// Arduino Five Coil Metal Detector 

/* V21 - Production Version with dynamic thresholds and auto calibrate, Adjusted LED Brightness to maximum

*/

int ledthreshold1 = 40;
int ledthreshold2 = 40;
int ledthreshold3 = 40;
int ledthreshold4 = 40;
int ledthreshold5 = 40;

int threshdiff = 15; // Add to average to become specific threshold where LED will light (Changed V21 from 25 to 20)

long pulse1 = 0; // Stores the length of pulses in microseconds  
long pulse2 = 0; // Stores the length of pulses in microseconds
long pulse3 = 0; // Stores the length of pulses in microseconds
long pulseav = 0; // Stores value of output for calibration

int minthresh = 20; // Minimum threshold for baseline reading 
int startdelay = 700; // Start at this value and work down for calibration


long pcounterA; // Counts the number of pulses in each cycle
long pcounterB; // Counts the number of pulses in each cycle
long pcounterC; // Counts the number of pulses in each cycle
long pcounterD; // Counts the number of pulses in each cycle
long pcounterE; // Counts the number of pulses in each cycle


int dly1 = 300; // Delay before sampling pulsewidth A
int dly2 = 300; // Delay before sampling pulsewidth B
int dly3 = 300; // Delay before sampling pulsewidth C
int dly4 = 300; // Delay before sampling pulsewidth D
int dly5 = 300; // Delay before sampling pulsewidth E


void setup()
{

Serial.begin(115200); // Setupserial interface for test data outputs

pinMode(2,INPUT); // Calibrate Button

pinMode(3,OUTPUT); // Pulse output from D3 Arduino
pinMode(4,INPUT); // Signal from LM339 in read by D4 on Arduino

pinMode(5,OUTPUT); // Pulse output from D5 Arduino
pinMode(6,INPUT); // Signal from LM339 in read by D6 on Arduino

pinMode(7,OUTPUT); // Pulse output from D5 Arduino
pinMode(8,INPUT); // Signal from LM339 in read by D6 on Arduino

pinMode(9,OUTPUT); // Pulse output from D5 Arduino
pinMode(10,INPUT); // Signal from LM339 in read by D6 on Arduino

pinMode(11,OUTPUT); // Pulse output from D5 Arduino
pinMode(12,INPUT); // Signal from LM339 in read by D6 on Arduino

pinMode(14,OUTPUT); // LED output to indicate a find on A0
pinMode(15,OUTPUT); // LED output to indicate a find on A1
pinMode(16,OUTPUT); // LED output to indicate a find on A2
pinMode(17,OUTPUT); // LED output to indicate a find on A3
pinMode(18,OUTPUT); // LED output to indicate a find on A4



}
void loop()
{
// Reset the pulse counter to zero for this cycle of waveform
pcounterA = 0;
pcounterB = 0;
pcounterC = 0;
pcounterD = 0;
pcounterE = 0;


// Auto Calibrate Coil Sensitivity if button pushed

if((digitalRead(2) == LOW) ){ 
  delay(100); // Debounce by waiting then checking again
  if((digitalRead(2) == LOW) ){ 
  // Carry out operation
  
  calibrate(); // Sets individual dly variable
  

  }
}



// Pulse and read Coil A three times  ---------------------------------------------

digitalWrite(7,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(7,LOW); // Set low on output pin
delayMicroseconds(dly1); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterA =   pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20);

digitalWrite(7,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(7,LOW); // Set low on output pin
delayMicroseconds(dly1); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterA =  pcounterA + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20);

digitalWrite(7,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(7,LOW); // Set low on output pin
delayMicroseconds(dly1); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterA =   pcounterA + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20);


// Pulse and read Coil B three times  ---------------------------------------------

digitalWrite(5,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(5,LOW); // Set low on output pin
delayMicroseconds(dly2); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterB =   pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20);

digitalWrite(5,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(5,LOW); // Set low on output pin
delayMicroseconds(dly2); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterB =   pcounterB + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20);

digitalWrite(5,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(5,LOW); // Set low on output pin
delayMicroseconds(dly2); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterB =   pcounterB + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20);

// Pulse and read Coil C three times ---------------------------------------------

digitalWrite(11,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(11,LOW); // Set low on output pin
delayMicroseconds(dly3); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterC = pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20);

digitalWrite(11,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(11,LOW); // Set low on output pin
delayMicroseconds(dly3); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterC = pcounterC + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20);

digitalWrite(11,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(11,LOW); // Set low on output pin
delayMicroseconds(dly3); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterC = pcounterC + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20);



// Pulse and read Coil D three times   ---------------------------------------------

digitalWrite(3,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(3,LOW); // Set low on output pin
delayMicroseconds(dly4); // Wait before reading pulses


pcounterD = pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20);

digitalWrite(3,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(3,LOW); // Set low on output pin
delayMicroseconds(dly4); // Wait before reading pulses


pcounterD = pcounterD + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20);

digitalWrite(3,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(3,LOW); // Set low on output pin
delayMicroseconds(dly4); // Wait before reading pulses


pcounterD = pcounterD + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20);



// Pulse and read Coil E three times     ---------------------------------------------

digitalWrite(9,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(9,LOW); // Set low on output pin
delayMicroseconds(dly5); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterE =   pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20);

digitalWrite(9,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(9,LOW); // Set low on output pin
delayMicroseconds(dly5); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterE =   pcounterE + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20);

digitalWrite(9,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(9,LOW); // Set low on output pin
delayMicroseconds(dly5); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pcounterE =   pcounterE + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20);

/*

Serial.print(pcounterA);
Serial.print(" ");
Serial.print(pcounterB);
Serial.print(" ");
Serial.print(pcounterC);
Serial.print(" ");
Serial.print(pcounterD);
Serial.print(" ");
Serial.print(pcounterE);

// Show delay variables

Serial.print("      ");
Serial.print(dly1);
Serial.print(" ");
Serial.print(dly2);
Serial.print(" ");
Serial.print(dly3);
Serial.print(" ");
Serial.print(dly4);
Serial.print(" ");
Serial.print(dly5);

Serial.print("      ");
Serial.print(pulse1);
Serial.print(" ");
Serial.print(pulse2);
Serial.print(" ");
Serial.print(pulse3);
Serial.print(" ");
Serial.println(pulseav);

*/

// Display results
digitalWrite(14,LOW); // Set the output pin to Low to deactivate the LED

if(pcounterA < ledthreshold1)
{
digitalWrite(14,HIGH); // Set the output pin to high to activate the LED
}

digitalWrite(15,LOW); // Set the output pin to Low to deactivate the LED

if(pcounterB < ledthreshold2)
{
digitalWrite(15,HIGH); // Set the output pin to high to activate the LED
}

digitalWrite(16,LOW); // Set the output pin to Low to deactivate the LED

if(pcounterC < ledthreshold3)
{
digitalWrite(16,HIGH); // Set the output pin to high to activate the LED
}

digitalWrite(17,LOW); // Set the output pin to Low to deactivate the LED

if(pcounterD < ledthreshold4)
{
digitalWrite(17,HIGH); // Set the output pin to high to activate the LED
}

digitalWrite(18,LOW); // Set the output pin to Low to deactivate the LED

if(pcounterE < ledthreshold5)
{
digitalWrite(18,HIGH); // Set the output pin to high to activate the LED
}



/* delay(10);  // Sets up LED brightness
// Turn off all LEDs
digitalWrite(14,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(15,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(16,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(17,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(18,LOW); // Set the output pin to Low to deactivate the LED
*/


}


// Subroutines


void calibrate()      {
  
// Turn off all LEDs
digitalWrite(14,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(15,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(16,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(17,LOW); // Set the output pin to Low to deactivate the LED
digitalWrite(18,LOW); // Set the output pin to Low to deactivate the LED

// Calibrate Coil A delay threshold ------------------------------------------------------------

dly1 = startdelay; // Start with very high threshold and work down in steps of 10
pulseav = 0;


while (pulseav <= minthresh ){

  digitalWrite(7,HIGH); // Set the output pin to high
  delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
  digitalWrite(7,LOW); // Set low on output pin
  delayMicroseconds(dly1); // Wait before reading pulses

  // Measure the number of pulses in each cycle produced by the LC circuit

  pulse1 =   pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20);  

  digitalWrite(7,HIGH); // Set the output pin to high
  delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
  digitalWrite(7,LOW); // Set low on output pin
  delayMicroseconds(dly1); // Wait before reading pulses

  // Measure the number of pulses in each cycle produced by the LC circuit

  pulse2 =   pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20);
  
    digitalWrite(7,HIGH); // Set the output pin to high
  delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
  digitalWrite(7,LOW); // Set low on output pin
  delayMicroseconds(dly1); // Wait before reading pulses

  // Measure the number of pulses in each cycle produced by the LC circuit

  pulse3 =   pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20)+ pulseIn(8,HIGH,20) + pulseIn(8,HIGH,20);
  
  pulseav = (pulse1 + pulse2 + pulse3)/3;
  
  // Decrement threshold if output too low
  if(pulseav < minthresh) {
    dly1 = dly1 - 10;
    }
  } 
  // Flash LED to prove something done
  digitalWrite(14,HIGH); // Set the output pin to high to activate the LED
  delay(5);
  digitalWrite(14,LOW); // Set the output pin to high to activate the LED

ledthreshold1 = pulseav + threshdiff; 

// Calibrate Coil B delay threshold  ------------------------------------------------------------

dly2 = startdelay; // Start with very high threshold and work down in steps of 10
pulseav = 0;


while (pulseav <= minthresh ){

digitalWrite(5,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(5,LOW); // Set low on output pin
delayMicroseconds(dly2); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse1 =   pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20);

digitalWrite(5,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(5,LOW); // Set low on output pin
delayMicroseconds(dly2); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse2 =   pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20);
  
digitalWrite(5,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(5,LOW); // Set low on output pin
delayMicroseconds(dly2); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse3 =   pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20)+ pulseIn(6,HIGH,20) + pulseIn(6,HIGH,20);
  
  pulseav = (pulse1 + pulse2 + pulse3)/3;
  
  // Decrement threshold if output too low
  if(pulseav < minthresh) {
    dly2 = dly2 - 10;
    }
  } 
  // Flash LED to prove something done
  digitalWrite(15,HIGH); // Set the output pin to high to activate the LED
  delay(5);
  digitalWrite(15,LOW); // Set the output pin to high to activate the LED
  
  ledthreshold2 = pulseav + threshdiff; 
  

// Calibrate Coil C delay threshold  ------------------------------------------------------------

dly3 = startdelay; // Start with very high threshold and work down in steps of 10
pulseav = 0;


while (pulseav <= minthresh ){

digitalWrite(11,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(11,LOW); // Set low on output pin
delayMicroseconds(dly3); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse1 = pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20);

digitalWrite(11,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(11,LOW); // Set low on output pin
delayMicroseconds(dly3); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse2 = pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20);
  
digitalWrite(11,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(11,LOW); // Set low on output pin
delayMicroseconds(dly3); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse3 = pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20)+ pulseIn(12,HIGH,20) + pulseIn(12,HIGH,20);
  
  pulseav = (pulse1 + pulse2 + pulse3)/3;
  
  // Decrement threshold if output too low
  if(pulseav < minthresh) {
    dly3 = dly3 - 10;
    }
  } 
  // Flash LED to prove something done
  digitalWrite(16,HIGH); // Set the output pin to high to activate the LED
  delay(5);
  digitalWrite(16,LOW); // Set the output pin to high to activate the LED
  
ledthreshold3 = pulseav + threshdiff; 


// Calibrate Coil D delay threshold  ------------------------------------------------------------

dly4 = startdelay; // Start with very high threshold and work down in steps of 10
pulseav = 0;

while (pulseav <= minthresh ){

digitalWrite(3,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(3,LOW); // Set low on output pin
delayMicroseconds(dly4); // Wait before reading pulses


pulse1 = pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20);

digitalWrite(3,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(3,LOW); // Set low on output pin
delayMicroseconds(dly4); // Wait before reading pulses


pulse2 = pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20);
  
digitalWrite(3,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(3,LOW); // Set low on output pin
delayMicroseconds(dly4); // Wait before reading pulses


pulse3 = pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20)+ pulseIn(4,HIGH,20) + pulseIn(4,HIGH,20);
  
  pulseav = (pulse1 + pulse2 + pulse3)/3;
  
  // Decrement threshold if output too low
  if(pulseav < minthresh) {
    dly4 = dly4 - 10;
    }
  } 
  // Flash LED to prove something done
  digitalWrite(17,HIGH); // Set the output pin to high to activate the LED
  delay(5);
  digitalWrite(17,LOW); // Set the output pin to high to activate the LED
  
  ledthreshold4 = pulseav + threshdiff; 
  

// Calibrate Coil E delay threshold  ------------------------------------------------------------

dly5 = startdelay; // Start with very high threshold and work down in steps of 10
pulseav = 0;

while (pulseav <= minthresh ){

digitalWrite(9,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(9,LOW); // Set low on output pin
delayMicroseconds(dly5); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse1 =   pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20);


digitalWrite(9,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(9,LOW); // Set low on output pin
delayMicroseconds(dly5); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse2 =   pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20);

digitalWrite(9,HIGH); // Set the output pin to high
delayMicroseconds(5000); // Delay 5000 microseconds before setting low on output pin
digitalWrite(9,LOW); // Set low on output pin
delayMicroseconds(dly5); // Wait before reading pulses

// Measure the number of pulses in each cycle produced by the LC circuit

pulse2 =   pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20)+ pulseIn(10,HIGH,20) + pulseIn(10,HIGH,20);


  
  pulseav = (pulse1 + pulse2 + pulse3)/3;
  
  // Decrement threshold if output too low
  if(pulseav < minthresh) {
    dly5 = dly5 - 10;
    }
  } 
  // Flash LED to prove something done
  digitalWrite(18,HIGH); // Set the output pin to high to activate the LED
  delay(5);
  digitalWrite(18,LOW); // Set the output pin to high to activate the LED
  
  
  ledthreshold5 = pulseav + threshdiff; 
  

}