Compass sensors

Some students wanted to make a real catapult which throws virtual objects into a virtual world.

Some considerations were given to calibrating the direction of the catapult using a compass sensor.

We did some searching to find the cheapest way to get (I2C) information from a compass sensor:

http://www.magnetometer.org/mag-magnetoresistive.php

HMC1051, a Honeywell chip
KMZ10B/B MAGNETFELDSENSO, but then you have to go building
( only 4.56 euro at conrad.nl )

http://www.convict.lu/Jeunes/CompassSensor.htm
http://www.sparkfun.com/commerce/product_info.php?products_id=7892
http://www.antratek.nl/Compass-modules.html

so the cheapest ready made sensor seems to be around 23 euro's and then sending costs...