Arduino Ultra Sonic Sensor always returns 0 -

i doing basic project in arduino uno connecting ultra sonic sensor (hc-sr04) should print in serial monitor distance of closest object print 0.

this code:

long distance; long time;  void setup(){   serial.begin(9600);   pinmode(4, output);    pinmode(2, input);  }  void loop(){   digitalwrite(2,low);   delaymicroseconds(5);   digitalwrite(2, high);   delaymicroseconds(10);    time = pulsein(4, high);   distance = int(0.017*time);     serial.print("distance: ");   serial.print(distance);   serial.println(" cm.");   delay(1000); } 

and breadboard:

the primary issue see code doesn't match wiring diagram.

for example, diagram shows trig connected pin 4. trig should output arduino have defined input.

the echo connected pin 2 , should input, have defined output.

finally, in loop(), not using pin 2 or pin 4, pins 9 , 8. issue timing use in setting trigger pulse - not match datasheet. (assuming connected pins shown in diagram):

#define sensortrigpin    4 #define sensorechopin    2  void setup() {     serial.begin(9600);     pinmode(sensortrigpin, output);     pinmode(sensorechopin, input); }  void loop() {     int pulsewidth = 0;      digitalwrite(sensortrigpin, high);     delaymicroseconds(10);     digitalwrite(sensortrigpin, low);      pulsewidth = pulsein(sensorechopin, high);      serial.print("pulse width: ");     serial.print(pulsewidth);     delay(1000); } 

note pulsewidth amount of time takes beginning of echo pulse going high end of same pulse (when goes low). still have calculate distance based on value of pulsewidth.

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update based on recent edit question

if change portion of loop() code this, should work:

void loop(){     digitalwrite(4, high);   //was (2, low)     delaymicroseconds(10);   //was (5)     digitalwrite(4, low);    //was (2, high)     //removed delay      time = pulsein(2, high);  //was (4,high);     ...  //keep rest of code same. }