TECHNICAL SUPPORT
Published 2026-02-14
Many friends will encounter a headache when playing with robots or making smart cars: How to control the steering gear? Watching it spinning around, it seems very simple, but once you get your hands on it, it either doesn't move or shakes randomly. In fact, the driving force behind all this is the PWM (Pulse Width Modulation) signal. Today we will break it apart and explain it clearly, ensuring that you will understand it after reading it.
The steering gear is essentially a sophisticated "position compliance system". You can think of it as a particularly obedient soldier. If you order it to turn to 45 degrees, it will never stop at 30 degrees. How to issue this order? What is used is a special "language" - PWM signal. This signal contains the position information you want. After the circuit board inside theservois interpreted, it will drive the motor to the corresponding angle. Without this standard control signal, theservodoesn't know what you want it to do, and naturally it won't work.
We can think of the PWM signal as a kind of "Morse code". It is a series of square waves with high and low levels. The servo only cares about the duration of the high level, which is the "pulse width". Typically, this pulse width is between 0.5 milliseconds and 2.5 milliseconds. For example, for a standard 180-degree servo, if you give it a pulse width of 1.5 milliseconds, it will return to the center (90 degrees); if you give it 0.5 milliseconds, it will turn to one end (0 degrees); if you give it 2.5 milliseconds, it will turn to the other end (180 degrees). You see, by changing this small pulse width, we give different angle commands to the servo.
The mainstream controllers on the market now, such as STM32 or ESP32, have built-in very convenient PWM generation functions. Taking the simplest one, you only need to use a simple function like.write(angle), and the microcontroller behind it will automatically calculate the corresponding pulse width for you and continuously output it to the servo. You don't have to manually calculate those complicated timer parameters at all. This allows us to focus more on the implementation of core functions rather than the underlying details for product innovation.
When you are ready to choose a servo for your product, in addition to looking at the torque and speed, its PWM signal requirements are a key parameter.️First, look at its working frequency.Most analog servos are 50Hz, which means the cycle is 20 milliseconds. Digital servos may support higher frequencies.️Second, look at its pulse width range.Some servos are 0.5ms-2.5ms, corresponding to 0-180 degrees; some may be 0.9ms-2.1ms. If you use the wrong range, the servo may not be able to reach the maximum turning angle, and may even "click" and damage the gears. Therefore, before buying a servo, you must go to the official website to download its data sheet.
This is so easily overlooked! Many friends find that the servo is shaking violently or is weak. Their first reaction is often that the code is written incorrectly. In fact, there is a high probability that the power supply has not kept up. The current required for the moment the servo rotates is very large. If the power supply is insufficient, the voltage will be pulled down. Once the voltage becomes unstable, the PWM signal waveform output by the microcontroller will be distorted, and the chip inside the servo will also work abnormally. It's like a hungry person. If you ask him to run, he will definitely stumble. Therefore, it is crucial to prepare an independent high-current power supply for the servo.
You may be curious, why are digital servos so popular? The secret lies in the way it handles the PWM signal. The analog servo receives a PWM signal once, moves once, and then waits for the next cycle. There is a more powerful "brain" inside the digital servo. After receiving the PWM signal, it will drive the motor by itself at a higher frequency (such as 300Hz). This is just like an analog servo listens to a command once per second, but a digital servo listens to a command once and then continuously corrects it many times within that second. Therefore, its response speed, positioning accuracy and holding force are far superior to analog servos.
After reading this, do you have a new understanding of PWM control of servos? So in the projects you are working on, have you ever encountered a situation where the steering gear does not obey the command? How did you investigate at that time? Welcome to share your experience in the comment area, and let’s communicate and make progress together! If you think this article is helpful to you, don’t forget to like it and share it with more friends who need it.
Update Time：2026-02-14
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