Introduction

Servo motors are very popular and widely used in many electronics projects for a few simple reasons, they are easy to use and provide motion and great position control.

Servomechanism date back to ancient times and evidence shows that the Greeks used wind-driven servo-motors to continuously adjust the heading of their windmills so the blades always faced into the wind. The industrial revolution marked a major turning point and by 1915 the term “servo motor” was firmly used by the electrical engineering community in the West and further development by GE & Northrup and other companies popularised the DC & AC servos.

Servos are controlled by sending an electrical pulse of variable width or pulse width modulation (PWM), through the control wire. They are considered electromechanical parts and here is a quick intro and history. Servo motors electronic parts were first used in the Remote Control (RC) world, usually to control the steering of RC cars or the flaps on an RC plane. Fast forward, the application of servo motors can be seen in use in robotics, automation, CNC turning, door accesses, and of course, small projects in combination with microcontrollers like Adafruits and Arduino.

What is a servo motor?

A servo motor is a closed-loop system that uses position feedback to control its motion and final position. The circuitry is built right inside the motor unit and has a positionable shaft, which usually is fitted with a gear. Therefore, this type of motor requires a closed feedback loop, integrated encoder, and drivers or control algorithm, the position and speed control they provide make them highly adaptable in a number of applications.

In simple terms, a servo motor is a rotational motor to which power is supplied by a servo amplifier and serves to apply torque or force to a mechanical system e.g. brakes or actuator.

How Do Servo Motors Work?

In order to understand how a servo works we need to understand what’s inside the servo. It’s made up of a drive motor, a potentiometer, and a circuit. The motor which is powered by AC or DC current is attached by gears to the control wheel. Since the motor is high speed and low torque, the gearbox tends to reduce the speed to around 60 RPM and at the same time increases the torque. As the motor rotates, the potentiometer’s resistance changes, so the control circuit can precisely regulate how much movement there is and in which direction. Eventually, when the shaft of the motor is at the desired position, the power supplied to the motor is stopped. The Servo motor will only run as hard as necessary to accomplish the task at hand making it very efficient as it will turn slowly when it’s near the desired position, otherwise it will turn fast.

One important thing to note is that servos are not inherently speed controlled. When you send the servo motor a position signal, and the servo is trying to get to that position as fast as possible. However, you can reduce the speed of the servo by sending it to a series of positions that lead to the end position which will affect the servo speed.

Connector Pinout: How do you Connect them?

As with most electronics using pinout connectors, it’s absolutely critical to ensure correct wiring is done servo. The majority of the servos follow a specific color code for Power (VCC), Ground (GND), and Control Signal.

See the table below for the three most common color-coding connections by electronics and electrical engineers on their servo connector projects. The pin numbering is almost universally the same but manufacturers may use different colors for the wires. If you are not certain or your servo does not match, do yourself a favour and double-check the documentation for your servo.

Types of Servo Motors

Just to be clear to readers that servo is not a specific type of motor but a motor referred to as a servo because of the way in which it’s driven, and its position, velocity, and acceleration are controlled.

The 5 types include positional rotation, continuous rotation, linear, AC and DC servos.

1. Positional Rotation servos that can rotate to 180 degrees with stops in the gear mechanism. This protects the output shaft from over-rotating.
2. Continuous Rotation servo motor has no rotation limit and range and can go either direction, clockwise and antoclockwise.
3. Linear Servos use a rack and pinion mechanism to change their output.
4. AC servos
5. DC servos

Servo Motor Applications

Here are several of the more common servo motor applications in use today.

1. Robotics especially in robotic arms to reduce human error.
2. Conveyor Belts which speed up processes in industrial production and elevators machines
3. Camera Auto Focus: by use of a very precise servo motor that corrects the lens to sharpen images until they’re in focus.
4. Robotic Vehicle
5. Solar Tracking System
6. Woodworking & CNC
7. Metal Cutting & Metal Forming Machines
8. Antenna Positioning
9. Textile weaving
10. Printing Presses/Printers i.e. it’s essential for them to be able to move the printing head to precise locations on the page to make sure the print appears in the layout precisely as planned.
11. Automatic Door Openers
12. Remote control toys for kids are precisely configured using servo motors to allow them control them with ease.
13. Rocket ships are worth billions of dollars and to get precise positioning and rotation you cannot rely on humans and this can only be done by using servo motors.

Conclusion

If you have any experience of using different types of Servo Motors, we will be very glad to have your opinions about their performance in the comments below.