International Journal of Advances in Electrical and Electronics Engineering Available online at www.ijaeee.com & www.sestindia.org
274
ISSN: 2319-1112
Design and Implementation of Astable Multivibrator for Different Applications in Communication System Rajender Kumar Sandeep Dahiya Krishan Kumar SES, BPSMV Sonepat, Haryana
[email protected] &
[email protected] ABSTRACT: This paper aims at presenting the design and implementation of astable multivibrator for various applications of communication system such as is digital data transmission, RFID system, FSK generator and pulse position modulation etc. An astable multivibrator is constructed for given specification one of which is, it must have a duty cycle of 0.75. The workability of the proposed circuits is confirmed through PSpice, SIMetrix and Tina pro simulations tools and finally the experimental work is compared. Through this paper one can get the idea about the use of PSpice, SIMetrix and Tina pro software and found the better results. Because they are low cost, fast simulation techniques for the linearity and accuracy of the circuit performance and reliability is reported by using these tools. The results are explored with browsing output data facility. Keywords: Astable Multivibrator, 555 Timer, Pspice, SIMetrix, Tina Pro, Simulation, Communication Systems.
I. INTRODUCTION A multivibrator find its main application in communication system as waveform generator which defined as an electronic circuit used to implement a variety of simple two state systems such as oscillators, timers and flip-flops. They are most commonly used type of relaxation oscillator as they produce a constant square wave output waveform as well as their simplicity, reliability and ease of construction. An astable multivibrator finds its applications in all types of communication system as a trigger, converter, moderator or divider in FSK generator, pulse position modulation and RFID system. They are also used in amateur radio equipment to receive and transmit radio signals. Astable multivibrators are also used in morse code generators, timers and systems that require a square wave including television broadcasts and analog circuits. An astable multivibrator which is often free running multivibrator is one which toggles between one stable state to another without the influence of any external control signal. It is used to generate rectangular waveform which can be produced by adding two resistors and a capacitor to the basic internal diagram of 555 timers IC. The time duration in which output is either high or low is determined by these two resistors (Ra & Rb) and capacitor (C) [1-3]. Finally, after theoretical design, astable multivibrator and FSK generator will be implemented using PSpice , SIMetrix and Tina Pro simulation softwares [4-6]. II. SIMULATION CONCEPT The integration of theory and practical in teaching and learning of timer IC 555 using simulation tool is quite important. The software packages such as PSPICE, Electronics Workbench, Multisim, SIMetrix, Tina Pro etc. tools are used to develop and harmonize the hypothetical concepts of timer IC 555 which is frequently used in communication system and to conduct virtual laboratory across the globe. Simulation tools are frequently used in teaching and research in engineering throughout the globe having the following advantages: (1) Understanding of theoretical concepts and principles by means of graphical/blocks/interactive simulations. (2) Provide an exposure to solve and design more complex system. (3) Solving technical computing problems faster than traditional programming languages. (4) Hands-on experimentations to supplement theoretical course contents for enhancing the quality education. (5) Enriched learning through simulation.
ISSN: 2319-1112 /V2N2:274-282 ©IJAEEE
IJAEEE ,Volume 2 , Number 2 Rajender Kumar et al. 2 In the ICT based knowledge society, it is utmost important for modern engineers to use and understand these software packages extensively to simulate, analyse, design the behavior of telecommunication, circuit & systems, hardware, software sectors etc. as per the industrial advancement. The simulation software used in the paper are PSpice, Simetrix and Tina Pro whose main features are shown in table 1 [4-8]. Table1. Comparison of various software
SN o
features
PSpice
SIMetrix
Tina Pro
1
Source
www.cadence.com/
www.simplistechnolo gies.com/downloads
www.tina.com
2
Analysis types which can be performed
AC, DC sweep, and Transient
AC, DC sweep and Transient
3
Limitations
Maximum of 10 transistors in circuit. Not support an iterative method of solution.
Do not have Simetrix AD plus Circuit, size limit apply
AC, DC sweep, Transient, steady state solver, Fourier analysis, digital timing analysis, digital VHDL simulation etc. Not allow users to open a selection of most recently used files and not allow to print virtual instrument display and setting.
In this paper, astable multivibrator is designed and simulated using 555 timers IC whose internal diagram is shown in figure 1. It was first introduced by Signetics for designing because of its versatility and ease of use. Some of main features of 555 timers IC are shown in table.2. Table 2. Features of 555 Timer IC
SNo
parameters
Features
1.
Year of Introduction
1971
2.
Manufacturer
Signetics Corporation
3.
Power supply
4.5 to 16 V
4.
Operating temperature
−65˚C to +150˚C
5.
Power dissipation
Less than 1 mW
6.
compatibility
TTL and CMOS logic
7.
temperature stability
Excellent & 0.005% per ˚C
8.
Operating modes
Monostable and astable
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276 Design and Implementation of Astable Multivibrator for Different Applications in Communication System 9.
Sinking or sourcing current
200 mA
10.
Duty cycle
Adjustable
The internal diagram of 555 timers IC consists of two comparators (simply op-amps), RS flip-flop, two transistors and a resistive network. (three equal resistor to act as voltage divider)[9-10].
Fig 1 Internal Diagram of 555 timer IC
III. THEORY AND DESIGN OF ASTABLE MULTIVIBRATOR An astable multivibrator, often called a free-running multivibrator, is a rectangular-wave-generating circuit[12]. This circuit does not require an external trigger to change the state of the output. The time during which the output is either high or low is determined by two resistors (Ra, Rb) and a capacitor (C), which are connected
ISSN: 2319-1112 /V2N2:274-282 ©IJAEEE
IJAEEE ,Volume 2 , Number 2 Rajender Kumar et al. 2 externally to the 555 timer. The basic circuit for astable multivibrator is shown
in figure 2.
Fig 2. Pspice implementation of Astable Multivibrator Period and frequency of oscillation: Let us consider Thigh and Tlow represents time during which output assume high state and low state respectively. The expression for Thigh and Tlow for astable multivibrator is given as Thigh= 0.693*(Ra+R)*C --- (1) and Tlow=0.693*Rb*C --- (2) The total time duration of oscillation is given by T= Thigh +Tlow => T=0.693*(Ra+2Rb)*C -- (3) The frequency being reciprocal of total time of oscillation is given by
F=
1.45 ---(4) ( Ra + Rb) * C
Finally the standard definition of duty cycle (D) which is often used for most pulse generator circuit is D=high interval*100/total time => D
=
Ra * 100 --- (5) Ra + Rb
Now we will design astable multivibrator which can generate a pulse of 1 ms duration with 25% duty cycle. For the same consider the value of capacitor (C) equal to 0.1uF and time duration for which output to be low and high is 0.25ms and 0.75ms respectively. Using the equations (2), value of Rb calculated is 3.6 KΩ & using equation (1), value of Ra comes out to be 6.8 KΩ. In the circuit another capacitor (C1) is used in between control voltage and ground to by-pass noise or ripple from the supply. Further, we have designed FSK generator using SIMetrix simulation which is shown in fig. 3, is frequently used in digital data communication system. It transmits binary data with frequency of 150 Hz by shifting a carrier frequency between two preset frequencies of 1070 Hz and 1270 Hz used as standard FSK signals.
ISSN: 2319-1112 /V2N2:274-282 ©IJAEEE
278 Design and Implementation of Astable Multivibrator for Different Applications in Communication System
Fig 3. SIMetrix implementation of FSK generator
When the input is high, transistor (Q3) is off and circuit will behave as normal astable multivibrator with same frequency as that of astable multivibrator and when input is low, transistor (Q3) is on then the parallel combination will provide the frequency given by Fa=1.45/((Ra//Rc)+2Rb)*C ---- (6) IV. SIMULATION RESULTS The results of PSpice ,SIMetrix and Tina Pro simulation software for astable multivibrator and its applications is shown in fig. 4 to 8 [11]. It can be seen that simulation results found good and resemble with theoretical calculated results using different equations. The comparison of simulated and theoretical results is shown in table 3 for the various spice based softwares. Table 3. Comparasion of Simulated Results
SN 0
Software
1
PSpice
2
SIMetrix
3
Tina Pro
Time duration (ms)
Voltage across capacitor(Volts)
Frequency of oscillation(KHz)
Theoreti cal Value (on,off)
Simulated value(on,off)
Theoretical Value(min, max)
Simulated value(min, max)
Theoretica l value
Simulated value
0.95ms( 0.70,0.2 5) 0.95(0.7 0,0.25)
0.96(0.74,0.2 5)
1.66,3.33
1.66, 3.38
1
1.012
0.96(0.71,0.2 4)
1.66,3.33
1.59,3.34
1
1.017
0.95(0.7 0,0.25)
0.130(1.125, 0.25)
1.66,3.33
1.67,3.3
1
0.803
Hence the FSK generator is designed and simulated which frequently used in digital data communication system. Although we have designed astable multivibrator and FSK generator theoretically but the same will be simulated using spice software's as discussed in next section.
ISSN: 2319-1112 /V2N2:274-282 ©IJAEEE
IJAEEE ,Volume 2 , Number 2 Rajender Kumar et al. 2
Fig 4. Pspice Simulated waveform of Atsable Multivibrator
Fig 5. SIMetrix Simulated waveform of Atsable Multivibrator
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280 Design and Implementation of Astable Multivibrator for Different Applications in Communication System T
4.00
vout capacitor charging
Voltage (V)
3.00
2.00
1.00
0.00 0.00
2.50m
5.00m Time (s)
7.50m
Fig 6. Tina Pro Simulated waveform of Atsable Multivibrator
Fig 7. SIMetrix Simulated waveform of Atsable Multivibrator as FSK generator
ISSN: 2319-1112 /V2N2:274-282 ©IJAEEE
10.00m
IJAEEE ,Volume 2 , Number 2 Rajender Kumar et al. 2
Fig 8. PSpice Simulated waveform of Atsable Multivibrator as FSK generator
V. CONCLUSION The workability of astable multivibrator and its applications in communication system using 555 timer IC are demonstrated through Pspice, SIMetrix and Tina Pro softwares. These circuits are composed of many passive and active components. Simulation results of three softwares are found to be conformity to the theoretical values as shown in table 3. These simulation results may be uniformly applied for testing the circuit performance and reliability under different changing conditions like temperature, pressure etc before actual circuit or product is ordered and thereby decided to be implemented in the real world. REFERENCE: [1] Rashid M.H. Microelectronics Circuit Analysis and Design, PWS Publishing Co, 1999 [2] Sanjay K Tupe, Sayyad SB, Behre S.H, Comparative study of different spice software’s using Astable Multivibrator in different Spice software,IJRTE,page-2829 vol2, No6, Nov 2009 [3] Gayakwad, R.A, Op-amps and Linear integrated circuits, Prentice-Hall India, 2000 [4] PSpice Schematics Evaluation Version 9.1, Cadence Design System, www.cadence.com [5] www.simplistechnologies.com/download [6] www.tina.com [7] L. V. Hmurcik, M. Hettinger, K. S. Gottschalck, and F. C. Fitchen, “SPICE applications to an undergraduate electronic program,” IEEE Trans. Educ., vol. 33, pp. 183–189, 1990. [8] L.K Maheshwari MM S Anand, Laboratory Experiments and PSPICE Simulation in analog Electronics,PHI.2007 [9] 555 timers, www.fairchildsemi.com [10] www.circuitstoday.com [11] Rashid M.H., Introduction to PSpice Using OrCAD for Circuits and electronics, Pearson Education., 2006 [12] Gayakwad, R.A, Op-amps and Linear integrated circuits, Prentice-Hall India, 2000
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282 Design and Implementation of Astable Multivibrator for Different Applications in Communication System
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