Hey Guys! Welcome you onboard. I feel pleasure to keep you updated with valuable information related to engineering and technology. Today, I'll discuss the details on the Introduction to PWM
. It stands for Pulse Width Modulation
- A techniques mainly used for getting analog pulses using a digital signal.
- It plays a vital role in controlling the servo and DC motors in the relevant project. Most of the industrial applications involve PWM, where load requires current in pulses rather than varying analog signal.
The PWM works like a controlled switch
that mainly handles the current being delivered to the load. When the switch
is off, it will indicate no current is available for the load and when a switch is On, it means the power is delivering to the load with no voltage drop.In this post, I'll cover a basic idea about PWM and how it is used in a variety of applications ranging from motors, heating systems, hydraulics, control valves, and pumps. Let's jump right in and get down to the information you need to know about PWM.
Introduction to PWM (Pulse Width Modulation)
PWM is a process mainly used for getting an analog signal using a digital source.
- It is nothing but a controller that controls and handles the input current applied to the load.
The PWM varies between high and low values where the high value indicates, 5V is applied and the low value indicating the ground signal is applied to the load.Note:
Not necessarily, the upper-value corresponds to 5V, it can be any value based on the voltage at which load operates. I have mentioned 5V just to give you an idea of how the PWM switches between high and low values.PWM controllers are mainly used where we need to keep the power losses minimum by providing the power to the load in pulses instead of continues manner.
- PWM technique can be easily defined in terms of duty cycle and the frequency it takes to repeat the duty cycle per second. The duty cycle highlights the amount time the signal switches between ON and OFF position. It is described in percentage. If the signal remains ON half of the total duty cycle and remains OFF in another half, then the duty cycle will be 50%.
The following figure shows the duty cycle in terms of percentage that mainly relates the ON and OFF digital signal on the waveform.
- The PWM controls the duty cycle of the signal which consequently controls the speed of the motor.
If the frequency of the duty cycle is 50 Hz, it means 50 duty cycles are completed per second, terming the ratio how fast it regulates between high and low values.
- The frequency requires for PWM process will vary as per the nature of the applications. Some require fast duty cycle for controlling the load at a faster pace while some need a low duty cycle in order to keep the process smooth and away from power losses. More often than not, the response time of the load sets the pathway for the frequency required for the PWM.
It is important to note that the motor speed is directly proportional to the duration of the duty cycle at which the signal remains turned ON. The longer the duration of ON signal, the faster the motor terminals will rotate similarly OFF duration will lead to the slow speed of the motor.
- Using PWM for controlling the motor has a leg over the simple varying the analog signal to the motor. As the analog signal applies the power to the motor with continuous variation, failing to keep the motor terminals completely OFF or ON, as a result, power loss occurs during this process, however, PWM delivers the power in pulses that keep the motor terminals either in fully ON or OFF state.
Controlling the RGB LED is a perfect example for understanding the concept of PWM. By varying the amount of duty cycle of each color and playing around with their brightness will give a specific color every time.Avoid adjusting the duty cycle with the same magnitude for every color, doing this will give a white light.
If you are applying red light with 10% duty cycle at 2 MHz speed, then most of the time red light will appear OFF as you see. Yes, it will turn on for the small amount of time but it appears as it is not taking part in the flash created by RGB LED.Similarly, applying red light with 10% duty cycle at 100 MHz will increase the contribution of the red light in the LED as it will turn on will greater pace as compared to applying it with lower frequency.
The computer motherboard is another example that requires PWM signals for its fan to be running with the power pulses. If power is given continuously without PWM, it may cause a severe harm to the board, as the board will run with full speed without any pause.Pulses of power keep the board in a constant loop, where power signals are given in quick successions that keep the fan running. If you buy a new computer, you may notice a 4 pin PWM header is added in the fan that controls the cooling process of the board.The point worth mentioning here is that the PWM generated with sloped duty cycle is preferred over generating it with a flat one. As the later one is more vulnerable to creating a clicking sound when the fan runs at low speed. Similarly, when the duty cycle approaches 100%, the fan will run with full speed, creating an unpleasant ticking sound.
In order to alleviate the bothering sound, some quality fans come with IC drive chips, allowing the fan to run smoothly without creating any sound. You may need extra bucks for buying the quality PWM fans that not only retain the quality but also help in increasing the overall lifetime of the board.
- DC and Servo Motors
- Heating systems,
- Control valves,
- Computer applications
That's all for today. I hope you have found this article useful. If you are feeling dubious about PWM and how it works and the topic you may notice that I have left uncovered related to PWM, you can approach me in the comment section below. I'd love to help you according to the best of my knowledge. You are most welcome to keep us updated with your valuable suggestions, so we keep coming back with quality content as per your needs and expectation. Thanks for reading the article.