void loop() {
long duration, distance;
digitalWrite(trigPin, LOW); // Added this line
delayMicroseconds(2); // Added this line
digitalWrite(trigPin, HIGH);
// delayMicroseconds(1000); - Removed this line
delayMicroseconds(10); // Added this line
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
distance = (duration/2) / 29.1;
if (distance >= 200 || distance <= 0){
Serial.println("Out of range");
}
else {
Serial.print(distance);
Serial.println(" cm");
}
delay(500);
}
It works fine, I can see the distance in the monitor, but after a short period of time, say 30 seconds, it just stops working and displays "out of range" continuously. What am I doing wrong?
I played with the HC-SR04 on Monday night for the first time. It depends on the 'material' that you use what is detected. I use a square metal can to reflect straight back and that works; the same metal can under an angle of 45 degrees gives a repeating sequence of incorrect readings and out-of-range. A piece of artificial fur gives a repeating correct reading followed by out-of-range.
So it depends on your material what the result will be; I think that it's somewhere stated that it has difficulty detecting people wearing clothes.
I used below code (a variation on your one). Note that I used different pins and had an RGB Led connected. I've added a counter for your convenience.
// HC-SR04 pins
#define ECHOPIN 7
#define TRIGGERPIN 8
// LEDS
#define LEDRED 9
#define LEDGREEN 10
#define LEDBLUE 11
// ranges in centimeters
#define MAXRANGE 350
#define MINRANGE 0
#define CRITICAL 5
// delay between HC-SR04 readings in milliseconds
// according to datasheet, this should be at least 60ms
// to prevent interference between trigger and echo
#define DELAY_HCSR04 500
void setup()
{
Serial.begin (9600);
pinMode(TRIGGERPIN, OUTPUT);
pinMode(ECHOPIN, INPUT);
pinMode(LEDRED, OUTPUT);
pinMode(LEDGREEN, OUTPUT);
pinMode(LEDBLUE, OUTPUT);
digitalWrite(LEDRED, LOW);
digitalWrite(LEDGREEN, LOW);
digitalWrite(LEDBLUE, HIGH);
digitalWrite(TRIGGERPIN, LOW);
delayMicroseconds(2);
}
void loop()
{
static unsigned long startDistancemeasurement = millis();
static unsigned long count = 0;
if (millis() - startDistancemeasurement > DELAY_HCSR04)
{
// timing
startDistancemeasurement = millis();
// counter to count iterations
count++;
// get distance
long distance = checkDistance();
Serial.print(count);
Serial.print(F(" "));
if (distance >= MAXRANGE || distance <= MINRANGE)
{
Serial.print(F("Out of range: "));
Serial.print(distance);
Serial.println(F(" cm"));
// out of range indicated by BLUE on and RED and GREEN off
digitalWrite(LEDRED, LOW);
digitalWrite(LEDGREEN, LOW);
digitalWrite(LEDBLUE, HIGH);
}
else
{
Serial.print(distance);
Serial.println(F(" cm"));
// in range, switch BLUE off
digitalWrite(LEDBLUE, LOW);
if (distance < CRITICAL)
{
// too close, RED on and GREEN off
digitalWrite(LEDRED, HIGH);
digitalWrite(LEDGREEN, LOW);
}
else
{
// safe, GREEN on and RED off
digitalWrite(LEDRED, LOW);
digitalWrite(LEDGREEN, HIGH);
}
}
}
}
unsigned long checkDistance()
{
// send a 10us trigger pulse
digitalWrite(TRIGGERPIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIGGERPIN, LOW);
// read duration of echo in milliseconds
unsigned long duration = pulseIn(ECHOPIN, HIGH);
// Serial.print(F("Duration: "));
// Serial.print(duration);
// Serial.println(F(" ms"));
// calculate and return distance in cm
return (duration / 2) / 29.1;
}
There is loss of precision if "duration" is an odd number. (tapdancing... He he). I get it that it works now and, it doesn't matter in this case because that loss is swamped by the division. But a more general approach that avoids the risk in cases where that is not true, would be:
Thank you.
It works but I still have the same problem, after some time (between 5 seconds and 1 minute) it stops working, I get the "out of range" message...
I'm not sure I get your question (total newbie here, sorry, I'm a PD user, completely new to Arduino). 5v to Vcc, is it what you asked?
Sterretje I just tried your code, and surprisingly it bugs in a slightly different way. It works as long as I keep an object in front of it. As soon as I remove it it displays "out of range", and it won't work again, unless I compile it again.
(tapdancing... He he). I get it that it works now and, it doesn't matter in this case because that loss is swamped by the division. But a more general approach that avoids the risk in cases where that is not true, would be: