Hi There,

Take a look at Popular Electronics Magazine (August 97).
It uses a single chip (well maybe two) to buld a compass.
Based on Hall Effect, it looks interesting.
Let me know what you think.

Bye for now
Eric


At 11:22 PM 7/5/97 -0400, you wrote:
>Hello all,
>
>I'm trying to make a simple fluxgate compass using a PIC. I constructed a
>fluxgate sensor by taking a 1 inch OD toroid and placing two windings of abt
>150 turns each around the toroid in the normal manner ( wound through the
>center ). These two windings are wound in phase and wired in parallel. I did
>this to simplify the task of winding with such a length of wire. Then, I
>wound two windings around the toroid at 90 deg to each other, wound around
>the outside of the toroid. These contain about 75 turns each. I have tried
>many different means of exciting the larger, main winding and nothing seems
>to get it to act like a second-harmonic fluxgate should!
>        I tried using the PIC to generate a 10KHz square wave. I then
>buffered this with a power transistor and ran it through the main winding at
>a peak current of abt 1 amp. This caused me to get a continuous 300mv 10KHz
>signal out of the outside windings. I tried lessening the current to abt 200
>mA peak and I just got less of a signal out. This output signal stayed the
>same amplitude regardless of the strength of the external static magnetic
>field. ( Which I changed from ambient to extreamly strong by varying the
>distance and orientation of a super strong permanent magnet from the sensor ).
>        I then tried putting 60Hz AC from a step-down transformer thru it.
>This cured the problem of continuously receiving a signal out the windings.
>However, I now needed to bring my very strong magnet right up to the winding
>to see any signal out at all! In fact, with abt 100,000 times amplification
>on the output, I had an ambient 80mV output unless I brought the magnet
>within 2 inches, in which case the signal shot up to 200mV and would peak at
>2.5 V when the magnet toutched it. This signal, however, was at 60Hz, not
>120Hz as the output of a 2nd Harmonic fluxgate should be.
>        I also tried this with 400Hz AC at several hundred mA and got a
>continuous signal out, similar to the 10KHz attempt.
>
>Please help! I'm sorry in advance for writing so long a message.
>Thanks,
>Sean
>