Vallon VMH3CS Mine Detector

[6666]

Hi.
I make a graphite coating based on PVA glue B3 or B4.
After drying, the layer is completely water repellent. There are no special proportions. I take 100 ml. glue in a separate jar with a lid.
I sprinkle three teaspoons of graphite. Add one spoon, stir every time. Mixing thoroughly, I make control smears on paper.
It is necessary to measure after complete drying. If the resistance is in the range of 400-600 Ohms per 1 cm, then this is normal.
If the resistance is large, I add more graphite. If the mixture is thick or then slightly thickened, it can be diluted with acetone or solvent 646.
Store the finished mixture in a tightly closed jar. Stir well before each use.

Hi, thanks for detailed reply, I am interested in your PVA glue B3 or B4, you must have different PVA glue to what we have in Australia, our PVA glue is water based, and mainly used for wood or crafts, sorry to be a pest but would you have an link to that glue so I can check it out please, as googleing it does not give good results thanks

[Myntmaster]

Hi, thanks for detailed reply, I am interested in your PVA glue B3 or B4, you must have different PVA glue to what we have in Australia, our PVA glue is water based, and mainly used for wood or crafts, sorry to be a pest but would you have an link to that glue so I can check it out please, as googleing it does not give good results thanks

Hi. I was a little mistaken not B3 and B4, but D3 - D4.
With these adhesives you can glue almost everything.
In D4, according to the specification, after complete drying, it is completely water resistant and even holds 4 hours in boiling water.

These glues cannot be diluted with water; they lose their properties.
And what is very good when drying gives a very strong shrinkage, this contributes to good contact between the particles of graphite.
http://www.polyline.lv/en/products/p...-internal-work
https://www.adkwik.co.uk/timbond-d4-waterproof-pva

PVA glue, which is not recommended to be diluted with water:
Universal glue (PVA-D3, D4).
Super PVA glue (PVA-D3, D4).
These types of adhesives have a white or slightly yellowish tint and when thickened they can be diluted with acetic acid or organic solvents (acetone, methanol, ethyl acetate, benzene ...).
These plasticized adhesives are amenable to partial dissolution with water, but at the same time their properties (frost and water resistance) are reduced.

[Myntmaster]

Vallon VMH3CS air test with 38 cm coil = 15 inches.
The test is conducted indoors. Settings * Normal mode *, and three measurements at different sensitivities 7.10 and 12.
At a sensitivity of 12, it starts to catch interference from the 220 volt network and the computer.
I perfectly understand that an air test is not like in the earth.
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[Ferric Toes]

Vallon VMH3CS air test with 38 cm coil = 15 inches.
The test is conducted indoors. Settings * Normal mode *, and three measurements at different sensitivities 7.10 and 12.
At a sensitivity of 12, it starts to catch interference from the 220 volt network and the computer.
I perfectly understand that an air test is not like in the earth.
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Your coils look great, and I hope they work as well as they look. I will be interested to hear if the graphite shielding is effective on a wet beach and prevents false signals when touching the beach or seaweed..

Indoor testing is never good due to the interference you mentioned. Also fluorescent lights and also, as I recently found out, the new LED lights.

Eric.

[Myntmaster]

Thank you.
In real conditions at sea, the best tests. But I'm sure there will be no problems with coils. Last year, I made homemade coils for my Garrett Infinitum LS. They worked just fine. They were with a graphite screen. A homemade 11x8 inch DD coil worked better than the original 10x14 DD. I will wait a bit, and there will be trials in the sea, here we have winter.

[Ferric Toes]

What type of housing will you use to go into the sea?

Eric.

[Myntmaster]

The case for the detector is completely home-made.
It is soldered from double-sided foil fiberglass.
Upon completion, it will be a fully enclosed blind structure. Like a tin can.
The plates are soldered on both sides with a small allowance where the epoxy is poured which additionally seals the solder joints.
I call this design "hi from the 80s"
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Curly holes for connectors are sawn in the case.
All IP68 connectors on the inside are further seated on a very strong rubber sealant.
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The operating mode knob is brought out through the gland.
https://www.distrelec.de/Web/Downloa...f?pid=16400006
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In the photo, the purpose of the connectors. Mount to the shaft.
The battery pack is separately in a sealed non-separable case.
Indication and control unit in a separate housing.
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After the case is ready. It will be painted with an 1k epoxy primer. Great thing.
It adheres very strongly to the surface and fills all microcracks. The main thing is to let it dry well.
Then the main painting ...
https://www.motipdupli.com/en/produc.../ipg-1216.html
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Well, something told.

[brinbrin]

Coil - Measuring resistance between the pins

Hello,

I've got a coil-related question. As Mr Foster stated in the post #18 "The 7 pin connector has the centre pin as live to the coax core and all six outer pins are wired together forming an outer shield and connected to the coax braid."

The pins are marked A, B, C, D, E, F for the outer pins, and G for the centre pin. I can measure ~ 5 Ohm between the centre pin and any other outer pin, but I measure ~ 2 Ohms between the outer pins. Is it OK ?

Best regards,

MC

[Qiaozhi]

What reading do you get on the meter if you short the probes together?

[Myntmaster]

What are you measuring, which device. It should not be. Close the probes of the measuring instrument, what shows?

[brinbrin]

When the two probes touch, I read ~ 2 Ohm, and when the do not, it displays 1 ... Does it mean my multimeter is fried ? I is set on 200 Ohm (see photo).

I'm not skilled in electronics. Sorry if my questions seems of a noob.

[Myntmaster]

Everything is normal, with closed contacts 2 ohms error. Now consider 5-2 = 3 ohms coil resistance. 2-2 = 0 ohm between contacts a, b, c, d, e, f

[tifred]

HI brin brin voisin ,
Looks like your connectors are oxidized?

[jarrett]

Brin,
You may have a small potentiometer or knob that you can use to zero the meter on the ohms scale when the 2 test probes are joined together.

[brinbrin]

Thank you all for your answers.

I checked and rechecked, but my multimeter has no potentiometer to adjust the zero. I checked in the battery case too , but there are only fuses. I'll go with -2 Ohm measures.
So I have ~ 3 Ohms between the centre pin and the outer pins. Is it OK ?
Still trying to figure out why my machine is noisy when I swing it.

Hello tifred. Fais moi signe si tu viens ? Boulogne ;-) Il reste de l'or.