Vallon VMH3CS Mine Detector

[kingswood]

I have done so much reading over the last couple of days that my eyes are sore !!!
You guys are way to smart for me!....I wish I had done an electrical engineering degree instead of an MBBS!!
To elaborate on my post above:
Some blokes (like Woody, Ishmael and Barry Johnson) did/do mods on the ML PI detectors that add a variable pulse frequency control, variable gain and a timing change switch. I dont understand the Vallon schematic so I dont even know if that would even be possible.
Has anyone ran simulations (using that neat computer program!) to see if its possible??
Hopefully someone way smarter than me can help
After deciding to try some salt lake detecting, my interest in the Vallon has been aroused again!

[kingswood]

Hi Kingswood,
I would guess that the Vallon will work fine, but would benefit from the firmware upgrade so that you could slow the response down a bit.
Eric.

Thats an interesting idea I know people doing mods on ML detectors (such as the SD and GP series) add in extra stuff that allows for timing changes...I wonder if thats possible on the Vallon?....I dont know enough about electrical engineering

[kingswood]

Hi Kingswood,
I used to correspond with Chris Hake who did a lot of nugget hunting on the salt lakes near Kalgoorlie. I built some special rectangular coils for him, which he mounted on a towable trolley. I seem to remember he used a SD2200 at the time and the combination worked fine. I would guess that the Vallon will work fine, but would benefit from the firmware upgrade so that you could slow the response down a bit, particularly when using bigger coils.

Unfortunately, Chris Hake, a very enthusiastic prospector with a great sense of humour, died a few year back.

Eric.

Thanks Eric. Shame about Chris
Yes there is still gold in lakes here....
I am waiting another week or 2 for the permit then its all systems go!! I have the old SD2000 with a choice of salt coils and DD's so have options if the Vallon doesnt like the mineralization! From what I have heard, my GPZ7000 will likely struggle due to the high salt content.
Will be very keen to see how the Vallon handles it!!

[Ferric Toes]

Well the Vallon will get a test run on a Western Australian Salt lake soon
I have put in a couple of permits to detect on one....The GPZ7000 will struggle apparently!
I will take a Vallon out to see if it can work on the lake and report back

Hi Kingswood,
I used to correspond with Chris Hake who did a lot of nugget hunting on the salt lakes near Kalgoorlie. I built some special rectangular coils for him, which he mounted on a towable trolley. I seem to remember he used a SD2200 at the time and the combination worked fine. I would guess that the Vallon will work fine, but would benefit from the firmware upgrade so that you could slow the response down a bit, particularly when using bigger coils.

Unfortunately, Chris Hake, a very enthusiastic prospector with a great sense of humour, died a few year back.

Eric.

[MTammet]

Hello ionut,

I will send you a private mail on what you can expect from 30 cm coil I made. It will have measures for several items . Then you can make your calculations. Measures are for mineral and normal modes. You will most probably loose small and half hammered with 60 cm coil. But hoard starts usually with first coin found.

[ionut_mtb]

I would like to make a 60cm coil for coin/hoard shooting only, inland use. does anyone hold the original uxo search head or anyone built bigger coil for vallon? what sensitivity to expect? for now i did not decide what kind of housing to make.

[MTammet]

I have noticed one feature. You can check your signal signature and amplitude switching in between mineral and normal modes. Low karat gold is not detected well in mineral mode but splendidly in normal mode. Pure gold detects equally in mineral and normal mode. For small gold (small 0.2 gram coins) I made 4.5x 6 inch small rectangular teflon coated 7/0.2mm wire coil. Detect 0.25 gram flat gold nugget at 0.5cm distance 0.3 round at 6cm. Small rectangular is very quiet coil. In normal mode compensate on hot rocks.

[kingswood]

Well the Vallon will get a test run on a Western Australian Salt lake soon
I have put in a couple of permits to detect on one....The GPZ7000 will struggle apparently!
I will take a Vallon out to see if it can work on the lake and report back

[MTammet]

Thank you Eric,

I will try to build one and share the results. I decided to use 28cm coil and inner 5,5 coil in 28 cm housing. Should I connect shielding of both coils in coil or at the switch. To prevent any eddy current detection from switch I will use longer lower shaft. It makes it easier to select coils during the target signature estimation process. As I have understood this three position switch was successfully tested between probe and coil. What about self test when coils are changed?
Best regards,
Mihkel

[Ferric Toes]

Hello Eric,

I hope that my explanation on shaft construction was enough detailed. To fix PVC poly fitting to the shaft I used plastic cable holders 6mm with the cut head. Otherwise the pipe will slip. Please tell what would be your design idea on proposed dual coil on Vallon. Detector switched in between. Can it be done? Dont they detect each other?

Best Regards,

Mihkel

I need to go to the local plumber's store to see if they have those fittings. If the parts don't solvent weld, I will use stainless steel screws which are undetectable.

Outer and inner coils need to have the same inductance and resistance. Switching and damping would best be done by a double pole, double throw switch with centre off. Centre off is needed so that the Vallon temporarily senses no coil, otherwise it goes berserk if switching directly from one coil to the other. Unused coil needs to have sufficient resistance switched across it to prevent ringing. There will be no coil interaction when this is done. I would put the switch and resistor in a small plastic box mounted on the lower shaft.

Eric.

[MTammet]

Hi,

Is it possible to use Garret BFO two coil setup as bases for Vallon two coil setup design?

Mihkel

[MTammet]

Hello Eric,

I hope that my explanation on shaft construction was enough detailed. To fix PVC poly fitting to the shaft I used plastic cable holders 6mm with the cut head. Otherwise the pipe will slip. Please tell what would be your design idea on proposed dual coil on Vallon. Detector switched in between. Can it be done? Dont they detect each other?

Best Regards,

Mihkel

[MTammet]

Hello Eric,

About mineralisation. I have noticed that when detecting on our settlements where there is lot of carbon and burned cobble stones minaralisation is somewhere at 5to 7 leds when ground balancing. it is however quite difficult to search in normal mode. What i have also noticed is that in mineralised mode small hammered silver coins sound deeper than small nails. So may be there is some way to estimate whether small item is deep burried coin /or similar or small nail when switching between small central coil and bigger coil. This setup needs of course testing with various coins and nails in mineralised soil. S.o called object specific coil approach is needed with Vallon. And may be a separate two coil setup for rings, gold nuggets ect . Just speculating.



Best regards,

Mihkel

[MTammet]

Hello,

Just came from my field. I live in a small wooden manor all my summers. Manor was founded in 16th century. Before that there was a convent so cnalled "table manor". Village itself dates back to 7th century. Detecting on nearby fields with Vallon today with that small rectangular coil I made. made tests on different targets I found. Mostly nails, but found also small round brooch from 16th century and a button. Nails sounded all like described in manual, even small nail points. I use that PVC 25mm poly waterpipe pipe coupling and 25mm cable pipe where I insert 20mm cable pipe for connector shell. 20 pipe coupling fits inside Vallon connector. Make it right size and that it. It is pretty good idea to use inner shell as small probe with separate switch sounds interesting. Use PVC polypipe and drill out all obstacles with 25mm drill to fit..

[Ferric Toes]

Hi,

Vallon has this "stricer pin" sound pattern described in manual. It works great also for all nails small 3cm and up to 10 cm (was the longest tested). It also gives special sound pattern for screw cap. Works much better in normal mode.

Hi Mihkel,
It looks like you are doing well with your Vallon. I have made rectangular fig. 8 coils; mainly for EM noise cancellations my workshop. They work well in that respect, but in the field the response pattern to coins and rings can be confusing. Fine on musket balls though.

On your home made lower shaft, have you found a plumbing coupling that has the same thread pitch? I would be interested to hear about that.

That is a good point re the striker pin identification. As you say, horizontal nails in a certain size range will behave similarly. The distance between signal peaks being the coil diameter. Much of the time I use home made 11.5 in coils for searching based on a Whites dual field shell. The inner ring (unused) could be for a smaller coil and the detector switched between the two. The result would be that the peaks of a nail signal would be closer together when the small coil is switched in. This would avoid wondering if it was two separate objects that had been detected, as the distance between signals in this latter case would not change.

I searched a field last year where there were lots of small nails and I found that running in mineralised mode was quieter and I was still getting very good range on coins. I expect that much depends on the ground balance setting at the time. This field was not particularly mineralised.

Eric.