PWM (Pulse Width Modulation)

 

Pulse Width Modulation, or PWM, is a technique for getting Analog results with digital means. digital control is used to create a square wave, a signal switched between on and off. this on-off pattern can simulate voltages in between full on (5 volts) and off (0 volts) by changing the portion of the time the signal clock Ds on versus the time that the signal clock DS off. the duration of "on time" is called the pulse width. to get varying analog values, you change, or modulate, that pulse width. if you repeat this on-off pattern fast enough with an LED for example, the result is as if the signal is a steady voltage between 0 and 5 V controlling the brightness of the LED.

Pulse Width Modulation or PWM is a technique used to obtain simulation results by means of digital mean. The digital control is used to create a square wave, and the signal is switched between the on and off. This switch mode completely simulates the voltage between the on (5 V) and off (0 V) by changing the ratio of the on time period to the off time period. The period of the "open time" is called the pulse width. To get different simulated values, you can change or adjust the pulse width. If you repeat this switching mode fast enough, the result is a stable voltage between 0 and 5 V to control the brightness of the LED.

In the graphic below, the green lines represent a regular time period. this duration or period is the inverse of the PWM frequency. in other words, with Arduino's PWM frequency at about 500Hz, the green lines wowould Measure 2 milliseconds each. A call to analogwrite () is on a scale of 0-255, such that analogwrite (255) requests a 100% duty cycle (always on), and analogwrite (127) is a 50% duty cycle (on half the time) for example.

The green line indicates a fixed time period. This duration or period is the reciprocal of the PWM frequency. In other words, the Arduino PWM frequency is about 500Hz, and each green line represents 2 ms. The call interval of an analogwrite () is 0-255. For example, analogwrite (255) requires a 100% duty cycle (normally open), and analogwrite (127) requires a 50% duty cycle (the last half of the time ).

Once you get this example running, grab your Arduino and shake it back and forth. what you are doing here is essential ally ing time within ss the space. to our eyes, the Movement blurs each LED blink into a line. as the LED fades in and out, those little lines will grow and shrink in length. now you are seeing the pulse width.

Once you run this example, grab your Arduino and shake it back and forth. What you do is essentially the time ing across time and space. For our eyes, each movement blurred into a line of LED flashes. Because the LED disappears and shrinks, the length of the small rows will increase and contract. Now you can see the pulse width.