ESP8266 Community Forum

- Sat Dec 23, 2017 1:17 pm #72666 Hello, first post here so hopefully I'm not breaking any rules!

I purchased a NodeMCU, and an Arduino starter kit to play with over my Christmas break and I'm trying to use the NodeMCU with an Ultrasonic Sensor(HC-SR04) but for some reason the sensor always reads zero for distance(when hooked up to the Arduino it reads properly so I know its not busted). I am fairly new to all of this but neither my own code nor the code from the guide I used to test worked. I have attached an image of my setup but just to clarify I have

VCC > 5V(Power supply)
GND > GND
Trig > D1
Echo > D2

The NodeMCU(Amica, actually a V2 board not V1 like the image) is being powered via USB to my Macbook and the Power Supply is powered via wall plugin.
I have 5V coming out of the power supply as I've tested it with my multimeter.(have also tested with a 3.3V supply as recommended online)

My code is as follows

Code: Select all// defines pins numbers

const int trigPin = 5;  //D1
const int echoPin = 4;  //D2

// defines variables
long duration;
int distance;

void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
Serial.begin(9600); // Starts the serial communication
}

void loop() {

// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);

// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);

// Calculating the distance
distance= duration*0.034/2;
// Prints the distance on the Serial Monitor
Serial.print("Distance: ");
Serial.println(distance);
delay(2000);
}

NodeMCU-US by carter clackson, on Flickr

If you have ever had this issue or see something glaringly wrong with my code please let me know! I can't seem to solve why it reads zero through my NodeMCU and correctly on my Uno.

- Sat Dec 23, 2017 4:22 pm #72667 I actually partially solved the problem in the last few hours. I am now getting data from the Ultrasonic sensor to the NodeMCU, but it seems as though ever 6-7 times it loops I get a nonsense value of between 0-5cm when it should be around 70cm. Is this just the nature of the sensor or is there something else going on?

Code: Select all// defines pins numbers

const int trigPin = 5;  //D1
const int echoPin = 4;  //D2

// defines variables
long duration;
long distance;


void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
Serial.begin(9600); // Starts the serial communication
}

void loop() {
int distance = sample_distance();
Serial.println("Distance: ");
Serial.println(distance);
delay(2000);
}


int sample_distance() {
  long duration, distance;

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(30);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  Serial.println("Duration: ");
  Serial.println(duration);
  distance = int((duration / 2) / 29.155);
  return distance;
}

Is my code now

- Sat Dec 23, 2017 8:02 pm #72671 The HC-SR04 won't work with 3.3v in, so make sure you are getting 5V at its VIN. However, if you send it 5V it will send back 5V, which could damage your 3.3V microcontroller without a level shifter.

- Sun Dec 24, 2017 9:18 am #72679 I have it hooked up to 5v. The image of the power supply just isn't the greatest. I have tested with a multimeter and its 5v. I got it working now but I get alot of garbage values, I will get 6-7 real distances in a row and then 3-4 that are like 0-4cm for no reason.