Ultrasonic Sensor Test Question

Other Hardware General Electronics
1

I need help understanding why when I put this code:

#define echoPin 4 // Echo Pin
#define trigPin 5 // Trigger Pin
#define LEDPin 13 // Onboard LED 
int maximumRange=200; //Maximum range needed
int minimumRange=0; //Minimum range needed
long duration,distance; //Duration used to calculate distance

void setup() {
Serial.begin(9600);
pinMode(trigPin,OUTPUT);
pinMode(echoPin,INPUT);
pinMode(LEDPin,OUTPUT);//Use LED indicator (if required)
}

void loop() {
digitalWrite(trigPin,LOW);
delayMicroseconds(2);
digitalWrite(trigPin,HIGH);
delayMicroseconds(10);

digitalWrite(trigPin,LOW);
duration = duration/58.2;

if(distance>=maximumRange||distance<=minimumRange){

Serial.println("-1");
digitalWrite(LEDPin,HIGH);
}
else{
  Serial.println(distance);
  digitalWrite(LEDPin,LOW);
}
//Delay 50ms before next reading.
delay(50);
}

to test the ultrasonic sensor to show me how far away it is from an obsatcle it gives me -1's all the time when the obstacles isn't that close to it. I am using a Keyestudio Mini Tank Robot and the obstacles avoidence just gives me -1's. Does anyone know how to fix this?

2

Please always do a Tools > Auto Format on your code before posting it. This will make it easier for you to spot bugs and make it easier for us to read.

You never define distance after the declaration so it will always be 0, which is equal to minimumRange, thus the prints of "-1". Your problem is this line:

thinker_17:

duration = duration/58.2;

This was intended to convert the ping duration to a distance measurement based on the speed of sound but you made a typo and defined duration where you should have defined distance.[/code]

3

Your code is similar to this link, and is missing the assignment to duration (line 40 in the link) as well as having the conversion incorrect as noted above.