Building Minelab Coils

[BG]

Hi All:

I was wondering if anyone has any info on building coils for the Minelab Explorer. I just got one... cool machine, but the choice of coils (and their $$$) leaves a little to be desired.

Might anyone have any specific info about building coils for these? I know Charles has built some... tried to email him directly, but his address is no longer valid. Primarily, I'm looking for the # of turns for a given size, pinouts at the cable... general specifics for one that has worked (or even one that hasn't worked)

Also... can I screw up my detector by fooling around with homemade coils?

If anyone has any thoughts or ideas, I'd love to hear them... thanks very much.

BG

[Dave Emery]

Re: Building Minelab Coils

BG, Yup you surely can mess up your detector if you wire the coil the wrong way. Most of the people who have made minelab type coils have only made coils for Minelab PI detectors. These are easier to make as they consist of a single coil of wire. They do however require a faraday shield and the construction has to be solid. The Explorer is not a PI. the coil it uses is a balanced type and is made using two D shaped coils which require perfect positioning of one coils edge over the other. This calls for the use of an oscilloscope. To make matters worse, the explorer uses a special type of cable (which is made just for Minelab) to connect the coil to the detector. These coils also require faraday shielding and a good construction.

[Charles (Upstate NY USA)]

Re: Building Minelab Coils

Hey BG,

Building a coil for an Explorer is not an easy task but can be done. The electronics part of building the coil is a no brainer, its assembling the coil thats tough.

Number of turns varies depending on the size of coil you are building, wire guage 20 for TX (transmit) and 28.5, 29, 29.5 for RX (receive).

The other guy was right, they use a funky cable which you can't find anywhere, its a 2 conductor each individually shielded. You can use a common S-Video cable though with good results. Its not as durable as the factory cable but does the job for experimenting. I also located a supplier who has a 3 conductor with 1 individually shielded. I use the shielded conductor for RX and the other two for TX.

You need an oscilloscope (ebay) to balance the coils and a LCR meter (I bought a new Extech) to both measure your factory coils and to measure your custom coils. Measure say 3-4 factory coils and establish a range for LCR (inductance, capacitance, resistance) then wind your coils within these specs, at least at first, I would get a coil working within these specs before trying a hot wind.

You need some 5 pin mic connectors, note the factory connectors have fat pins, some US suppliers have thin pins. You can jam a thin pin female into the factory fat pin male but they are tough to get apart.

Okay so you got your magnet wire, cable, and connector, now all you have to do is assemble the coil, thats going to take pages to discuss so shoot me an email at [email protected]

[Pedro]

Re: Building Minelab Coils

Hello Charles

Looks to me that you have already made some experiments with explorer home made coils...

Some months ago a made some measures to my Explorer II standard coil, because I'm thinking in made a smaller coil or even a pinprobe (like the one that is selled by a well known company)

I made this mesures with a professional RLC meter, and here are the data I got, and the conclusions I take (I don't know if they are right)

TX - 590 uH / 0.6 Ohms
RX - 510 uH / 6.6 Ohms

I think that each coil have a diameter of 20 cm, so:

TX - 34 turns / 0.8mm Wire
RX - 30 turns / 0.3mm Wire

Well, this is what I think there is inside my explorer DD coil...

Can you comment this info ( probably the calculations are wrong it looks strange to have more turns in TX coil then in RX)

For the cable I was thinking to use 4 thin coaxial cables like RG178, but your idea of a computer monitor video cable, looks very good....and inexpensive!

Thanks for all your info
Best Regards