How about three? Rate gyros. Murata and others make them. They were used in 'Gyropoint' mice which are now long off the market, but which I sometimes see at garage sales. If you have a couple hundred to spend, you can get a quite accurate fiber optic 3 axis gyro system from Rockwell?? You can also make your own ultrasonic rate gyro. If I recall correctly, and article it Nuts and Volts 2 years ago spelled out exactly how (1" length of 1" aluminum tubing, transucer crystals, some analog and micro. R Padu wrote: > The rover will have a gps unit, but I'd like to have two sources of > direction > > ----- Original Message ----- > From: "Josh Koffman" > To: "Microcontroller discussion list - Public." > Sent: Friday, February 11, 2005 5:15 PM > Subject: Re: [EE] Compass (magnetic sensor) > > > >>If your unit is always moving and has a line of sight to the sky, you >>could use GPS. Not an ideal solution, I know. There used to be a bunch >>of compass sensors, but at most they gave you 16 cardinal points I >>believe. >> >>Josh >>-- >>A common mistake that people make when trying to design something >>completely foolproof is to underestimate the ingenuity of complete >>fools. >> -Douglas Adams >> >>On Fri, 11 Feb 2005 15:59:39 -0800, 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 -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist