TECHNICAL SUPPORT
Published 2026-03-13
Hey, have you also encountered this situation? I happily wrote a line of code for theservoto turn it to 90 degrees. As a result, it either moved to one side or stayed motionless. Anyway, it just couldn't reach the point you wanted. This problem is indeed quite troublesome, especially when it comes to critical moments when making robots or models. Don't worry, the problem is most likely not that theservois "broken", but that we missed some small details during setup. Let’s sit down today and explain this matter clearly.
The most common reason why the steering gear does not turn accurately is that there is a problem with the signal. The angle of theservois determined by the pulse width of the PWM (Pulse Width Modulation) signal you send to it. Different steering gear brands and models may have different definitions of pulse width corresponding to "90 degrees". For example, the "neutral position" of the servo you are using may not be the standard 1.5 milliseconds. If it is slightly off, the angle will be off. This is just like everyone's understanding of "seventy percent full" is different, and the steering gear also has its own "temper".
In addition, unstable power supply voltage is also a troublemaker. The voltage is low and the steering gear is not strong enough. Even if you want to turn to that position, it may be stuck halfway by the mechanical structure. You can observe it. If the servo keeps shaking at a certain angle, it is likely that the power supply cannot keep up, or the force at that position is too great and it cannot be twisted.
Now that we know that the problem may lie in the definition, we have to manually teach it where the real 90 degrees is. Many slightly better servos support adjustment through a "calibration mode". You need to check the manual of the servo you have to find out how to enter the calibration. This is usually achieved by sending a signal within a specific range at the moment of power-on.
After entering the calibration mode, you send what you think is a 1.5 millisecond pulse width signal, and then use a small screwdriver to carefully rotate the potentiometer (a small knob) inside the servo until the servo's rocker arm really stops at the physical 90-degree position. This process requires a little patience. The range of rotation is very, very small, and you may be able to pass it if you move it a little. It's like turning the knob on an old radio. You have to slowly find the station that's most clear to you.
When we write a program, the commonly used servo library functions may directly let you write the number "90", but the bottom layer actually converts it into a specific pulse width value. You have to figure out how many microseconds of pulse width your program corresponds to 0 degrees and 180 degrees. For example, common settings are 0 degrees corresponding to 0.5ms, and 180 degrees corresponding to 2.5ms. But the actual range that your servo can recognize may be 0.6ms to 2.4ms.
In this way, the corresponding pulse width of 90 degrees converted in your program may be 1.5ms, but this value exceeds the effective range of your servo, or deviates from its neutral position. The correct approach is to first find its actual pulse width range through the servo manual, and then modify the corresponding parameters in the program. For example, using the Servo library, you can use.( pin, min, max )to accurately set the minimum and maximum pulse width values.
This is a very subtle but extremely common problem. Your servo may be nominally powered by 6V, but if you use a battery pack with insufficient power, or directly supply power to it through the 5V pin on the development board, this will cause a big problem. When the servo needs to be turned to 90 degrees, but the load is slightly larger, the voltage will be pulled down instantly, causing the "brain" of the servo control chip to have unstable power supply, issue incorrect instructions, or even restart directly.
The symptom in this case is that the servo rotates well when it is unloaded, but gets stuck or shakes as soon as something is loaded or turned to a certain angle. The solution is not complicated. Just prepare a better quality power supply for your servo, such as a few reliable batteries, or a voltage stabilizing module that can output enough current. Separate the power cable and signal cable of the servo, connect the signal cable to the development board, connect the power cable directly to the external power supply, and connect the GND (ground wire) on both sides together to ensure stable operation.
Yes, and it's a physical issue. You send a 90-degree command to the servo, and the motor inside the servo is indeed spinning hard, but if the connecting rod or rocker arm it drives is blocked by something before it reaches 90 degrees, then it can only stop there and tell you "I tried my best, but I really can't make it." Over time, not only will the positioning become inaccurate, but the gears inside the servo may also be damaged due to the force exerted.
Therefore, if you encounter an inaccurate rotation angle, don't rush to change the program first. Gently move your mechanical structure with your hands to feel whether the entire stroke from 0 degrees to 180 degrees is smooth. Is there any point that feels particularly astringent, or has a "clicky" step? If so, you need to adjust the length of the connecting rod or polish the stuck parts to ensure that the mechanical movement itself is free and without interference.
There are two common types of servos on the market, one is analog servos and the other is digital servos. The analog servo relies on continuous pulse signals to maintain its position. If the pulse width you give is slightly off, or the signal jitters, it will "fine-tune" near that position, which is what we often call "rudder jitter". There is a small processor inside the digital servo, which will lock the position at a higher frequency, respond faster, and the positioning will be more accurate and stable.
If your project requires relatively high angle accuracy, such as making a small robotic arm or photography gimbal, then spending more money and choosing a digital servo will save you a lot of worry. It will better respond to the 90-degree instructions written in your program and reduce errors caused by the fuzzy control signal itself. Of course, no matter which one you choose, the power supply and mechanical issues mentioned above are the basis for their accurate positioning.
After talking so much, in fact, most of the time when the servo is not adjusted correctly, it is these details that cause trouble. You can go back and check your project to see if the power supply is not fed, or is the mechanical structure stuck? Have you ever encountered a particularly stubborn steering gear angle problem, and how did you solve it in the end? Welcome to share your experience in the comment area so that more people can avoid detours. If you find this article useful, don’t forget to like and share it with your friends who play electronics together!
Update Time：2026-03-13
Contact Kpower's product specialist to recommend suitable motor or gearbox for your product.
