General Topics – STEPPERCHINA

1.The defination of servo motors
A servo motor is an electric motor that converts electrical power into mechanical power. It’s commonly used in dynamic systems where fast movements are required. To achieve this, the servo motor needs to have low inertia or mass and possess high force or torque for acceleration. These requirements impact the design and construction of the servo motor. Low inertia is achieved in a rotating servo motor by employing a slender rotor or a flat “pancake” rotor design. High torque can be attained by using powerful permanent magnets.

2.The history of servo motors
Since the 80s of the 20th century, with the development of integrated circuits, power electronics technology and AC variable speed drive technology, permanent magnet AC servo drive technology has developed prominently. AC servo system has become the main development direction of contemporary high-performance servo system, so that the original DC servo is facing the crisis of being eliminated. After the 90s, the AC servo system that has been commercialized in various countries around the world is a fully digitally controlled sine wave motor servo drive. The development of AC servo drives in the field of transmission is changing with each passing day.

3.Main types of servo motors
First is the AC servo motor. This type of servo is currently used today by most companies. AC servo motors are mostly used in industrial fields. AC servo motors are AC motors that rely on encoders. These types of servo motors work through controllers providing feedback and closed-loop control. They are known to function at a high accuracy and are easily controllable.
Second is the DC servo motor. These kind of servo motors were used in the past by Fuji Electric but are rarely used nowadays, as AC servo motors are easier to use, more effective, advanced, and reliable.

4.The advantages of servo motors
High efficiency
High output power relative to their size
More constant torque at higher speed
Closed-loop control
Highly reliable and acceleration
High ratio of torque to inertia
High-speed performance
Torque control
Smooth running
High accuracy
Well suited to varying load applications

In conclusion
In the grand symphony of automation, the AC servo motor stands as a virtuoso performer, harmonizing precision and power in a seamless blend.

Following chapter is a very high overview. Please read further down about more practical info about the drive and motor types. But basics presented here is pretty universal and widely used in DIY community.

So- what we need to get these motors going? Let’s break it down to components and explain each part briefly. Commonly you need following parts to drive a stepper motor.

Driver
Microcontroller
Power supply

I didn’t include a power supply for (micro)controller here since it’s self-explanatory. A microcontroller like in this case Arduino- gets its power from the USB cable or battery.

What do you need to get a stepper motor running?

Stepper Motor Driver
As we know- stepping motor can be moved one step at a time by applying electricity to coils in the correct order (and polarities). You could do this manually with some switches– step by step, but it has no practical use other than learning. This is where the driver comes into play.

The driver is doing the heavy lifting and it hides all the complexity behind a simple interface. It makes correct windings to be excited in the correct way based on the input signals. They usually have only 2 input pins which take commands in form of digital high and low. One sets the direction of rotation and other is for step commands.

Steps are given as digital pulses. After each step (HIGH) there must be (LOW) input for a moment. So drive can detect when new step command is given. If there is are no pulses given- there will be no steps done by the drive and motor.

Direction input pin can be LOW or HIGH all the time, while steps are made, depending on the direction needed. Direction does not need impulses.

Note: Some small unipolar stepper motors are driven via transistor arrays or chips like uln2003 and ln2004. There can be 4 control wires instead of 2 from the microcontroller. In that configuration, the microcontroller is directly telling which wires (coils) to energize by turning correct ones on each step “manually”. Look at example schema on the Arduino page.

Microcontroller
It’s possible to make motors move by touching the step pin on driver manually with HIGH wire. But that would not be very practical other than testing. This is why microcontroller comes into play. Microcontrollers can give many hundreds or even thousands of impulses per second so the motor can be rotated very fast and accurate.

Which has higher torque? nema 17 or nema 23？

How to choose the NEMA 23 or the NEMA 34 stepper motors?

Category: General Topics

Development and advantages of servo motors

What do you need to get a stepper motor running?