Vallon VMH3CS Mine Detector

[Ferric Toes]

I don't think we'll learn all it can do any time soon. Perhaps it is not a good idea to try mimicking what it does either. It may serve as an inspiration to try something else.
My relationship with Vallon was brief and memorable. It is simply a great machine. Balance, weight, vibration, handy control... it is a completely another league.

That is why I am fascinated by it. We may not know exactly what is going on inside that internal silver box, but whatever it is can be put to good use in land, beach and shallow waterhunting. As has been said, it has very good response to small metallic objects; very good ground balance; very stable and easy to use once you get your head round the various setting that are possible. I can now make alternative coil sizes and shapes that work and have adapted the high impedance piezo audio for ordinary phones. Next on the list is to make these alternative size coils easily interchangeable with the stock Vallon one. That project is coming along nicely, as is a clear, illustrated, instruction book to show how the VMH3CS can be set up for hobby use.

Buying used units, restoring them and sometimes repackaging the innards, developing accessories, doing field tests etc. is as much fun as developing circuits ever was. And I don't have to worry about infringing any patents.

Eric.

[Davor]

I don't think we'll learn all it can do any time soon. Perhaps it is not a good idea to try mimicking what it does either. It may serve as an inspiration to try something else.
My relationship with Vallon was brief and memorable. It is simply a great machine. Balance, weight, vibration, handy control... it is a completely another league.

[Qiaozhi]

Err... any PI emitting both polarities may hardly qualify as a standard PI. Adding the transmission charge kick, an interesting phenomenon indicating sampling waaaay within a flyback, a mH coil finding rice-sized pieces of metal, and a fact it works for hours on less than 2 pounds of batteries...
No. It most definitely is not a standard PI.
From such a machine you may expect a trick or two beyond the ordinary.

That is exactly why I added the proviso: "... I mean that it works in a conventional PI manner ... although there's nothing conventional in the way it achieves the results that it does.", which you left out of your quote.

[Davor]

...I was referring to the Vallon, which is a standard PI...

Err... any PI emitting both polarities may hardly qualify as a standard PI. Adding the transmission charge kick, an interesting phenomenon indicating sampling waaaay within a flyback, a mH coil finding rice-sized pieces of metal, and a fact it works for hours on less than 2 pounds of batteries...
No. It most definitely is not a standard PI.
From such a machine you may expect a trick or two beyond the ordinary.

[6666]

Just Google george paltoglou, metal detector patent, australia and you will have everything you need to know.

Eric.

Thanks Eric, the full expression narrows the search right down to what I am trying to find, cheers.

[Ferric Toes]

Davor would you happen to have a link to his patent that describes his method please ? searching only seems to throw up a bunch of unrelated stuff, thanks.

Just Google george paltoglou, metal detector patent, australia and you will have everything you need to know.

Eric.

[Ferric Toes]

I recently bought a VMH3CS which I am confident has not been opened since manufacture. This is based on it's very clean condition and that the circular date label is intact. I measured 1.5mm projection on the battery tube end, so I would take that as being the figure to aim for. With my prior experience in military airborne radar there are setting up jigs for everything and everything has a tolerance. I will now change the instructions to 1.5mm +/- 0.5mm, which is easily done with a workshop ruler.

Eric.

[TH'r]

If yours comes in a canvas bag, do not breathe the dust, the battery cap can be a bit dicky when you first insert the d cells
so switch the machine on, then slowly screw on the cap until the machine starts up, this gives you a better feel for how much
pressure the cap needs to make good contact, and how tight it should be.
The manual has a few strange comments in it and does not describe all the functions and processes fully in good english.

Look at post 649 where Eric links instructions for adjusting the battery tube. Mine was among the ones that the tube projected too far, and made the cap difficult to engage. Yours may not project far enough and thus making only intermittent contact with the cap.

[Mdtoday]

Thanks, yeah, you never know.

Brian

[6666]

Err... G. Paltoglou might object to this, although his method relies on the imperfection of PI that happens with Tx ON period being shorter than the Rx last sample time.

Davor would you happen to have a link to his patent that describes his method please ? searching only seems to throw up a bunch of unrelated stuff, thanks.

[6666]

Hi 6666,

Thanks for the heads up on the dust and battery cap.
I can only imagine where these things have been.
How are you going with your unit, are you using it much?

Brian

I have not had much time to use it, so have not found any gold yet.

[6666]

Hmm, sorry 6666, were you referring to asbestos dust in the canvas by any chance?

Brian

MY reference was to the "unknown" desert dust that was thick in all the pockets etc, could be contaminated.

[Mdtoday]

Hmm, sorry 6666, were you referring to asbestos dust in the canvas by any chance?

Brian

[Mdtoday]

If yours comes in a canvas bag, do not breathe the dust, the battery cap can be a bit dicky when you first insert the d cells
so switch the machine on, then slowly screw on the cap until the machine starts up, this gives you a better feel for how much
pressure the cap needs to make good contact, and how tight it should be.
The manual has a few strange comments in it and does not describe all the functions and processes fully in good english.

Hi 6666,

Thanks for the heads up on the dust and battery cap.
I can only imagine where these things have been.
How are you going with your unit, are you using it much?

Brian

[Qiaozhi]

@Qiaozhi
Err... G. Paltoglou might object to this, although his method relies on the imperfection of PI that happens with Tx ON period being shorter than the Rx last sample time.
A certain company made a ritual out of it by creating silly Tx timing schemes.
Discrimination is doable with PI.

I wasn't referring to any designs by G. Paltoglou, or to any company that makes "a ritual out of it by creating silly Tx timing schemes". I was referring to the Vallon, which is a standard PI. By "standard", I mean that it works in a conventional PI manner ... although there's nothing conventional in the way it achieves the results that it does.