Arduino Nano PI Main Discussion

[Qiaozhi]

Just got the book and typing in the sketch. The ISR seems to be missing a line of code above the switch statement, but not 100% certain. I just see a bracket pairing mismatch. Anyone have any ideas? Is there a repository that contains the code? Not against typing it in, but do not want it to be harder than it should be.

Everything you need is here -> Arduino Nano Pulse Induction Metal Detector Project - Published March 2021

It appears that you have spotted an error at the top of page 23. The missing line is "ISR(TIMER1_OVF_vect) {".
I'll create an errata in the above link.

[Agme]

https://www.geotech1.com/forums/showthread.php?26505-Arduino-Nano-Pulse-Induction-Metal-Detector-Project-Published-March-2021

this link is the thread with all the files.

This thread is for questions and discussions the info you are looking for is in the technical papers and books section.

[jhughes1010]

Just got the book and typing in the sketch. The ISR seems to be missing a line of code above the switch statement, but not 100% certain. I just see a bracket pairing mismatch. Anyone have any ideas? Is there a repository that contains the code? Not against typing it in, but do not want it to be harder than it should be.

[mermelado]

The salinity when constantly submerged in the salt water is uniform as opposed to swinging in and then out of the surf.

Then would it be correct to say that a PI detector is more stable under the sea than outside of it? and by the way, does anyone have any links to build submersible coils and types of submersible cables for them?

[Qiaozhi]

What is the size of the pcb?

3.25" x 3.00" (82.6mm x 76.2mm)

[ionut_mtb]

What is the size of the pcb?

[surfdetector]

Hi Carl: And using it underwater with a waterproof coil, since the salinity is similar everywhere, will that effect occur?

The salinity when constantly submerged in the salt water is uniform as opposed to swinging in and then out of the surf.

[mermelado]

Some comments...

If the Earth field is perfectly homogeneous and you sweep the coil perfectly flat then there should be no EFE. In the field most people slightly tilt the coil at the ends of the sweep, or there can be slight field anomalies due to mineral variation (which might be somewhat deep) which is why EFE still shows up.

I wonder if lamoiz's problem is related to battery level.

In general, PI detectors are notorious for a wet salt "breathing" effect. If you walk parallel to the surf line, as you sweep the coil toward the water the PI picks up a greater concentration of conductive salt and gives a positive response, as you sweep away from the water there is a lower concentration and the response goes negative (quiet, usually). This is exacerbated on heavily sloped beaches and will create a slow response that is exactly in sync with the coil sweep. The best shielding in the world won't stop this. The 2 ways to deal with it are 1) turn the pulse delay up or 2) turn the SAT speed up until it is manageable.

Edit: Third way to deal with it is to hunt perpendicular to the surf; that is, walk straight into the surf, then straight back out of it. Keep the swing arc down to 45 degrees or so.

Hi Carl: And using it underwater with a waterproof coil, since the salinity is similar everywhere, will that effect occur?

[lamoiz]

I would replace R24 by a 47k resistor in series with a 1M pot, then you can adjust from unreasonably fast to unreasonably slow.

I will do that !

[Carl-NC]

I would replace R24 by a 47k resistor in series with a 1M pot, then you can adjust from unreasonably fast to unreasonably slow.

[lamoiz]

Yes, you can speed up the SAT. The default is 470n*220k = 100ms, try a 100k resistor.

ok thank you carl, I change r24 with 100k or by a potentiometer on the front to adjust on the ground of the beach. I'm going back to the ocean at the beginning of September and I'm testing this!

[Carl-NC]

Yes, you can speed up the SAT. The default is 470n*220k = 100ms, try a 100k resistor.

[lamoiz]

Some comments...

If the Earth field is perfectly homogeneous and you sweep the coil perfectly flat then there should be no EFE. In the field most people slightly tilt the coil at the ends of the sweep, or there can be slight field anomalies due to mineral variation (which might be somewhat deep) which is why EFE still shows up.

I wonder if lamoiz's problem is related to battery level.

In general, PI detectors are notorious for a wet salt "breathing" effect. If you walk parallel to the surf line, as you sweep the coil toward the water the PI picks up a greater concentration of conductive salt and gives a positive response, as you sweep away from the water there is a lower concentration and the response goes negative (quiet, usually). This is exacerbated on heavily sloped beaches and will create a slow response that is exactly in sync with the coil sweep. The best shielding in the world won't stop this. The 2 ways to deal with it are 1) turn the pulse delay up or 2) turn the SAT speed up until it is manageable.

Edit: Third way to deal with it is to hunt perpendicular to the surf; that is, walk straight into the surf, then straight back out of it. Keep the swing arc down to 45 degrees or so.

no, it's not a battery problem, I actually noticed everything that carl has just described. the problem was much less when I was above the water. and more present when on the dry to wet transition. the shielding of my coil is very efficient, so it is after this that I asked myself lots of questions ..
as I am back in the workshop, I was able to control the 12v regulation system ... and there is no problem ...
how to deal with the problem on the nano ..? SAT ..?

[Carl-NC]

Some comments...

If the Earth field is perfectly homogeneous and you sweep the coil perfectly flat then there should be no EFE. In the field most people slightly tilt the coil at the ends of the sweep, or there can be slight field anomalies due to mineral variation (which might be somewhat deep) which is why EFE still shows up.

I wonder if lamoiz's problem is related to battery level.

In general, PI detectors are notorious for a wet salt "breathing" effect. If you walk parallel to the surf line, as you sweep the coil toward the water the PI picks up a greater concentration of conductive salt and gives a positive response, as you sweep away from the water there is a lower concentration and the response goes negative (quiet, usually). This is exacerbated on heavily sloped beaches and will create a slow response that is exactly in sync with the coil sweep. The best shielding in the world won't stop this. The 2 ways to deal with it are 1) turn the pulse delay up or 2) turn the SAT speed up until it is manageable.

Edit: Third way to deal with it is to hunt perpendicular to the surf; that is, walk straight into the surf, then straight back out of it. Keep the swing arc down to 45 degrees or so.

[lamoiz]

otherwise, the nano with the 32 coil works really well; the guys who are with me at the beach all have ctx3030 eq800 and sovereing minelabs. we did the depth test with the sovereing elite, and the nano. the result is very very close if the nano uses the boost.

I specify, following my last message here, that the sovereign who was with me on the depth test, had an ULTIMATE 33cm disc and that the discrimination was on, but at zero.