How do you calculate the duty cycle and frequency of a pulse-width modulation (PWM) signal?
1 Answer
To calculate the duty cycle and frequency of a Pulse Width Modulation (PWM) signal, you need to understand the basic properties of PWM. PWM is a method of encoding information onto a square wave by varying the ratio of time the signal is ON (high) to the time it is OFF (low) within a single period. The duty cycle is the percentage of time the signal is ON during a single period, and the frequency is the number of periods that occur in one second. Here's how you can calculate them:
Duty Cycle (DC):
The duty cycle is expressed as a percentage and represents the ratio of time the PWM signal spends in the high state (ON time) compared to the total time of one period. It is usually denoted by the symbol 'D' or 'DC'.
Formula for Duty Cycle:
(
)
=
×
100
%
DutyCycle(D)=
Total time
ON time
×100%
ON time refers to the time the PWM signal is in the high state (ON), and Total time is the complete period of one cycle (ON time + OFF time).
Frequency (f):
Frequency is the number of complete cycles of the PWM signal that occur in one second and is measured in Hertz (Hz).
Formula for Frequency:
(
)
=
1
Frequency(f)=
Time period
1
Time period is the time taken for one complete cycle of the PWM signal, i.e., the sum of the ON time and OFF time.
Now, to calculate the duty cycle and frequency of a PWM signal, you need to measure the ON time and the total time of one period. Here's a step-by-step process:
Step 1: Capture the PWM signal using an oscilloscope or a suitable hardware tool.
Step 2: Measure the ON time (time the signal is high) and the Total time (complete period) of the PWM signal.
Step 3: Use the formulas mentioned above to calculate the Duty Cycle and Frequency:
(
)
=
×
100
%
DutyCycle(D)=
Total time
ON time
×100%
(
)
=
1
Frequency(f)=
Total time
1
For example, let's say the ON time is 1 ms, and the Total time (ON time + OFF time) is 5 ms.
(
)
=
1
5
×
100
%
=
20
%
DutyCycle(D)=
5ms
1ms
×100%=20%
(
)
=
1
5
=
200
Frequency(f)=
5ms
1
=200Hz
So, the PWM signal has a duty cycle of 20% and a frequency of 200 Hz.
Duty Cycle (DC):
The duty cycle is expressed as a percentage and represents the ratio of time the PWM signal spends in the high state (ON time) compared to the total time of one period. It is usually denoted by the symbol 'D' or 'DC'.
Formula for Duty Cycle:
(
)
=
×
100
%
DutyCycle(D)=
Total time
ON time
×100%
ON time refers to the time the PWM signal is in the high state (ON), and Total time is the complete period of one cycle (ON time + OFF time).
Frequency (f):
Frequency is the number of complete cycles of the PWM signal that occur in one second and is measured in Hertz (Hz).
Formula for Frequency:
(
)
=
1
Frequency(f)=
Time period
1
Time period is the time taken for one complete cycle of the PWM signal, i.e., the sum of the ON time and OFF time.
Now, to calculate the duty cycle and frequency of a PWM signal, you need to measure the ON time and the total time of one period. Here's a step-by-step process:
Step 1: Capture the PWM signal using an oscilloscope or a suitable hardware tool.
Step 2: Measure the ON time (time the signal is high) and the Total time (complete period) of the PWM signal.
Step 3: Use the formulas mentioned above to calculate the Duty Cycle and Frequency:
(
)
=
×
100
%
DutyCycle(D)=
Total time
ON time
×100%
(
)
=
1
Frequency(f)=
Total time
1
For example, let's say the ON time is 1 ms, and the Total time (ON time + OFF time) is 5 ms.
(
)
=
1
5
×
100
%
=
20
%
DutyCycle(D)=
5ms
1ms
×100%=20%
(
)
=
1
5
=
200
Frequency(f)=
5ms
1
=200Hz
So, the PWM signal has a duty cycle of 20% and a frequency of 200 Hz.