Ultrasonic Distance Measurement using HC-SR04 sensor and PIC16f887

[ronexg]

Hello friends,

I want to share my small project...Ultrasonic distance measuring.

Compiler : MikroC Pro V.6
Xtal : 16MHz
Sensor : HC-SR04 from ebay
LCD : 20x4

Trigger pin was connected to RC3
Echo pin connected to RD0

Duration measure formula:

Duration(us) = TMR * Clock speed per instruction(Fosc/4) * timer pre-scale(1:4)

Clock speed per instruction(Fosc/4) : 16/4= 4MHz

Here i am using 1:1 Prescaler

So we get us = TMR*0.25*1............ 4MHz == 250 Nano sec == 0.25 us
for distance in centemeter divide by 58

Suppose we get 9327 as TMR value, the distance in mm is: (9327/58)*25 == 4020 mm (25 is 0.25 * 100 for avoiding floating value)

 

[paulfjujo]

hello,

Good application !
Thank's for sharing..

you can also increase accuracy by adding air temperature measurement ,
to correct sound speed in the air... you can earn any % of accuracy..

// Via la mesure de temperature LM35DZ en °C
// reajuste  la vitesse son dans l'air f(Temperature)
// y = 0,5803x + 328,39
     Sound_Speed= Filtered_Temp *0.5803 + 328.39;
     fltToa (Sound_Speed, ValFt2,1); // 1 decimale
     k=fprintf(_H_USART,(Flash_Mem *)"Vs=%s;",ValFt2);

but , written with C18 MPLAB.. with Pick18F26K22 ...
So it's just the formula to use...

you must add ADC measure for LM35DZ 0 to 50°C .. no measure in Alaska !
and use the new air sound speed for distance calculation..

i will try to translate it in MikroC for 16F8x7 and gives feed back to this post..