TECHNICAL SUPPORT
Published 2026-02-21
Have you ever encountered this embarrassment when playing with aservo: you want it to keep turning, but the speed cannot be controlled? Ordinary 180-degreeservos can also use PWM to control the angle, but 360-degree continuous rotationservos have no speed adjustment function. Today we will talk about how to solve this pain point and enable the 360-degree servo to achieve true speed control.
The position potentiometer is actually removed from the 360-degree continuous rotation servo, so it only recognizes the signal direction and not the angle. If you want to make the rotation slower, the core principle is to modify the pulse width range of the input signal. The neutral point of the standard servo is generally 1.5ms pulse width. If it deviates slightly from this value, it will start to rotate. The greater the deviation, the faster it will rotate.
You can achieve speed regulation by outputting PWM waves of different pulse widths from the microcontroller. For example, when using the Servo library, normal write(90) stops, but if you want to transfer slowly, you can try write(85) or write(95). The closer the value is to 90, the slower the rotation speed, and the further away from 90, the faster the speed.
The good news is that in most cases there is no need to change hardware at all. Ordinary 360-degree servos themselves support speed adjustment within a certain range, but many friends don’t know this feature. As long as your controller can output an accurate PWM signal, you can directly start trying to adjust the speed.
However, it should be noted that if you are using a particularly cheap servo, its control chip may not support fine speed adjustment. In this case, you can consider replacing it with a better quality digital servo, or modifying the servo yourself and replacing the main control chip inside. But for novices, don’t rush to change the hardware yet, try adjusting the software.
In fact, programming is not difficult. I will understand it after I walk through the ideas with you. Taking for example, you only need to understand the two key functions of the Servo library: () and (). () allows you to precisely control the pulse width to the microsecond level, which is more precise than the write() angle mode.
️ The specific steps are as follows:
1. First use () to specify the pin to which the servo is connected.
2. Then gradually change the pulse width value through the loop
3. For example, slowly increasing from 1500 microseconds to 1700 microseconds, the servo will gradually accelerate from stop to the fastest speed.
4. If you want to slow down, do the opposite and let the pulse width slowly return to 1500.
Ordinary PWM is completely sufficient, the key is that you have to ensure the frequency and resolution. Most servos work at a frequency of 50Hz, which is a cycle of 20ms. Within this cycle, the high-level time you output needs to be accurate to the microsecond level.
If the PWM resolution of your microcontroller is not enough, for example, it only has 8-bit resolution (0-255), the speed regulation accuracy will be limited. At this time, you can try to use a timer interrupt to simulate PWM yourself, or directly switch to a 16-bit resolution microcontroller, such as STM32, which is much more accurate than an 8-bit AVR.
I've also encountered unstable speeds, mostly caused by power supply problems or interference. The current when the servo is started is very large. If the power supply is not strong enough, the control signal will be inaccurate once the voltage drops. It is recommended to provide a separate power supply for the servo and not share a power supply with the microcontroller.
In addition, the signal line should be as short as possible. It is best to use shielded wire or add a magnetic ring. If speed fluctuations are found in the software, a simple filtering algorithm can be added, such as taking the average of several speeds and then outputting it. Another trick is to add delay compensation to the program to make pulse width changes smoother and avoid sudden acceleration and deceleration.
This is indeed an advanced gameplay, and the effect is quite good. The PID algorithm can automatically adjust the output pulse width based on the target speed you set and the actual speed measurement feedback to stabilize the speed near the set value. To achieve this, you need to add an encoder or Hall sensor to the servo to measure speed.
However, for most entry-level projects, PID is a bit overkill. Unless you want to do precise car tracking or robotic arm control, open-loop control with a simple filter is enough. If you want to make it simple, try the look-up table method first, measure the corresponding relationship between pulse width and speed, and make a table to call directly.
If you want to know more about steering gear control techniques or need selection suggestions, you can search the official website of "Foshan Sicheng Electromechanical". Their technical documents are very down-to-earth. What project are you working on recently that requires the use of 360 servo speed adjustment? Let's talk about it and think about it together, maybe we can come up with a better solution.
Update Time：2026-02-21
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