Question about gyro

Other Hardware Sensors
1

Ok, so I've been working on a project randomly off and on for a bit now, and it's effectively trying to create a vr like system. Chip/arduino/screen attached to head, with input to the 3d world on current rotation, direction, etc. What I'm wanting to know mainly is I have the rotation for looking up and down, and the spinning the head clockwise/counter_clockwise from looking straight. Problem is, with just an accelerometer, you can't get a looking left or right. Is that what a gryo is for, or would I need something like a digital compass? It seems kind of stupid to pay $150 for a tilt compensated digital compass if I could simply put a gyro on it.

Would it work for what I'm wanting it to? Oh, and the part in question is this one: Gyro Breakout Board - LY530AL - 300°/s - SEN-09165 - SparkFun Electronics

The thing is, it'd be cool to make my own vr like game. I've been using Unity3d for a bit now, and can easily get serial signals from the arduino. I'd like to experiment a bit more and see how good I can get it to fail. If this is what I need, could I get a triple axis gryo and use that for moving the head forward and back and left and right, but not spinning, or are gyros only spinning?

@_@ I get so confused about things like this sometimes.

2

Gyro only measure rotation. Specifically, they measure the rotational velocity, such that the faster it is spinning, the higher the output. If you want absolute rotational measurement (knowing exactly what angle you are facing,) then you have to integrate (calculus) the gyro output. A digital compass actually works very well for absolute angle measurement, except that nearby magnets* and computers (D'oh!) decrease the accuracy.

However, if you are willing to do the compensating programming work, a tilt compensation-ready compass can be had for ~$30 from sparkfun. I'm not sure whether the programming is easier to do the integration work with a gyro or the tilt compensation with the compass, but I do know that the compass wont have any drift issues, which the gyro can and probably will (especially using an Arduino, which is relatively slow for that kind of work.)

*Fun way to waste several minutes: Make a robot that spins to face a specific direction, then fool with a magnet near the sensor.