing provision has been kept for future use. Manual deletion facilitates to protect the reduction of computer speed as well as loss of memory cell of the computer. The data can also be sent to MSword/Excel for further graphical presentation to evaluate the performance of the desired generator or machine. 5.3.2.

Software Details

This software has 1 Base module and 4 form module, each having code module for giving interactive instructions. However, this base module is named as Aip.bas. It is kept to declare the entire public variables, constants and object/controls. In this module, sub-procedures have been created to input analog signals to the PC via LPT1 port and output the digital dataset to the external control circuitry. The relevant codes will be made available if required. There are 4 views; functions of each are briefly discussed below:  The first form is the PC Consol as depicted in figure-4. This is the main form from where the operator will monitor and control the generators on board ship. This console has 8 switches to switch on/off eight generators by sending digital signal from the computer via external circuitry. Despite, it has more 8 channels connected to the generator voltage output via external circuitry. The operator can monitor all the generators’ output variation individually through these channels by receiving analog signals from generators. The main significance of this console is its real time graphical presentation of the variation of the generators’ output. From this graph, the operator can calculate the variation of the generator output per millisecond by recording the time interval between start and stop time also be able to probe the transient fluctuation by the sudden up-down of peaks. It has also a digital voltmeter. Besides, this console has in-built desk watch. It’s setting button open the setting form and record button the record form as and when required.

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Figure-4: PC Consol – PC-based YVFPS  The second form is the setting view as shown in figure-5 (a). This vies has the facilities to change clock rate, X-axis division, variance, number of record stored, X-axis interval, temperature and pressure calibration if required (expandability).

Figure-5: (a) Data Table View and (b) Setting View  The third form is the record view as shown in figure-5(b), which has the facility to provide the variations of voltage output over long time as per the selections of the setting view. From this view, the

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operator can generate a report of the variations of generator output over time. It has also the facility to delete all the old records.  6.

The fourth form is the instruction view, which is actually an internet browsing form. But, here is being used to call help view. Title and project description views are just word.doc.

Expandability

This project can be expanded with minor change in various views to design temperature control system for laboratory use, to monitor temperature changes in generators, motors and other electrical/electronic/mechanical appliances. Beside, with minor modification of the associated circuits and using pressure gauge this system converted into a system for vehicles to monitor, pressure of lubricant as well. However, on board ship, this system can be used to monitor, water level of drinking water, lubricant pressure level, fuel level etc. 8.

Conclusion

PC-based TVFPS is low cost but may be very effective system to probe transient voltage fluctuation of generator output under “no and on load” conditions. Although web based and standalone many such systems using microcontroller already have been designed and some of them also are commercially available in the mean time, but this type of probing system is rare to date. With minor modification and required sensors, this system can be realized as power monitoring and control system (PMCS). However, the mastery of this project helps the students of both under graduate and post graduate levels to understand the basics of interfacing software, use of LPT1 port and conversion of signals from analog to digital and digital to analog. In that the students are encouraged to work with this project for realizing its expandability features. Acknowledgement All contributors (including Cdre K K Hasan, (L), psc, BN and Capt Niaul Hauque, (L), BN) to this project duly acknowledged. Reference [1]

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