adapting am radio metal detector to arduino board

I have seen on the net simple metal detector circuit which you can build yourself in 20 mint. See link www.talkingelectronics.com/html/MetalDetector.html to make clear to my last post, I used this ciruit and adapt it to arduino board to make arduino metal detector see vedio  https://www.youtube.com/watch?v=1Vw4EAmZyls  use the same sketch as befor-

// Arduino based metal detector

// (C)Dzl july 2013

// http://dzlsevilgeniuslair.blogspot.dk/

// Connect search coil oscillator (20-200kHz) to pin 5

// Connect piezo between pin 13 and GND

// Connect NULL button between pin 12 anf GND

// REMEMBER TO PRESS NULL BUTTON AFTER POWER UP!!

#define SET(x,y) (x |=(1<<y))                 //-Bit set/clear macros

#define CLR(x,y) (x &= (~(1<<y)))             // |

#define CHK(x,y) (x & (1<<y))                 // |

#define TOG(x,y) (x^=(1<<y))                  //-+

unsigned long t0=0;         //-Last time

int t=0;                    //-time between ints

unsigned char tflag=0;      //-Measurement ready flag

float SENSITIVITY= 1000.0;  //-Guess what

//-Generate interrupt every 1000 oscillations of the search coil

SIGNAL(TIMER1_COMPA_vect)

{

  OCR1A+=1000;

  t=micros()-t0;

  t0+=t;

  tflag=1;

}

void setup()

{

  pinMode(13,OUTPUT);    //-piezo pin

  digitalWrite(12,HIGH); //-NULL SW. pull up

  //-Set up counter1 to count at pin 5

  TCCR1A=0;

  TCCR1B=0x07;

  SET(TIMSK1,OCF1A);

}

//-Float ABS

float absf(float f)

{

  if(f<0.0)

    return -f;

  else

    return f;

}

int   v0=0;  //-NULL value

float f=0;   //-Measurement value

unsigned int FTW=0;    //-Click generator rate

unsigned int PCW=0;    //-Click generator phase

unsigned long timer=0; //-Click timer

void loop()

{

  if(tflag)

  {

    if(digitalRead(12)==LOW)  //-Check NULL SW.

      v0=t;                   //-Sample new null value

    f=f*0.9+absf(t-v0)*0.1;   //-Running average over 10 samples

    tflag=0;                  //-Reset flag

    float clf=f*SENSITIVITY;  //-Convert measurement to click frequency

    if(clf>10000)           

      clf=10000;

    FTW=clf;

  }

 

  //-Click generator

  if(millis()>timer)

  {

    timer+=10;

    PCW+=FTW;

    if(PCW&0x8000)

    {

      digitalWrite(13,HIGH);

      PCW&=0x7fff;

    }

    else

      digitalWrite(13,LOW);

  }

}

It does not detect gold, only metals.

arduino metal detector

Arduino metal detector

Arduino metal detector

I have seen arduino metal detector circuit on net. see circuit

And see sketch cod: https://dl.dropboxusercontent.com/u/2248531/blog/metal_detector/metal_detector.ino

I have tried it on my arduino Uno r3 at mega 328 r-b ,it did not work. When up

loading sketch (library found not working).some did work for them, some are not.

To check if my circuit correct and working

 I checked circuit by powering it with 9 v battery near am radio and moved piece of metal over the coil, radio responding to metal movement.  

I think the reason was the timers.

He mentioned oscillator circuit feeds at around 160kHz signal to pin 5 of the Arduino

So checking if reason not working was timers of my arduino, I choose similar circuit with less kHz pulsing and it was am radio blf metal detector oscillator feeds 120 kHz. See circuit

And to make it work on my arduino with same code sketch, I just connected a wire from transistor E side to arduino pin 5 digital and reload same sketch and that is it, it worked. See modified sketch