Calculating speed using an IR sensor

I am using the sharp GP2Y0A21YK IR sensor. The code below (taken from allows me to calculate the proximity of an object from the sensor

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 - Serial.println(distance); // print the distance delay(100); // arbitary wait time.


Now I need to calculate the speed of an object as it moves away or closer to the sensor. any help?

speed is rate of change of distance over time. Thus if you measure distance d1 at time t1, d2 at t2, calculate (d2-d1)/(t2-t1).

how about float distance TFDU4301 IR sensor arduino code ?