SHARP 2Y0D21

GP2Y0D21YK0F is a distance measuring sensor unit, composed of an integrated combination of PSD (position sensitive detector) , IRED (infrared emitting diode) and signal processing circuit.

http://sharp-world.com/products/device/lineup/data/pdf/datasheet/gp2y0d21yk_e.pdf

Code arduino http://arduino103.blogspot.fr/2011/06/detecteur-de-proximite-infrarouge-sharp.html

D'après http://luckylarry.co.uk/arduino-projects/arduino-using-a-sharp-ir-sensor-for-distance-calculation/

// Sharp GP2Y0A02 
int IRpin = 1;                                    // analog pin for reading the IR sensor

void setup() {
  Serial.begin(9600);                             // start the serial port
}

void loop() {
  float volts = analogRead(IRpin)*0.0048828125;   // value from sensor * (5/1024) - if running 3.3.volts then change 5 to 3.3
  float distance = 65*pow(volts, -1.10);          // worked out from graph 65 = theretical distance / (1/Volts)S - luckylarry.co.uk
  Serial.println(distance);                       // print the distance
  delay(100);                                     // arbitary wait time.
}