The PWM Signal: The Language of Speed

To tell the ESC how fast to spin, the Arduino uses Pulse Width Modulation (PWM). It is not the voltage that changes, but the duration of a pulse sent every 20 milliseconds (50Hz).

• 1000 µs (microseconds): The ESC stays in safety mode, the motor is stopped.
• 1500 µs: Intermediate power, ideal for hovering.
• 2000 µs: Full power, maximum thrust.

Control Code Example (Arduino)

Using the Servo.h library, controlling a drone motor becomes as simple as controlling a standard servomotor:

#include <Servo.h>

Servo esc;

void setup() {
  esc.attach(9); // PWM signal on pin D9
  // Arming procedure: the ESC needs to receive the minimum signal at startup
  esc.writeMicroseconds(1000); 
  delay(2000); 
}

void loop() {
  // Sending a speed command (e.g., 1200µs for a slow test)
  esc.writeMicroseconds(1200);
}

Troubleshooting and Assembly Tips

• Reverse rotation direction: If your motor spins in the wrong direction, simply swap two of the three wires between the ESC and the motor. There is no fixed color order; it’s all in the phase sequence.
• Calibration: Every ESC model has its own range. It is crucial to perform a “high throttle / low throttle” calibration so that your flight controller knows the exact limits of your motorization.
• Vibrations: A poorly secured motor or an unbalanced propeller generates electronic “noise” that the gyroscope will struggle to filter, making the drone unstable.

By mastering this chain — from the PWM signal to three-phase switching — you have understood the very essence of modern electric flight. The next step consists of coupling these motors to a PID feedback loop for automatic stabilization.