Acrob030

Following text will show You a basic connection and operation of the digital compass module.

Product page: #29123 Hitachi HM55B Compass Module

• Documentation (.pdf)
• Chip datasheet (.pdf)

Schematic diagram:

Demo program:

Demo software:

Download from here...

Arduino page about HM: http://www.arduino.cc/playground/Main/HM55B

Theory behind

What actually measures magnetic sensor? Yes, the strength of the magnetic field. It is just random coincidence, that current north magnetic pole is near the geographic one. Also, the Earth magnetic field is very unhomogenous. See picture:

http://netdaw.com/wp-content/uploads/2010/10/solar_wind1.jpg

Also beware of the magnetic inclination and declination... More:

• http://www.compassdude.com/compass-declination.shtml
• http://earthsci.org/education/fieldsk/declin.htm
• http://www.nationalatlas.gov/articles/geology/a_geomag.html
• Inclination and Declination calculator:
  http://ngdc.noaa.gov/geomag/magfield.shtml

You will need Your home coordinations. Determine Your location using Google Maps or GPS.

Tip: how to find lat and lon without the GPS: http://astro.unl.edu/naap/motion1/tc_finding.html