Problem with my ultrasonic sensor

Using Arduino Sensors
1

Hi I am a beginner, so I may have obvious mistakes.

I am struggling to make a mechanism which can detect the movement and send a voice signal by buzzer when it detects a movement.

My buzzers is keep working even though there is no movement.

Here is my code, thanks in advance:

#include <SoftwareSerial.h>

//ultrasonic pins
int trigger = 9;
int echo = 8;
long duration;
int distance;
long duration2;
int distance2;
int buzzer = 7;
int led = 2;

// motor pins
int lDIR = 13;
int lPWD = 3;
int rDIR = 12;
int rPWD = 11;

void setup() {
pinMode(trigger, OUTPUT);
pinMode(buzzer, OUTPUT);
pinMode(lDIR, OUTPUT);
pinMode(lPWD, OUTPUT);
pinMode(rDIR, OUTPUT);
pinMode(rPWD, OUTPUT);
pinMode(echo, INPUT);

}

void loop(){

motorStop();
delay(5);
getDistance();
delay(5000);

if (distance > distance2) {
runBuzzer();

}

else if (distance < distance2) {
runBuzzer();
}

else {
runLed();

}

delay(5000);
}

long getDistance() {
digitalWrite(trigger, LOW);
delay(5);
digitalWrite(trigger, HIGH);
delayMicroseconds(5000);
digitalWrite(trigger, LOW);
duration = pulseIn(echo, HIGH);
distance = duration * 0.034 / 2;
digitalWrite(trigger, LOW);
delay(5);
digitalWrite(trigger, HIGH);
delayMicroseconds(5000);
digitalWrite(trigger, LOW);
duration2 = pulseIn(echo, HIGH);
distance2 = duration2 * 0.034 / 2;
}

void runBuzzer(){
tone(buzzer, 1000); // Send 1KHz sound signal...
delay(1000); // ...for 1 sec
noTone(buzzer); // Stop sound...
delay(1000); // ...for 1sec

}

void motorStop() {
digitalWrite(lDIR, ILERI);
digitalWrite(rDIR, ILERI);
analogWrite(lPWD, 0);
analogWrite(rPWD, 0);
}

void runLed(){
digitalWrite(led, HIGH);
delay(1000);
digitalWrite(led, LOW);
delay(1000);
digitalWrite(led, HIGH);
delay(1000);
digitalWrite(led, LOW);
delay(1000);
digitalWrite(led, HIGH);
delay(1000);
digitalWrite(led, LOW);
delay(1000);
}

2

If you've got two ultrasonic rangers, I'd slow down the aggregate ping rate.

Please remember to use code tags when posting code.

(Code needs a MASSIVE tidy-up)

3

Actually there are not two, I couldn't figure out how to detect the movement.

4

Sorry,I just saw two distance variables and assumed you had two sensors - didn't notice that you had only one set of trigger/echo pins.

I don't know why you'd do that.

5

That seems awfully long.

If you trigger the sensor again immediately after the first reading, it is possible that the second reading will be fooled by a late echo from the first reading. You should delay about 30 milliseconds between readings.

6

a quick scan of your code I see you are pinging your sensor twice after a 5ms delay, then comparing the two measured distances--that sounds reasonable.

However in your loop processing I see

if (distance > distance2) {
runBuzzer();
}
else if (distance < distance2) {
runBuzzer();
}

Meaning unless distance = distance2 the buzzer will always ring. These sensors are not going to give the same exact distance on multiple reads. Note: I have these sensors mounted to a wall in my garage measuring the distance between the wall and bumper (so I can park always 10 inches away. I average 5 readings every 100ms or so, and still i'll get +/- 1 inch of movement event when the car is stopped.

One way to fix this is to have some threshold distance (I use 2 inches and seems to work well)

something like

if (abs(distance - distance2) > 2) {
// where 2 is your allowable distance before buzzer goes off
// i'm not sure what units distance is but need at least a few inches
runBuzzer();
}

also, maybe use floats for distance and distance 2 so you can get a slightly more accurate distance? Make sure you force all calcs to force float... 0.034 / 2 will return and int use 0.034/2.0

Hope this helps

7

That doesn't sound reasonable at all - a 200Hz ping rate is probably unsustainable, with the late returns problem noted above.

8

No. When one side of the divide is a float and the other side is an int, the int gets converted to float. See 'usual arithmetic conversions':
https://en.cppreference.com/w/cpp/language/operator_arithmetic#Conversions

9

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