MPU6050 Digital Level: Tilt Angles from the Accelerometer

About the project

The MPU6050 is a cheap module (GY-521) with a 3-axis accelerometer and a 3-axis gyroscope. We turn it into a spirit level: two tilt angles, roll (sideways) and pitch (front-back), on an LCD 1602.

What you need

• ESP32 DevKit
• MPU6050 (GY-521) module
• LCD 1602 with an I2C backpack
• The Adafruit MPU6050 library (pulls in Adafruit Unified Sensor) and LiquidCrystal_I2C

Wiring

Both modules share one I2C bus:

For two MPU6050s on one bus, tie AD0 of the second one to VCC: its address becomes 0x69.

Where the angles come from

A still accelerometer measures the gravity vector, g ≈ 9.81 m/s². Lying flat, the module sees all of it on the Z axis. Tilt it, and part moves over to X and Y. The ratio of the projections gives the angles:

• roll = atan2(ay, az)
• pitch = atan2(−ax, √(ay² + az²))

Unlike atan, atan2 takes the signs of both arguments into account and works in all four quadrants. RAD_TO_DEG converts radians to degrees.

The angle around the vertical (yaw, the heading) cannot be found this way: gravity does not depend on it. A heading needs a magnetometer.

Code

// Digital level: MPU6050 → roll/pitch angles → LCD 1602
#include <Adafruit_MPU6050.h>
#include <LiquidCrystal_I2C.h>

Adafruit_MPU6050 mpu;
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.init();
  lcd.backlight();
  if (!mpu.begin()) {
    lcd.print("MPU6050 missing");
    while (true) delay(1000);
  }
  mpu.setAccelerometerRange(MPU6050_RANGE_2_G);   // highest sensitivity
}

void loop() {
  sensors_event_t a, g, t;
  mpu.getEvent(&a, &g, &t);
  float ax = a.acceleration.x, ay = a.acceleration.y, az = a.acceleration.z;
  float roll = atan2(ay, az) * RAD_TO_DEG;
  float pitch = atan2(-ax, sqrt(ay * ay + az * az)) * RAD_TO_DEG;
  char line[17];
  snprintf(line, sizeof line, "Roll  %6.1f", roll);
  lcd.setCursor(0, 0);
  lcd.print(line);
  lcd.write(223);   // the HD44780 degree sign
  snprintf(line, sizeof line, "Pitch %6.1f", pitch);
  lcd.setCursor(0, 1);
  lcd.print(line);
  lcd.write(223);
  delay(100);
}

Accelerometer or gyroscope

• The accelerometer gives an absolute angle, but it is noisy and wanders with any motion: a shake looks like a tilt.
• The gyroscope measures the rotation rate (°/s). Integrating it gives an angle that is smooth and fast but drifts: the error accumulates, and after a minute you are degrees off.
• A complementary filter combines both: angle = 0.98 * (angle + gyro * dt) + 0.02 * accAngle. It is the next step for drones and balancing robots.

What next

Beep when both angles are within ±0.5°, and you have a proper shelf level. Or draw a "bubble" on an OLED instead of numbers.