Electrical – Measure rpm of a DC motor using two timers/counter and IR sensor (atmega 328p)

I'm trying to measure the speed of a DC motor. I have an IR speed sensor connected to the T1 pin(PD5) of an ATMega 328p. My idea is when there is a change from LOW to HIGH, a counter is incremented and for this I'm using TIMER2 to create a 1 second interrupt and TIMER1 to count the pulses.

First problem is that the TCNT1 is giving me random values even if I pass only one time in the sensor (counts from 0 to 200).

Second problem is that its counting both changes from LOW to HIGH and HIGH to LOW.

My sensor is www.botnroll.com/pt/sensores/957-motor-speed-sensor-module.html

Here is my current code:

#include <avr/io.h>
#include <avr/interrupt.h>

volatile unsigned int overflow;
volatile unsigned int timer_counts = 0;

void conf_timer2()
{
    //prescaler = 256
    TCCR2B |= (1 << CS22)|(1 << CS21);

    TCNT2 = 0;
    // overflow interrupt
    TIMSK2 |= (1 << TOIE2);

    overflow = 0;
}

void config_timer1()
{
    TCCR1B |= (1<<CS10) | (1<<CS11) | (1<<CS12);    //rising edge
    TIMSK1 |= (1<<TOIE1);   //enable overflow interrupt

    DDRD &= ~(1 << DDB5);
    //PORTD |= (1 << PORTD5);
}

ISR(TIMER2_OVF_vect)
{
    overflow++;
}

ISR(TIMER1_OVF_vect)
{
    //overflow1++; 
    //no need since it will never reach 65536 in 1 sec 
}

int main()
{
    sei();
    config_timer1();
    conf_timer2();
    char aux2[10];
    char aux1[10];

    unsigned int rpm;

    while(1)
    {       
    if(overflow >= 152) // for 1 sec
    {
        if(TCNT2 > 149) //for 1 sec 
        {
            timer_counts = TCNT1;
            rpm = timer_counts * 60;

            itoa(rpm, aux2, 10);
            itoa(timer_counts, aux1, 10);
            USART_putstring("Rot. per sec: "); //print values
            USART_putstring(aux1);
            USART_putstring("\n");
            USART_putstring("Rot. per min = ");
            USART_putstring(aux2);
            USART_putstring("\n");

            TCNT1 = 0;
            overflow = 0;
            rpm = 0;
        }
    }
}
return 0;

}

Any1 help is valuable!