TECHNICAL SUPPORT
Published 2026-02-07
You are trying to use aservoto make a robot arm move, or you want to add precise control to the steering mechanism of a car, only to find that it is either unresponsive or shaking like you have Parkinson's disease. This is probably not because your skills are not good, but because you do not understand its "language" - PWM signal. As the most commonly used actuator to control model joints and robot movements, PWMservos seem simple, but if used in the wrong place or the parameters cannot be adjusted properly, it can "paralyze" your project in minutes. Don't worry, we will figure this out today.
You can think of the PWM signal as the command note you give to theservo. There are no specific words written on this note, but the message is conveyed through a special rhythmic "switch" flashing. For example, the servo will make an agreement: in the pulse signal you send every second (this frequency is fixed), if the high level (can be understood as the "light on" time) lasts for 1 millisecond, I will turn to the far left; if it lasts for 1.5 milliseconds, I will turn to the middle; if it lasts for 2 milliseconds, I will turn to the far right. What the controller (for example) has to do is to accurately control the length of this "light on" time.
Therefore, the core of PWM steering gear is "obedience". There is a small circuit board inside it that interprets the PWM pulse width you send, then drives a small motor to drive the gear set, and finally rotates the output shaft to the corresponding angle. You change the pulse width, and it changes the angle. The whole process is a closed-loop control. The servo will constantly compare the actual position and the target position and strive to maintain consistency. This is why it controls the position much more accurately than a regular DC motor.
There are two most common reasons for jitter: the signal is "dirty" and "not full". The signal is not clean. It may be that your signal line is too long and unshielded, causing interference; it may also be that the PWM waveform output by the control board you are using (such as some Raspberry Pi pins) is not stable enough. It's like someone giving instructions in a vague voice in your ear, and you will naturally hesitate about what to do. The solution is to shorten the signal line as much as possible, stay away from interference sources such as power supplies, or use a more stable hardware timer to generate PWM signals.
"Not enough to eat" refers to power issues. When the servo is started and the load changes suddenly, the instantaneous current can be very large. If the battery capacity you use is too small, or the power cord is too thin or long, the voltage will be instantly pulled down. When the voltage is low, the control circuit inside the servo will be "out of accuracy", causing jitter or even reset. My suggestion to you is: be sure to power the servo separately, use a fast-response voltage stabilizing module, the power cord should be thick and short, and it is best to connect a large capacitor (for example, 470uF or above) in parallel to the power supply end of the servo to buffer the current impact.
When choosing a servo, you can't just look at the price, you have to look at several hard indicators. The first is torque, the unit is kg·cm, which means how much objects can be lifted when the servo arm is 1 cm long. If you make a robotic arm to grab something, it won’t have enough torque to lift it up at all. Second is the speed, the unit is seconds/60°, which refers to the time required to rotate 60 degrees. The movement of a slow servo will appear very slow. Then there’s the size and weight. Every gram of weight on a model aircraft is precious. Finally, there is the working voltage, which is commonly seen as 4.8V, 6V, 7.4V, etc. The higher the voltage, the greater the torque and speed.
For example, if you are making a small six-legged robot, the joint servos of each leg need to be light in weight and have enough torque to support the body and move quickly. In this case, you may choose a "digital metal tooth servo." If you are just making a slow-turning display stand, then a common cheap servo will suffice. Remember, there is no "best" servo, only the "best" for your current project. Before buying, go to the brand's official website to check the parameter list and compare it.
Wiring is the first step, be sure not to connect it backwards. The servo generally has three wires: brown or black is the ground (GND), red is the positive power supply (VCC), and orange or yellow is the signal wire (SIG). ️ Be sure to connect the GND of the servo and the GND of the control board together. This is called "common ground", otherwise the signal cannot be recognized correctly. It is best to supply the power independently. If it must be shared with the control board, be sure that your power module can provide sufficient current.
For control, taking the most commonly used one as an example, you can directly use theServolibrary. The code is as simple as just a few lines: import the library, define the servo object, specify the signal pin, and then use thewrite()function in the loop to give the angle value (0-180 degrees). The library will automatically help you convert the angle into the corresponding PWM pulse width. The Raspberry Pi can use the GPIO library to simulate PWM. At the beginning, use the code to make the servo slowly sweep between 0 degrees and 180 degrees to test whether it is working properly. This is the most basic diagnosis.
Its application is so wide that it can be seen almost everywhere where precise angle control is required. The most classic ones are the rudder control of aircraft and ship models, the various joints of robots (bionic hands, humanoid robot legs), and the steering mechanism of smart cars. In these areas, servos provide direct, reliable position servo. The fingers of the robotic arms you see that can flexibly grasp objects of different shapes often have several micro-servos working together.
Go a little deeper, such as making a camera gimbal that automatically tracks people. The gimbal requires two servos, one for horizontal control (Pan) and one for vertical control (Tilt). The camera recognizes the position of the face, calculates the angle difference between the center of the face and the center of the screen, and then converts this difference into a PWM signal and sends it to the two servos, which can drive the camera to rotate and always keep the face in the center of the screen. This is a typical "perception-decision-execution" closed loop, with the steering wheel playing the final execution role.
The steering gear is a mechanical component, and correct installation can greatly extend its life. When installing, make sure there is no skew stress between the output shaft and the load. It is best to use the matching steering wheel and connecting rod. What hurts the servo the most is "stuck rotor" - that is, when the servo is turned to the end and you continue to send it rotation signals, the motor is stuck but is still exerting force, the current increases sharply, and the motor or driver chip can be burned out in a few minutes. Be sure to set physical limits on the mechanical structure, or avoid issuing out-of-range instructions in the software.
In daily use, try to work at the nominal voltage. Overvoltage will accelerate aging. If you are driving a heavy load, you may consider adding a heat sink to the servo. For high-value servos, it is also a good habit to regularly check the gears for wear and add some grease. For those servos that work in a vibrating environment, use double-sided sponge tape or shock-absorbing ball heads to install them, which can effectively reduce the impact. A little tip: If the project allows, letting the servo work in a "relaxed" state instead of maintaining a position under continuous force can also reduce heat and wear.
After reading so much, what kind of creative project do you most want to use PWM servo to realize? Is it a robotic arm that helps you turn the pages of books, or a sunlight tracker that can automatically water your plants? Share your thoughts in the comment area. If you think this article has helped you avoid a lot of pitfalls, don’t forget to like and share it with more friends in need!
Update Time：2026-02-07
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