Ping Sensor

I've been sitting around the house sick with a cold. I haven't had the energy to do any serious projects but I threw together a little gadget to make people leave me alone.

It started out with a ping sensor. I mounted it on a Make protoshield I had and connected the on board LEDs to a couple pins. Then I figured it wouldn't take much to add a piezo buzzer I had.

What I ended up with is a ping sensor that turns on the green LED if you get within 12 inches and the red LED if you get within 6 inches. It also starts to play a tone if you're within 24 inches and increases the pitch as you get closer.

It's an easy little project to help you understand how the ping sensor, map function, if else function and tone library work.

Material:

1 x Arduino UNO

1 x ProtoShield (I used the Maker's Shield)

1 x Piezo Buzzer

1 x Ping Sensor (I used the Parallax one)

Several Jumper Wires

The Circuit:

It's a pretty simple circuit. Just connect power to the ping sensor. Connect the output from the ping sensor to pin 7. Connect the green LED to pin 5 and the red LED to pin 6. Connect the ground of the piezo to ground and the positive to pin 9.

The Code:

The code is pretty simple and I tried to leave it commented enough so you'll understand a little of what it's doing. It includes some serial commands for debugging or if you want to see what distance the ping sensor is reading. 

//sets the pin used for the ping sensor const int pingPin = 7; void setup() { // initialize serial communication: Serial.begin(9600); pinMode(5,OUTPUT); pinMode(6,OUTPUT); } 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); cm = microsecondsToCentimeters(duration); Serial.print(inches); Serial.print("in, "); Serial.print(cm); Serial.print("cm"); Serial.println(); //this section turns on the leds connected to pins 5 and 6 //dependant to the range if (inches < 12) { digitalWrite(5, 1); } else { digitalWrite(5, 0); } if (inches < 6) { digitalWrite(6, 1); } else { digitalWrite(6, 0); } //this maps the distance in inches to different pitches int thisPitch = map(inches, 24, 6, 120, 1500); // play the pitch if something is within 24 inches if (inches < 24) { tone(9, thisPitch, 10); } //changing this delay varies the sound from a solid tone //to a series of beeps delay(20); } 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; } long microsecondsToCentimeters(long microseconds) { // The speed of sound is 340 m/s or 29 microseconds per centimeter. // The ping travels out and back, so to find the distance of the // object we take half of the distance travelled. return microseconds / 29 / 2; }

Now just plop down on the couch and leave this on the coffee table and if anyone comes over to bother you they'll be turned away by blinking lights and an annoying tone.