Arduino Nano PI Main Discussion

[green]

If you look at a Goldscan 2 schematic, you will see that it uses the same integrator circuit as the MPP, and the GS2 includes ground balance.

I stand corrected if it works. Found a schematic, looks like an integrator for target signal and one for ground signal(both have same gain). Don't know what switch on times are. On times effect frequency integrator response. Still don't know why it works unless on times are the same and gain change is after integrators.

[6666]

Thanks Bruce. If I shielded it with Copper tape, what would I ground to the tape? And, would I have to leave a gap like you do when copper shielding a monocoil? Is it Battery negative and the coil connector cos' I'm not certain with ever only using Aluminium enclosures? Regards, Marty

Hi, just treat it the same as a solid metal box, ground will be circuit ground, no gaps needed, but watch out for head phone jacks and how they are wired

[lc516]

On TP3（ICL7660 PIN5）I get -1.34v，

what is wrong ？

ICL7660 PIN8 is 5v

[godigit1]

https://www.geotech1.com/forums/show...814#post199814 I can adjust target sample time to cancel ground signal from my back yard with GB switched on and the see target as long as it doesn't fall in the hole with my PI. Figure8 Rx coil reduces ground signal and signal from a zip lock bag from back yard is about 1/5 the signal. Figure8 coil can cancel the California bag if positioned between the figure8 Rx coils. Don't know how difficult it would be to keep the signal low enough swinging the coil over the California ground, no problem in the yard with GB on(not usable with GB off). I think 1/5 the signal is still fairly high? Dirt from back yard, almost nothing sticks to magnet.

I see the decay chart reply #46 from above thread states Calif ground 80 times Al ground but chart shows over 3 times. Two many stupid pills? I measured 5 times this morning at integrator out.

Hi Green ,
Now I see good old mother load red volcanic dirt clay just 3 hours away may not be the exact dirt but will get some soon.
also see why its not east to separate it magnetically.



Looks like Tahoe sand though with all the magnetic rocks. In the picture even the granite pebbles are magnet to some extent .

My ground balance on a bi polar machine cannot handle this ground with the stock coil no matter how slow I sweep it see's too much change in the ground and too much soil volume within any 6 inches to stay balanced.
A smaller mono coil is capable of hunting the ground but at a very slow swing.
Magnetite is not supposed to effect a PI and funny that holds true but not in Gb mode on this machine I still have to run down there after a windy night with the Tdi and see if It suffers the same fate.

My Mpp Board has 4 14538's its quite bulky to run that way that's why I wanted to try the arduino.

Your way ahead of me on my understanding of the physics of GB. I'm just thinking samples and switches still.
You have given me allot to think about and allot of studying I need to do yet.

After I made the pro Q board I'm thinking I may have to add a second integrator but wanted to see if I could do it by sample cancellation either way It should still be a place to start.

My TdI had some sand I could hear in it so I pulled it apart last night for the first time.
All the test points are there Im going to look at timing samples and pulse delay and high and low timings to see how it all comes together.
I will not post those here Unless Carl was good with it. For your study I would Email to you but its going to be a couple days to list the test points.

[lc516]

On TP3（ICL7660 PIN5）I get -1.34v，

what is wrong ？

ICL7660 PIN8 is 5v

When I disconnect the resistor R1,I get 4.75v on TP3

[green]

Hi Green ,
Now I see good old mother load red volcanic dirt clay just 3 hours away may not be the exact dirt but will get some soon.
also see why its not east to separate it magnetically.

[ATTACH]54886[/ATTACH]

Looks like Tahoe sand though with all the magnetic rocks. In the picture even the granite pebbles are magnet to some extent .

My ground balance on a bi polar machine cannot handle this ground with the stock coil no matter how slow I sweep it see's too much change in the ground and too much soil volume within any 6 inches to stay balanced.
A smaller mono coil is capable of hunting the ground but at a very slow swing.
Magnetite is not supposed to effect a PI and funny that holds true but not in Gb mode on this machine I still have to run down there after a windy night with the Tdi and see if It suffers the same fate.

My Mpp Board has 4 14538's its quite bulky to run that way that's why I wanted to try the arduino.

Your way ahead of me on my understanding of the physics of GB. I'm just thinking samples and switches still.
You have given me allot to think about and allot of studying I need to do yet.

After I made the pro Q board I'm thinking I may have to add a second integrator but wanted to see if I could do it by sample cancellation either way It should still be a place to start.

My TdI had some sand I could hear in it so I pulled it apart last night for the first time.
All the test points are there Im going to look at timing samples and pulse delay and high and low timings to see how it all comes together.
I will not post those here Unless Carl was good with it. For your study I would Email to you but its going to be a couple days to list the test points.

Tried what I thing would be comparing a MPP vs a 1C integrator in Excel. First delay 4us for small nuggets. Hole is lower for MPP. Would expect MPP noise to be 4times higher with GB enabled. Peak noise is about 3times higher when I enable GB on my detector, so maybe a little less noise with a higher TC hole. Can attach excel program if anyone wants. Have in the past but might have made some changes.

[Qiaozhi]

When I disconnect the resistor R1,I get 4.75v on TP3

Have you programmed the Nano?
You must do that before you can measure -5V at TP3, as the Nano generates the external clock for the 7660.

[MartyJ1963]

Thanks again Bruce,,,Will do. Regards, Marty.

[lc516]

Have you programmed the Nano?
You must do that before you can measure -5V at TP3, as the Nano generates the external clock for the 7660.

yes,I think I know what's wrong after excluding other possible problems.
I used a unmatch "MC7660", it can't runing on1k external clock.
I'll buy a new icl7660.


thanks for your information

[useus]

I've also been experimenting with the new Raspberry PI Pico, but I'm not sure whether it makes a good candidate for a metal detector project. It's physically bigger than the Arduino Nano (despite being called Pico) and is more difficult to set up. The Pico can be programmed using MicroPython (I've used Python before, and it's somewhat similar) but my impression at this point is that the Arduino is an overall more pleasant experience. Obviously the Pico is a more powerful device than the Nano, with a lot more memory, so I might change my mind later as I get more familiar with it.

In my opinion, if you work on the pico, it could become an excellent Voodoo-style hybrid. in the specifications I read that it has two programmable fast i / o that could lead to a considerable increase in performance.
among other things, by doing a search on the net, someone is already working on a PI with a simple circuit.

[Qiaozhi]

among other things, by doing a search on the net, someone is already working on a PI with a simple circuit.

Do you have a link?

[useus]

Do you have a link?

google rp2040 metal detector

1st link

[surfdetector]

Do you have a link?

xaj_v2_03042021 doc.pdf

I believe that this is the document referenced.

[surfdetector]

xaj_ schematics.pdf

Here is the schematic for the above pdf

[Qiaozhi]

google rp2040 metal detector

1st link

Found it -> https://sourceforge.net/projects/met...sed-on-rp2040/

It appears to be based on the Spirit PI.
Minimum sample delay is 20us, and TX pulse rate can be varied between 20pps and 160pps.
There is no Earth Field Elimination (EFE).
Interrupts are not used, as the timings are all generated by software delays.
Detection of a one Euro coin is claimed to be 20cm.

There may be a problem trying to implement the timings using low-level hardware timers and interrupts, as the Pico only has one 64-bit timer. Looking at the Pico SDK documentation, it seems that the timer peripheral is incremented every micro-second which could also be a problem, although there are 4 alarms tied to the lower 32-bits. Maybe this could be worked around using some assembler code, but (as I said previously) the Pico is much more complicated to use than the Arduino, and may not add any extra value in this application. I suspect the Arduino Nano will still generate more interest in the Geotech community due to its ease of use.