SG90 servo with Wemos D1 mini — full 180° on the ESP8266

A servo on a D1 mini is the core of a Wi-Fi blind opener, a pet feeder or a remote switch-presser. Signal on D5, power from the 5V pin for a single light-duty SG90, and a common ground.

The ESP8266 has its own built-in Servo library, and it differs from the Arduino Uno one in a way that catches everyone: a narrower default pulse range. This guide sets it right so the SG90 swings the full 180°.

Wiring

Board quirks

• The ESP8266 core ships its own Servo library (no install needed), but its default pulse range is 1000–2000 µs, which turns an SG90 only about 90°. servo.attach(D5, 500, 2400) gives the full sweep; narrow it if your servo buzzes at the ends.
• The core generates the pulse in software from a timer, on any pin except D0 (GPIO16). D5 is used because it is quiet during boot — a servo on D3/D4 can twitch when the board resets.
• A moving or stalled SG90 pulls a few hundred mA. Drawn from the USB 5 V the D1 mini also runs from, that can dip the 3.3 V rail and reset the ESP8266 — the classic “board reboots every time the servo moves”.
• Type an angle and press Enter. Serial.parseInt() waits up to a second for digits but yields while it waits, so the watchdog stays fed.

Code

// SG90 servo on a Wemos D1 mini (ESP8266), using the Servo library built into the ESP8266 core.
// SIG → D5 (GPIO14), VCC → 5V, GND → GND.
// Type an angle (0-180) in the Serial Monitor and press Enter.
#include <Servo.h>

const uint8_t SERVO_PIN = D5;  // GPIO14 - not a boot pin, and quiet during reset
Servo servo;

void setup() {
  Serial.begin(115200);
  Serial.println();
  // The ESP8266 core's Servo defaults to 1000-2000 us, which moves an SG90 only about 90 degrees.
  // 500-2400 us gives the full sweep on most SG90s; narrow it if yours buzzes at the ends.
  servo.attach(SERVO_PIN, 500, 2400);
  servo.write(90);
  Serial.println("SG90 on D5 - type an angle 0-180");
  Serial.println("Angle 90");
}

void loop() {
  if (Serial.available()) {
    int angle = Serial.parseInt();  // waits up to 1 s for digits; yields to the system meanwhile
    while (Serial.available()) Serial.read();  // drop the line ending
    if (angle >= 0 && angle <= 180) {
      servo.write(angle);
      Serial.printf("Angle %d\n", angle);
    } else {
      Serial.println("Use 0-180");
    }
  }
}

// SG90 servo on a Wemos D1 mini (ESP8266), using the Servo library built into the ESP8266 core.
// SIG → D5 (GPIO14), VCC → 5V, GND → GND.
// Type an angle (0-180) in the Serial Monitor and press Enter.
#include <Servo.h>

const uint8_t SERVO_PIN = D5;  // GPIO14 - not a boot pin, and quiet during reset
Servo servo;

void setup() {
  Serial.begin(115200);
  Serial.println();
  // The ESP8266 core's Servo defaults to 1000-2000 us, which moves an SG90 only about 90 degrees.
  // 500-2400 us gives the full sweep on most SG90s; narrow it if yours buzzes at the ends.
  servo.attach(SERVO_PIN, 500, 2400);
  servo.write(90);
  Serial.println("SG90 on D5 - type an angle 0-180");
  Serial.println("Angle 90");
}

void loop() {
  if (Serial.available()) {
    int angle = Serial.parseInt();  // waits up to 1 s for digits; yields to the system meanwhile
    while (Serial.available()) Serial.read();  // drop the line ending
    if (angle >= 0 && angle <= 180) {
      servo.write(angle);
      Serial.printf("Angle %d\n", angle);
    } else {
      Serial.println("Use 0-180");
    }
  }
}

Library: Servo (Arduino).

Expected serial output

SG90 on D5 - type an angle 0-180
Angle 90
Angle 0
Angle 180

SG90 on D5 - type an angle 0-180
Angle 90
Angle 0
Angle 180

Common errors