The Moodz detector lives !

[moodz]

..detecting an Australian 50 cent piece at 50 cm with a 11 inch mono coil ...

https://www.youtube.com/watch?v=Q81fx6uGIaw

specs ...

32 bit processor.
Digital audio.
Monocoil only ( monos are pure coils ) for deeeep targets
Lipo power
Variable pulse power ( up to 5 amps )
Ground resistant ( resistant ..not cancelling )
EMI resistant.
Bluetooth ( user fitted ) interface.
Android / Iphone / tablet / computer command interface.
Sampling down to 5 us.

More advanced models on the bench now ...

[WM6]

Excellent work moodz. Go ahead.

What sort of coil did you use, mono "bunch" winded or center tapped (pretty unbelievable with 5 micro seconds sampling time)?

I am not able to hear any signal signal voice in this video - probably you use earphone?

[Chet]

Hi Moodz


Video audio is very weak but I got it by using max volume on my end. 50 cm (19.5”) is outstanding performance. Can you say more about Ground resistant and EMI resistant?


Thank you,
Chet

[moodz]

Thanks guys ..its a bunch wound i think commercial 11 inch mono. The ground and emi resistance is due to ideas i have published here ;-) before ...sorry about the sound it was coming from headphones into phone cam. Will post another with better audio.

[moodz]

Excellent work moodz. Go ahead.

What sort of coil did you use, mono "bunch" winded or center tapped (pretty unbelievable with 5 micro seconds sampling time)?

I am not able to hear any signal signal voice in this video - probably you use earphone?

Hi WM6 ... I have grown tired of secret squirrel detector projects so very shortly I will gather the documents and publish my design for a kickass PI detector.
This detector can resolve X and R signals from a MONO coil in the time domain ... and using only two samples ( this provides ground rejection AND opens the door to discrimination on a PI )

See Pix below ....

[WM6]

Hi Moodz, thanks for interesting scan and block scheme.

According your description: GB and discrimination possibilities using Mono coil only, are really good news reading.

Are this signal from your scan to support sampling?:



What sort of synchronization exist between parts 402, 406 and 410 from your block scheme?

Hope you have in plan to end with offer something like PCB, kit, or even better: populated PCB?

[moodz]

Hi Moodz, thanks for interesting scan and block scheme.

According your description: GB and discrimination possibilities using Mono coil only, are really good news reading.

Are this signal from your scan to support sampling?:



What sort of synchronization exist between parts 402, 406 and 410 from your block scheme?

Hope you have in plan to end with offer something like PCB, kit, or even better: populated PCB?

Hi WM6 ... those 2 lines are just markers on the CRO to measure the peak to peak levels.... they are not part of the signal.

Switch 402 is the PI TX switch. Switch 406 turns on only during flyback and Switch 410 very briefly at falling edge of flyback ( it is the "X" sample for the control loop ) and measures the residual voltage after flyback which is the "error" voltage for the control loop.

I will be able to offer parts / PCB etc ...

[6666]

Thanks Moodz.

[moodz]

https://www.youtube.com/watch?v=u7plhjw5B7c

Video number 2 with headphones held closer to camera this time ....

Same target Aus 50 cent piece at 50 cm from 11 inch mono ...

Control interface also shown in video ( small tablet )

[moodz]

...and the dreaded coke can test.

coke can at 1 meter with moodz 18 inch spider mono ... ( not gonna dig a hole deeper than 1 meter for a coke can LOL )
Wire reel on detector box to stop it rolling off the "test platform" ha ha.


https://www.youtube.com/watch?v=tFYVkZI5IbE

[simplejohn]

Hey Moodz, Interesting , when do you think PCB/kit will be avail?
how does it go on viscous ground.

will you be offering the same for your constant current design...?

[moodz]

Hey Moodz, Interesting , when do you think PCB/kit will be avail?
how does it go on viscous ground.

will you be offering the same for your constant current design...?

I need to make some minor changes to the board to make it double sided ... its single sided with groundplane at the moment but that means you need to run about 13 short jumpers for single sided version.

... which constant current design are you referring ... the bipolar pulsing one ?

[Davor]

Aha!
I wondered for some time how you do it, but it is obvious now. That's how it goes with all nice things.
I noticed a method for direct X sampling by detecting the change of voltage at a snubber. With flyback controlled by snubber you get preferably a flat top voltage, and it is dependant upon the changes in permeability of the coil surroundings, or a presence of ferrous objects. The way you do it enables using the same front end for both X and R.
I observed the same effect with active damping using a MOSFET as a constant current device. Initial overshoot is inevitable, as the effective resistance at the beginning of Rx period is too much for a meaningful damping, but after the other hump it stabilises at proper resistance values and effectively it is faster than the critically damped coil. Detecting the first hump for X component is brilliant.
Well done

[moodz]

Thanks Davor ... you are right .... Initially I was only after faster damping ... the "X factor" was a bonus.

[Geo]

Nice work moodz