Skip to main content

How to use magnetometer

The Codi:bit magnetometer sensor allows you to detect magnetic fields and create compass applications. This guide will show you how to use the magnetometer effectively.

Overview​

The magnetometer uses the MMC5603 sensor to measure magnetic fields in three axes (X, Y, Z) and provides compass functionality. It's perfect for:

  • Compass applications: Determine direction (North, South, East, West)
  • Magnetic field detection: Measure magnetic field strength
  • Metal detection: Detect nearby metal objects
  • Navigation: Create direction-finding applications

Basic Setup​

Import and Initialize​

from codibit import *

# Initialize the magnetometer
magnetometer = Magnetometer()

Basic Reading​

# Read individual axis values
x = magnetometer.get_x()
y = magnetometer.get_y()
z = magnetometer.get_z()

# Read all values at once
x, y, z = magnetometer.get_values()

# Get magnetic field strength
strength = magnetometer.get_strength()

# Get compass heading (0-360 degrees)
heading = magnetometer.get_heading()

Practical Examples​

Example 1: Simple Compass​

Create a basic compass that shows the current direction:

from codibit import *
import time

magnetometer = Magnetometer()

# Calibrate the magnetometer for accurate readings
print("Starting magnetometer calibration...")
print("Please hold the board in the air and slowly draw figure-8 patterns")
print("for about 20 seconds to calibrate the sensor...")
magnetometer.calibrate()
print("Calibration complete!")

def get_direction_name(heading):
    """Convert heading angle to direction name"""
    if 315 <= heading < 45:
        return "NORTH"
    elif 45 <= heading < 135:
        return "EAST"
    elif 135 <= heading < 225:
        return "SOUTH"
    elif 225 <= heading < 315:
        return "WEST"
    else:
        return "NORTH"

while True:
    heading = magnetometer.get_heading()
    direction = get_direction_name(heading)

    print(f"Direction: {direction} ({heading:.1f}°)")
    time.sleep(0.5)

Example 2: Magnetic Field Monitor​

Monitor magnetic field strength and detect strong magnetic fields:

from codibit import *
import time

magnetometer = Magnetometer()

# Calibrate the magnetometer for accurate readings
print("Starting magnetometer calibration...")
print("Please hold the board in the air and slowly draw figure-8 patterns")
print("for about 20 seconds to calibrate the sensor...")
magnetometer.calibrate()
print("Calibration complete!")

while True:
    strength = magnetometer.get_strength()
    x, y, z = magnetometer.get_values()

    print(f"Magnetic Field Strength: {strength:.3f}")
    print(f"X: {x:.3f}, Y: {y:.3f}, Z: {z:.3f}")

    if strength > 100:
        print("⚠️ Strong magnetic field detected!")
    elif strength > 50:
        print("🔍 Moderate magnetic field")
    else:
        print("✅ Normal magnetic field")

    print("-" * 30)
    time.sleep(1)

Example 3: Calibration​

Calibrate the magnetometer for accurate readings:

from codibit import *
import time

magnetometer = Magnetometer()

print("Starting magnetometer calibration...")
print("Please hold the board in the air and slowly draw figure-8 patterns")
print("for about 20 seconds to calibrate the sensor...")

# Perform calibration
magnetometer.calibrate()

print("Calibration complete!")
print("The magnetometer is now ready for accurate readings")

Example 4: Compass with Display​

Create a compass application that shows direction on the OLED display:

from codibit import *
import time

magnetometer = Magnetometer()

# Calibrate the magnetometer for accurate readings
print("Starting magnetometer calibration...")
print("Please hold the board in the air and slowly draw figure-8 patterns")
print("for about 20 seconds to calibrate the sensor...")
magnetometer.calibrate()
print("Calibration complete!")

def get_direction_name(heading):
    """Convert heading angle to direction name"""
    if 315 <= heading < 45:
        return "NORTH"
    elif 45 <= heading < 135:
        return "EAST"
    elif 135 <= heading < 225:
        return "SOUTH"
    elif 225 <= heading < 315:
        return "WEST"
    else:
        return "NORTH"

while True:
    heading = magnetometer.get_heading()
    direction = get_direction_name(heading)

    # Clear display and show compass
    display.clear()
    display.draw_text("COMPASS:", 0, 0)
    display.draw_text(f"{heading:.0f}°", 0, 15)
    display.draw_text(direction, 0, 30)
    display.show()

    time.sleep(0.5)

Advanced Features​

Calibration​

For accurate compass readings, calibrate the magnetometer:

# Calibrate before use
magnetometer.calibrate()

Magnetic Field Strength Monitoring​

Monitor the overall magnetic field strength:

strength = magnetometer.get_strength()

if strength > 100:
    print("Strong magnetic field detected")
elif strength > 50:
    print("Moderate magnetic field")
else:
    print("Normal magnetic field")

Coordinate System​

The magnetometer uses a 3-axis coordinate system:

  • X-axis: Left-right direction
  • Y-axis: Forward-backward direction
  • Z-axis: Up-down direction

Compass Directions​

  • 0°: North
  • 90°: East
  • 180°: South
  • 270°: West

Best Practices​

1. Calibration​

  • Calibrate the magnetometer before first use
  • Calibrate before taking measurements
  • Calibrate if readings seem inaccurate

2. Environment Considerations​

  • Keep away from metal objects during calibration
  • Avoid strong electromagnetic fields
  • Use in a stable, level position for compass readings

3. Reading Frequency​

  • Don't read too frequently (use delays between readings)
  • Consider the sensor's update rate (max 100Hz)

4. Error Handling​

try:
    magnetometer = Magnetometer()
    heading = magnetometer.get_heading()
    print(f"Heading: {heading}°")
except Exception as e:
    print(f"Magnetometer error: {e}")

Troubleshooting​

Common Issues​

  1. Inaccurate readings: Calibrate the sensor
  2. No response: Check I2C connections
  3. Erratic values: Move away from metal objects
  4. Wrong direction: Ensure board is level

Debug Information​

# Print all sensor information
x, y, z = magnetometer.get_values()
strength = magnetometer.get_strength()
heading = magnetometer.get_heading()

print(f"Raw values: X={x:.3f}, Y={y:.3f}, Z={z:.3f}")
print(f"Strength: {strength:.3f}")
print(f"Heading: {heading:.1f}°")

Applications​

  • Create a digital compass
  • Build direction-finding applications
  • Implement navigation systems

Metal Detection​

  • Detect nearby metal objects
  • Create security applications
  • Build treasure hunting games

Science Projects​

  • Measure magnetic field strength
  • Study magnetic properties
  • Create educational demonstrations

Summary​

The Codi:bit magnetometer provides powerful magnetic field detection and compass capabilities. With proper calibration and usage, you can create accurate compass applications and magnetic field monitoring systems.

Remember to:

  • Calibrate before measurements for accurate readings
  • Consider environmental factors
  • Handle errors gracefully
  • Use appropriate reading frequencies

The magnetometer opens up many possibilities for navigation, detection, and educational applications on the Codi:bit platform.