Arduino Nano PI Main Discussion

[Olly]

Great job Olly! I bet your wife is well pleased with the matching pair of pro-looking detectors! Don't forget to post the results of your finds in Jersey,,,Enjoy your Hols! Regards, Marty.

Just back from Jersey, both detectors worked very well in the wet sand but mostly found a lot of junk on the beach I'm afraid. Lots of pull tabs, bottle tops and old cans. They do find very deep though and my wife found an old Brittania Farthing in some concretion, it's not in very good condition but seems to be from around late 1700's to early 1800's so very happy with that.

I did find some odd interference between the two detectors though and when they are within around 20 yards of each other they both beep intermittently. No problem once we kept some space between us though.

[Qiaozhi]

Just back from Jersey, both detectors worked very well in the wet sand but mostly found a lot of junk on the beach I'm afraid. Lots of pull tabs, bottle tops and old cans. They do find very deep though and my wife found an old Brittania Farthing in some concretion, it's not in very good condition but seems to be from around late 1700's to early 1800's so very happy with that.

I did find some odd interference between the two detectors though and when they are within around 20 yards of each other they both beep intermittently. No problem once we kept some space between us though.

Glad to hear you had an enjoyable time with your two ANPIs.
If you change the txPeriod on line 29 in the Arduino sketch and re-flash one of the detectors, then the slight different in TX pulse rate should allow them to operate closer together.

[Olly]

Glad to hear you had an enjoyable time with your two ANPIs.
If you change the txPeriod on line 29 in the Arduino sketch and re-flash one of the detectors, then the slight different in TX pulse rate should allow them to operate closer together.

Cool thanks, I'll give that a try.

[MartyJ1963]

Great stuff Olly! Thanks for posting. Mine are nearly boxed up so I'll hopefully be taking them out soon to test. Regards, Marty.

[Agme]

My Nano PI Build Experience


I am ~90% finished with the Nano Pi Detector and was just going to share the things I learned.
My Background:
I am not a dirt fisherman. I have a friend who is obsessed with the sport, so I have been a few times. However, I was intrigued on how they work. I was occasionally looking for information on how they work when I ran across Inside the Metal Detector and Nano PI books. I bought both and read them then found this forum and I decided to build the Nano PI. I was already familiar with Arduino so I figured it was an easy place to start. I have some soldering experience (perf boards, headers, etc.) but I have never populated a PCB.
Components/BOM:
I tried to buy everything from digikey, but some of them were out of stock or were not exactly the same description as the book. So I decided to use the BOM provided by dingbatca from Tayda. I have never used them before but they were cheap, looked to be pretty good quality, and the datasheets were easy to find. The shipping was fast and I will use them again.

I made a few changes to the BOM or where I found the other parts:
2-pin term 4 A-804
female 2 pin 4 A-826
3-pin term 3 A-805
Female 3pin 3 A-827
Crimps 18 A-837
Headphone Socket 1 A-3575
Rubber Boot for switches 2 A-5248
15 pin Socket for Arduino 2 A-1669
5 PINS FEMALE CIRCULAR CONNECTOR 12MM GX12 1 A-5579
5 PINS MALE CIRCULAR CONNECTOR 12MM GX12 1 A-5573
I added an additional 10K pot for the Coil testing setup.

Amazon
Arduino Nano Elegoo (I had to download the CH340 driver from Elegoo but worked fine)

Digikey
3R3 (2W) R3 RSB-3.3RCT-ND (I had a hard time finding a 2W 1% this is a 3W)
Coax C1188-50-ND (I also had a hard time finding this I ended up buying a spool. I hope I use it somewhere)
Gland Strain Relief PMS12BK080-ND (sized for the coax)

DIYDetector
I bought the PCB board thru DIY detector. I chose the ?snail mail? option and it took exactly 2weeks to get to the US. Boards arrived in good condition and worked good.

Coil stuff
Wire: I miss read the book "1mm thickness, with insulation" I thought this ment 1mm wire (18AWG) with insulation and I had some 18 AWG hookup wire so I decided to use it. (.110" OD (2.794 mm))oops.
I had some spiral wrap, material unknown.
I had some ducting foil tape for shielding (3M 3340 foil tape) A mistake I think.

Build:
I followed the book instructions, and everything went smoothly. I found Surfdetector's YouTube videos extremely helpful.
I started building the coil and noticed it didn't really look like the other ones on the forum/book. That's when I realize the wire I was using was big I didn't want to buy new wire so I just finished it / re calculated what it would take with this diameter and ended up with the following:

9" ID/ 26 turns (18AWG-.11" OD) /.8 Ohms/300uH
I put way too much overlap on the foil tape. There was a lot on there.
Rd = 360 Ohm

Coil Issues:
I realized while testing the coil was not very fast. The response was ~100us. I cut the shielding off of the coil and it was a lot better but had a lot of noise. I think I put way too much shielding material on the coil and it was thick, so it was doing weird stuff to the coil. Attached are scope pictures of both (before and after). I didn't retest the dampening resistor so it may be able to be optimized from what its at now.
It seems to be working pretty good but there is a lot of noise. I ordered some proper shielding tape and I am looking forward to finishing it.

Advise needed:
1)I would like to make a new coil. I was going to buy some new wire, but I got overwhelmed with all the opinions of the forum. Would yall recommend a wire size and insulation. What I have concluded is that Teflon insulation is a favorite (I think), but actual wire size is all over the place. And 3DSS coils seem to be a favorite over the Fast coil documentation.
2) I would like to build a VLF next, could you recommend a project to try. I saw the IDX pro is available from DIY detector and I not sure I want to attempt making PCBs yet.

Thanks for the help.

[gallico58]

Hi, I have successfully built arduino nano pulse.
if possible I wanted some advice, the damping resistance better directed in the coil or better on the circuit, on the base?
does the rg58 cable affect a lot in both cases?
sorry english translated Thanks!

[Qiaozhi]

Advise needed:
1)I would like to make a new coil. I was going to buy some new wire, but I got overwhelmed with all the opinions of the forum. Would yall recommend a wire size and insulation. What I have concluded is that Teflon insulation is a favorite (I think), but actual wire size is all over the place. And 3DSS coils seem to be a favorite over the Fast coil documentation.
2) I would like to build a VLF next, could you recommend a project to try. I saw the IDX pro is available from DIY detector and I not sure I want to attempt making PCBs yet.

Thanks for the help.

Firstly ... well done on a successful build, and thank you for reporting back to the forum on the results.

You don't need to be obsessed with making a fast coil for the ANPI as it's designed for metal detecting on the beach, not for gold nugget detecting. A simple mono coil is more than adequate, and Teflon insulation would be good. You can use the Coil Calculator at the top of the Coils forum to estimate the correct number of turns for a specific wire diameter.
If you do want to reduce the sampling delay then have a look at ->
https://www.geotech1.com/forums/show...l-Illumination
The "Investigation of UXO Paper.pdf" includes a modification to the transmitter circuit which turns it from passive to active switch-off. This reduced the sample delay of 24us to 17us (out of saturation at 15us) for the sample test coil.
I have made good coils with 0.56mm, 0.63mm, and 0.71mm copper enameled wire, and also with simple hookup wire, so it's not really that critical.
Make sure that you adjust the damping resistor accurately to provide critical damping.

Regarding a VLF detector project ... TGSL or IDX Pro are probably your best options.

[Qiaozhi]

Hi, I have successfully built arduino nano pulse.
if possible I wanted some advice, the damping resistance better directed in the coil or better on the circuit, on the base?
does the rg58 cable affect a lot in both cases?
sorry english translated Thanks!

As described in Chapter 4, the best position for the damping resistor is on the back of the coil connector. This provides the most flexibility when using different coils.
You could also put the resistor in the coil shell, but this may stop the coil being used on a different detector.
There is a place provided on the PCB, but this is also restrictive as all coils will then need to have identical damping requirements.

[Vadim18]

Agme - 45uS for delay is quite large number. U know, probably you need to check or replace frontend opamp first.
And 360 Ohm dumping resistor is a bit low, try 390, 470.

[Agme]

Thanks,
I have a spare opamp I will see if there is any difference.

Dampening resistor - I just followed the instructions and adjusted the resistance while monitoring the scope. I also looked at surfdetector's video.

[Agme]

Firstly ... well done on a successful build, and thank you for reporting back to the forum on the results.

You don't need to be obsessed with making a fast coil for the ANPI as it's designed for metal detecting on the beach, not for gold nugget detecting. A simple mono coil is more than adequate, and Teflon insulation would be good. You can use the Coil Calculator at the top of the Coils forum to estimate the correct number of turns for a specific wire diameter.
If you do want to reduce the sampling delay then have a look at ->
https://www.geotech1.com/forums/show...l-Illumination
The "Investigation of UXO Paper.pdf" includes a modification to the transmitter circuit which turns it from passive to active switch-off. This reduced the sample delay of 24us to 17us (out of saturation at 15us) for the sample test coil.
I have made good coils with 0.56mm, 0.63mm, and 0.71mm copper enameled wire, and also with simple hookup wire, so it's not really that critical.
Make sure that you adjust the damping resistor accurately to provide critical damping.

Regarding a VLF detector project ... TGSL or IDX Pro are probably your best options.

Thank you for the suggestions. Thank you for the books and support here.

[surfdetector]

Advise needed:
1)I would like to make a new coil. I was going to buy some new wire, but I got overwhelmed with all the opinions of the forum. Would yall recommend a wire size and insulation. What I have concluded is that Teflon insulation is a favorite (I think), but actual wire size is all over the place. And 3DSS coils seem to be a favorite over the Fast coil documentation.
2) I would like to build a VLF next, could you recommend a project to try. I saw the IDX pro is available from DIY detector and I not sure I want to attempt making PCBs yet.

Thanks for the help.

Regarding the VLF project, I think that the TGSL is the best documented so you might want to look at that project to start.

[Agme]

Itsy Bitsy display for ANPI

While looking at the scope I realized that TP10 (after the integrator) was pretty stable indication correlating to the audio signal. I first connected this to an extra Nano (A0) and used the Arduino IDE serial plotter and realized that it could be possible to make an indicator. I had this little OLED screen so I connected it and made a rolling graph. I originally thought it might be possible to connect it to the Nano on the ANPI, but I did not try it. I was worried about how to keep it from messing with the timing and I am a novice programmer. The extra Nano and display add roughly .027 amps to the system. My crappy code is attached if anyone wanted to explore further.

https://imgur.com/HBfN8jf

md_Display_Test_20.zip

Edit: I forgot to add reference to where I got the starting code for the rolling graph in the code. I found it here and modified it. https://youtu.be/6-SRpThOZ5I

[Qiaozhi]

While looking at the scope I realized that TP10 (after the integrator) was pretty stable indication correlating to the audio signal. I first connected this to an extra Nano (A0) and used the Arduino IDE serial plotter and realized that it could be possible to make an indicator. I had this little OLED screen so I connected it and made a rolling graph. I originally thought it might be possible to connect it to the Nano on the ANPI, but I did not try it. I was worried about how to keep it from messing with the timing and I am a novice programmer. The extra Nano and display add roughly .027 amps to the system. My crappy code is attached if anyone wanted to explore further.

https://imgur.com/HBfN8jf

[ATTACH]55841[/ATTACH]

Edit: I forgot to add reference to where I got the starting code for the rolling graph in the code. I found it here and modified it. https://youtu.be/6-SRpThOZ5I

Nice.

I downloaded the code and compiled it. It takes 47% of the program space, so would probably fit on an Arduino Nano with the PI code. However, the overhead of the display might affect the audio response of the detector as you suspected. In this case, having a separate display driver is a good solution.

You might also want to look at the Arduino Voodoo code where I used a very similar OLED (an SH1106 as opposed to an SSD1306). In that example I used the U8x8lib instead of the Adafruit_SSD1306 library. -> https://www.geotech1.com/forums/show...883#post287883

[MartinB]

While looking at the scope I realized that TP10 (after the integrator) was pretty stable indication correlating to the audio signal. I first connected this to an extra Nano (A0) and used the Arduino IDE serial plotter and realized that it could be possible to make an indicator. I had this little OLED screen so I connected it and made a rolling graph. I originally thought it might be possible to connect it to the Nano on the ANPI, but I did not try it. I was worried about how to keep it from messing with the timing and I am a novice programmer. The extra Nano and display add roughly .027 amps to the system. My crappy code is attached if anyone wanted to explore further.

https://imgur.com/HBfN8jf

[ATTACH]55841[/ATTACH]

Edit: I forgot to add reference to where I got the starting code for the rolling graph in the code. I found it here and modified it. https://youtu.be/6-SRpThOZ5I

Looks really good. Are you using a display with a yellow portion at the top or are using a RGB display?