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Published 2026-03-05
Talking aboutservos, have you ever encountered this situation: you bought aservowith great joy, but after a lot of fiddling with it, it either kept shaking, or it got stuck halfway through the rotation, completely refusing to obey your orders? Don't worry, this is probably because you don't understand how it turns. Only by understanding the working principle of the steering gear can you truly control it and make it obey your words.
You may be curious, why can theservostop steadily at the specified angle if you give it a signal, instead of spinning around like an ordinary DC motor? This is thanks to its internal "closed-loop control system". To put it simply, the steering gear integrates a motor, a reduction gear, and a position sensor (usually a potentiometer).
When you send a target position command to the servo through the signal line, the control circuit will immediately compare the current position with your desired target position. If there is a deviation, it will drive the motor to rotate until the position fed back by the sensor is consistent with the target position you gave, and the motor will not stop. This process can be carried out dozens or hundreds of times per second, so the servo movement you see is both precise and smooth.
This is probably the most confusing part. We usually use the GPIO port of a microcontroller (like a microcontroller) to send a PWM wave to the servo. How can it become a turning force? In fact, the control chip inside the servo is like a translator, which specializes in interpreting this PWM signal.
This PWM signal has a key parameter called "pulse width", which is the duration of the high level. For most standard servos, this time varies between 0.5ms and 2.5ms. After the control chip interprets this length of time, you will know which angle you want it to turn to. For example, a pulse width of 1.5ms usually corresponds to the middle position (90 degrees), while 0.5ms and 2.5ms correspond to two extreme angles (0 degrees and 180 degrees) respectively.
If you take the steering gear apart and look at it, you will find that there is a delicately designed micro system inside. The core brain is the small control circuit board that receives your instructions and makes judgments. The execution part is a powerful DC motor, which can rotate at high speed but with small torque.
In order to allow the power output from the motor to actually drive the heavy steering wheel, the reduction gear set comes in handy. They reduce the high-speed rotation of the motor and at the same time amplify the torque dozens or even hundreds of times. The last key part is the feedback position potentiometer, which is connected to the output shaft and reports to the brain in real time, "Sir, we are now moving to this position!" These four parts work closely together to form a complete steering gear that controls where to hit.
Many friends will use the continuous rotating servo as an ordinary servo, only to find that it is completely out of control and thought it was broken. These two types of servos are essentially different in principle. For a standard servo, what we control is its absolute position and let it stop at a certain angle.
When the servo is continuously rotated, the internal potentiometer feedback is disconnected, and the control circuit is changed to a speed and direction controller. At this time, the PWM signal you send no longer represents the target angle, but represents the rotation speed and direction you want. A pulse width of 1.5ms means stop, if it is less than it, it will turn in one direction, if it is greater than it, it will turn in the opposite direction. If you need to drive wheels, choose the right one, don't mix it up.
After understanding the principle, the next step is how to choose a steering gear. You can't expect a 9g micro servo to push the big arm of the robotic arm, it will definitely smoke. The key is to look at three core parameters: torque, speed and angle range.
️Torque: Usually expressed in kg·cm, it means how many kilograms of weight the moment arm can pull when it is 1 cm long. The heavier something you're dragging, the more torque you'll need.
️Speed: refers to how many seconds it takes for the servo to turn 60 degrees, such as 0.12 seconds/60 degrees. The faster the speed, the more responsive it will be, but the corresponding power consumption and jitter may also be greater.
️Anglerange: Most are 180 degrees, but there are also 360 degrees and special angle servos. If your project requires multiple rotations, such as for a gimbal, then standard servos will not work. You must use the continuous rotation servos or multi-turn servos mentioned above.
This is the most common and troublesome problem when playing with servos. You write the program and turn on the power with full expectation, but the servo shakes like a convulsion, becomes weak, or turns to a strange position. Nine times out of ten, the problem is the power supply.
The current demand when the servo is started and locked is very large. The instantaneous current of a standard servo may reach 1-2 amps. If you directly use the 5V pin to power it, it will be pulled down instantly, causing the voltage to drop and the control system to reset. This is like if the voltage in the community is unstable, the computer will restart. The solution is simple: power the servo separately, and connect its power and ground wires to the ground wire of the control circuit to ensure that the "brain" and "muscles" have their own meals.
After talking so much, from signal interpretation to internal structure, to model selection and power supply, I believe you already have a clearer understanding of servos. I don’t know what interesting function you most want to use the servo to achieve in your actual project? Welcome to leave a message in the comment area to share your creativity, let's discuss it together! If you think this article is helpful to you, don’t forget to like and share it with your friends who also play electronics~
Update Time：2026-03-05
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