SG90 servo with NodeMCU ESP8266 — wiring and full 0–180° code

An SG90 makes a NodeMCU move things: a door latch, a fish feeder, a pointer on a dashboard. The signal is a 3.3 V pulse from D5; the power must come from VIN or, better, its own 5 V supply.

Unlike the ESP32, the ESP8266 needs no extra library — the Servo that comes with the core works. The catch is its default pulse width, which is why the sketch sets 500–2400 µs explicitly.

Wiring

Board quirks

• The ESP8266 core ships its own Servo library — don’t install ESP32Servo or the AVR one. Its default pulse range is 1000–2000 µs, which turns an SG90 only about 90°; the sketch calls attach(D5, 500, 2400) for the full sweep.
• Never power the servo from 3V3. The NodeMCU’s regulator feeds the ESP8266, and a moving servo pulls hundreds of mA — the 3.3 V rail sags and the board resets or the Wi-Fi drops.
• D0 (GPIO16) can’t generate servo pulses. Avoid D3, D4 and D8 too: the servo’s input can upset the boot levels, and D4 toggles at start-up, which makes the arm twitch every reset.
• The pulses are made by the core’s software waveform generator, not a hardware timer. Heavy Wi-Fi traffic can add a little jitter; a separate PCA9685 board fixes that for robot arms.

Code

// SG90 micro servo on a NodeMCU (ESP8266), using the Servo library that ships with the core.
// SIG → D5 (GPIO14), VCC → VIN (5 V from USB, one unloaded SG90 only), GND → GND.
#include <Servo.h>

const uint8_t SERVO_PIN = D5;  // GPIO14 — PWM-capable, no boot role (D0 can't do servo pulses)
Servo servo;

void setup() {
  Serial.begin(115200);
  Serial.println();
  // The ESP8266 Servo library defaults to 1000–2000 µs, which only moves an SG90 about 90°.
  // 500–2400 µs gives the full 0–180°. Narrow it if your servo buzzes at the ends.
  servo.attach(SERVO_PIN, 500, 2400);
  Serial.println("Sweeping 0 <-> 180 deg on D5");
}

void loop() {
  for (int a = 0; a <= 180; a += 30) {
    servo.write(a);
    Serial.printf("Angle %d deg\n", a);
    delay(600);
  }
  for (int a = 150; a >= 30; a -= 30) {
    servo.write(a);
    Serial.printf("Angle %d deg\n", a);
    delay(600);
  }
}

// SG90 micro servo on a NodeMCU (ESP8266), using the Servo library that ships with the core.
// SIG → D5 (GPIO14), VCC → VIN (5 V from USB, one unloaded SG90 only), GND → GND.
#include <Servo.h>

const uint8_t SERVO_PIN = D5;  // GPIO14 — PWM-capable, no boot role (D0 can't do servo pulses)
Servo servo;

void setup() {
  Serial.begin(115200);
  Serial.println();
  // The ESP8266 Servo library defaults to 1000–2000 µs, which only moves an SG90 about 90°.
  // 500–2400 µs gives the full 0–180°. Narrow it if your servo buzzes at the ends.
  servo.attach(SERVO_PIN, 500, 2400);
  Serial.println("Sweeping 0 <-> 180 deg on D5");
}

void loop() {
  for (int a = 0; a <= 180; a += 30) {
    servo.write(a);
    Serial.printf("Angle %d deg\n", a);
    delay(600);
  }
  for (int a = 150; a >= 30; a -= 30) {
    servo.write(a);
    Serial.printf("Angle %d deg\n", a);
    delay(600);
  }
}

Library: Servo (Arduino).

Expected serial output

Sweeping 0 <-> 180 deg on D5
Angle 0 deg
Angle 30 deg
Angle 60 deg
Angle 90 deg

Sweeping 0 <-> 180 deg on D5
Angle 0 deg
Angle 30 deg
Angle 60 deg
Angle 90 deg

Common errors