I always thought...

On a sunny day (Thu, 19 May 2011 19:07:39 -0700 (PDT)) it happened George Herold wrote in :

No, I will probably make a litte coil former, piece of PVC pipe, make some grooves in it, put core in it (with driver coil), then wind the 2 pickup coils at right angles in the grooves. Bit of glue... And sure, one could 'calibrate' it with some values in PIC's EEPROM, it will have RS232 anyways. I found some unused HC4053 chips in the box, to do the sampling of the peaks, maybe I will use those, add some LM324 opamp for gain. USe the PIC ADC (2 channels), What I am curious about is if I can get away with software like this, where the drive coil is between 2 PIC output pins 'P1' and 'P2':

main_loop: set loop counter ; maybe 10 x

loop: set P1 ; drive coil current ->

clear P2

switch 1 on ; sample high pulse amplitude into RC network 1 swicth 1 off

switch 3 on ; sample high pulse amplitude into RC network 2 switch 3 off

delay ; used 33 kHz, say 15 us delay, the core wil lsaturate during this delay (L di/dt).

clear P2 ; drive coil current ADC1 in | \ S2 | | |----------------0 \------- === ( | C1 ( north south coil | | /// ///

\ S3 ----------------0 \------- | |---------- R 2 ------------- opamp x 50 ----->

ADC2 in | \ S3 | | |----------------0 \------- === ( | C2 ( east west coil | | /// ///

Very few discrete components.

This is what I workled out last night. BTW that IP address is now finally no longer working. So I have moved the picture to here:

On a sunny day (Fri, 20 May 2011 11:32:47 +1000) it happened Clifford Heath wrote in :

cores :-)

I am not sure what core is the best, I bought a bunch of these small grey ones cheap, they seem very easy to saturate. I tried some bigger black ones that did not work so good.

Amazing that you can have 3 coils for axis on one core, I would expect to need a second core at least.

As you probably noticed, half the number of switches will do:-) Good, that means I can use one HC4053 even for a 3 axis version.

What I am curious about is if I can get away with software like this, where the drive coil is between 2 PIC output pins 'P1' and 'P2': main_loop: set loop counter ; maybe 10 x

loop: set P1 ; drive coil current - clear P2

switch 1 on ; sample high pulse amplitude into RC network 1 swicth 1 off

switch 2 on ; sample high pulse amplitude into RC network 2 switch 2 off

delay ; used 33 kHz, say 15 us delay, the core wil lsaturate during this delay (L di/dt).

clear P2 ; drive coil current

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=A0 =A0 ...Jim Thompson

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e quoted text -

Jim, is the Honeywell product HMR2300R-485?

~$1k at digikey.

George H.

Could be. When it comes to final product I'm treated like a mushroom ;-)

I'll inquire. ...Jim Thompson