PWM

Vary power output of digital output pin

Description

Use pulse-width modulation (PWM) to vary the power output of a digital output pin.

The block input value sets the percentage of time that the digital square-wave is on within a specific period. This time percentage is called duty-cycle.

The block input, In, accepts a range of values from 0 to 1 (from 0% to 100% of the duty cycle). The data type of the input value is a double.

For example:

  • The maximum input value, 1, sets the duty-cycle to 100%, or full power.

  • The minimum input value, 0, sets the duty-cycle to 0%, or no power.

  • An intermediate input value, such as 0.333, sets the duty cycle to 33.3%, or 1/3 power.

  • Out-of-range input values, such as -0.2 or 1.2, output minimum or maximum power.

The frequency of the PWM signal establishes the period of each PWM signal. For example, if the frequency is 3000 Hz, the period of each signal is approximately 333.33 microseconds. At 3000 Hz, setting the input value to 33.3 turns the digital pulse on for 111.11 microseconds, and then off for 222.22 microseconds.

Changing the polarity of the PWM signal inverts the digital signal. With an input value of 33.3, setting the polarity to Negative turns the digital pulse off for 111.11 microseconds, and then on for the remaining 222.22 microseconds.

The block input inherits the data type of the upstream block, and internally converts it to double.

During simulations without the hardware, this block does nothing. See Block Produces Zeros or Does Nothing in Simulation (Simulink).

Parameters

Pin

Select the digital output pin.

Click View pin map to locate the pin.

Do not specify the same pin more than once within a given model.

Frequency

Set the frequency of the PWM signal.

By default, this value is 3000 Hz.

Polarity

Set the polarity of the PWM signal.

By default, this value is Positive, which sets the digital pulse high (on) for the duty-cycle, and off for the remainder of the period.

Setting polarity to Negative sets the digital pulse low (off) for the duty-cycle, and on for the remainder of the period.

See Also