Reading and analyzing reflected signal in metal detector

[Yakhor]

Hi every one,
I am working in PI metal detector but I have problem in reading reflected signal in pin A0 in arduino.

pls any one help me how I can read signal and process it and then output it to the speaker (programmly)

I want to write arduino code to felezjoo PI me
tal detector, I know it has hex file but I need my code to modify it as I need.
I use arduino UNO.
thanks.

[F117]

Hi,
Do you want to mimic / emulate the felezjoo using an Arduino board ?
For all my Arduino (nano) projects, I standardize on cheap graphical OLED displays instead of the old-fashioned LCDs.
Something like https://www.tinytronics.nl/shop/nl/d...pixels-wit-i2c
Connect it to the Arduino over SPI or I2C. I use this library to write/draw on it : https://github.com/olikraus/U8g2_Arduino
As a user interface, I don't use pushbuttons but a rotary encoder / pushbutton combination.
This allows you to scroll up/down + select a menu item with the pushbutton.

A possible scenario could be ( many examples on this forum - and also in the book "inside the metal detector"):
You start by giving a pulse to the BS170/IRF. You can make the pulse width variable ( 50 - 500 microseconds eg).
You can also make the pulse frequency variable ( 50 / 60 Hz mains interference ).
After this pulse, you can take 1 or more samples on the analog input.
Measure the input pulse with an oscilloscope first.
Make sure that the DC level you want to measure is within range of the analog input and in range of the ADC reference voltage.
Make the delay of the analog samples after the current pulse adjustable in a menu.
If you take multiple samples per pulse, you can do all sorts of calculations on them ( add / subtract / ....)
Put the results in eg a moving average array.
Compare the actual sample with the average sample.
Make the audio threshold adjustable and produce a tone (with the Arduino tone() function .. ) that represents the deviation of the current sample with the average.

Using an OLED / rotary encoder combination opens up a lot more possibilities and is very easy to implement on the Arduino.
If only I had more time, I would love to build a detector like this...

[waltr]

What does the signal out of the preamp look like on an O'scope???
This needs to be the FIRST thing you do to ensure the TX pulse, flyback and target decay signal is what you expect.
.

[David_1]

What does the signal out of the preamp look like on an O'scope???
This needs to be the FIRST thing you do to ensure the TX pulse, flyback and target decay signal is what you expect.
.

Is there a how to, or a video explaining more about this, I am trying to learn, but a little on topic reading would great

[waltr]

Lots of threads about building and troubleshooting PI detectors...
Spend some time searching the forum and reading about PI detector. Take notes and copy/paste info to a doc to reference.

There are a few videos posted, I never like video instructions much so tend to ignore them in favor of good written description, drawings and scope pictures.

PI's are simple in theory but have subtle characteristics to get them working well.

Do you have a O'scope? If not beg, borrow or buy one.

[David_1]

PI's are simple in theory but have subtle characteristics to get them working well.

Do you have a O'scope? If not beg, borrow or buy one.

Oscope several and a spectrum analyzer just bought a decent LCR meter. So I can measure it I do digital electronics quite well and fail to understand the black art of analog LOL

[waltr]

Keep experimenting and reading. It will come to you.

Do you have the "Inside the metal detector" book? This is a great resource on getting started.

[David_1]

Keep experimenting and reading. It will come to you.

Do you have the "Inside the metal detector" book? This is a great resource on getting started.

not allowed to answer that !

[kt315]

I know it has hex file but I need my code to modify it as I need.

---
thinking you can take a code from George and modify. the project VOODOO in a book The Voodoo Project - Published October 2020 - Geotech Forums (geotech1.com)

[Yakhor]

Hi,
Do you want to mimic / emulate the felezjoo using an Arduino board ?
For all my Arduino (nano) projects, I standardize on cheap graphical OLED displays instead of the old-fashioned LCDs.
Something like https://www.tinytronics.nl/shop/nl/d...pixels-wit-i2c
Connect it to the Arduino over SPI or I2C. I use this library to write/draw on it : https://github.com/olikraus/U8g2_Arduino
As a user interface, I don't use pushbuttons but a rotary encoder / pushbutton combination.
This allows you to scroll up/down + select a menu item with the pushbutton.

A possible scenario could be ( many examples on this forum - and also in the book "inside the metal detector"):
You start by giving a pulse to the BS170/IRF. You can make the pulse width variable ( 50 - 500 microseconds eg).
You can also make the pulse frequency variable ( 50 / 60 Hz mains interference ).
After this pulse, you can take 1 or more samples on the analog input.
Measure the input pulse with an oscilloscope first.
Make sure that the DC level you want to measure is within range of the analog input and in range of the ADC reference voltage.
Make the delay of the analog samples after the current pulse adjustable in a menu.
If you take multiple samples per pulse, you can do all sorts of calculations on them ( add / subtract / ....)
Put the results in eg a moving average array.
Compare the actual sample with the average sample.
Make the audio threshold adjustable and produce a tone (with the Arduino tone() function .. ) that represents the deviation of the current sample with the average.

Using an OLED / rotary encoder combination opens up a lot more possibilities and is very easy to implement on the Arduino.
If only I had more time, I would love to build a detector like this...

Hi,
first I am sorry I were in my weekly vacation.
ok now I give a pulse to the BS170/IRF with frequency of 200 HZ and duty cycle of 95% approximately, because the signal in the original was like this when I measured it.
so I will do as you mention, and I hope it will come.

thank you very much Mr.F117

[Yakhor]

What does the signal out of the preamp look like on an O'scope???
This needs to be the FIRST thing you do to ensure the TX pulse, flyback and target decay signal is what you expect.
.

Hi,
I am sorry I were in my weekly vacation.
I measure all signals in the original copy, and I give pulse for coil as in the original.
the feedback signal is irregular, my problem is how to measure irregular analog signal in arduino.

thanks

[Yakhor]

I know it has hex file but I need my code to modify it as I need.

---
thinking you can take a code from George and modify. the project VOODOO in a book The Voodoo Project - Published October 2020 - Geotech Forums (geotech1.com)

Thanks Mr.kt315, I will read it and try to benefit from it.
I hope it will come nearly.

thanks again

[Hattusa]

Hi,
I am sorry I were in my weekly vacation.
I measure all signals in the original copy, and I give pulse for coil as in the original.
the feedback signal is irregular, my problem is how to measure irregular analog signal in arduino.

thanks

did you solve your problem? If the problem is not resolved, I will help you.