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Post  bubbazoo on Tue Oct 30, 2012 12:58 am

Hi all,

My name is David and i am new to this site.

I am getting ready to purchase a ML 5000 and being handy i was thinking of creating some of my own large mono coils. Is anyone else doing this? is there a bank of knowledge regarding inductance / Q values required for various sizes.

Has anyone created a list of ready-made coils and measured the inductance values used?

Does anyone know the min and max values that are acceptable for the ML machines?

Current / voltages that these coil are subject to?

Any experimenters out there?

Regards David


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Post  getascripter on Tue Oct 30, 2012 11:07 pm

Wow! You lost me after "My name is David and i am new to this site" ... I'm really VERY tech challenged! Very Happy Very Happy Very Happy

But G'day and welcome to the forum, David! My name is Kate & I'm over here in SA.
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Post  Guest on Tue Oct 30, 2012 11:20 pm

G'day David and welcome to the forum... I would not suggest making your own coil due to ML probably would not cover the warranty on your detector if something went wrong... But there are a few people on here who are into the electronic side of things who may have some ideas...

Cheers.

Mike. cheers

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Post  bubbazoo on Thu Nov 01, 2012 1:35 am

Thanks Kate and Mike for your welcomes. I am an electronics tech so experimentation is in the blood! Very Happy

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Post  davsgold on Thu Nov 01, 2012 8:26 pm

G'day bubbazoo

I'm with the others and just buy one when I need or want a new one.

But this may be of some use which I copied from http://www.geotech1.com/forums/showthread.php?17769-Measured-inductance-on-DIY-surf-PI-coil

"the coil should have 300 microHenry +/- 50
my coil a made of 0,5 or 0,6 mm lackered copper wire 23cm diameter in range of 18-24 turns"
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Post  bicter on Thu Nov 01, 2012 10:22 pm

Have a read here http://www.geotech1.com/forums/forumdisplay.php?6-Coils for heaps of information.

BTW welcome aboard Smile
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Post  bubbazoo on Fri Nov 02, 2012 12:37 pm

Thanks guys that's pointed me in the right direction, I will start my experimentation using my old SD2000 so as to minimise risking my new 5000 when it comes. regard David Smile

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Post  byronbinalong on Mon Nov 05, 2012 9:00 am

Welcome Bubbazoo and have fun
What really would be good is another type of battery for the GPX eg Lifepo4 using the 18650 rechargable or something similar that is as reliable and cheaper than the original and less weight ... I am electronically challenged at the best of time, cant even programme the DVD player unless it is plug and play .... heh heh heh What a Face
Cheers
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Post  Mechanic on Mon Nov 05, 2012 11:53 pm

HI David,

Work on this, 300uH, .4 ohms, peak current for a 240us tx @7.4v is about 3A. Strand size .2mm about 32 strands. You can either make some litz or use tin plated copper wire. You will need to use a wire that has a low dielectric constant insulation to keep capacitance to a minimum. Also the windings need to be shielded, the more space between the windings and shielding the better as it will reduce capacitance, raising the resonant frequency. Also good to pot your windings as this helps prevent false signals when the coil is bumped. The hardest part will be finding some coaxial cable with suitable parameters to carry the current, not support eddy currents, and low capacitance.
Then you need to put it in a housing!!!!

Good luck!

Cheers Mick

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Post  Wedge on Thu Mar 28, 2013 10:38 pm

byronbinalong wrote:
What really would be good is another type of battery for the GPX eg Lifepo4 using the 18650 rechargable or something similar ...

The standard Minelab GPX battery uses Sanyo UR18650F cells which are a Lithium Cobalt chemistry. Changing to LiFePO4 battery would be a downgrade in terms of specific energy (Watt hours per kg) and energy density (Watt hours per cubic metre). In other words a LiFePO4 battery would be bigger and heavier, or wouldn't last as long.

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Post  Azza76 on Tue May 07, 2013 8:39 pm

The guys from "Meteorite Men" made a large one and pulled it behind a motorbike.

Here's a couple of links on some info
http://www.treasurenet.com/forums/tech-talk/213726-homemade-detector-seen-meteorite-men.html
http://www.geotech1.com/cgi-bin/pages/common/index.pl?page=metdet&file=projects.dat

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