#define IR_PIN 3
#define TIME 3000

long nextUpdateTime = 0;
int collisionsCount = 0;
int irValue = 0;

int setup()
{
    Serial.begin(9600);
    pinMode(IR_PIN, INPUT);
    nextUpdateTime = millis() + TIME;
}

int loop()
{
    if (nextUpdateTime >= millis())
    {
        Serial.print("Pocet preruseni: ");
        Serial.println(collisionsCount);
        collisionsCount = 0;
        nextUpdateTime = millis() + TIME;
    }
    else
    {
        irValue = digitalRead(IR_PIN);
        if(irValue == HIGH)
        {
            collisionsCount++;
        }
    }
}