Pulse Width Modulator PWM

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• Pulse Width Modulator (PWM)

EE 3331-002 Group 4 Joshua Teel Marvin
Basa Richard Howell
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• Objective
• Design a digitally controlled PWM signal
  generator with 4 bits of control.

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• What is a PWM?

4 bits of input change the output to one of 16
different duty cycles ranging from 0 to 94
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• Schematic

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CircuitMaker Results
Pspice would not model the 74LS85 comparator so
we used Circuit maker to simulate our circuit.
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Waveforms Countdown from 15 to 0
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Input of 0
8
Input of 15
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Input of 7
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Building the Circuit
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74HC14 Schmitt Trigger
5 V
0 V
Frequency F1/CR C 1.07 µF R2.16
KO Calculated 432 HZ Actual 445 HZ
difference 2.8
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Problems
Input of 8
5 V
0 V
13
Input of 4
5 V
0 V
14
Input of 0
5 V
0 V
15
Input of 1
5 V
0 V
16
Input of 2
5 V
0 V
17
Input of 3
5 V
0 V
18
Input of 4
5 V
0 V
19
Input of 5
5 V
0 V
20
Input of 6
5 V
0 V
21
Input of 7
5 V
0 V
22
Input of 8
5 V
0 V
23
Input of 9
5 V
0 V
24
Input of 10
5 V
0 V
25
Input of 11
5 V
0 V
26
Input of 12
5 V
0 V
27
Input of 13
5 V
0 V
28
Input of 14
5 V
0 V
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Input of 15
5 V
0 V
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• Uses for a PWM
• Fan speed control
• Motor speed control
• Servo control
• Any system that requires a linear varying voltage
  source

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Budget
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Gantt Chart
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References http//homepages.which.net/paul.hills
/Circuits/PwmGenerators/PwmGenerators.html http/
/www.semiconductors.philips.com http//www.ti.com
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Questions?