12/3/2020
Project 1.2.6 Understanding Analog Design: The Random Number Generator
PLTW ENGINEERING
Project 1.2.6
Understanding Analog Design: Random
Number Generator
Distance Learning Support
Check with your teacher about:
Using Multisim Live for the Circuit Design Software
What work you need to turn in and how to submit it
Collaboration strategies
INTRODUCTION
The field of analog electronics is a unique discipline, distinct from the study of
digital electronics. We have only scratched the surface of what you would learn if
you continue your studies in analog electronics. This project will be the last activity
in our brief journey into the world of analog electronics.
In this activity, you will use the Circuit Design Software (CDS) to build and test the
complete analog section of the Random Number Generator design.
EQUIPMENT
Computer with Circuit Design Software (CDS)
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Project 1.2.6 Understanding Analog Design: The Random Number Generator
RESOURCES
Understanding Analog Design
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Project 1.2.6 Understanding Analog Design: The Random Number Generator
Procedure
Shown below is the analog section of a Random Number Generator circuit.
Distance Learning Support
You have not seen a Random Number Generator circuit in this Distance Learning
adaptation of the course, but you will see it in the next project. The analog clock
signal from this 555 Timer will be used as an input to the digital section of the
larger Random Number Generator circuit.
Analog Section - Random Number Generator
Unfortunately, there are two issues with simulating this circuit as shown. First, it is
difficult to obtain accurate simulation results using the push-button switch, Press to
Roll. Additionally, the 100 μf capacitor (C1) causes the simulation to run too long.
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Project 1.2.6 Understanding Analog Design: The Random Number Generator
To fix these issues, we must make two simple changes to the circuit. First, you can
replace the push-button switch with an SPST switch. Second, you can change the 100
μf capacitor to 50 μf. These changes are shown below. Also shown are the
oscilloscope connections (highlighted).
Modified Analog Section – Random Number Generator
1
Using the CDS, enter the modified analog section of the Random Number
Generator shown.
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Project 1.2.6 Understanding Analog Design: The Random Number Generator
Distance Learning Support
Create the circuit in Multisim Live using the TLC555 timer.
Hide
2
With the switch closed, start the simulation.
Distance Learning Support
The SPST switch can be closed using the configuration pane to toggle
its State value.
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Project 1.2.6 Understanding Analog Design: The Random Number Generator
3
Open the oscilloscope tool and adjust the scale of the time base and
channels, so that the three signals are easy to see and measure.
Distance Learning Support
In the Multisim Live Grapher, the signals are shown overlaid on each
other.
The color of the signal matches the color of the voltage probe you
placed in the circuit.
Recall you can configure the Grapher. In the Axes section, change
the scale of the x-axis (Time) by adjusting Time/Div.
4
Restart the simulation.
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Project 1.2.6 Understanding Analog Design: The Random Number Generator
5
After the first few square waves are observed on the output signal, open the
switch. Let the simulation run until the output signal stops oscillating. When
the oscillation stops, stop the simulation. This may take a few minutes.
6
Adjust the oscilloscope to display the first few square waves of the output
signal. Using the oscilloscope’s markers, measure the period of the first signal.
Use this data to calculate the frequency. Record your result in the table.
Distance Learning Support
To see the first few square waves of the output signal, set Axes Time
Minimum to 0 and set Maximum to around 125m.
Signal
First Square Wave
Period
15.571ms
Frequency
.064
Middle Square
Wave
Last Square Wave
7
Repeat step 6 for a signal in the middle of the simulation, approximately
halfway between the first and last square waves observed.
Distance Learning Support
Adjust Axes Time Minimum and Maximum values to view different
sections of the graph.
8
Repeat step 6 for the last square wave observed prior to the oscillation stop
point.
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CONCLUSION
1
When the Random Number Generator is activated, the 555 Timer will
oscillate at approximately 65 Hz. If you want the oscillation to start at 100
Hz, what value would you apply to C2?
2
The values of RA and C1 determine the time from when the push-button is
released to when the oscillation stops. If you wanted to lengthen this time
period, what changes would you make to one or both of these
components? Explain.
Proceed to project
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