GOLD coil hunter

[Tibuck19]

Good evening Ladies and gentlemen, As some of you know I was tinkering with the Barracuda and also Polished off the Surf PI 1.2 that works like a charm with a fast 10inch coil, Now on too the MMP REV-D, I would like to make this one a GOLD hunter not only gold rings but more like a tinny gold nugget predator hahaha , I'm sure a mono coil is still the way to go, but interested on what you guys suggest in this particular case? Size, UH, shielding..... As always, thank you of any and all advice you can share.

[geoscash1]

Ive done a bunch of tests with different coils and so far the best working coil is 300uH (300 to 320uH) in the 7 to 8 inch range. I as well as other guys here have used a multitude of different wires.

For my particular setups (modified for gold only) the 250/46 litz wrapped on a 3dss form has been the best performer (see pic below) with 175/46 litz coming in second then 24awg Teflon coated 7 strand silver plated last. All 3 perform well but the 250/46 with double sleeve seems to be best for my particular boards.

Depending on how you build the MPP, that will be the deciding factor on performance. lots of testing is the only way to find whats best for your board.

Just make sure and follow the build doc step for step and check each stage with a scope if you have access. I would recommend building it to spec first like in the build doc then modify later or get another board to modify.

example coil = 3dss 250/46 litz 309uH

[Tibuck19]

I see the basket coil you made, Is there a mono coil inside ? i have tried making a few but the thing is , im not smart enough to figure out what uH it comes out with, Example, Making a mono coil calculations is simply a matter of knowing the radius and wire thickness and number of turns, But i have no clue how to calculate for a basket coil, All three coils work ok with the surf pi, and Barracuda, with exception of the red coated aluminum magnetic wire, It simply over heats the mosfet on the Cuda, however they work no better but no worst then the mono coil i ended up, but much more time consuming to make.

[kt315]

ok. i reminder some definitions from the f-cking physics.

The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.

As the dielectric constant increases, the electric flux density increases, if all other factors remain unchanged. This enables objects of a given size, such as sets of metal plates, to hold their electric charge for long periods of time, and/or to hold large quantities of charge. Materials with high dielectric constants are useful in the manufacture of high-value capacitors.

A high dielectric constant, in and of itself, is not necessarily desirable. Generally, substances with high dielectric constants break down more easily when subjected to intense electric fields, than do materials with low dielectric constants. For example, dry air has a low dielectric constant, but it makes an excellent dielectric material for capacitors used in high-power radio-frequency (RF) transmitters. Even if air does undergo dielectric breakdown (a condition in which the dielectric suddenly begins to conduct current), the breakdown is not permanent. When the excessive electric field is removed, air returns to its normal dielectric state. Solid dielectric substances such as polyethylene or glass, however, can sustain permanent damage

[Tibuck19]

ok. i reminder some definitions from the f-cking physics.

The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.

As the dielectric constant increases, the electric flux density increases, if all other factors remain unchanged. This enables objects of a given size, such as sets of metal plates, to hold their electric charge for long periods of time, and/or to hold large quantities of charge. Materials with high dielectric constants are useful in the manufacture of high-value capacitors.

A high dielectric constant, in and of itself, is not necessarily desirable. Generally, substances with high dielectric constants break down more easily when subjected to intense electric fields, than do materials with low dielectric constants. For example, dry air has a low dielectric constant, but it makes an excellent dielectric material for capacitors used in high-power radio-frequency (RF) transmitters. Even if air does undergo dielectric breakdown (a condition in which the dielectric suddenly begins to conduct current), the breakdown is not permanent. When the excessive electric field is removed, air returns to its normal dielectric state. Solid dielectric substances such as polyethylene or glass, however, can sustain permanent damage

Correct me if i'm wrong but it sounds like your quoting pages from a book, Understandably it betters my knowledge, of the role that electrical FLUX comes into plays with metal detecting, but nonetheless does not help share knowledge from many peoples experiences and trial and error that prevents all of us to keep going down the same old "rabbit hole" so to speak. basically you have not aided in anyway, But thank you for the lesson professor, I do not mean to be rude, It could just be a language barrier between you and I, or your way of explaining that rubs me the wrong way, But I have asked politely in a PM message use put down remarks, they are not wanted! and simply replacing a U by a - doesn't make it better. If any of you think what Kt315 said is part of the answer im looking for and I totally missed it, please let me know.

[kt315]

what is ideal FAST coil. you try to get basket coil but use plexglass and plastic. while ideal is a wire IN AIR just cause
nothing more the dielectric constant is lower of there is. ITS RULE BUDDY. so GOOD material NOT plexglass
you doing big capacitor with, but simple fiberboard. JUST CAUSE F PHYSICS.

GOD GIVE THOSE PEOPLE THE MIND.

[kt315]

[kt315]

[kt315]

http://www.k****ij-iitjee.com/Study/...apter26/46.jpg

[Qiaozhi]

I see the basket coil you made, Is there a mono coil inside ? i have tried making a few but the thing is , im not smart enough to figure out what uH it comes out with, Example, Making a mono coil calculations is simply a matter of knowing the radius and wire thickness and number of turns, But i have no clue how to calculate for a basket coil, All three coils work ok with the surf pi, and Barracuda, with exception of the red coated aluminum magnetic wire, It simply over heats the mosfet on the Cuda, however they work no better but no worst then the mono coil i ended up, but much more time consuming to make.

As far as I know there is no calculator available for basket weave coils due to complex shape. You would have to measure some test coils with an inductance meter, and guesstimate how many turns are needed to create a particular inductance. Either that or you could simply copy someone else's existing coil which you know works. I assume that the one you tested on the Baracuda had a really low inductance, as that design does not possess a series current-limiting resistor. The maximum current could get quite high, causing the MOSFET and the coil itself to get hot.

[Qiaozhi]

I do not mean to be rude, It could just be a language barrier between you and I, or your way of explaining that rubs me the wrong way,

Don't take KT315's [sometimes abrupt] comments personally. It's mainly an issue with the language barrier.

[homefire]

Link Not Found from here.

[geoscash1]

I see the basket coil you made, Is there a mono coil inside ? i have tried making a few but the thing is , im not smart enough to figure out what uH it comes out with, Example, Making a mono coil calculations is simply a matter of knowing the radius and wire thickness and number of turns, But i have no clue how to calculate for a basket coil, All three coils work ok with the surf pi, and Barracuda, with exception of the red coated aluminum magnetic wire, It simply over heats the mosfet on the Cuda, however they work no better but no worst then the mono coil i ended up, but much more time consuming to make.

You will need an LCR meter to measure the uH.

with the spider or 3dss coil (like I pictured earlier) it has 6 layers of 5 turns for each layer, x6 = 30 turns give or take, I measure after winding more than needed then removing a layer at a time, not cutting the extra but leaving it connected in one length until I am close to the 300uH I am looking for. usually it ends up close or in a range from 300 to 315uH and around 27/30 turns depending on wire used which in my case is perfect.

edit - looks like a couple replies before I finished typing...lol...

[Tibuck19]

@kt315
Now that was very helpful, Thank you Very much, I think the F physics was not what I thought you meant and for that I am sorry, I have to admit A mono loop coil is what was thinking also, but I did want to explore other possibilities also. If we look at the most popular Gold coils like the coiltek elite.... they are all mono loops. This also triggered other questions for me, the difference between a lower 300Uh VS higher 500Uh, Does a coil with more inductance, mean better depth and better and slower decay on metals such as gold or there is no importance and the Uh is simply to match the board circuits ?I will dig deeper into Dielectric constants subject as it seems to play an important roll here.

[kt315]

Don't take KT315's [sometimes abrupt] comments personally. It's mainly an issue with the language barrier.

thats barrier between soviet school level and their capitalistic. their basic knowledge is FULL ZERO. so why to waste a time in the school if they bring nothing from it? shame.