Education

SG90 Servo Motor

A Tiny But Mighty Motor!

The SG90 Servo Motor is a small, precise motor that moves to a specific position instead of spinning continuously like a regular motor. Think of it like a robotic arm that can be told to move to an exact angle—great for robots, cars, and automation projects!

How Does a Servo Work?

Imagine you’re playing with a steering wheel on a toy car:

Control Arm = Steering Wheel: The servo's arm moves left and right, just like a steering wheel turning the car.

Signals Tell It Where to Move: The Arduino sends signals to tell the servo exactly which angle to turn to (like 0°, 90°, or 180°).

Power and Control Wires: The servo has 3 wires:

• Red (VCC): Power supply (5V).

• Black/Brown (GND): Ground connection.

• Orange/Yellow (Signal): The Arduino sends signals through this wire to control movement.

The Physics Behind It

Imagine a robotic arm that can move to pick up a cup.

• Inside the servo, there are tiny gears that precisely control how much the arm moves.

• The Arduino sends pulses that tell the motor exactly how far to turn—just like telling a toy car how much to steer!

Understanding PWM (Pulse Width Modulation) and How It Controls a Servo Motor

When we control a servo motor or adjust LED brightness, we don’t just send "ON" or "OFF" signals. Instead, we use PWM (Pulse Width Modulation), a special technique that lets us create smooth and controlled movements. Let’s break it down!

What is PWM?

PWM stands for Pulse Width Modulation. It’s a way to control the amount of power sent to a device by turning it ON and OFF really fast—so fast that the human eye or a motor doesn’t notice the blinking, but instead sees smooth motion or dimming.

Think of it like a fan speed control:
🔹 If you give the fan full power, it spins fast.
🔹 If you give it half power, it spins slower.
🔹 If you keep switching the power ON and OFF really fast, you can control how fast it moves!

This is exactly how PWM works.

Duty Cycle – The Key to PWM

The most important part of PWM is the Duty Cycle.

A duty cycle is the percentage of time the signal is ON versus OFF in each cycle.

Example of Duty Cycles:

How PWM Controls a Servo Motor

A servo motor doesn’t just spin like a normal motor—it moves to an exact position between 0° and 180° based on the PWM signal it receives.

The Arduino sends a PWM signal to the servo’s signal wire (usually on pin 9 or 10), which tells it what angle to move to.

Servo Timing with PWM

For an SG90 servo, the PWM signal works like this:

What’s Happening in the Graph?

🔹 Top Line (0% PWM) → Servo Stays Still at 0° (Leftmost Position)

• The signal is almost always OFF (very short pulses).

• The servo doesn’t move much—it stays all the way left.

🔹 Middle Line (50% PWM) → Servo Moves to 90° (Middle Position)

• The signal is ON and OFF equally.

• The servo moves halfway and stays in the center.

🔹 Bottom Line (100% PWM) → Servo Moves to 180° (Rightmost Position)

• The signal is almost always ON (very long pulses).

• The servo moves all the way to the right.

How to connect servo motor on the Blue Elixer Board

Code Snippet Breakdown

Pin Setup – Telling Arduino Where the Servo Is

#include <Servo.h> // Include the Servo library

Servo myServo; // Create a Servo object

void setup() {
  myServo.attach(9); // Connect servo signal pin to Arduino pin 9
}

What’s happening?

• Include the Servo library (#include <Servo.h>) so we can control the motor.

• Create a Servo object (Servo myServo;) to control the motor.

• Attach the servo to pin 9 (myServo.attach(9);) so the Arduino knows where to send signals.

Moving the Servo to Different Positions

void loop() {
  myServo.write(0);   // Move servo to 0°
  delay(1000);        // Wait 1 second

  myServo.write(90);  // Move servo to 90°
  delay(1000);        // Wait 1 second

  myServo.write(180); // Move servo to 180°
  delay(1000);        // Wait 1 second
}

What’s happening?

• The servo moves to 0°, 90°, and 180° in a loop.

• The delay(1000); command makes it wait for 1 second before moving again.