Calculating speed using an IR sensor

Using Arduino Sensors
1

I am using the sharp GP2Y0A21YK IR sensor. The code below (taken from http://luckylarry.co.uk/) 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 = 65pow(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.
}

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

2

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).

3

how about float distance TFDU4301 IR sensor arduino code ?