Making Robot Beep When Object Detected?

So, I have a working autonomous robot that works with a ping))) sensor and a rear motor and a directional forward motor. I have a piezo speaker laying around, not many specs on it but it works with the example sketch called 'toneMelody'. I'm not much of a code guy but ANY help is appreciated. I have an IF function and I should be able to just add something to it but im not sure what method/function to add. Heres my code.

/*
RC Car to Robot Conversion
by Nathan Brown

Used to convert an RC car into a robot that uses a PING sensor to avoid obstacles,
and an Arduino motor shield for motor control.

For more information see:
http://www.instructables.com/id/RC-Car-to-Robot/
Built atop sketch by Randy Sarafan which was
Built atop Ping example code by Tom Igoe
*/

// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 7;

void setup() {
  
  //establish motor direction toggle pins
  pinMode(12, OUTPUT); //drive motor -- HIGH = forwards and LOW = backwards
  pinMode(13, OUTPUT); //turn motor -- HIGH = left and LOW = right
  
  //establish motor brake pins
  pinMode(9, OUTPUT); //brake (disable) the drive motor
  pinMode(8, OUTPUT); //brake (disable) the turn motor

  //Turns brake off for drive motor
  digitalWrite(9, LOW); 

  //Turns brake on for turn motor
  digitalWrite(8, HIGH); 

  //Sets initial speed of drive motor
  analogWrite(3, 200);
  
  //Sets initial direction of drive motor
  digitalWrite(12, HIGH);
}

void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);

  //
  //if objects are less than 12 inches away
  //the robot reverses and turns to the right
  //for 2 seconds
  //
  
  if (inches < 24){
    
    //brake drive motor and pause 1/10 second
    digitalWrite(9, HIGH);
    delay(100);

    //
    //setting turn motor
    //
    
    //turn off brake for turn motor 
    digitalWrite(8, LOW);

    //set turn motor direction
    digitalWrite(13, HIGH);

    //activate turn motor
    analogWrite(11, 255);
    
    //
    //setting drive motor
    //
    
    //turn off brake of drive motor
    digitalWrite(9, LOW); 
    
    //set drive motor backwards direction
    digitalWrite(12, LOW);
    
    //activate the drive motor
    analogWrite(3, 200);

    
    //backup for 2 seconds
    delay(2000);
    
    //
    //stopping
    //
    
    //brake both motors
    digitalWrite(8, HIGH);
    digitalWrite(9, HIGH);
    
    
  }
  
  //
  //when nothing is within 12" 
  //the robot simply drives forwards
  //
  
  else{
    
    //
    //Setting drive motor
    //
    
    //set drive motor forward direction
    digitalWrite(12, HIGH);
    
    //turn off brake of drive motor
    digitalWrite(9, LOW);    
    
    //activate drive motor
    analogWrite(3, 200);
  
  
  }
  
  delay(100);
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

Maybe even add an LED flash to it?

There are two things I do not understand. The ping))) sensor assesses space using sonar. Not for detecting objects. How do you modify that kind of device for your robot? Also Piezoelectric speakers are often used as beepers in watches and other electronic gadgets. For what purpose are you going to use that kind of device?
I am sorry that I could not help with your code.

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if the piezo speaker uses less than 30 mA (almost all do unless it's extremely large) then you can attach the red wire to a arduino pin and the black to ground. to code it you would make the pin a output as usual. to play noise through it you would put this for example.
tone(piezoPin,2000,500);
this would play a 2000 hertz square wave on the piezo pin for 500 milliseconds

arduinopi:
if the piezo speaker uses less than 30 mA (almost all do unless it's extremely large) then you can attach the red wire to a arduino pin and the black to ground. to code it you would make the pin a output as usual. to play noise through it you would put this for example.
tone(piezoPin,2000,500);
this would play a 2000 hertz square wave on the piezo pin for 500 milliseconds

Thank you so much. I used this code and it worked perfectly, it plays a bit of a two tone beep when it realizes hey, theres 'something' 2 feet ahead of me, let me put my breaks on, play this for 200 milliseconds, wait 300 milliseconds, and play this tone for 300 milliseconds. :slight_smile: I'm showing it off at work tomorrow :smiley:

I am using your code also with some modifications for 2 drive wheels and a ping)) with a piezo buzzer on detection. usina a uno r3 thruhole a r3 motorshield, an a magician chassis from sparkfun. Here is the modded code. please help me toggle a led on when the piezo sounds.

// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 6;
const int piezoPin = 5;

void setup() {
 

  
  //establish motor direction toggle pins
  pinMode(12, OUTPUT); //drive motor A -- HIGH = forwards and LOW = backwards
  pinMode(13, OUTPUT); //drive motor B -- HIGH = forwards and LOW = backwards
  
  //establish motor brake pins
  pinMode(9, OUTPUT); //brake (disable) the drive A motor
  pinMode(8, OUTPUT); //brake (disable) the drive B motor

  //Turns brake off for drive A motor
  digitalWrite(9, LOW); 

  //Turns brake off for drive B motor
  digitalWrite(8, LOW); 

  //Sets initial speed of drive 1 motor
  analogWrite(3, 255);
  
  //Sets initial speed of drive 2 motor
  analogWrite(11, 255);
  
  //Sets initial direction of drive motor 1
  digitalWrite(12, LOW);
  
  //Sets initial direction of drive motor 2
  digitalWrite(13, LOW);
}

void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);

  //
  //if objects are less than 12 inches away
  //the robot reverses and turns to the right
  //for 2 seconds
  //
  
  if (inches < 12){
    
    
    //make a beep for indication of wall
    
    tone(piezoPin,2000,500);
    
    //brake drive motors 1 and 2 and pause 1/10 second
    digitalWrite(8, HIGH);
    digitalWrite(9, HIGH);
    delay(100);

    //
    //setting turn routine
    //
    
    //turn off brake for drive 1 and 2 motor 
    digitalWrite(8, LOW);
    digitalWrite(9, LOW);
    //set drive 1 and 2 motor direction
    digitalWrite(12, LOW);
    digitalWrite(13, HIGH);

    //activate drive 1 and 2 motor
    analogWrite(3, 200);
    analogWrite(11, 200);
    
   //backup for 2 seconds
    delay(800);
    
    //
    //stopping
    //
    
    //brake both motors
    digitalWrite(9, HIGH);
    digitalWrite(8, HIGH);
    
    
  }
  
  //
  //when nothing is within 12" 
  //the robot simply drives forwards
  //
  
  else{
    
    //
    //Setting drive motor
    //
    
    //set drive motor 1 forward direction
    digitalWrite(12, LOW);
    
    //set drive motor 2 forward direction
    digitalWrite(13, LOW);
    
    //turn off brake of drive motor1
    digitalWrite(9, LOW);    
    
    //turn off brake to drive motor 2
    digitalWrite(8, LOW);
    
    //activate drive motor 1
    analogWrite(3, 200);
  
    //activate drive motor 2
    analogWrite(11, 255);
  
  }
  
  delay(100);
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

the mismatched pwm settins are there to make it drive straight forward.