lesson 1456 experiment 3 4 overview oyou are going to vary the frequency of the astable...
TRANSCRIPT
![Page 1: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/1.jpg)
The Astable Multivibrator
Lesson 1456 Experiment 3
![Page 2: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/2.jpg)
Astable Operation
A timer IC produces an astable (or
free running) square-wave output
whose frequency can be varied by
changing the external RC time
constant.
![Page 3: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/3.jpg)
Astable Multivibrator
OAstable Multivibrators generate a
rectangular waveform.
OThis rectangular-wave oscillator
is useful in generating signals for
digital circuitry, lamp flashers,
sound generators and various
other applications. .
![Page 4: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/4.jpg)
Basic operation
OThe astable multivibrator works
with both comparators tied
together .
OThis means that pin 6 of the
upper comparator is tied to pin 2
of the lower comparator.
![Page 5: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/5.jpg)
O When power is applied, C1 is
discharged and the flip-flop is
reset.
O C1 begins to charge through RA
and RB.
O When the voltage across C1
reaches 2/3 VCC, the upper
![Page 6: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/6.jpg)
O comparator is activated and the
flip-flop is set.
O This turns on the DISCHARGE
transistor, which discharges C1
through RB.
O The lower comparator is reset
when the voltage across C1 drops
to 1/3 VCC.
![Page 7: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/7.jpg)
Things to note before constructing Figure 11
OYou will not be asked to measure
the period or frequency
OThis is due to the wide tolerances
of the Electrolytic Capacitors.
![Page 8: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/8.jpg)
OElectrolytic Capacitors have a
tolerance on their marked values
which can range from -20%,
+80%.
OThis means the capacitor you use
can have a value which is quite
different than the one we used
preparing the experiment.
![Page 9: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/9.jpg)
Astable Multivibrator, Fig 11
![Page 10: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/10.jpg)
Discussion on Experiment 3
OYou will be changing the
values of RA and RB to help
you understand how these
values affects the duty cycle
of the astable multivibrator.
![Page 11: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/11.jpg)
OWhat is the Duty Cycle?
OThe time the output of the
astable multivibrator is high
(t1).divided by the period of
the waveform (T). D = t1 /T
OThe duty cycle is usually
expressed as a percentage of
the period of the waveform
![Page 12: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/12.jpg)
OThe astable’s frequency is
determined by two time periods.
O (t1 ) is the time it takes for C1 to
charge up through RA and RB.
t1 = 0.693(RA+RB)C1
O (t2) is the time it takes for C1 to
discharge through RB.
t2 = 0.693(RB)C1
![Page 13: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/13.jpg)
What is the Period of the waveform?
OT = t1 + t2 = 0.693(RA + 2RB)C1
Frequency is the reciprocal of time
or the reciprocal of the period T.
O f = 1/T = 1.44/(RA + 2RB)C1
OWhen using an oscilloscope, you
may often be converting the
period of the signal to frequency.
![Page 14: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/14.jpg)
Building your circuit
ORemember the basics
ORemember where Pin 1 and
8 are located on the IC
OCenter the IC on the divider
strip on the Breadboard
![Page 15: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/15.jpg)
OMake sure you do not short out
the component leads
OSpread your circuit out to make it
easier to follow the connections.
OUse different color jumpers for
the VCC and GND connections
![Page 16: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/16.jpg)
OMake sure you pay attention to component polarities
OElectrolytic capacitors have a polarity which you need to follow.
ODiodes have a polarity as well
OThe band is the cathode on a diode
OThe short lead or notch side on an LED is the cathode
![Page 17: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/17.jpg)
Astable Multivibrator Built
![Page 18: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/18.jpg)
Astable Multivibrator, Fig 11
![Page 19: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/19.jpg)
Close-up of Astable Multivibrator
![Page 20: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/20.jpg)
Modify Fig 11 as indicated
OChange RB to the 100KΩ potentiometer (on the trainer) in series with a 10kΩ Resistor.
OChange C1 from 100µF to 10µF.
OThis will give you the Variable-frequency oscillator of Fig 12.
![Page 21: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/21.jpg)
Variable Frequency Oscillator
![Page 22: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/22.jpg)
Fig 12 Variable Freq. Osc.
![Page 23: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/23.jpg)
Close-up of Variable Freq. Osc.
![Page 24: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/24.jpg)
Brief Review of Experiment 3
OWe have seen changing the
components in the external RC
circuit changes the frequency and
duty cycle of the oscillator .
![Page 25: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/25.jpg)
OPin 3 output was high when the
capacitor was charging through
RA and RB
OPin 3 output was low when the
capacitor was discharging
through RB.
![Page 26: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/26.jpg)
Experiment 4 Overview
OYou are going to vary the frequency
of the astable multivibrator using
two methods;
1. Vary the frequency using a
variable RB
![Page 27: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/27.jpg)
2. Vary the frequency by using a
control voltage on Pin 5.
3. It is important to keep your
working circuit from experiment 3
intact.
a) Modify the previous circuits as
needed to build Figs. 13, 14 &15.
![Page 28: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/28.jpg)
b) You will be changing the output
device and the timing circuit
OYou are again going to vary the
frequency of the astable
multivibrator using two methods;
![Page 29: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/29.jpg)
1. Vary the frequency using a
variable RB.
2. Vary the frequency by using a
control voltage on Pin 5.
O Remember: Pin 5 should be
connected to GND through a
capacitor when not in use.
![Page 30: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/30.jpg)
Questions?
![Page 31: Lesson 1456 Experiment 3 4 Overview OYou are going to vary the frequency of the astable multivibrator using two methods; 1. Vary the frequency using a variable R B 2. Vary the frequency](https://reader031.vdocument.in/reader031/viewer/2022030423/5aaab74d7f8b9a9a188e944d/html5/thumbnails/31.jpg)
The End
Developed and Produced by the Instructors in the CIE Instruction Department.
© Copyright 01/2012
All Rights Reserved / Jan. 2012