TECHNICAL SUPPORT
Published 2026-02-24
You must have encountered this situation: you happily installed aservoon a robot or smart product and wanted it to turn at an accurate angle. As a result, it either kept shaking, or it couldn't turn in place, or even didn't respond at all. What's the problem? Nine times out of ten, you haven't really understood the control principle of PWM (Pulse Width Modulation)servo. Don't be intimidated by these tall English letters. If you understand them clearly, yourservowill be able to point where to hit.
To put it bluntly, the PWM signal is a "secret signal" that uses square waves to transmit information. You can think of it like using a flashlight to send out Morse code, except that the flashlight turns on and off instead of the voltage. The reason why the servo can understand this code depends on a small circuit board in its belly. This circuit board is like a loyal sentinel, always watching the PWM signal you send it.
The key information hidden in this signal is not how high the voltage is, nor how fast the frequency is, but something called "high level duration", which is the pulse width. The sentry of the servo will measure this width, and then drive the motor in the servo to rotate the output shaft to the corresponding angle based on this length of time. This is its most basic underlying logic.
For most standard servos, the "universal language" they recognize is a PWM signal with a period of 20 milliseconds. In this cycle, the duration of the high level (that is, the pulse width) changes from 0.5 milliseconds to 2.5 milliseconds, corresponding to the rotation range of the servo output shaft from 0 degrees to 180 degrees.
Give a specific example and you will understand:
️ When you give the servo a high-level signal lasting 0.5 milliseconds, it understands that it is going to the 0-degree position.
️ When this time becomes 1.5 milliseconds, it turns to the middle position of 90 degrees.
️ If it lasts 2.5 milliseconds, it knows to point to 180 degrees.
Therefore, you only need to accurately control the time of this high level, and you can command the servo to rotate to any angle as you like. The whole process is like using a ruler, and time is the scale on it.
This is definitely the biggest headache for both newbies and veterans. The servo vibrates, just like you stuttering when speaking. The core reason is that the signal sent to it is "not clear". There are two most common situations: first, the control board (for example) you use to generate the PWM signal is not stable enough, or there is a problem with the code, causing the high level to last for a long and short time.
Insufficient power supply! The servo requires a relatively large current when starting and turning. If the battery or voltage stabilizing module cannot keep up, the voltage will be pulled down, causing the control board to crash or the signal to be distorted. It's like a person working hungry, his hands and feet will naturally tremble. Therefore, when the servo shakes, don't immediately suspect that the servo is broken. Check your power supply and control code, which can often solve the problem.
Nowadays, mainstream microcontrollers, for example, have made it extremely simple to generate PWM signals. You don't need to manually calculate the subtle time of each high level at all, you only need to call a few ready-made functions.
Here, libraries like Servo.h are your good helpers. All you need is:
1. #
2. .(9) Connect the signal line of the servo to pin No. 9.
3. .write(90) Look, it’s that simple! This line of command will cause the servo to turn directly to 90 degrees.
The library file does all the complex timer configuration and pulse generation work for you behind the scenes. You only need to pay attention to how many degrees you write, and it will do the rest, which greatly lowers the entry barrier.
This is particularly easy to confuse. Many people buy the wrong servo and then adjust the program incorrectly. What we usually call a 180-degree servo is an "angle servo". It has a feedback potentiometer inside, which can know where it is turning. If you give it a pulse, it will go to a fixed position.
The 360-degree continuous rotating servo looks exactly like the 180-degree servo, but the internal structure has been changed. It no longer cares about which angle you turn it to, but interprets the pulse width as "speed and direction." It is also a 1.5 millisecond pulse. For 180-degree servos, it stops in the middle, and for 360-degree servos, it stops completely. If it is less than 1.5 milliseconds, it will reverse at full speed; if it is greater than 1.5 milliseconds, it will rotate forward at full speed. To put it simply, one is the instruction "where to go" and the other is the instruction "how to move".
Only by understanding the control principles and choosing the right steering gear can your project be successful. In addition to determining whether you need 180 degrees or 360 degrees, there are two key parameters you must look at: torque and speed. Torque determines how powerful the servo is, and the unit is usually kg·cm, which means how many objects the servo can pull at a distance of 1 cm from the center of the output shaft.
If your robot arm needs to lift heavy objects, it will definitely not work if the torque is small. Speed determines how fast the servo rotates, and the unit is seconds/60 degrees. These two parameters are often contradictory. The stronger servo usually turns slower. You need to find a balance between strength and speed based on the actual needs of your project. For example, when making a camera gimbal, smooth speed is more important than strength.
After talking so much, I wonder what is the strangest or most difficult problem you have encountered when using the steering gear? Share it in the comment area and let’s see if we can solve it using the principles we talked about today! If you find this article useful to you, don’t forget to like it and share it with your friends who are also playing with hardware.
Update Time：2026-02-24
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