TECHNICAL SUPPORT
Published 2026-02-28
When playing with the steering gear, have you ever encountered this situation: the steering gear doesn't obey the command, either shaking constantly, or unable to turn to the position you want? Many friends who have just started making robots or model airplanes are likely to get stuck on "controlling the pulse width". In fact, once you understand it, you will be able to control theservo.
To put it simply and directly, for most standardservos, the control pulse width is usually between 1 millisecond and 2 milliseconds. This is a common baseline range. When you send a pulse signal with a width of 1.5 milliseconds to the servo, the output shaft of the servo will stay in the middle position, which is what we often call a 90-degree angle. This concept is like a "secret signal" we give to the steering gear, telling it where to turn.
This is actually a signal conversion process. There is a control circuit inside the servo, which is always "watching" the pulse width you send it. At the same time, the potentiometer inside the steering gear will feedback the current actual position in real time. The control circuit will compare these two values, just like the gap between the target in our mind and the actual position. If the pulse width sent is 1.3 milliseconds, which is shorter than 1.5 milliseconds, the circuit will know "Oh, turn to the left" and then drive the motor to turn until the value fed back by the potentiometer corresponds to the 1.3 millisecond signal, and the motor will stop.
No, you should pay special attention to this. Although the standard range is 1ms to 2ms, many servos on the market, especially some "360-degree servos" or digital servos that support a wider rotation range, may have a wider pulse range, such as 0.5ms to 2.5ms. It's like everyone has different tastes. Some servos are "salty" and some are "light". Therefore, when you get a new servo, the first thing to do is to check its data sheet to confirm its specific pulse width range. This is a critical first step to avoid burning the servo or causing inaccurate control.
To measure accurately, you need a tool, the most common one is a microcontroller, such as STM32. You can write a small piece of code to make a pin of the microcontroller output a continuous pulse signal. Then use an oscilloscope or logic analyzer to clamp on that pin, and you can see the actual waveform. You can see with your own eyes whether the "high level" lasts for the 1.5 milliseconds you set. If these professional tools are not available, some high-precision PWM signal generators can also directly read the values, which is very convenient.
️Checkthe wiring: First check if the power and ground wires are connected? The power of the servo is usually not small. If it is powered by a single-chip microcomputer, it is easy to be unable to drive it, causing the voltage to be pulled down and the servo to become unresponsive. You can try using an external power supply to power the servo separately, and connect the ground wire of the power supply to the ground wire of the microcontroller.
️Checkthe frequency: The pulse width is only part of the control. Another important parameter is the pulse period, which is usually 20 milliseconds, which is a frequency of 50 Hz. If the PWM frequency set in your program is wrong or too far off, the servo will not be able to recognize the signal.
️Confirmrange: If the pulse signal you give exceeds the range that the servo can recognize, it may remain motionless or get stuck at the extreme position. At this time, you can slowly adjust the pulse width value in the code, starting from 1.5 milliseconds, and fine-tune it to both sides to see if the servo responds.
For those who are just getting started, in addition to looking at the torque and speed when choosing a servo, you must also look at its "control signal" or "PWM" specifications. The first choice is a servo that is clearly marked with "standard 1ms-2ms" control, which will make your subsequent programming and debugging much simpler. In addition, you can pay attention to the "dead zone" of the servo, which is the minimum pulse change it can recognize. The smaller the dead zone, the higher the positioning accuracy of the servo, and the more delicate the rotation will be. These parameters are usually found on the product details page or manual of the servo.
Here is a little formula to help you: target pulse width = minimum pulse width + (desired angle of rotation/maximum rotation angle)(maximum pulse width - minimum pulse width). Assume that your servo can rotate up to 180 degrees, the minimum pulse of 1ms corresponds to 0 degrees, and the maximum pulse of 2ms corresponds to 180 degrees. If you want it to rotate to 90 degrees, the calculation is 1 + (90/180)(2-1) = 1.5ms. Calculate this value and write it into your code to achieve very precise positioning. Many advanced servo control libraries also automatically calculate for you based on this principle.
What is the strangest phenomenon you have ever encountered when debugging the servo? Welcome to share it in the comment area, and everyone can help you analyze it. If you find this article useful, don’t forget to like and save it so that more friends who play servos can see it!
Update Time：2026-02-28
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