i wanna build a distance measure using ultrasonic and i have the module vm125 by vellemanusa on this link here

it suppose to measure distance between range: 0.66-8.20ft or 20.12-249.94cm

the module has an analog output which represent the distance and it has rating of voltage output 0-5v

am using pic microcontroller and in my case 16f876 but am confused i can't measure the right distance and i guess there is some thing wrong in my calculation


the adc has a resolution of 10bit and the analog output is 5v so the analog reading will represent the distance using this formula

distance = adc reading * (5/1024) but when i tested it gives me wrong result can any one help me here plz

i include her the code and photos of the circuit

void initialize(){
 PORTA=0x00;
 TRISA=0x01;
 ADCON1=0b10001110;
 ADCON0=0b10000000;
 ADCON0.f0=1;

 Lcd_Init(&PORTB);
 Lcd_Cmd(Lcd_CLEAR);
 Lcd_Cmd(Lcd_CURSOR_OFF);
}

void ad_read(){
 ADCON0.f2=1;
 while(ADCON0.f2==1){}
   ad_res=0;
   ad_res=ADRESH;
   ad_res=ad_res<<8;
  ad_res=ad_res+ADRESL;
  distance=ad_res*(5/1024);
  Lcd_Cmd(Lcd_Clear);
  FloatToStr(distance, ad_res_txt);
  Lcd_Out_Cp(ad_res_txt);
  Lcd_Out_Cp("cm");
  Lcd_Cmd(LCD_SECOND_ROW);
  WordToStr(ad_res, ad_res_txt);
  Lcd_Out_Cp(ad_res_txt);
 }

 

try:
distance=ad_res*(250/1024);
instead of
distance=ad_res*(5/1024);

I think there is something else wrong because I would expect a value between 0-5 with your current calculation.
Maybe you have the ADC result in the left shifted instead of right shifted format.

 

the adc result is already fight justified since i wrote ADCON1=0b10001110; so the bit7 ADFM is equal 1 which is a right justified

and when i used you formula the result gives me zero !!!