TECHNICAL SUPPORT
Published 2026-03-27
Friends who have worked on a Raspberry Pi know that if you want to make it move, especially controlling theservo, the program can sometimes get stuck for several days. Have you ever encountered that even though you connected the cables according to the tutorial and the program started running, theservojust didn’t move or shook like a sieve? Don’t worry, today we will talk about how to clearly write and adjust the Raspberry Pi’sservoprogram so that the innovative project at hand can “move” steadily.
There are actually only a few mainstream solutions on the market. One is to directly use the RPi.GPIO library to simulate PWM (pulse width modulation) signals through software. It's like driving a car with a manual transmission. You can control it, but the precision and stability are not that good. Especially when you control multiple servos at the same time, when the CPU is busy, the signal becomes unstable and the servos start to squirt.
Another more recommended method is to use hardware PWM, such as usingthis library. It is equivalent to installing an automatic gearbox on your Raspberry Pi, and leaves the delicate work of generating precise pulse signals to the underlying hardware for processing, without occupying CPU resources. In this way, whether you are controlling a robotic arm or making a gimbal, the movement of the servo will be very smooth and the jitter will almost disappear, which is crucial for applications that require precise positioning.
It's not difficult at all, and you don't need to be an electronics engineer. The core of the servo's work is to look at the width of a pulse. You can think of it as giving instructions to the servo: "If the high level lasts for 1 millisecond, you will turn to 0 degrees; if it lasts for 1.5 milliseconds, you will turn to 90 degrees; if it lasts for 2 milliseconds, you will turn to 180 degrees." It's that simple.
What we need to do when writing a program is to generate a pulse with a width between 1 and 2 milliseconds every 20 milliseconds. Send this pulse to the servo through the GPIO (General Purpose Input and Output) port, and the servo will know which position it should turn to. Once you understand this, you will find that controlling the servo is essentially controlling the pulse width number, and you will have a clear idea.
Let’s take the most commonly usedRPi.GPIOandLet’s compare. The advantage ofRPi.GPIOis that it is quick to get started. There are tutorials everywhere. You can start the servo with just two lines of code. But its PWM is simulated by software. When your Raspberry Pi needs to handle other tasks, such as image recognition, the PWM waveform it generates is not accurate.
Although installation is a little more involved, the advantages are obvious. It supports hardware timing, can accurately control up to dozens of servos at the same time, and can read the position of the servos' feedback in real time. If your project has requirements for accuracy, stability and scalability, or requires multiple servos to work together, such as making a six-legged robot, chooseIt will definitely save you a lot of worry.
The first importance of stability is "the wiring must be stable and the program must be precise." When wiring, remember that the red wire (power supply) of the servo is best not to take power directly from the 5V pin of the Raspberry Pi, especially when your servo requires large torque. The current of the Raspberry Pi is not enough, and the power will cause the Raspberry Pi to restart. The correct way is to use an external 5V power supply to power the servo, and just connect the GND of the Raspberry Pi and the GND of the external power supply together.
When writing a program, remember to clean up at the beginning and end of the program. For example, useLibrary, be sure to callpi.stop()to release resources before the program exits. Otherwise, the next time you run the program, you may find that the GPIO port is occupied and the error message cannot be controlled. With these details in place, your program can run stably 24/7.
Problem 1: The servo vibrates or buzzes. This is usually due to unstable PWM signal or insufficient power supply. The solution is as mentioned earlier, switch to using a hardware PWM library (eg) and connect an external power supply. If that doesn't work, you can connect a capacitor in parallel between the signal line and the ground line to filter out the noise.
Question 2: The servo can only turn in one direction. There is a high probability that the pulse range setting is wrong. Check the minimum and maximum pulse width values in your program. Different brands of servos may have slightly different requirements, and some require a range of 0.5ms to 2.5ms. You can find the correct range corresponding to your servo by writing a simple test program and slowly adjusting the pulse width value.
Debugging can be done in three steps. The first step is the "printing method". Where you send the control command, print out the final pulse width value to be sent to see if it is within the range you want. For example, if you want it to move to the middle, and the result printed is the maximum value, then the program logic must be wrong.
The second step is the "quarantine method". Take out the servo program separately and write the simplest loop to let it rotate. If it works normally, it means there is a conflict between your main program and the servo control, or there are too many tasks causing the control signal to be delayed. At this time, we need to consider multi-thread programming and put the servo control in a separate thread to ensure that it responds in time.
I want to ask you a question: In the product you are designing, is there a scene that requires the cooperation of several servos to make complex actions? Share your thoughts in the comment area, and let’s see how to use the Raspberry Pi to choreograph these “dance steps” more elegantly.
Update Time：2026-03-27
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