PWM Signals - Aeroclub-IITM/UAV GitHub Wiki
A PWM Signal is a method for generating an analog signal using a digital source. It is used to reduce the average power (i.e. the average voltage) delivered by an electrical signal, by sending signals in discrete parts. This is done by sending signals of a particular voltage, for different intervals of time (in a particular cycle) at a fast rate. Main components of PWM signal are duty cycle and frequency.
In the following image, the blue plot shows the digital input, and red plot shows the approximate analog output produced.
β The duty cycle describes the amount of time the signal is in a high (on) state as a percentage of the total time of it takes to complete one cycle. It is usually represented as percentage.
β The frequency determines how fast the PWM completes a cycle and therefore how fast it switches between high and low states.
As PWM signals are sent at a high frequency, they can be approximated as an analog signal. This resultant analog signal depends on the duty cycle of PWM signal. It is therefore very efficient to use as duty cycle can be varied easily. Therefore, the effective voltage would be equal to (duty ratio) x (Input voltage of PWM signal). We can increase the effective voltage by increasing the duty ratio of pulse.
For example:
To create a 3V signal from a digital source that can be either on (at 6V) or off (at 0V), we need a duty cycle of 50%, i.e. the digital source is on for 50% of the period of one cycle. 6 x 0.5 = 3V. The frequency of PWM signal depends on the response time of the receiver. If the receiver has a slow response time (such as a DC motor, because of inertia it wonβt react quickly to minute changes in pulse) the frequency can be low, at 5-10 kHz.
Some uses of PWM signals are:
β Controlling Servo Motors
β Telecommunications
β Voltage regulation