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Published 2026-02-28
Understandthe control principle of theservoto make your product move more obediently
Many friends will encounter a headache when making robots, smart cars or model airplanes: How can the motor turn to the precise angle I want? Ordinary motors either keep turning or they don't turn. It feels more difficult to get the steering gear (that is, theservomotor) to stop at a certain position accurately. In fact, behind this isthe control principle of the steering gearat work. To put it simply, the steering gear is a "small joint" that can listen to your words and hit where you point. By understanding its temperament, you can make the product make various smooth and precise movements.
The reason why the servo can understand your instructions depends on a signal called PWM (Pulse Width Modulation). You can think of this signal as you sending Morse code to the servo. This signal is a series of high and low level pulses, and the key to the "code" lies in the duration of the high level, which we call "pulse width".
Different pulse widths correspond to different rotation angles of the steering gear. Normally, in a signal with a period of 20 milliseconds, a high level of 1 millisecond will cause the servo to turn to the far left, 1.5 milliseconds to the middle, and 2 milliseconds to the far right. After the circuit board inside the steering gear receives this pulse width signal, it will compare it with its current position, and then drive the motor to rotate until the two are consistent.
You may be curious, how does the servo know where it is now? This is due to a core component inside it - the potentiometer, also called a variable resistor. This potentiometer is connected to the output shaft of the servo. Wherever the shaft turns, the resistance value of the potentiometer changes.
This is like a "position sensor". The circuit inside the servo will always detect this resistance value to grasp the current angle of the servo arm in real time. Then, it will compare the target angle signal you sent with the actual angle. If a deviation is found, it will immediately drive the motor to make corrections until the target angle and the actual angle perfectly coincide. This closed-loop control method is the secret of the steering gear's ability to achieve precise positioning.
If you want to activate the rudder, the steps are actually not complicated. Follow me and do it. First, you need a control board that can generate PWM signals, such as STM32 or Raspberry Pi. Connect the three wires of the servo: the brown or black wire is connected to the negative pole of the power supply (GND), the red wire is connected to the positive pole of the power supply (usually 5V or 6V), and the remaining yellow or white wire is connected to the PWM signal output pin of the control board.
️Step one: Download and install the programming software for your control panel.
️Step 2: Find a ready-made servo control library, such as the "Servo.h" library, which can save you the trouble of writing underlying code.
️Step 3: Write a few lines of simple code, such as ".write(90);", which is commanding your servo to turn to the 90-degree position.
Upload the program and you will see the servo rotate in a "swish" motion.
When you start to choose a servo, are you a little confused when you see a bunch of parameters such as torque, speed, and angle? Don't worry, I'll translate it for you. Torque determines how powerful the servo is. The unit is usually kilogram·cm (kg·cm), which means how much weight the servo arm can pull 1 cm away from the center of the rotation axis. If you want to use it as a robot leg, you have to choose one with a larger torque.
The speed parameter usually refers to how many seconds it takes for the servo to turn 60 degrees (for example, 0.12 seconds/60 degrees). The smaller the value, the faster and more sensitive the action will be. As for the angle, there are two common ones on the market: one is a standard servo that can only rotate 180 degrees, and the other is a 360-degree servo that can rotate continuously. The latter is more like an ordinary motor in terms of control method.
When debugging a product, I'm most afraid of the servo shaking inexplicably, like a Parkinson's patient. There are usually several reasons for this. The most common one is insufficient power supply. Just like your hands will shake when you work on an empty stomach, the servo will also shake if the current cannot keep up. At this time, changing to a power supply with stronger current output capability or adding a large capacitor can solve the problem.
Another possibility is that your control signal itself is unstable and has interference. At this time, you can check your wiring and try to keep the signal lines away from high-current power lines to avoid interference. If the angle is changed rapidly in the code, it may also cause jitter. Adding a little delay to allow the servo to have time to react can usually improve this problem.
Of course! Don't think that the servo is just a simple angle controller, it can play new tricks in many places. For example, you can transform it into a "winch" and use the continuously rotating servo to retract and retract the rope to make some lifting devices. With some linkage mechanisms, the linear motion of the steering gear can also be converted into complex curved motion.
Even in some more advanced applications, you can use the feedback signal of the servo to read its current position in real time. In this way, your product can not only move the rudder, but also "perceive" changes in its position from the outside world, thereby realizing some interactive functions. For example, if you make a robotic arm, when you move it with your hands, it can record your movements and then reproduce them, which is very interesting.
After reading this, do you feel more confident about steering gear control? In your latest project, what interesting function do you plan to use the servo to achieve? Welcome to share your creativity in the comment area, let’s communicate together! If you find the article useful, don't forget to like it and share it with more friends who need it.
Update Time：2026-02-28
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