The Moodz detector lives !

[moodz]

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

It works really well ... here is a movie .... a ferrite target ( first half of video ) vs a 20 cent coin - non ferrous / magnetic ( second half of video ).

https://www.youtube.com/watch?v=8r9iW-qbIrY

[moodz]

Hello Moodz by batteries using your pi and which consumption ?

I use LIPO batteries and its a 4 cell so it runs between 16.5 volts charged to 12 volts discharged. The current is 330 mA at 16 volts and 430 mA at 12 volts.

[Orbit]

Hello Moodz by batteries using your pi and which consumption ?

[6666]

I'm interested in bipolar to.

[simplejohn]

HI Moodz, yep the bipolar one,

Also on the vids noticed that the audio is predictably unstable... Target is clearly heard though, Is this a result of EMI in the surbs?

[Geo]

Nice work moodz

[moodz]

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

[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]

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 ?

[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]

...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

[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 )

[6666]

Thanks Moodz.

[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 ...

[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?