TECHNICAL SUPPORT
Published 2026-02-27
This project you are working on is quite interesting. It requires a continuous rotatingservo, but you find that you only have an ordinary microservo. Do you feel a little confused? Don’t worry, many friends who are engaged in product innovation will encounter this problem. Let’s talk today about how to turn the ordinary microservoyou have on hand into the continuous rotating servo you need.
Ordinary micro servos, such as the SG90, have a potentiometer inside, which is like a small angle sensor. By reading the value of this potentiometer, the control chip can understand the current angle to which the servo arm is rotating. Therefore, when given a specific signal, it will accurately turn to the corresponding position, such as 90 degrees. From its original design, it focuses on precise control of angles rather than endless rotation in circles.
Its operating principle is based on the information fed back by the potentiometer, and the control chip drives the steering arm to the specified angle based on this information. This makes the servo play an important role in many scenarios that require precise angle positioning. Whether in simple model building or complex automation equipment, ordinary micro-servos such as SG90 can provide reliable support for specific actions by virtue of their precise angle control characteristics, ensuring that each component operates according to a predetermined angle, thereby ensuring the normal operation of the entire system.
If you give it a continuous signal, it will only compete at that angle instead of spinning in circles. It's like asking a soldier pointing in the direction to stand still. He will only pose and not actually run. Once we understand this principle, we know how to transform it.
If you want it to rotate continuously, the core idea is to deceive the "eyes" inside the steering gear. We need to replace the potentiometer used to detect the angle with two resistors with fixed resistance. In this way, the steering engine's brain doesn't know where the arm is turning, and it thinks it is always in the middle position.
The operation steps are roughly as follows: First, carefully open the back cover of the servo. When the back cover is successfully opened, you will see three gears and a circuit board. Then, gently remove the top gear so that you can clearly see the axis of the potentiometer. Subsequently, use a soldering iron to disassemble the potentiometer, and then replace the potentiometer with two resistors of the same resistance (for example, two 5K ohm resistors) for welding. Finally, install the gear back in its original shape, and the entire operation is complete.
After the modification is completed, the way you control the servo will completely change. In the past, a pulse width signal was sent to make it rotate to a specified angle. Now, a signal is sent to make it rotate at a certain speed. Usually, if you send a pulse width signal of 1.5ms, it will stop; if you send a pulse width signal of 1.3ms, it will run forward at full speed; if you send a pulse width signal of 1.7ms, it will reverse at full speed.
It's like driving an electric car without gears. The size of the signal you give determines its speed and direction. You can fine-tune this pulse width signal to make the servo rotate at different speeds to achieve very flexible control. This simply opens the door to a new world for making cars, gimbals, or mechanisms that require continuous rotation.
Not all servos are easy to modify. The most common micro servos on the market, such as SG90 and MG90S, have simple structures and are easy to disassemble and assemble. There are also a lot of online tutorials, which are most suitable for novices to practice. They also have enough space inside for you to solder two small resistors.
In addition, the modification methods of digital servos and analog servos are slightly different, but the core principles are the same. The control chip of the digital servo may be more sensitive and require higher precision of the resistor, which may require a little debugging. It is recommended to start with a cheap, ordinary analog servo. The success rate is higher, and you won’t feel bad even if it is modified.
Before you get started, there are a few things you should keep in mind. First, when disassembling the gear, be sure not to lose the small gaskets and springs inside. They are very important for the smooth operation of the steering gear. Second, when soldering the resistor, move quickly to prevent the pad from overheating and warping. It is best to tin the resistor pins first so that soldering can be done more quickly.
Another most critical thing is that the two resistors must have exactly the same resistance, otherwise the servo may not be able to stop completely and there will be a slight "drift" phenomenon. If this happens, you can slightly adjust the resistance of one of the resistors, or fine-tune the pulse width of the stop signal in the program, which usually solves the problem.
After soldering the resistors and carefully reinstalling the case, it was time to try out the results. First, connect the servo to your controller, like this. Then write a simple test code: first let the servo start to rotate, for example, set it to rotate forward at full speed for 3 seconds, then stop for 1 second, and then perform reverse rotation at full speed for 3 seconds. Finally, carefully observe whether the servo rotates smoothly and whether it can really stay still when stopped.
After completing the above steps, further check whether the connection between the servo and the controller is stable and whether there is any sign of looseness. At the same time, check whether there is any error message during the running of the test code. If so, it needs to be checked and corrected in time. Confirm again whether the angle of the servo is accurate each time it rotates, and whether it can perform actions strictly in accordance with the time and speed set by the code. Through these detailed inspections, we ensure that the steering gear is in optimal operating condition to meet possible subsequent use needs.
If it is found that there is jitter or slow rotation when stopping, it means that the pulse width of the stop signal is not correct. You can fine-tune the pulse width value that represents stopping in the program, such as fine-tuning from 1.5ms to 1.48ms or 1.52ms until it is completely still. This debugging process is very simple. You can find the most suitable value by trying a few times.
Regarding the continuous rotation of the servo, or more subtle uses of the servo, I suggest you search our company's official website. There is a case library on the official website, which contains many ready-made solutions for reference.
After talking so much, I would like to ask you next, which of your creative products do you plan to apply this modified continuous rotating servo to? Welcome to leave a message and share it in the comment area. If you think this article is valuable, don’t forget to like it and forward it!
Update Time：2026-02-27
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