Spirit PI 4 Pro A

New version (Beta):

In this version this metal detector works with a smartphone or without a smartphone with the possibility of adding an LCD screen. Now Spirit Pi is more stable and reaches more depth. The diagram and the PCB can be found below, also in the file you will download will be gerber file in case someone wants to order the PCB on the JLCPCB page. JLCPCB is a page where we can order the PCBs we want for a very low price, we just have to upload gerber file of the circuit and that’s it.


Now in this detector we have 3 buttons: “+”, “-“, and the “M” menu. With these buttons we can adjust the pulse width, sensitivity and frequency. Instead of the TL072 amplifiers we will use NE5532. The micro controller will use an Arduino nano. The coil is still 25 turns with 0.5 mm wire and the radius 20 cm.


The components I usually buy on Aliexpress for the low price. In this way we can make a good metal detector and spend little money. Below I will leave the links where you can buy these components to make this metal detector!

44 thoughts on “Spirit PI 4 Pro A”

  1. Hello Sergey,

    I have a bunch of TLV2375IN Quad-Amp laying around and would to use one to build a Spirit Pro, because I don’t have any NE5532 at hand. The TLV is noisier and a bit slower (2.4 V/us) and has a smaller bandwidth, 3 MHz. More critically, in split supply it accepts a maximum of +/- 8 Vdc.
    Do you believe it can be used to build a Spirit Pro 4 without serious performance degradation?


    1. Hello Gustavo! It is difficult to say without to see the op-amp under the oscilloscope. It will work but maybe you will need to adjust some values of resistance. You can try if you have some problem ask me i try to help you. Make sure the pinse in your op amp is the same like ne5532

      1. Hello Sergey,

        Thanks by your answer. The whole problem os that I don’t have a scope. I was plannig to use the smartphone with a custom board as a simple scope (the SmartScope app is a great one) but, somehow, I fried the phone’s ADC when trying to make the RFinder circuit work (it didn’t work with BC558, A733P, C945P. I Googled about the somewhat unusual Peltz oscillator topology used in the RFinder circuit, but it didn’t help).
        I plan to make a simple scope using an Uno/nano board, but I guess it may not be enough for a decent circuit analysis.

        Anyway, I will build a Spirit PI next month (awaiting Aliexpress delivery…) and, if time allows, try the Pro 4 version. Pinout is easy to solve, I redraw every schematic in CAD before a try to ensure pinouts and PCB layout are appropriate before heating the soldering iron.

        I’ll report the success (or failure) for you when done, just as a feedback. If things go really well, I plan to make an all-smd version just to make thinks really, really portable.

  2. Eduardo Vergara Gonzalez


    1. A simple algorithm using machine learning can be developed to discriminate between many metals, including a rough estimation of size and depth. What is needed is a reliable and stable circuit, the full capture of the pulse decay and a lot of samples taken from real metals in real terrain. If data is available, will be a pleasure for me to run the methods and implement the algorithm in an Arduino board.

  3. Sergey,

    Other very useful, and easy to implement, option for the metal detector is a flashlight. Using few white LEDs near the coil should work without much (if any) interference, and a single tactile switch can be used to turn the light On, Off, or to dim the light when continuously pressed. A double clink event resets the light to maximum power. Easy to implement with already available libraries for Arduino.

  4. Hi Neco
    I want build the Spirit Pi in ESP32 Version, but the App is not working at my Smartphone. The Smartphone is an LG G5 with Android 8.0.0
    Have you an Idea wath is the Problem.

    best regards

  5. Hi Neco, great job. I want build Spirit PI 4 Pro A.
    A quick question for you :
    based on schematics and video R3 is a trimmer and R14 is a potentiometer.
    Am I coorect ?
    can you tell how to tune R3 ?
    Several resistors have a * what does it mean ?! Several resistors (I don’t know if also other components) have different values in the schematic compared with the BOM. What are the right values ?
    thank you

  6. Hello neco your project is very good and interesting l want to build this project. can you help me about hex file for arduino? Tanks

  7. Martin Brightmore

    Hi Sergey
    Working fine now.
    Discovered that Sens is default is 255 but needs to be around 10 to be effective>

  8. Hi Neco,
    I am having difficulty with the device. The balancing time is very short and the ring is not detecting anything. Pl help.

  9. Olá NECO. Montei o seu projeto. Ficou muito bom. Funciona perfeitamente. Fiz pequenas modificações devido aos componentes que utilizei. Parabéns pelo seu trabalho. Tenho somente uma dúvida: como faço para mostrar o nível da bateria no display?

  10. Hallo Sergey ,
    Beautiful project, I have also started it and have everything ready only it is impossible for me to adjust the voltage on pin 1 of the NE5532 to 8 Volt, whatever setting I do the voltage on pin 1 always remains 11.35v, at I also measure the voltage on pin 3 and it varies nicely between 2 and 10 volts, I have already exchanged the NE5532 with 2 other copies but the result is always the same, maybe you know what to do? Thanks Alex Jacobs Belgium

  11. Hi Sergey,
    A great project, I have rebuilt it in the meantime, but I cannot adjust the voltage on pin 1 of the NE5532 to 8v, regardless of the position of the trimpot, the voltage remains at 11.35v. I have already replaced the Ne5532 with 2 other copies but without success, you have some idea what is going on. Thanks Alex Jacobs Belgium

  12. Mohammad alzoubi

    Hi neco
    Is the PDF file for the pcb board found in the version Spirit PI 4 Pro A does it support esp32 or ardeno nano

  13. Hi Neco,
    I would like to make your Spirit Pi 4 pro but I don’t find gerber files for the controls pcb (3 buttons). Did you integrate this new function on main PCB ?

  14. Hello Sir
    Spirit PI 4 Pro A is very nice project. I want to download schematic but I’m facing update problem in 2nd page.If possible please help me.

  15. Hello Sergey,

    Interesting work. Do you have a system or a way to use coils with 2 or 3 windings rather than 1? I am more for looking to build something that works very well without looking at the price tag…. Would you be able to have something built like a hi end PI metal detector? What about discrimination or metal indication?


  16. Hello Neco , you did a great job . I am buildind the lcd version , can you explain why you drive the signal via Q1 and not directly to SU2 ? Could you give some light over the balancing process ?
    Best regards

  17. hello neco
    i have a problem
    i follow u step by step but when turn it on stay on balancing…
    i adjust the resistor variable and nothing change
    plz help me

  18. hello neco
    i made this project but doesn work with me like yours
    its stay at balancing when turn it on
    i adjust the resisitor variabl R16 and nothing change
    but where is the position L1-2 of resistor 1M on the pcb ???
    i think my spirit pi doesnt detect the coil …
    can you help me plz ?

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