HMC5883l magnetometer sensor vehicle counting

Projects Programming
1

How can i stop counting when data transmitted z-axis is less than threshold level more than one time which indicates the car stop moving above the sensor? Then count continue again if the next car passby.
Need help pls, thx.

#include <RH_ASK.h>// TX library for RF 433MHZ interfacing
#include <SPI.h> // Not actually used but needed to compile
#include <Wire.h> //I2C Arduino Library
#define address 0x1E //0011110b, I2C 7bit address of HMC5883

//Create ASK Object
RH_ASK rf_driver;

//Define Pin
const int TXPin= 12;
const int ledPin =13;
int sensorPin1 = A4;  //Analog input 4 I2C SDA
int sensorPin2 =A5;   //Analog input 5 I2C SCL

//Variables
int num = 1;   //number of magnetometer sensor #1
int count = 0; //initially zero
int x,y,z;     //triple axis data
const int threshold = 0;   //threshold level z-axis
char Array [20];


//Subfunction
void txdataTrans();

void setup() {
  Serial.begin (9600);
  Wire.begin();
  
  //Put the HMC5883 IC into the correct operating mode
  Wire.beginTransmission(address); //open communication with HMC5883
  Wire.write(0x02); //select mode register
  Wire.write(0x00); //continuous measurement mode
  Wire.endTransmission();

  rf_driver.init();   //Intialize ASK Object
  pinMode(ledPin,OUTPUT);
}

void loop() {
  txdataTrans();
  digitalWrite(ledPin, HIGH); // sets the digital pin 13 on to show transmitting
  digitalWrite(ledPin, LOW);  // sets the digital pin 13 off 
}

void txdataTrans(){
   
  //Tell the HMC5883 where to begin reading data
  Wire.beginTransmission(address);
  Wire.write(0x03); //select register 3, X MSB register
  Wire.endTransmission();
  
 //Read data from each axis, 2 registers per axis
  Wire.requestFrom(address, 6);
  
  if(6<=Wire.available()){
    x = Wire.read()<<8; //X msb
    x |= Wire.read(); //X lsb
 
    z = Wire.read()<<8; //Z msb
    z |= Wire.read(); //Z lsb

    y = Wire.read()<<8; //Y msb
    y |= Wire.read(); //Y lsb
  }

    if(z<threshold){            //if z-axis less than threshold, start counting number of vehicle
       count++;
    }
    
   sprintf(Array, "%d,%d,%d,%d,%d.",num,x,y,z,count);    //converts all variables into a string 
   rf_driver.send((uint8_t *)Array, strlen(Array));      //Send out the string including ",".
   rf_driver.waitPacketSent();
  
 //    Message transmitted
    Serial.print("#");
    Serial.print(num);
    Serial.print(", x:");  // x axis
    Serial.print(x);
    Serial.print(", y:");  // y axis
    Serial.print(y);
    Serial.print(", z:");  // z axis
    Serial.print(z);
    Serial.print(", Vehicle counted:");
    Serial.println(count);
    delay(250);
  
}
2

More members will see your code if you post it in accordance with the forum guidelines.

3

Usually, you want to detect whether a sensor value is within some range and then, leaves that range. Count only on the first instance of entering the range.

This code will decide whether a car is present.

if (sensor_value >= lower_threshold && sensor_value <= upper_threshold) car_present = 1;
else car_present = 0;

Then, you need state change code that remembers the last value of car_present and takes appropriate action when there is a change. See the Arduino State Change example.