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Section 5. Pedagogy
Shyshkin Gennadiy Aleksandrovich, Docent, Ph. D, Berdyansk State Pedagogical University E-mail: [email protected] Bandurov Sergey Olegovich, A Third Year Student Faculty of Physics and Mathematics, Berdyansk State Pedagogical University E-mail: [email protected]
Digital electronics in an educational experiment in physics
Abstract: This paper considers the problem of reducing the level of physics education in Ukraine which connected an acute lack of laboratory and demonstration equipment. Offers the solution through self-development and production of digital technology electronic devices for use with personal computers.
Keywords: physics experiment, analog-digital converter, measurement system, analog sensors.
Formulation of the problem. In modern conditions, rapid development of science and technology, manufacturing and mass media, the society demands from pedagogical science new innovative approaches in the organization of the educational process of young people. Particular attention should be paid to improving of the level and quality of physics education, because the physics is a theoretical basis of technological development. Successful students should mastering the basics of modern science is important for the formation of the personality of the modern human in the technological society.
Modernization of physics education is not possible without improving the educational experiment. Physical experiment plays an important role in teaching of physics. On this basis, students are introduced to the basis of physics phenomena and through experiment determine the relationship between them, check the validity of laws and theories. With the help of physical experiments formed and skills ofworking with instrumentation.
Last years in Ukraine, we are seeing a trend of sharp decrease in the level of knowledge in physics, as in secondary and higher education institutions. One of the main reasons for this situation we see in the lack of material resources of the cabinets and laboratories of physics education.
According to the results of monitoring of the state, the level of school teaching aids in Ukraine is about 30 % of the required. Material base of the cabinets of natural sciences laboratory and demonstration equipment is about 15 % [8]. The majority part, are the instruments of old production, which in most cases are technically outdated. The use of such laboratory and demonstration equipment for training purposes does not bring the expected positive pedagogical results.
The lack of material support of educational institutions is connected with the difficult economic situation in the country. Educational institutions are not able to purchase the necessary equipment, which leads not only to reduction of the quality of education, but also to reduction of students interests in the study of physics and mathematical sciences. For this reason, the priority goal of the improving of physics education is an upgrade of educational physics equipment and devices.
The purpose of writing this article — is to familiarize the reader with the use of elements of digital technology in the physics education experiment by using computer technology.
Analysis of recent research and publications. The analysis of methodological literature, results of scientific research, dissertations and personal experience indicates inadequate organizing and conducting ofeducational physics experiment in all types of educational institutions of Ukraine. Along with this, in the construction of electronic devices for improving the educational experiment in physics were involved many scientists and methodologists. Most electronic devices developed by V P. Vovkotrub, N. V. Fedishevoy, O. S. Martyniuk can be use with personal computer. The method of application of analog-to-digital converters, both industrial and independently developed, studied
M. Galatyuk, V. I. Tyshuk, and V. P. Shevchuk. The possibilities of application of the analog-digital converter (ADC) together with computers in the educational physics experiment. In the similar direction worked R. V. Meyer, O. Danilov, R. V. Akatov,
N. S. Stepanov, M. Alykova, and S. V. Eremin.
The basic material and the results of the study. In the period of rapid development of electronics, which is connected with microprocessor technology, the creation of multifunctional computers and process of mass globalization of society. Computerization of all spheres of human activity could not affect on the educational process. Implementation in educational process of modern information and technical resources allows to put education to a new level.
The most advanced spheres of computer technology in the teaching physics we see in improving equipment for performance of the educational experiment. The economic situation in the country does not allow to fully provide the education institutes with necessary training equipment, which leads to reduction of the quality of physics education.
To partially solve the problem in the current conditions, we are working on the development and production of electronic devices, which can be used together with PC, it allows to realize all opportunities of cabinets and laboratories for the educational physics experiment. Personal computer we use as a measuring device and as a means of visual display of the studying dynamical processes on the screen.
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Digital electronics in an educational experiment in physics
Complex use of personal computers and electronic analog signal converters can be successful during the laboratory and demonstration experiments. Using of PC allows to put demonstration experiments to a new level, to develop and implement a demonstration in their various combinations.
We have developed electronic devices connected to the PC, which gives us the measurement system shown in Figure 1, which is able to replace a number of physical instrumentation.
Functional diagram of the developed measuring complex is shown in Figure 2. The complex consists of three functionally interconnected units. The first unit of measuring
complex is a set of analog sensors that measure physical quantities such as pressure, temperature, humidity, velocity, acceleration, force, current, voltage and others.
At the output of the sensor, the amplitude of the analog signal is typically tens of millivolts, which does not allow study and measure signal in detail. To amplify the signal coming from the analog sensor serves the amplification unit of the analog signal (SA). This unit is a precision amplifier for amplifying a voltage of analog sensors, photocells and thermocouples. The output circuits, the signal goes to an analog-to-digital converter (block 3) and then goes directly to a personal computer.
Fig. 1. Measuring complex, where: 1 - solar battery, 2 - power supply signal amplifier, 3 - signal amplifier, 4 - analog-to-digital converter, 5 - power supply analog-to-digital converter, 6 - thermocouple
Fig. 2. Functional diagram of the measuring complex
Schematic diagram ofthe amplifier is shown in Fig. 3 [1; 5]. The main element is the amplifier chip LM 358, its choice is motivated by the fact that it includes two independent operational amplifier with common power supply that allows you simultaneously amplify analog signals on two channels. The amplifier is configured so that the maximum output voltage may reach 3V. The sensing elements are connected to the terminals 1.2-1.5 according to the polarity shown on (Fig. 3). Outputs 1.6-1.7 are outputs of the amplified signal. Supply voltage (OA) may vary from 7.5 V. to 12 V. and connected to pin 1.1. Variable resistors R13, R20 define (gain), the maximum measured value depending on the used sensor elements. Variable resistors R10, R17 is set to zero. Setting the output (OA) is performed above mentioned variable resistors. The settings procedure is individual, depending on
the use of the sensor element. If it is necessary, this block may be removed and the voltage from sensor can be sent directly to the block 3 (Fig. 2).
For converting, the amplified analog signal (block 2) in the digital signal for further sending to a PC has been developed a third unit, the analog-to-digital convertor. We assembled this unit and it is a multichannel ADC, the circuit diagram is shown in Fig. 4 [3; 6].
The computer operates on discrete values, so an ADC is a physical part of the measuring system, which uses analog sensors. This device is intended to convert the analog voltage supplied on its input into digital form. Sensor, on which output present voltage of the measured physical quantity, can be matched to the ADC, if the output voltage of the sensor does not exceed the maximum voltage on the ADC input [2].
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Fig. 4. Is a circuit diagram of ADC
Development of the unit was based on a circuit diagram that is described in the literature [6]. The device has 5 analog inputs J1-J5, and 6 digital outputs 1-6 which can be used to record additional digital signals. The device is able to convert analog signals to digital simultaneously with five sensors, with an amplitude not exceeding 5V Resistors R2, R4 (analogously to subsequent channels resistors R5, R7; R8, R10; R11, R13; R14, R16) formed divider which defines the range of input supply voltage and is calculated in such a way that its output was not more than 5 V. Increased allowable amplitude for one of the input channels will lead to distortion in the other inputs. Calculation of the voltage divider can be performed on the formulas.
Substitute the formula (2) (3) and get:
v = UR
R2 + R.
From this formula, we find 11
kR<
r2 + r4
-, or R2 + R4 = kR4. The
The current flowing through the divider is given by:
1 R + R4'
where U.n — the voltage applied to the divider. Output voltage divider:
UR
U = IR = -
r2 + r4
(1)
(2)
where U0 = 5V constant amplitude of the input signal to the MC. Reduction Factor voltage divider defined by the formula:
k = . The voltage applied to the divider:
Un = kU
(3)
resistance of the resistor R2 can be calculated according to the formula R2 = (k - 1)R4.
Figure 3 divisors set the width of the input voltage range of the ADC, 0 to 10 V while the measurement accuracy ADC
will be: U = 9,7мВ ; where U, - the maximum value of
1023 1
the input range is 10V.
Clock frequency is 20 MHz. MC that has been modified by installing an external crystal frequency 4 MHz. on Z1. The maximum sampling rate depends on the bandwidth speed serial communication RS-232 and lies in the aisles of 0.5 kHz.
The device is powered from the separate stack-mounted and stabilized power supply unit (PSU). Its capacity of 2,4W. and the output voltage is 9V. Communication with the PC uses the interface Bu1, RS-232 (com - port) the data exchange rate is 9600 baud. Moreover, it is possible to use the RS-232 to USB adapter, which enables commutate the signal from RS 232 to USB interface painlessly.
To program the microcontroller we have assembled «EXTRA — PIC » programmer [4; 7] and used the program «WinPic800».
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Digital electronics in an educational experiment in physics
The device is able to convert analog signals simultaneously with five sensors. After converting the signal from the ADC is fed to the computer. By PC specific requirements.
The main element of the ADC is a programmable 10-bit microcontroller (MC) PIC16F876A. This microcontroller was programed according to the text of the program, see [6].
By means of program “UM-ADC-1” performed charting monitoring and recording. The “UM-ADC-1” is designed for 5-channel ADC and allows simultaneous monitoring all five channels. The program has a function of the input signal emulation, which allows to evaluate the configured settings. With the functions of the program, can be set different units of measurement in different numerical ranges, i. e. adapted for use of specific sensors. In case of exceeding of the limits of the input signal, audible and visual alert will be triggered.
The program allows you to set the desired recording speed and bandwidth of the measured values. The “detail” saves the results of the experimental data in a format txt for further detailed review and study of the results.
Production and setting of the proposed complex is possible in physics cabinets and technical workshops, problematic student labs. The proposed electronic devicemeasuring complex does not use expensive and scarce elements. Manufacture of such devices by students studying at schools and extracurricular work contributes to the solution of a number of educational issues: professional orientation of teaching physics; improvement of the material base of educational institutions; development of students’ practical skills; effective use of personal computers for educational purposes.
References:
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2. Данилов О. Е. Создание компьютерного измерительного комплекса с аналоговыми датчиками для школьного кабинета физики/О. Е. Данилов//Дистанционное и виртуальное обучение. - № 3. - 2013. - C. 93-102.
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8. Розпорядження Кабшету Мiнiстрiв Укра!ни вЦ 27 серпня 2010 р. № 1720-р «Про схвалення Концепцй Державно! цыково! сощально! програми тдвищення якоста шшльно! освти на перюд до 2015 року». - [Electronic resource]. - Access mode: http://zakon4.rada/gov.ua/laws/show/1720-2010- %D1 %80 (дата звернення 06.02.2014).
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