SG90 servo with Arduino Nano — wiring, power and Serial control

The SG90 is the 9-gram servo in every robot kit, and the Nano drives it with the standard Arduino Servo library. The signal goes on D9; any digital pin works, but D9 keeps the wiring neat on a breadboard.

Type a number between 0 and 180 in the Serial Monitor (115200 baud, “Newline”) and the horn moves there. For anything heavier than an empty horn, give the servo its own 5 V supply.

Wiring

Board quirks

• On USB the Nano’s 5V pin goes through a diode and the USB port’s current limit. A stalled SG90 can pull 500–700 mA, which resets the Nano or drops the USB port — the classic “servo jitters and the board restarts”.
• The Servo library uses Timer1: analogWrite() on D9 and D10 stops working once a servo is attached. Use D3, D5, D6 or D11 for PWM LEDs or motors.
• SG90 wires: brown = GND, red = 5 V, orange = signal.
• attach(pin, 500, 2400) gives the full 0–180° travel on most SG90s; the default 544–2400 µs stops a little short.

Code

// SG90 micro servo on an Arduino Nano, angle set from the Serial Monitor (type 0-180 + Enter).
// SIG → D9, VCC → 5V (one unloaded SG90 only), GND → GND.
// The Servo library takes Timer1, so analogWrite() stops working on D9 and D10.
#include <Servo.h>

const uint8_t SERVO_PIN = 9;
Servo servo;

void setup() {
  Serial.begin(115200);
  servo.attach(SERVO_PIN, 500, 2400);  // SG90 pulse range in microseconds
  servo.write(90);
  Serial.println(F("Servo at 90. Type an angle 0-180:"));
}

void loop() {
  if (Serial.available()) {
    long angle = Serial.parseInt();
    while (Serial.available()) Serial.read();  // drop the line ending
    angle = constrain(angle, 0, 180);
    servo.write(angle);
    Serial.print(F("Moved to "));
    Serial.println(angle);
  }
}

// SG90 micro servo on an Arduino Nano, angle set from the Serial Monitor (type 0-180 + Enter).
// SIG → D9, VCC → 5V (one unloaded SG90 only), GND → GND.
// The Servo library takes Timer1, so analogWrite() stops working on D9 and D10.
#include <Servo.h>

const uint8_t SERVO_PIN = 9;
Servo servo;

void setup() {
  Serial.begin(115200);
  servo.attach(SERVO_PIN, 500, 2400);  // SG90 pulse range in microseconds
  servo.write(90);
  Serial.println(F("Servo at 90. Type an angle 0-180:"));
}

void loop() {
  if (Serial.available()) {
    long angle = Serial.parseInt();
    while (Serial.available()) Serial.read();  // drop the line ending
    angle = constrain(angle, 0, 180);
    servo.write(angle);
    Serial.print(F("Moved to "));
    Serial.println(angle);
  }
}

Library: Servo (Arduino) — compiled with Servo 1.3.0.

Expected serial output

Servo at 90. Type an angle 0-180:
Moved to 0
Moved to 180

Servo at 90. Type an angle 0-180:
Moved to 0
Moved to 180

Common errors