The PWM PWM principle of pic single chip microcomputer

1, what is PWM

What is PWM, the professional point of the pulse width modulation , popular point is the constant output high and low level. For example, the microcontroller 40ms time output high and then 60ms time output low and then continuously periodically alternating output and low level this is the typical PWM wave. High-level output time 40ms is the legendary pulse width , 40ms+60ms=100ms is the PWM cycle. Suppose we set the cycle to 100ms. We can increase or decrease the high-level time according to our needs, such as high-level output time to 80ms. Then the low-level time becomes 20ms. It is also possible to reduce the high-level output time to 20ms. Then the low-level time becomes 80ms. That is, the pulse width modulation is this high level of time. At high level (pulse width) in the period, the proportion of time occupied is called the duty cycle. A mathematical formula is used to denote the time/period of the high level = duty cycle.

2, How to implement PWM

How do we let the microcontroller output PWM wave. There are two ways to directly use the I/O output, another way to take advantage of the module.

2.1 Output PWM with I/O port

If your microcontroller does not have a PWM output function module, then you can write your own program output PWM wave. Because PWM is not high and low level. an I/O in addition to a timer, for any single-chip computer is easy to do.

2.2 Using the module output PWM

for Pic MCU, the function module with output PWM is provided. Using the module output PWM is actually simpler and more accurate than using the I/O output PWM.

3, The role of PWM

PWM can be used to do what PWM more typical application is the LED dimming and motor speed regulation. The PWM is how to adjust the light and speed, actually also very good understanding. To give the LED dimming as an example. The LED is the brightest that always has a power led. Do not give the LED power off LED is not bright. That if in a very short period of time to the led constantly power off. The feeling of the eye is that the LED is bright, but the brightness is low.

If the single-chip microcomputer gaoping output LED is bright. The longer the high-level output in the PWM wave, the brighter the LED, and the darker the vice.

To be continued ........ ........ Hi! You've been there all the time.

The PWM PWM principle of pic single chip microcomputer