Project 2 - Measuring distance of an object using ultrasonic sensor (HC-SR04)

Project 2 - Measuring distance of an object using ultrasonic sensor (HC-SR04)

Answers:

1. ATmega16 microcontroller needs to transmit at least 10 us trigger pulse to the HC-SR04 Trig Pin.
2. After getting a trigger pulse, HC-SR04 automatically sends eight 40 kHz sound waves and the microcontroller waits for rising edge output at the Echo pin.
3. When the rising edge capture occurs at the Echo pin which is connected to an input of ATmega16, start Timer of ATmega16 and again wait for a falling edge on the Echo pin.
4. As soon as the falling edge is captured at the Echo pin, the microcontroller reads the count of the Timer. This time count is used to calculate the distance to an object.

Calculation (distance in cm) (H1)

Sound velocity = 343.00 m/s = 34300 cm/s

The distance of Object (in cm) = Sound velocity *Timer/2

= 32300*Timer/2

= 17150*Timer

Now, here we have selected an internal 8 MHz oscillator frequency for ATmega16, with No-presale for timer frequency. Then time to execute 1 instruction is 0.125 us.

So, the timer gets incremented after 0.125 us time elapse.

= 17150 x (TIMER value) x 0.125 x 10^-6 cm

= 0.125 x (TIMER value)/58.30 cm

= (TIMER value) / 466.47 cm

CODE:

OUTPUT: