Competition!

[Op04]

Since Sir Invconic bring this "complicated" question, That is what I need to know also...but I want to add a question: Does increasing frequency or PPS will also increase Ampere Turn?

[August]

Hello GeoMax.
I was answering Ivconic, to his question

[GeoMax]

Hi August,

for what detector electronic do you want to make a coil?

[Xtrem]

ivconic , what you dont know are the turns from the original coil, if you make more turns you lost the smaller targets ,
test the original coil with different targets, small medium bigger , it is response the same? (30% better)?
Bifilar winding would increase the capacitance of the coil at the same turns, same wire.

[August]

"I can't get litz. Except me to looking for power cables, but the "channels" in the enclosure are so tight that the PVC litz won't fit there, as many windings as I think I'll need.
Question; would it change anything if I wind bifilar with 0.3mm? Or should I take 4 x 0.15mm? Or similar?"

Hello.
It is possible to use any wire diameter. It is also possible to combine wires with different diameters to achieve the required resistance and inductance for a given number of turns.

[pito]

[FONT

I have in my place a friend with the original PS2 Pro with a 45cm coil. When I compare; the original works at least 30% better.
\[/FONT]

compare transmitting power your and friend, show a picture of the coil.

Post#193https://www.geotech1.com/forums/foru...e13#post415559

[ivconic]

Joseph, it's good to have you here, you rarely appear, you don't write often... but you always write good and useful things.
Maybe this is off topic... I have a dilemma, your opinion would help and mean a lot to me.
I make copies of Pulse Star 2 (analog version). Not that often, maybe once or twice a year. I work with the detector until it is sold.
I am not aggressive about advertising and selling that detector. The initial motive for making it was for personal use.
That's why I didn't bother to establish one and the same coil for it. I usually make a coil from currently available material.
If you've ever seen a PS2 (either analog or digital "Pro" version); you must have noticed that there is a switch for Sample Delay on the front panel, with 4 positions.
Position "1" is the shortest delay. And 90% of the time I use the detector like that. And the coils that I have made so far were generally from 18cm to 42cm in diameter.
Not because I intended it to be; but because I mostly found such coil "cases" (lids made of plastic bins and similar handy material).
With the 18cm coil detector works almost unbelievably well! With such a small coil diameter; the ranges are incredible.
The 18cm coil has an inductance of ~380mH and a resistance of no more than 3 ohms. Damper at it is 680 ohms.
But as I increase the coil diameter; thus the detection results decrease. It's still good, but not as "sensational" as with 18cm.
Some time ago I acquired (from a friend from another country) 3 coil enclosures with 56cm diameter.
And since then I've been trying to make a good coil for those cases/enclosures. Alas... I fail. I tried with wires 1mm, 0.8mm, 0.5mm and now almost with 0.55mm.
I use regular Cu wire. No litz, because I can't find it.
I am "chasing" the inductance of 0.68mH-0.7mH because it is that much on the original PS2 45cm coil. And resistance no higher than 2 ohms.
Apparently, a 0.6mm wire would be suitable, which I don't have now but plan to get.
But even with 0.55mm I got very close specs. But the detection is still not "sensational". But very average.
I have in my place a friend with the original PS2 Pro with a 45cm coil. When I compare; the original works at least 30% better.
And someone recently mentioned to me in a conversation that he knows for sure that the original is wound with litz.
I still don't know the damper value in the original.
But the value of that resistance is not a problem, it will be established by observing the RX signal on oscilloscope and using a "jig" to adjust. (potentiometer and resistor in parallel with the resistor)
Somehow I feel in advance that even with a 0.6mm wire I will not be happy.
I can't get litz. Except me to looking for power cables, but the "channels" in the enclosure are so tight that the PVC litz won't fit there, as many windings as I think I'll need.
Question; would it change anything if I wind bifilar with 0.3mm? Or should I take 4 x 0.15mm? Or similar?
How many wires in the litz are actually necessary to achieve an effect similar to the original coil? (A similar question applies to all ML coils).
What most of us declaratively know; it is that litz is always better than single wire. But few of us understand all aspects of that story.
And so far, I haven't found anywhere that anyone has done experiments with "multi-filar" attempts, not from originally purchased litz, but from hand-prepared wire.
I would like to hear the opinion of someone who knows it much better than I do.
Thanks in advance to you and to anyone else who would know what to say on this topic.

[ivconic]

I like the post!

[bbsailor]

I would like to share another point of view about metal detecting.

1. Search location,
2. target types sought,
3. target time constants sought,
4. coil size,
5. detection method being used,
6. optimization methods to better find desired targets.

While detecting on the beaches in Ocean county and Atlantic county NJ I had to find ways to optimize my detecting effort to find more targets more easily.
1. Choose beaches that are densely populated
2. Choose a coil size that best finds desired targets
3. Use circuits that optimize the signal to noise ratio
4. Observe when the weather conditions result in sand and coins are being thrown up onto the beach
5. Use a half inch square wire mesh to make a 1 foot diameter by 1 foot tall sifting basket to quickly retrieve targets from sand
6. Place a magnet in a small plastic bag with a string attached to throw on the beach when I came upon black sand to see if it is organic or magnetic sand.

Once I understood how PI metal detectors work, I began to appreciate why the TX pulse lasts about 3 coil time constants. The total coil circuit resistance along with the coil inductance will govern the shape of the TX pulse with the current rising to almost horizontal when the TX pulse turns off. This ensures that any currents induced into targets at the initial current turn on have died out at about 3 time constants when the TX pulse turns off and the intended stimulus of the target occurs and then in a mono coil the TX coil becomes the RX coil. The time between the TX turn off and the RX turn on is called delay. The delay is based on how quickly the TX oscillations can be damped so the coil can be in the RX mode. The more capacitance that the coil sees, the lower value the damping resistance needs to be to quickly damp these oscillations. However, during the delay time, the induced eddy currents in the target are decaying and may not be there when the RX coil turn on. This is why I wrote the Fastcoil.pdf article. I set up my workbench with a signal generator and an oscilloscope to measure coil seen capacitance from coil winding capacitance, coil to shield capacitance and any other coil seen capacitance that I could minimize to reduce the delay. Coil to shield capacitance using a single layer of Scotch24 mesh is less than using a solid foil shield.

Being competitive with metal detecting requires an interest in selecting the right detector type and coil size for the desired targets, detecting location and environmental conditions. It also depends on how deeply you are willing to go to optimize your metal detector, what test equipment you have access to, and how deeply you are willing to dive into tinkering with your working metal detector or building one from scratch.

Learn about a concept called dielectric constant of a materiel. Lower is better as it loads the coil with less seen capacitance. Teflon insulation is about 2 while PVC is about 6. Remember, making a hand made coil could take some time but you can apply a low dielectric constant spiral wrap to secure the coil winding as well as provide a good spacer between the coil windings and the Scotch24 shield.

Abstract concepts used for a practical purpose become less abstract once you experience the results and visualize how the pieces finally all fit together.

I came to Geotech1, I researched, I wrote an article and I found some targets.

Joseph J. Rogowski

[Op04]

No need for such a bulky addon.
One single battery and stepup solves the problem and everything can be packed nicely into the existing battery compartment.
But ok, that's an idea too, why not!

Okay above 30Watt it's quite bulky and only start from 30W possible using above 15 Volt. But it's charging simplicity just by using Type C chargers for smartphone