Arduino Nano PI Main Discussion

[Qiaozhi]

I have a question about the coil:

Is it ok to use a 8 inch coil from an "old" White's detector (rebranded Sears "GEB/TR Discriminator")?

It depends on the inductance of the coil and what you want to do with the detector.
It's very easy to make your own mono coil.

I have another question about the hardware:

Where do you source the stem, handle, armrest, etc in the US? Do you just buy a cheap one on ebay/amazon and ditch the electronics and possibly the coil?

Probably the simplest way is to use a donor detector (either one that no longer works and cannot be repaired) or a cheap one from China.
Some metal detector dealers also sell shafts, armrests, etc., as spare parts.

[Qiaozhi]

Is there an E-book copy of this book?

No.

[ugocapeto]

I have a question about the coil:

Is it ok to use a 8 inch coil from an "old" White's detector (rebranded Sears "GEB/TR Discriminator")?

I have another question about the hardware:

Where do you source the stem, handle, armrest, etc in the US? Do you just buy a cheap one on ebay/amazon and ditch the electronics and possibly the coil?

[Nightryder]

Is there an E-book copy of this book?

[Spectrum]

Interesting point George. As you say, the pi pico is nearly 10x faster and has ADC that can reputedly return 10-bit ADC at up to 500k/s at a push. Here's an example of a pi pico doing FFT...
https://www.hackster.io/AlexWulff/ad...pi-pico-f883dd
I'm much stronger on software/firmware than I am on hardware, so I'd be interested to see if I can digitise the interesting bits of the flyback signal and then process it in software. Strongly suspect that this sort of processing might be better done with the help of a dedicated DSP chip ? Also, it's probably unlikely that a pi pico has the grunt to keep up.

Pls can you make a complete pi code for esp32 board

[SaltyDog]

Suggest an improved MOSFET FQA9P25 that has half the output capacitance Coss (170pF) of the IRF9640, that together with a fast coil will improve the device for small gold. The above is similar in all other respects.

[Qiaozhi]

The schematic you have posted is nothing to do with the Arduino Nano PI.
It looks like the sample pulse generator for the old Baracuda PI (not the Geotech version).

[pito]

[Teleno]

Qiaozhi Hi George, just letting you know that with the code from Teleno on https://www.geotech1.com/forums/foru...ge4#post420147 thread, I have been able to get a degree of discrimination for gold .. the method is:

Set the delay to where it is most sensitive for gold. REDUCE the delay to where gold does not respond, but other metals still respond. By just these two delay settings, you can tell if you have gold or not, even "just" discriminates against pull tabs I had my wife do a blind test with various samples of target, and I was able to pick the gold out every time.

I could not achieve that with your existing code, so feel it is a worthwhile improvement to the project.

Here's the sketch SaltyDog was refering to.

https://www.geotech1.com/forums/file...etch?id=420111

Nano pins 8 and 10 need to be swapped like this

https://www.geotech1.com/forums/foru...069#post420069

The one he linked that also does f modulation requires an extra mod as explained in the post.

[SaltyDog]

I asked cause you linked to the sketch that also does the f modulation. Anyway the timing is just the same.

Yep, sorry, should have linked earlier on. I will try the freq modulation post wedding and update your thread then, no time now. I have also ordered an OLED for the delay display.

[Teleno]

No, just with your release prior to that.

I asked cause you linked to the sketch that also does the f modulation. Anyway the timing is just the same.

[SaltyDog]

So you tried the frequency/amplitude modulation. How did it go?

No, just with your release prior to that.

[Teleno]

Qiaozhi Hi George, just letting you know that with the code from Teleno on https://www.geotech1.com/forums/foru...ge4#post420147 thread, I have been able to get a degree of discrimination for gold .. the method is:

Set the delay to where it is most sensitive for gold. REDUCE the delay to where gold does not respond, but other metals still respond. By just these two delay settings, you can tell if you have gold or not, even "just" discriminates against pull tabs I had my wife do a blind test with various samples of target, and I was able to pick the gold out every time.

I could not achieve that with your existing code, so feel it is a worthwhile improvement to the project.

So you tried the frequency/amplitude modulation. How did it go?

[SaltyDog]

Qiaozhi Hi George, just letting you know that with the code from Teleno on https://www.geotech1.com/forums/foru...ge4#post420147 thread, I have been able to get a degree of discrimination for gold .. the method is:

Set the delay to where it is most sensitive for gold. REDUCE the delay to where gold does not respond, but other metals still respond. By just these two delay settings, you can tell if you have gold or not, even "just" discriminates against pull tabs I had my wife do a blind test with various samples of target, and I was able to pick the gold out every time.

I could not achieve that with your existing code, so feel it is a worthwhile improvement to the project.

[SaltyDog]

To answer your question the aim was to standardise the software loop time and ISR times to allow the ISR to complete without interrupting itself thus causing jitter. Most of the ISR time was spent bit banging the outputs, hence fast digital write instead. While attempting that it became obvious that other sections of code were adding to loop time, such as floating point maths in the pulse timing routine. So in for a penny.... I eliminated conditional statements as stated in the comments and used integer variables wherever possible. As stated by Teleno it is not about absolute accuracy but more about consistancy in pulse timing by hardware (preferred) and/or software.

Perfect, thanks ...