Vallon VMH3CS Mine Detector

[Altra]

A long time ago. There were frequency changing headphones marketed as "Rat Phones". When the inventor went out of business he posted the schematic. It uses a cmos 555 timer and is self powered by the audio signal. I never built it but this may be perfect for the Vallon.

[kingswood]

Thanks Eric.
Yes, I can balance very well on the ground I was in today...But the occasional hot rock (or 30!!) gave a solid signal...kicked most out of the way...dug quite a few!
One patch was covered in rocks, and was able to GB, but still had a few rocks cause signals. Where I noticed it the most was when I walked down onto the flatter part where an old stream had been. Here the GB was great, but ironstone hot rocks went off where they were buried in the clay like ground! I did try GB to one of the individual rocks and it balanced well...but then I got more "squeaks" when moving over the ground that had many less rocks

[Ferric Toes]

Its here somewhere...Just need to locate it
Had an interesting 2 hours this morning. Went to a spot I have not been to previously...a down sloping hill littered with broken quartz and banded ironstone. GB was spot on and easy...but I spent most my time digging up hot rocks. Need Eric to design a DD coil for me

Do the hot rocks balance out if you reset the GB? You shouldn't detect conductive rocks but sometimes a iron mineralised rock will have a slightly different decay than the surrounding ground. I mentioned recently that searching at night or after rain often quietens the ground down, as temperature variations on the ground in hot sun shifts the decay slightly.

Until we know more about how the electronics works, I can't see any way of using a DD which has the RX and TX coils separate. Even if we could, the changes needed to connect the coil to the electronics would be difficult.

Eric.

[Ferric Toes]

Good work Eric
I am toying with the idea of trying some type of signal booster so that I can alter the tone.....something with a treble/bass/gain adjustment. I wonder if a mini 9v battery powered guitar booster effect pedal would work??...
There are signal boosters for minelab and these could possibly be made to work too...

I will have a look at the audio waveform on a scope and see what can be done. I was thinking that a simple divide by two circuit might help to bring the frequency range down; then filter the sharp edges off to make it more pleasant to listen to.

I had a SD2200 and you certainly need a booster for that. I used a small Koss device that you could alter the high, medium and low tones plus having some amplification. It was an EQ something, but I no longer have it as I sold it with the detector some years back. You don't need boost with the Vallon but you do need the transform the high impedance for piezo devices down to something lower for standard phones.

Eric.

[kingswood]

Getting closer to the yellow stuff Kingswood

Its here somewhere...Just need to locate it
Had an interesting 2 hours this morning. Went to a spot I have not been to previously...a down sloping hill littered with broken quartz and banded ironstone. GB was spot on and easy...but I spent most my time digging up hot rocks. Need Eric to design a DD coil for me
On a very positive note, I ended up directly under overhead electrical wires and no issue with EMI at all.
Got the biggest signal I have had so far...then noticed the Water Dept's locator sign indicating where the underground water pipe is ha ha

[Mdtoday]

This is the newer two piece arm rest. $100.00+ and any tariffs. An additional $10.00 will get you the arm strap.

Thanks for the info Carolina, wow a little on the expensive side after US to AUS$ conversion but interesting all the same
I will probably machine and fit a Garret or similar piece to fit later as Eric has done.

Brian

[Carolina]

This is the newer two piece arm rest. $100.00+ and any tariffs. An additional $10.00 will get you the arm strap.

[Mdtoday]

Getting closer to the yellow stuff Kingswood

[Mdtoday]

Nice work Eric!

I just noticed in the photo, the arm rest top section screws on, the one I have is a single piece.

Brian

[kingswood]

Good work Eric
I am toying with the idea of trying some type of signal booster so that I can alter the tone.....something with a treble/bass/gain adjustment. I wonder if a mini 9v battery powered guitar booster effect pedal would work??...
There are signal boosters for minelab and these could possibly be made to work too...

[Ferric Toes]

Fun day out with the Vallon.
Picked up a 0.5g round shot gun pellet easily..maybe an inch under the surface.
Many (and I mean many!!) bits of wire, lead and metal scrap....worked an old mine area that had heaps of trash
I was surprised to find a bit of aluminium foil that I think was the outside wrapper from aspirin...It made a slight signal and I found it at about 2 inches...Lucky it was scrunched up as when I unscrunched it, the coil would not even detect it!
I am actually enjoying swinging this detector...It "feels" right to me...Much more comfortable than the others I have used. The GB is awesome. I have not had an issue in a long time with the standard coil.
Now I just need a bit of gold to prove to myself that it's all been worth the effort!

I'm pleased that the GB is awesome. That was the one thing that I thought the Vallon might fail on, as all the official tests I read were on soils that are considerably weaker in ferric mineralisation than those in Australia.

I have being doing a bit of further refinement on the Vallon but have not had time to go out and do any real hunting. I have tidied up the audio jack that I re-routed to the rear end and added a 'speaker' that is louder than the internal one. This can be plugged in instead of phones. There was just enough room for the step down transformer inside the main box. The speaker is an old moving armature telephone insert of 150 ohms impedance and mounted the way shown gives better air loading on the diaphragm. It could be mounted on pillars straight off the Vallon case, but I did not want to drill into that as the speaker feature is still experimental.

Eric.

[6666]

Thanks Eric, just googled it, if you are quick you can read it online

http://www.dailymail.co.uk/news/article-4567836/Hero-s-account-disarmed-entire-Taliban-minefield.html

[Ferric Toes]

The real use of a Vallon

In today's (3rd June) Daily Mail is an article entitled 'Bomb Proof' by an army staff sergeant. The article and accompanying picture, which includes a Vallon VMH3CS, shows clearly the horrendous situations in which these mine detectors were used.

Many of the used ones that we have now, that are being turned into treasure detectors, must have witnessed some terrible scenes. How many lives were saved; how many lost. Food for thought.

Eric.

[kingswood]

Fun day out with the Vallon.
Picked up a 0.5g round shot gun pellet easily..maybe an inch under the surface.
Many (and I mean many!!) bits of wire, lead and metal scrap....worked an old mine area that had heaps of trash
I was surprised to find a bit of aluminium foil that I think was the outside wrapper from aspirin...It made a slight signal and I found it at about 2 inches...Lucky it was scrunched up as when I unscrunched it, the coil would not even detect it!
I am actually enjoying swinging this detector...It "feels" right to me...Much more comfortable than the others I have used. The GB is awesome. I have not had an issue in a long time with the standard coil.
Now I just need a bit of gold to prove to myself that it's all been worth the effort!

[nelson]

An AA to D battery converters , works excellent on my valon too. It rest lots of weight