What Is The Difference Between Stepper Motors And Servos? Beginner’s Guide To Selection And Pitfall Avoidance

Have you ever had trouble with stepper motors andservos when tinkering with a small invention or designing a new product? The two little guys look quite similar, and they can both make things move, but when it comes time to choose, their heads are too big. If you choose the wrong one, the project progress bar will be stuck directly and the effect will not come out. Today we will sit down and talk about the difference between stepper motors andservos, and how to choose the "right person".

What is the difference between stepper motor and steering gear?

Fundamentally, they both work differently. The stepper motor is like an obedient soldier. If you send it a pulse (command), it will take a step forward. The size of this step is fixed, which is called the step angle. How many pulses you send will determine how many steps it will take. It relies entirely on the number of pulses to calculate whether it is walking in the right position, and it will not look back.

The steering gear is like a flexible fat man with eyes. In addition to the motor, it also has control circuits and reduction gears. You tell it "turn to 90 degrees" and it will stare at the internal position sensor and will not stop until it turns to 90 degrees. So, one just walks along, while the other watches to make sure everything is in place while walking.

Which one has higher accuracy, stepper motor or steering gear?

️ This question needs two answers. The accuracy of the stepper motor depends on the angle of each step of its rotation. For a common 1.8-degree step angle on the market, one revolution is 200 steps. By subdividing the driver, each step can be cut more finely, and the theoretical accuracy can be very high. And its biggest advantage is that it does not accumulate errors. If you make a slight mistake this time, you will not make the same mistake again next time.

️ The accuracy of theservomainly depends on the potentiometer and control chip inside. Ordinary analog servos have a dead zone, and the angle will swing a little near the target value. A better digital servo will have much better accuracy and response speed. However, the servo can generally only turn half a turn or more than half a turn. If you want it to turn several turns in a row, it will not work.

How to control stepper motors and servos

1. Controlling stepper motors requires a little patience. You generally need a driver, and then use a microcontroller (for example) to send pulse signals to the driver. Control the frequency of pulses and the motor will rotate faster; control the total number of pulses and it will rotate to the specified position. It sounds complicated, but there are a lot of ready-made libraries and tutorials on the Internet. Once you get through it, you will feel a sense of accomplishment.

2. The steering gear control is simply "fool-like". Once the three lines are connected, the signal line is connected to the PWM port. Using the Servo library, write a line.write.write(90);and it will turn to 90 degrees with a "swish". Do you ever find this too convenient? It is precisely because of this simple control method that it is so popular in the field of robotics.

Where are stepper motors and servos used?

Stepper motors most often appear in precision equipment that require "pointing and hitting". For example, the 3D printer on your desk requires precise movement of the X, Y, and Z axes in order to stack the models layer by layer. There are also the feed axis of CNC machine tools and the shipping carousel of vending machines. They are all its home field, and the requirement is to be accurate, even if it is slow.

The steering gear is the main force of robot joints and model steering surfaces. Imagine that a robot can flexibly turn its head and lift and lower its arms, all relying on the servo to exert force on the joints. There are also the elevators and rudders of remote control aircraft and the steering wheels of remote control cars, all of which are servos working silently behind the scenes. It has great strength and small size, making it very suitable for this kind of swinging back and forth work.

Which one is more likely to break, the stepper motor or the steering gear?

In fact, as long as they are used in the right place, they have a long life. The stepper motor itself has a simple structure and has no brushes, so it is difficult to break during normal use. The biggest fear is that the driving current is not set properly, causing it to overheat and work. As time goes by, the magnetism weakens and the power becomes smaller. Therefore, it is important to equip it with a suitable driver and pay attention to heat dissipation.

The weak link in a servo is usually the pinion gear and position sensor inside. The gears of cheap plastic gear servos are prone to collapse when subjected to severe impact or overload. After being used for a long time, the potentiometer inside will also wear out, resulting in inaccurate position. Therefore, in situations where the force is large, it is recommended to directly install the metal gear servo. In addition, don't let it sit for a long time, as it can easily burn the motor.

How to choose stepper motors and servos

This question is the most practical. I will teach you the simplest way to judge: first think clearly about your exercise pattern. If your machine needs to rotate many times continuously, such as a pan/tilt that can monitor 360 degrees, or you want the conveyor belt to rotate continuously, then don't hesitate to choose a stepper motor.

If your movement is just from point A to point B, such as a robot dog raising its legs or a mechanical claw opening and closing, then the servo is tailor-made for you. After considering the space and budget, servos are usually small in size and large in torque, but more expensive at the same level; the stepper motor system may be cheap as a whole, but the size and weight will be larger. You can go to the official websites of some companies that specialize in motion control, such as "Lesai" or "Buke", and look at the application cases on their product pages. The parameters and application scenarios are clear at a glance, which can help you make a decision faster.

In the projects you have worked on, have you ever experienced "overturning" due to improper motor selection? Come to the comment area to talk about your story, give it a like and share it, so that more friends can avoid the pitfalls you have stepped on!