Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus®...
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Transcript of Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus®...
![Page 1: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/1.jpg)
Chapter 14
Multivibrators and the 555 Timer
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 2: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/2.jpg)
Multivibrators
• Changes between two digital levels– continuous, free-running– on demand
• Three types– bistable (S-R flip-flop)– astable– monostable (one shot)
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 3: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/3.jpg)
Capacitor Charge and Discharge Rates
• RC circuit
• See Figure 14-1– RC circuit– charging curve– discharging curve
• Exponentially changing - time constant ()
• Solving the equation for t - See Equation 14-2
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 4: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/4.jpg)
Figure 14-1
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 5: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/5.jpg)
Equation 14-2
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 6: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/6.jpg)
Astable Multivibrators
• Single Schmitt Inverter and an RC circuit
• See Figure 14-5
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 7: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/7.jpg)
Figure 14-5
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 8: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/8.jpg)
Monostable Multivibrators
• See Figure 14-8– block diagram– waveforms
• Built from NAND gates– See Figure 14-9
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 9: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/9.jpg)
Figure 14-8
Figure 14-9
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 10: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/10.jpg)
IC Monostable Multivibrators
• 74121– nonretriggerable– connect RC components for proper pulse width– two active-LOW trigger inputs– one active-HIGH trigger input– See Figure 14-12
• block diagram
• function table
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 11: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/11.jpg)
Figure 14-12
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 12: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/12.jpg)
Retriggerable Monostable Multivibrators
• 74123– new timing cycle each time new trigger applied– See Figure 14-15
• comparison waveforms
– See Figure 14-16• logic symbol
• function table
– See Figure 14-17• component selection chart
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 13: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/13.jpg)
Figure 14-15
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 14: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/14.jpg)
Figure 14-16
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 15: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/15.jpg)
Figure 14-17
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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Astable Operation of the 555 IC Timer
• One shot or astable oscillator
• Voltage divider
• Comparators
• S-R flip-flop
• Discharge transistor
• See Figure 14-20
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 17: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/17.jpg)
Figure 14-20
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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Astable Operation of the 555 IC Timer
• 50% Duty Cycle Astable Oscillator– RA cannot = 0 ohms
– RA = RB and short RB with a diode
– See Figure 14-23
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 19: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/19.jpg)
Figure 14-23
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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Monostable Operation of the 555 IC Timer
• See Figure 14-24
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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![Page 21: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/21.jpg)
Figure 14-24
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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Crystal Oscillators
• Quartz crystal• Size and shape determine specific frequency• Accurate to more than five significant digits• Integrated circuit packages or use external
quartz crystal• 74S124
– voltage controlled oscillator
• See Figure 14-28William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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Figure 14-28
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
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Summary
• Multivibrator circuits are used to produce free-running clock oscillator waveforms or to produce a timed digital level change triggered by an external source.
• Capacitor voltage charging and discharging rates are the most common way to produce predictable time duration for oscillator and timing operations.
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 25: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/25.jpg)
Summary
• An astable multivibrator is a free-running oscillator whose output oscillates between two voltage levels at a rate determined by an attached RC circuit.
• A monostable multivibrator is used to produce an output pulse that starts when the circuit receives an input trigger and lasts for a length of time dictated by the attached RC circuit.
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 26: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/26.jpg)
Summary
• The 74121 is an IC monostable multivibrator with two active-LOW and one active-HIGH input trigger sources and an active-HIGH and an active-LOW pulse output terminal.
• Retriggerable monostable multivibrators allow multiple input triggers to be acknowledged even if the output pulse from the previous trigger had not expired.
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
![Page 27: Chapter 14 Multivibrators and the 555 Timer William Kleitz Digital Electronics with VHDL, Quartus® II Version Copyright ©2006 by Pearson Education, Inc.](https://reader035.fdocuments.us/reader035/viewer/2022081417/551c4a97550346b1458b49f6/html5/thumbnails/27.jpg)
Summary
• The 555 IC is a general-purpose timer that can be used to make astable and monostable multivibrators and perform any number of other timing functions.
• Crystal oscillators are much more accurate and stable than RC timing circuits. They are used most often for microprocessor and digital communication timing.
William KleitzDigital Electronics with VHDL, Quartus® II Version
Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.