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PC and microcontrollers applications in the laboratory exercises of the electrical engineering

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Development of the new technologies in telecommunications, electronics and electrical engineering is a very dynamic process. It creates the need of constantly improving teaching programs in the field of electrical engineering. That includes exercise-related items like the use of computers and microcontrollers in automatic control systems. Accordingly, the presented examples of laboratory exercises can significantly contribute to better understanding of the planned curriculums.
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PC and microcontrollers applications in the
laboratory exercises of the electrical engineering
Olivera Tasić*, Viša Tasić**, Darko Brodić***, Vladimir Despotović***, Marijana Pavlov**, Dragan R.
Milivojević**
*
Mechanical and Electrical High School, Bor, Serbia
**
Mining and Metallurgy Institute, Bor, Serbia
***
Technical Faculty in Bor, University of Belgrade, Bor, Serbia
e-mail: visa.tasic@irmbor.co.rs
Abstract - Development of the new technologies in
telecommunications, electronics and electrical engineering is
a very dynamic process. It creates the need of constantly
improving teaching programs in the field of electrical
engineering. That includes exercise-related items like the use
of computers and microcontrollers in automatic control
systems. Accordingly, the presented examples of laboratory
exercises can significantly contribute to better
understanding of the planned curriculums.
I. INTRODUCTION
Non scholae, sed vitae discimus (not for school but for
life we learn). The old Latin phrase describes the goal of
any educational system. Mechanical and Electrical High
School Bor was established in 1990 by the decision of the
Municipal Assembly of Bor, on the basis of Secondary
Education Low, as an independent institution for
education pupils in mechanical and electrical engineering
[1]. School covers three education profiles: electrical
engineering, mechanical engineering and transportation.
The educational scope in electrical engineering covers
several educational profiles, such as electrical technician
for: multimedia, computers, computer networks,
automation, and electronics and electrical energy. Rapid
development of the new technologies in electronics,
telecommunications and electrical engineering creates the
need to constantly improve teaching Practical experience
that pupils gain in the laboratory is of particular
importance for their understanding of the applicability of
theoretical knowledge. Simple, clear, and interesting
experiments and exercises are essential to motivate them
to expand their knowledge.
Selected examples of laboratory exercises based on the
application of microcontrollers and computers in
automatic control systems are presented in the paper. Due
to well cooperation established between educational
institutions and commercial enterprises, our pupils
perform their practical exercises not only in laboratories
within the school, but also in laboratories of other
scientific institutions and enterprises within the town [2].
II. COMPUTER AND MICROCONTROLLERS
APPLICATION IN AUTOMATIC CONTROL SYSTEMS
In this part of paper, some examples of laboratory
exercises that use Intel, Motorola, Siemens, and
Microchip microcontrollers and microprocessors will be
shown. It is well known that microcontrollers are designed
for embedded applications. A microcontroller is a single
chip that contains the processor (CPU), non-volatile
memory for the program (ROM or flash), volatile memory
for input and output (RAM), a clock and an I/O
(Input/Output) control unit.
A. Traffic Light
The first example is a simple control application for
programming the traffic light using different
microcontrollers and PC software.
The first control application is realized using Siemens
Logo! 12/24RC logic module. In its basic configuration it
has integrated display and operator panel, 8 digital inputs,
of which 2 can be used in analog mode and 4 relay
outputs. Number of inputs/outputs can be increased using
the extension modules. The Logo control system is
perfectly suited for educational purpose, as it simplifies
the automation process by replacing many time switches
and relays, counters and protective relays with logic
modules. Well designed exercises can encourage pupils to
realize their own small-scale automation projects.
Figure 1. Simple model of traffic light realizes with Siemens Logo!
12/24RC logic module
Figure 2. Programming the traffic light in Logo! Soft Comfort
software using the functional block diagrams
Figure 1 presents a model of traffic light, realized with
Siemens Logo logic module [3]. Figure 2 shows an
example of the program created with Siemens Logo! Soft
Comfort software. This programming software enables
control programs to be created, tested, edited, archived
and printed out on a PC. The process of creating a
program involves positioning and linking up program
components from the predefined library (see left side in
the Figure 2) on a "drawing board". One particularly user-
friendly feature is the offline program simulation facility
which enables simultaneous display of multiple function
statuses. Except in simulation mode programs can be also
uploaded into the Logo logic controller and executed in
real-time. Logo! Soft Comfort provides two options for
creating circuit programs: a) functional block diagram (see
Figure 2) or b) ladder diagram (see Figure 3).
Ladder logic is a programming language that
represents a program by a graphical diagram based on the
circuit diagrams of relay logic hardware. Ladder diagram
programming is important when a programmable logic
controller (PLC) is used primarily to replace relays,
timers, and counters [4]. Analog quantities and
arithmetical operations are unsuitable to be expressed in
ladder logic, and each manufacturer has different ways of
extending the notation for these problems [5].
Programming the same application in many different
programming environments is very rewarding experience
for pupils and students. For this reason, the same exercise
was realized using the Microchip PIC16F877A CMOS
FLASH-based 8-bit microcontroller (see Figures 4 and 5).
MPLAB Integrated Development Environment (IDE) is
used to develop the embedded application for PIC
microcontrollers. It runs under Microsoft Windows
operating systems and includes code editor (supports
assembler and C languages), simulator with the debugger,
and project manager [6].
However, a special development environment, named
DLadder, is developed in Borland Delphi 7 programming
language, for programming the PIC16F877A
microcontroller. It allows programming using ladder
logic, interpretation and compilation of programs into
native code, debugging and the real-time simulation. It
also allows the contents of the microcontroller ports and
Figure 3. Programming the traffic light in Logo! Soft Comfort
software using the ladder diagrams
Figure 4. The traffic light electric scheme realized with the
PIC16F877A microcontroller [5]
memory locations real time presentation [5]. The primary
motive for DLadder IDE developing is a desire to develop
programs for PIC microcontrollers using the concept of
visual programming. Although there are a number of
development environments for PIC microcontrollers on
the market, few of them allow writing the programs in
ladder logic. Writing a ladder diagram is performed by
selection the required elements from the object toolbar
(shown in Figure 6) and setting them in the appropriate
position on the screen.
Figure 5. Model of traffic light realized with the PIC16F877A
microcontroller
Figure 6. Programming the traffic light in DLadder software
The function objects support the arithmetic operations,
logic operations, etc. An example of a simple ladder
program, which simulates operation of the traffic light, is
shown in Figure 6. Once the code has been built and
checked from the syntax point of view, it should be tested.
When SIMULATOR option in DLadder is selected, the
program appears on the screen with the energized (true)
branches highlighted (red color), as shown in Figure 6.
The debugging process is simplified in this way.
Furthermore, the traffic light program can be written in
assembler language for 8086 microprocessor and executed
under the assembler and microprocessor emulator
EMU8086 [7], as shown in Figures 7 and 8. EMU8086
supports user-created virtual devices that can be accessed
from assembly language program using in and out
instructions. The traffic light lamps are controlled by
sending data to I/O port 4 [8]. There are 12 lamps: 4
green, 4 yellow, and 4 red. One can set the state of each
lamp by setting its bit:
1 - the lamp is turned on, 0 - the lamp is turned off.
Only 12 low bits of a word are used (0 to 11), last bits
(12 to 15) are unused. For example:
MOV AX, 0000001011110100b
OUT 4, AX
Figure 7. The semaphore example: assembler language code in the
emulator EMU8086 editor window [7]
Figure 8. The semaphore simulation in the emulator EMU8086 [8]
B. Stepper motor
Next exercise is related to the development of the
program to control a stepper motor. Stepper motor is an
electric motor that can be precisely controlled by signals
from a computer. The motor turns through a precise angle
each time, when it receives a signal. By varying the rate at
which signal pulses have been produced, the motor can be
run at different speeds or can be turned through an exact
angle and then stopped [8].
The first part of this exercise refers to the use of a
stepper_motor.asm example in the emulator EMU8086
[7]. Figure 9 shows a basic 3-phase stepper motor. It has 3
magnets controlled by bits 0, 1 and 2. Other bits (3..7) are
unused. The stepper motor is controlled by sending data to
I/O port 7. When a magnet is working, it becomes red.
The arrow in the Figure 9 shows the direction of the last
motor move. In the stepper motor example, the code
below will do three clock-wise half-steps:
MOV AL, 001b; initialize.
OUT 7, AL
MOV AL, 011b; half step 1.
OUT 7, AL
MOV AL, 010b; half step 2.
OUT 7, AL
MOV AL, 110b; half step 3.
OUT 7, AL
Figure 9. The stepper motor simulation in the emulator EMU8086 [8]
Figure 10. The pin assignment of PC parallel port connector
Figure 11. The electric scheme realized to control the stepper motor by
use of the PC parallel port
The second part of this exercise refers the use of the
PC parallel port (shown in Figures 10, 11 and 13) to
control the stepper motor. For this purpose, an appropriate
program is created in Borland Delphi 7. The input
parameters of the program are: number of steps, direction
of rotation, and delay between steps, coil to be switched
on, and parallel port address, as shown in Figure 12.
C. Temperature Control
This example is also very simple, but very practical.
The short program, shown in Figures 14 and 15, written in
the assembler language for Intel 8086 microprocessor
presents how to keep a constant temperature using the
heater and the thermometer [7].
Figure 12. The main window of the program to control the stepper
motor with four coils
Figure 13. The interface board realized to control the stepper moto
Figure 14. The temperature control example: assembler language code
in the emulator EMU8086 editor window [7]
Figure 15. The temperature control example [7]
Figure 16. The interface board realized to control the temperature by
use of the PIC18F4550 with the LM35 temperature sensor
The second part of this exercise refers to the use of the
microcontroller PIC18F4550 to measure the temperature.
The LM35 integrated temperature sensor is used [10]
(linear scale factor is +10 mV/°C). It does not require any
external calibration or trimming to provide typical
accuracies of ± 1⁄4 °C at room temperature. Appropriate
program is created in DLadder environment and uploaded
to microcontroller. While the program is running, the
actual value of temperature has been displayed on LED
display, as shown in Figure 16. The sensor output is
connected to one of the microcontroller analog inputs, as
shown in Figure 17.
D. Other Lab Exercises
Laboratory exercises in the field of process control and
distributed control systems on the various types of
industrial microcontrollers are also carried out. MMS
(Microprocessor Measuring Station) is the representative
of such equipment, which is still in use [2]. Pupils learn
how to configure the MMS and to adjust and verify its
validity. The dedicated software for real time operation is
executed at the PC workstation, with standard SCADA
functions, designed for the use in network environment
[9]. Pupils learn and practice how to set the monitoring
properties of the program related to the configuration of
the input parameters. Furthermore, MMS with power
transducers serves to introduce pupils to the principles of
measurement of electrical power and control of power
consumption [2]. Power transducer output signals are led
to the MMS analog inputs. Measurement procedure
consists of input signal A/D conversion, and processing of
obtained numerical values. The power transducer gives
the standard voltage signal (0 - 5 V DC) as an output,
proportional to the active and reactive power. Laboratory
exercise consists of setting of the output signal from the
power transducers by setting the value of consumer's load
and setting of MMS analog inputs based on A/D
conversion results from readings [2].
III. CONLUSION
Interesting and simple experiments and exercises are
essential to motivate pupils to expand their knowledge.
Shown exercises can be equally used in the courses that
deal with programming languages, as well as in the
courses that deal with the elements of automatic control
systems. One should note that good cooperation between
educational institutions and commercial enterprises is
essential to the quality of the teaching process, which
enables the use of external laboratories as education bases.
Figure 17. The electric scheme realized to measure the temperature by
use of the PIC18F4550 with the LM35 temperature sensor
ACKNOWLEDGMENT
This work is supported by a grant from the Ministry of
Education, Science and Technological Development of
Republic of Serbia, as a part of project No. TR33037
Development and Application of Distributed System for
Monitoring and Control of Electrical Energy Consumption
for Large Consumers."
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Exercises at the Laboratory of Applied Electronics and Computer
Engineering”, Proceedings of 6th. International Scientific
Conference Computer Science 2011, 01.-03.09.2011. Ohrid, FJR
Macedonia, pp. 429-434, ISBN 978-954-438-914-7.
[3] http://www.automation.siemens.com (accessed 10 January 2013)
[4] W. Bolton, Programmable Logic Controllers, Fifth Edition,
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V.Miljković, Dladder - an Integrated Environment for
Programming PIC Microcontrollers, Proceedings of XLVII
International Scientific Conference on Information,
Communication and Energy Systems and Technologies ICEST
2012, 28.6.-30.6.2012, V.Trnovo, Bulgaria, vol. 2., pp. 577-580.
[6] Microchip Inc., MPLAB ICD 2 In-Circuit Debugger User’s Guide,
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[8] http://www.ziplib.com/emu8086/virtual_devices.html (accessed
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ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
Monitoring and control of technological processes in many production units demands transfer of information and interaction with the process from remote distances For this purpose, the process control systems have been designed and developed In the first project phase, the separate production lines were covered by independent control systems In the second phase, the individual control systems were interconnected in a large heterogeneous industrial network, forming the distributed control system (DCS) This paper presents results of development of specific hardware and software solutions for monitoring of technological processes, with special regards to communication systems structure
Chapter
This chapter presents an introduction to the programmable logic controller, its general function, hardware forms, and internal architecture. A programmable logic controller (PLC) is a special form of microprocessor-based controller that uses a programmable memory to store instructions and to implement functions such as logic, sequencing, timing, counting, and arithmetic to control machines and processes. It is designed to be operated by engineers with perhaps a limited knowledge of computers and computing languages. Input devices and output devices in a system being controlled are connected to the PLC. The operator enters a sequence of instructions, that is, a program, into the memory of the PLC. The controller then monitors the inputs and outputs according to this program and carries out the control rules for which it has been programmed. PLCs are now widely used and extend from small self-contained units for use with perhaps 20 digital inputs/outputs to modular systems, which can be used for large numbers of inputs/outputs, handle digital or analogue inputs/outputs, and also carry out proportional-integral-derivative control modes. A PLC system has the basic functional components of a processor unit, memory, power supply unit, input/output interface section, communications interface, and programming device. It consists of a central processing unit (CPU) containing the system microprocessor, memory, and input/output circuitry. The CPU controls and processes all the operations within the PLC.
Practicing of Lab Exercises at the Laboratory of Applied Electronics and Computer Engineering
  • V Tasić
  • D Brodić
  • D Milivojević
  • M Pavlov
V.Tasić, D.Brodić, D.Milivojević, M.Pavlov, "Practicing of Lab Exercises at the Laboratory of Applied Electronics and Computer Engineering", Proceedings of 6th. International Scientific Conference Computer Science 2011, 01.-03.09.2011. Ohrid, FJR Macedonia, pp. 429-434, ISBN 978-954-438-914-7.
MPLAB ICD 2 In-Circuit Debugger User's Guide
  • Microchip Inc
Microchip Inc., MPLAB ICD 2 In-Circuit Debugger User's Guide, Microchip Technology Inc., 2005. http://ww1.microchip.com/ downloads/en/devicedoc/51331b.pdf (accessed 10 January 2013)
Dladder-an Integrated Environment for Programming PIC Microcontrollers
  • V Tasić
  • D Milivojević
  • V Despotović
  • D Brodić
  • M Pavlov
  • V Miljković
V.Tasić, D.Milivojević, V.Despotović, D. Brodić, M.Pavlov, V.Miljković, "Dladder-an Integrated Environment for Programming PIC Microcontrollers", Proceedings of XLVII International Scientific Conference on Information, Communication and Energy Systems and Technologies ICEST 2012, 28.6.-30.6.2012, V.Trnovo, Bulgaria, vol. 2., pp. 577-580.