### Project 12 Servo

**1. Description**

This servo features high performance and high precision with a maximum rotation angle of 180°. Weighting only 9g, it is perfectly suitable for any mini device in multiple occasions. What's more, it enjoys short startup time, low noise and strong stability.

**2. Working Principle**

**Angle range:** 180° (360°, 180° and 90°)

**Drive voltage:** 3.3V or 5V

**Pin:** Three wires

![](./media/A49.png)

**GND:** Grounded(brown)

**VCC:** A red pin that connects to a +5v (3.3V) power

**S:** A orange signal pin that controlled via PWM signal

![](./media/A50.png)

**Control Principle**: The rotation angle is controlled via duty cycle of PWM. Theoretically, standard PWM cycle is 20ms(50Hz), so pulse width should distribute within 1ms~2ms. However, the actual pulse width reaches 0.5ms~2.5ms, which corresponds to 0°～180°. Pay attention that, for the same signal, the rotation angle may vary from servo brands. 

**3. Wiring Diagram**

![](./media/A51.png)

Add an external power source instead of just using USB for power.

![](./media/A52.png)

**4. Test Code**

```
int servoPin = 4;//servo PIN

void setup() 
{
  pinMode(servoPin, OUTPUT);//servo pin is set to output
}

void loop() 
{
  for(int i = 0 ; i <= 180 ; i++) 
  {
   servopulse(servoPin, i);//Set the servo to rotate from 0° to 180°
  delay(10);//delay 10ms
  }
  for(int i = 180 ; i >= 0 ; i--) 
  {
   servopulse(servoPin, i);//Set the servo to rotate from 180° to 0°
  delay(10);//delay 10ms
  }
}

void servopulse(int pin, int myangle) 
{ //Impulse function
  int pulsewidth = map(myangle, 0, 180, 500, 2500); //Map Angle to pulse width
  for (int i = 0; i < 10; i++) 
  { //Output a few more pulses
    digitalWrite(pin, HIGH);//Set the servo interface level to high
    delayMicroseconds(pulsewidth);//The number of microseconds of delayed pulse width value
    digitalWrite(pin, LOW);//Lower the level of servo interface
  }
}
```

**5. Test Result**

After connecting the wiring and uploading code, the servo starts to rotate from 0° to 180° and then reverse.