🛠 Piloter un servo moteur avec le PWM et un potentiomètre

Objectives

Control a servo motor using the Servo library on a PWM pin of the Micro (3, 5, 6, 9, 10, 11, or 13) and command it with a potentiometer, while properly managing power: the Micro is powered via Vin (7-12 V) or USB, and the 3V3 pin provides only 50 mA.

Hardware

• 1 Arduino Micro
• 1 SG90/MG90S type servo motor (orange signal, red +5V, brown GND)
• 1 10 kΩ potentiometer on A0 (wiper to A0, ends to 5V/GND)
• External 5 V power supply for the servo if using multiple servos, or Vin 7-12 V on the Micro; common GND is mandatory

Complete code

// Servo sur broche PWM 9, commande par potentiometre sur A0.
#include <Servo.h>

const uint8_t KNOB = A0;
const uint8_t PIN_SERVO = 9;   // broche PWM : 3,5,6,9,10,11,13
Servo monServo;

void setup {
  monServo.attach(PIN_SERVO);   // signal PWM 50 Hz
  Serial.begin(9600);
}

void loop {
  int brut = analogRead(KNOB);          // 0..1023
  uint8_t angle = map(brut, 0, 1023, 0, 180);
  monServo.write(angle);
  Serial.println(angle);
  delay(20);
}

Expected verification

The servo arm follows the potentiometer between 0 and 180 degrees, without jerking. At the end of the range, the servo buzzes slightly then goes silent once the angle is held.

Common errors

• Powering a large servo directly from the Micro's 5 V pin while connected via USB: current spikes cause the board to restart (the USB polyfuse cuts off at 500 mA); use a separate power supply with a common GND.
• Forgetting the common GND between the servo and the Micro: the servo vibrates or does not move.
• Connecting the servo to 3V3: this pin is limited to 50 mA, which is insufficient.
• Using a non-PWM pin for the signal: the Servo library works on other pins as well, but sticking to a PWM pin simplifies troubleshooting.
• Expecting a standard analogWrite signal: the Servo library emits calibrated pulses; do not mix it with analogWrite on the same pin.