TECHNICAL SUPPORT
Published 2026-03-12
Let’s talk about the annoying problem of theservonot turning today. When playing with robots or making small inventions, I often encounter situations where theservogets stuck and I feel anxious. In fact, there are only a few reasons why theservocannot turn. As long as you figure it out and take the right medicine, it is not a big problem.
Many friends doubted whether the servo was broken as soon as they started. In fact, it is most likely that the power supply has not kept up. The little guy named Servo is very powerful, but he is also an electric tiger. If the voltage of the battery you use is not enough or the current output is too small, it’s like a person who doesn’t have enough to eat. How can he have the strength to work? Especially for those high-torque servos, the instantaneous starting current is very large. An ordinary battery pack or voltage stabilizing module can easily be pulled down, causing a voltage drop, and the servo will naturally not be able to rotate.
The solution is actually quite simple. First read the specifications of your servo to find out its working voltage and locked-rotor current. Then calculate whether your power supply can meet this demand. ️ For example, you can directly switch to a battery with higher voltage and stronger discharge capacity, or use a separate BEC (voltage stabilizing module) to power the servo instead of competing for power with the main control board. This will basically solve the problem.
If there is no problem with the power supply, then we have to look at the signal line. The steering gear can move by receiving the PWM (Pulse Width Modulation) signal from the controller. If the signal is unstable or no signal at all, it stays in place and doesn't move. This situation usually occurs when the connection is not done properly online, such as the plug is loose, or the solder joint is detached, or the signal frequency or pulse width range may be set wrong in the code.
How to check? You can first gently pull the signal line of the servo with your hand to see if there is a bad contact. Then use a multimeter to measure the voltage of the signal line to see if there are normal pulses. As for the code, you can find a simple test program that is known to work and flash it in to see if the rudder moves. If it works after changing the program, then the problem is probably in your original code logic.
The servo itself is fine, but it won't turn after it's installed. At this time, most likely its "joint" is stuck by something. Think about it, the servo is connected to other components through the steering wheel. If the connecting rod is installed too tightly, or there are burrs or foreign objects in the connecting parts, or even if there is something blocking the range of motion, and the servo cannot move even though it tries its best, then you can only stare. Especially when newbies are making things, it is easy to overlook the smoothness of moving parts.
At this time, you need to manually turn the connected mechanism to feel whether the resistance is strong. Ideally, it should be very smooth when turned by hand. If there is any jamming, you need to check the connection carefully to see if the screws are tightened too tightly or if there is any interference. ️ Solution: 1. Add some lubricating oil to the rotating shaft. 2. Use a file to smooth the rough surface. 3. Adjust the length of the connecting rod to make sure it doesn't stiffen throughout its travel.
What I just mentioned are all external causes. Now we have to see if the steering gear itself is "internally injured". There are a bunch of precision plastic or metal gears inside the steering gear. If it is subject to excessive external force impact or is overloaded for a long time, the teeth of the gear may be broken. This is what we often call "sweeping teeth". If the gears are broken, it will definitely not be able to transmit the rotation of the motor. It sounds like the motor is buzzing, but the output shaft is motionless.
How to judge whether it is a tooth scan? A very simple way is to remove the steering wheel and then twist the output shaft of the steering gear by hand. You can't turn the normal steering gear because of the resistance of the motor and reduction gearbox. If it feels like it can turn easily and there is a "clunking" hollow feeling when turning, it is basically certain that the gear inside is broken. There is nothing to fix in this situation. Either buy a set of gears of the same model and replace them, or just replace it with a new servo.
This reason is a little more subtle, but quite common. The reason why the servo can turn to the angle you specify depends on a small part called a potentiometer to feedback the position. You can think of it as a rotating variable resistor. As the servo shaft rotates, its resistance value will also change. If this potentiometer is worn, dirty, or has poor contact, the servo controller will not know where the axis is now, and will not be able to drive it accurately. It will appear to be shaking, weak, or simply not turning.
This kind of failure usually has a characteristic, that is, if you give it a signal, it may tremble a few times, or may not respond, but if you help it turn to an angle with your hands, it can maintain itself. This is basically a problem with the potentiometer. Repairing it requires a little welding work, you have to disassemble the servo and replace the aging potentiometer. If you have a used servo of the same model on hand, it is also a good idea to remove one and replace it.
Finally, there is a situation where there is a problem with the board that controls the steering gear. The servo will generate a reverse induced electromotive force when it is working. Although it is very small, if the power supply is not handled well, or if you plug and unplug the servo while it is powered, the instantaneous voltage spike may burn out the pin on the main control board responsible for outputting the PWM signal. If the pin is broken, naturally it will not be able to give commands to the steering gear.
It's easy to confirm this. You plug the servo signal line you suspect is broken into another PWM output port on the board that you haven't used, and then change the control pin to the new port in the program. If the servo spins happily on the new port, it means that the original port has indeed been sacrificed. In this case, just use another port. If all the ports are broken, you may have to consider replacing the control board.
The problem that the servo cannot turn basically lies in the aspects of electricity, signal, and mechanical structure. You can follow what I just said, start with the simplest power supply, and narrow down the scope step by step. What project have you been working on recently, and what kind of steering gear problems did you encounter? Let’s talk about it in the comment area and let’s study it together! If you find this article useful, don’t forget to like it and share it with your electronic friends around you~
Update Time：2026-03-12
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