Vallon VMH3CS Mine Detector

[MTammet]

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.

[MTammet]

Thought to make figure 8 folded in coil " dual field" suggested by Reg. Have you tried that configuration on Vallon before?

Mihkel

[MTammet]

While testing Vallon found that when you detect in normal mode and hear faint small two led signal and when you switch to mineral and that signal disappears, it is in most cases not rusty nail. Faint rusty nail signal is in 70 % cases still there at mineral mode. If signal is still there it is in most cases iron junk. Have you experienced same behavior?

[MTammet]

It is bit more stable in EMI environment than original. I was detecting yesterday 3 hours at the wet beach close to the water an it was super. 2 euro cent coin at 26 cm. Found no gold. I dug only small shallow and small deep targets. Pinpoints very good. And separates two 10 cent euro coins at 14 cm. It made it pretty easy to estimate target size. Dug few iron hair pins and nails, but not much rubish. Was extremely sensitive for small alloy probably from coke 5mmx5mm. When you make that coil wrap it really tight with the spiral wrap. I mean really tight. If you are using putty. Try using glassfiber putty. If making fraday gap 1cm in shieldig make it close to the corner where you leave coile wires. Do not overlap copper tape. use solid leading wire for connecting shielding to coil end wire.

[jaypay]

that looks interesting, how does it compare with the original coil ? (good work by the way)

[MTammet]

Hello!

I tried to follow the overall concept of Vallon design and made a direct to Vallon shaft for my small 4.5x6" coil.

[MTammet]

Hello!

Made small rectangular coil 4.5"x6". Stranded pvc 7/0.21 mm, 68 turns, copper tape with conductive glue. Measured 1.15 mH and 2.6 Ohm added 1 ohm resistor at connector. Super result. Self test takes a bit longer, but no chattering at all only confidence click. 0.25 gram hammered coin 13 cm and 1 gram hammered coin 24 cm. I am really satisfied with the result. No problem with bit lower inductance.
BR
Mihkel

[MTammet]

Hello!

Connector coupling for the coil and shaft i figured out. PVC 25 mm water pipe connector and garden water hose coupling. Threads accordingly 37mm and 2/3" two pin connector made from automobile electricity connector kit. For coil housing used Chinese kids detector. Whole project 50 euros including copper winding, coax and copper tape.And my prefered setup for detecting with Vallon using colour marker and VLF for disc. I work mostly at the archaeological field work.

BR

Mihkel

[6666]

Hello!

Have not followed this forum for years, started again only recently because of Vallon mine detector used at missions all around. Obtained one and made one 5 inch coil 66 turns, 0,4 mm, 4.1 ohms, mini coax cable rg174 2m, 1445 mH. Coil is erratic and chatering calms down when EMI and magnetic field disturbancies- from high way 70m from where i live- are low. It takes one Livonian penny 0.27 g at 18 cm. Tried on infested mediaeval settlement previosusly heavily detected. Horseshoe nails at 24+25 cm. Dug them well. Vallon lights 3 leds for mineralisation at that site but site has lot of "fireplace anomalies" and hot rocks. Mainly gneiss with porphyrite with hematite and magnetite content, all are glacial erratic stone pebbles. We have lot of that stuff in West Estonia. Vallon is especially good detecting beside these anomalies and hot rocks. I own Explorer and XTerra they give iron signal for thin hammered close to these minerals. Vallon outperforms them.

BR

Mihkel

Interesting post and information , thanks.

[MTammet]

Hello!

By the way I made one observation with Vallon. You probably are familiar with. When detecting iron response signal from horse shoe nails will stay and attenuates longer than with small hammered coin 0,5 g and smaller. Sometimes I had to compensate to stop signal and return to detecting.The cut off with small hammered is fast. Signal strength with sub 0,3 small pennies will not exceed 8-9 leds even at very close distance. Detection distance with these small hammered coins is ofcourse modest 2" or 5cm. When you get detection signal and it will not follow your coil and stayes at 7-8 leds and object mesured with coil is small it is most probably something else, but not nail. What i noticed and is in my opinion good. My Vallon will not detect tiny small chocolate foil. With xterra I have that serious issue.

BR

Mihkel

Mihkel

[MTammet]

Hello!

Have not followed this forum for years, started again only recently because of Vallon mine detector used at missions all around. Obtained one and made one 5 inch coil 66 turns, 0,4 mm, 4.1 ohms, mini coax cable rg174 2m, 1445 mH. Coil is erratic and chatering calms down when EMI and magnetic field disturbancies- from high way 70m from where i live- are low. It takes one Livonian penny 0.27 g at 18 cm. Tried on infested mediaeval settlement previosusly heavily detected. Horseshoe nails at 24+25 cm. Dug them well. Vallon lights 3 leds for mineralisation at that site but site has lot of "fireplace anomalies" and hot rocks. Mainly gneiss with porphyrite with hematite and magnetite content, all are glacial erratic stone pebbles. We have lot of that stuff in West Estonia. Vallon is especially good detecting beside these anomalies and hot rocks. I own Explorer and XTerra they give iron signal for thin hammered close to these minerals. Vallon outperforms them.

BR

Mihkel

[Rocketdemon]

My Repackaged Vallon

Here is my latest project, all working very well, used the shaft from an old Fisher 1210-X.

Audio transformer is in the project box.

Coil is temporarily sealed in place using a Whites coil cover using silicon sealant, will soon be testing her down the beach.

Could anyone in the UK suggest a part number or make of Epoxy Resin I could use to permanently seal the coil up with? That's not using the coil cover, the epoxy would provide the bottom surface/finish of the whites former.

Regards

Pete

[KingJL]

Hi KingJL, If the coil you made resonates at 267kHz, then presumably the switch off rate of the TX current is considerably faster, particularly as it approaches zero. If it were possible to to reduce the delay, then the Vallon would be even more sensitive to small objects and/or improved range on existing objects.

Eric.

After TX switch off, the coil discharge rate is mainly affected by the 0.01 uF energy capture/boost circuit until the coil voltage has decayed below the forward biasing point of the steering diodes (~1.4 - 1.8 V which occurs ~4.5 usec after turn-off). After that point, I would assume that the decay would normally be somewhat faster. But that is about the same time that the damping circuit is switched in and the coil is temporarily shunted for about 500 nsec.

[Ferric Toes]

Eric has posted that the average of 10 units where he measured the coil characteristics was a resonant frequency of 160 kHz. That was coils designed and manufactured by Vallon. So I would suggest that the "ideal world" would be 160 kHz as designed. That being said, the Vallon will operate with significantly higher coil resonant frequencies. The coil I made for my re-packaged "Predator II" resonates at 267 kHz and works great. If the resonant frequency gets too high (I didn't measure the frequency when it happened) you will get the dreaded "ADC error" code. This happened with my probe coil wound on a ferrite rod (155 turns AWG 24 enameled wire wound on a 4" x 0.5" type 33 ferrite core). I tested it on the Vallon before I added the shielding and got the error code. After shielding the probe, the Vallon worked with no error code. I definitely would not go any lower than the 160 kHz for resonant frequency.

Hi KingJL, If the coil you made resonates at 267kHz, then presumably the switch off rate of the TX current is considerably faster, particularly as it approaches zero. If it were possible to to reduce the delay, then the Vallon would be even more sensitive to small objects and/or improved range on existing objects.

Eric.

[KingJL]

I've read about the resonant frequency of the coil, but what should it be in the ideal world for the Vallon and why?

Eric has posted that the average of 10 units where he measured the coil characteristics was a resonant frequency of 160 kHz. That was coils designed and manufactured by Vallon. So I would suggest that the "ideal world" would be 160 kHz as designed. That being said, the Vallon will operate with significantly higher coil resonant frequencies. The coil I made for my re-packaged "Predator II" resonates at 267 kHz and works great. If the resonant frequency gets too high (I didn't measure the frequency when it happened) you will get the dreaded "ADC error" code. This happened with my probe coil wound on a ferrite rod (155 turns AWG 24 enameled wire wound on a 4" x 0.5" type 33 ferrite core). I tested it on the Vallon before I added the shielding and got the error code. After shielding the probe, the Vallon worked with no error code. I definitely would not go any lower than the 160 kHz for resonant frequency.