Simple magnetometer

[Davor]

I'm thinking of alternative ways of connecting Rx units to the base. Radio links or optical. Primary goal would be rearrangement of the existing IB machines to 2box, but why not a large distance gradiometer?

Say, you place a sensor at home and transmit field value so that while roaming the hills you have a reference. There you have a single sensor arranged with a gyro or a pendulum counter balance, and you listen to the resultant frequency of the two. Just thinking aloud.

[ivconic]

You'd be amazed what kind of magnetometers are sold as utility pipe detectors. Downright silly, but effective when in proximity of a large pipe. So why not?!

Maybe with a little bit of our "diy magic" some of those can be turned into really nice prospecting toy!?
I have made dozen epe gradiometers so far. Also i am having decent field experience with those.
Under certain (objective) conditions those can be very powerful tool in our hobby.

[Davor]

You'd be amazed what kind of magnetometers are sold as utility pipe detectors. Downright silly, but effective when in proximity of a large pipe. So why not?!

[ivconic]

Yes it has limitations.
It was upon WM6 desire for as simplest as possible magnetometer.
It will do the job for which is predicted.
Instead 4013 i could use direct f/v conversion and later make simple voltage comparator.
Will elaborate that later in winter. Not here in public, of course!
Maybe that will become "commercial" at the end, that's why!

[Davor]

I think you can't call this a heterodyne in full sincerity, as the flip-flop produces exclusively a difference frequency, and also not interchangeable as clock input must have higher frequency than D input, otherwise the output just latches and nothing happens. So in this case you'd have indication of FGM lowering frequency below the clock frequency, and not the other way around.

Also C2 should not be there.

Otherwise I like this idea.

[ivconic]

Hey how about two sensor solution?

Or even three!
Ok, let's focus on two for now.
Remove (lower on schematic, U2) referent oscillator and replace it with second FGM-3.
Tuning those two sensors is than achieved by their most proper alignment.
Most proper alignment method is already described in Carl's article " Fluxgate Magnetometer".
I guess you can find that article somewhere here on forum, i tried to attach it here but from some strange reason i can't!?
Look up in Carl's articles, you will find it.

[WM6]

Hey how about two sensor solution?

[ivconic]

I get constant time out here!?
I can stay logged in barely few minutes... 3 to maybe 5 minutes and than i have to log in again.
This is pretty annoying.

[ivconic]

Since this is "bulk" straight from my rich imagination; most probably some component values are not in proper range.
This will need further checking and corrections.
Now... we could use some help from those "simulator lovers" here on forum!
C'mon nerds, it's your move now!
You can't take Ph.D so easy... just like that! Earn it!

[ivconic]

Or... we can go even further and play even more!

[ivconic]

More better now:

[ivconic]

It was initial idea (you provoked me to think on), but now, looking at it again; i see few minor lacks.
Wait a bit and i will make some modifications. Minor ones, not so dramatic.

[WM6]

Great simplicity. I like it. Thanks.

I will try this, but first to get FGM-3.

[ivconic]

Simple heterodyne principle.
CD4049 is forming referent oscillator, tuned by R2, producing referent frequency, which is subtracted from FGM-3 frequency.
Result of subtraction is frequency presented at pin 1. of 4013.
74HC14 stage converts frequency to voltage. R3 adjusts the voltage level.
Voltage is than fed to VCO based on NE555, giving audible indication.
Whole setup can be made on very small pcb and build in inside walking stick.
Instead referent oscillator part; another FGM-3 sensor can be used, but than precise tuning is achieved by most proper sensors alignment.

[ivconic]

On the other forum i just posted this.
This is just an idea, not checked in reality yet.
Sort of sublimation from several different schematics.
R2 can be understood as "Tune" and R3 as "Treshold" (right Davor!?)