The Moodz detector lives !

[moodz]

... thanks for all comments ... the current design only has one channel ( or two depending on your point of view ) ... was not expecting the discrimination frontend to work so well for this version. With "one" channel I can sample X or R or some subtractive combination ... however any sort of subtraction is probably going to leave a target hole. So I am leaning towards two tone .... one tone ( channel X ) for X and one tone ( channel R ) for R similiar to some VLF detectors ... will this be effective ?

Will need to add the additional channel hardware to the design at any rate...( re-lay the PCB ) .... maybe the handling of X and R can be user configurable ?

The current design is surface mount ... makes the PCB cheaper but trickier assembly for some constructors ?

Probably should also note that gains in the signal chain are only set to 20% of potential and timings are also conservative ... could decrease sampling time by 60% at least ( sub 3 us ?) for very small targets.

Hot ground and salt water tests for discrimination ?? May need DD coil / fig 8 coil ?? Change sampling or gain ?? Cant answer just yet.

DD coils etc ...?? Only tested for MONO coils ( I like mono coils ;-) because they are "pure" coils ) ... however need to add additional channel(s) to board for these also ??

moodz

[Mechanic]

Good work Moodz

Would be nice to see how the disc with some hot ground in the mix works. Even if it didn't work in hot ground, it would be nice to have the disc for mullok heaps.

Cheers Mick

[trojdor]

This is the most impressive thing I've seen in the PI world in a very long time.
I'm impressed...

About how long, you feel, until kits are available?

[Altra]

Good work Moodz!

How does does the x channel handle resistive minerals like saltwater?

Thanks

[6666]

Works now thanks

[moodz]

Says
This video is private.

whoops .. try now.

[6666]

https://www.youtube.com/watch?v=a7vaqyAi6uI

For the 11 inch mono its not too bad detecting the 1cm x 1cm aluminium foil target at 30 mm.

Says
This video is private.

[moodz]

discrimination waveform is improved ( again )

...and here are the discrimination results. Detector signal chain is set up to reject ferrite ( X ) and respond to conductive ( R ).

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

Four targets are used in order
1. Ferrite ( touching coil )- strong X response ...very little R response from detector audio.
2. Copper at 40 cm - strong R response ... very little X response
3. Steel at 30 cm - About equal X and R response
4. foil at 5 cm - some X and some R. ( X due to inductive surface effect ... eddy current cannot go deep in foil )

The detector is a lot more sensitive than those ranges ... had to move targets close enough to demonstrate effect on waveform which is then amplified / sampled.

by sampling an X and R channel in conjunction with a ground tracking means .... target discrimination and ground rejection is achieved with very high signal to noise ( ie discrim at depth )

Clearly a new age of discriminating, sensitive and deep punching ( works with monos ... ) PI detectors is possibly within reach.

moodz

PS .. the noisy junk on the waveform was due to a dry joint ... now corrected ( but I could not be bothered reshooting the video :-) )

[moodz]

10 mm aluminium foil target test ....

https://www.youtube.com/watch?v=a7vaqyAi6uI

For the 11 inch mono its not too bad detecting the 1cm x 1cm aluminium foil target at 30 mm.

[moodz]

Achillion, I have seen that one before but thanks alot anyway .. if it is the one I am thinking of with the box car integrator in software it is OK in air but needs more work to track the ground and still discriminate. The difficult part is doing it with weak targets eg at long range or small targets.

[Achillion]

Moodz, I'm not sure how you establish your discrimination but I picked up something from the web that may be of use.

It's based on sampling around the zero crossing and integrate a section of the X and R component of the signal.

Well, probably best way to explain is to have a look at the attached picture

[soverey]

I'm also interested in this project, thank you!

[Geo]

i am interesting also for this project!!!

[Polymer]

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 ....

Hi moodz, you really got me howling with laughter with the " ...secret squirrel... " expression. I've never heard the expression before and luv it.
It also hits the head of the nail from my perspective. Way to go!

I'm looking forward to your project coming out into the light and hopefully there will be pcb's and/or pre-programmed cpu's.

Thank you for bringing this out.

Godspeed to you!

Have a great weekend, Polymer

[Orbit]

Thank you Moodz so I thought about consumption !