Some linear Hall sensors arranged around a decent magnetic (needle type)
compass.  You should be able to calculate sin and cos of the needle end
position.  From that you should be able to calculate a heading.  Perhaps
a bit Rube Goldberg, but I don't see why it wouldn't work.  Of course it
probably won't meet your needs, but it might be fun anyway. ;-)

Padu wrote:
> Quick question, I'm selecting a "magnetic heading" solution for my
> autonomous vehicle platform. I've already searched the pic archives
> and some robotics sites on the internet, and here are the main
> suppliers that I found:
>
> -Honeywell HMR line - too expensive, although they have one model
> under $100
> -Dinsmore - bad resolution or bad frequency (2.5s update rate)
> -Devantech - I liked this one, is not too expensive (around $50), 1Hz
> update and 0.1 deg resolution (5deg acc)
>
> Do you have any other pointers?
>
> What is important to me: 1) cost 2) update rate (2Hz is desireable,
> 1Hz is ok) 3) resolution (1 degree is fine already) 4) accuracy (5
> deg is ok I guess)
>
> And of course, easy to integrate with a PIC

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