TECHNICAL SUPPORT
Published 2026-02-13
Have you ever encountered this situation: you got aservowith great joy and wanted to make it move, but as a result, you wrote a lot of code and theservoeither didn't move or shook like a convulsion? Don't worry, this is probably because I don't understand PWM (Pulse Width Modulation). Simply put, PWM is like a specific "signal" sent to the steering gear. By changing the width of the pulse, it tells it to "turn to this angle" or "turn to that angle." In this article, we will thoroughly understand this "secret signal" and make your steering gear obedient.
If you want the servo to turn to a specified angle, the core is to send it a PWM signal with a period of 20 milliseconds (ms), and then adjust the duration of the high level, which is the pulse width. Generally, a pulse of 1ms corresponds to -90°, 1.5ms corresponds to 0°, and 2ms corresponds to +90°.
In the code, you don't need to manually count these tens of microseconds. Most development boards (like) have ready-made library functions. For example, using theServo.hlibrary, you only need to.write(90), and it will automatically calculate the corresponding pulse width for you, and continue to output the signal, and the servo will steadily turn to 90°.
Jitter is definitely the most annoying thing for newbies. The most likely reason is that the current supply to the servo is not enough. The servo requires a relatively large current when rotating. If you directly use the 5V pin on the development board to power it, the voltage will easily become unstable, resulting in signal confusion and the servo starting to twitch. At this time, prepare a separate external power supply for the servo, such as several batteries, and connect the ground wire of the power supply to the ground wire of the development board, and the problem can basically be solved.
Another common cause is interference on the signal line. If your connection line is very long, or there are strong electrical equipment such as motors and transformers nearby, interference signals will mix in. The solution is to use shorter DuPont lines as much as possible, or keep the servo signal lines away from interference sources.
There are three PWM parameters most relevant to the performance of the servo: frequency, duty cycle and resolution. The PWM frequency required by the servo is fixed at 50Hz, which is a period of 20ms, and this cannot be changed randomly.
The duty cycle is the proportion of high-level time to the entire cycle. For example, at a high level of 2ms, the duty cycle is 10%. We adjust the angle of the servo by changing this ratio. The resolution refers to how many parts your control panel can subdivide a cycle. For example, 8-bit resolution is divided into 256 parts. The higher the resolution, the smoother and more precise the servo rotation will be, without the feeling of jumping from frame to frame.
When you first start writing code, the most common mistake you make is forgetting to initialize. I only wrote.(9), but forgot to write it insetup()function, or the pin number was written wrong, and of course the servo did not respond. Remember to check your code to make sure the servo object is correctly connected to the pin you actually plugged it into.
Another pitfall is about the time function. If you want to realize "first turn 90°, wait 2 seconds, and then turn 0°", don't use a lot ofdelay()inforloop to achieve slow rotation, otherwise the entire program will be stuck. The correct approach is to use the()function for timing, or use.write()with a non-blocking method of gradually increasing the angle value, so that the servo can handle other tasks while making a smooth transition.
When you need to make an arm for a robot and control several servos at the same time, it is okay to simply connect the pins one by one, but it will take up a lot of pin resources, and the code will be very complicated to write. A better option is to use a servo driver board, such as this one .
It can control up to 16 servos through two signal lines (I2C protocol), and the pulses of each channel can be adjusted independently. In the code, you only need to call the corresponding library function, such aspwm.(0, 0, 300), to control the servo on channel 0. In this way, your main control board is freed up, the code structure is much clearer, and it is easy to control dozens of servos.
Once the code is written, how do you quickly know if it is correct? The simplest thing is to write a "sweeping leg" program: slowly turn the servo from 0° to 180°, and then back again, and the cycle continues. If there is no lag or jitter during the rotation, and the angle range is accurate, it means that your basic hardware connection and code logic are basically fine.
️ The specific steps are very simple:
1. Insetup(), connect the servo to the specified pin.
2. Inloop(), first use aforloop to increase the angle from 0 to 180, increasing by 1 degree each time, and adding a small delay.
3. Use anotherforloop to reduce the angle from 180 back to 0, and also add a delay.
Watching the servo swing back and forth smoothly with your own eyes gives you a much greater sense of accomplishment than directly fixing it at an angle, and it also helps you understand the essence of PWM control.
Seeing this, you should have a good idea of how to use PWM to control the servo. Hurry up and give it a try. If a servo is used in your project, do you think the biggest headache is the power supply problem or the coding of multi-channel control? Welcome to share your views in the comment area, and don’t forget to give it a like and share this useful information with more friends who need it!
Update Time：2026-02-13
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