hall effect sensor to measure speed reading in KPH or in RPM

Other Hardware Sensors
1

hi! im new to this kind of sensor, can somebody help me how to use this sensor to measure speed, btw this is the code i saw from the internet, but my problem is why is this code has no input from the sensor? like the analogRead syntax? can somebody change this code to a code that can measure a speed. and what is the meaning of the attachIntterupt? what is the 0 pin use for? thanks for the help! :smiley:

volatile byte half_revolutions;
unsigned int rpm;
unsigned long timeold;
void setup()
{
Serial.begin(115200);
attachInterrupt(0, magnet_detect, RISING);//Initialize the intterrupt pin (Arduino digital pin 2)
half_revolutions = 0;
rpm = 0;
timeold = 0;
}
void loop()//Measure RPM
{
if (half_revolutions >= 20) {
rpm = 30*1000/(millis() - timeold)*half_revolutions;
timeold = millis();
half_revolutions = 0;
//Serial.println(rpm,DEC);
}
}
void magnet_detect()//This function is called whenever a magnet/interrupt is detected by the arduino
{
half_revolutions++;
Serial.println("detect");
}

2

Please post a wiring diagram for the sensor and explain the physical situation.

Have you attached a magnet to a wheel?

3

why is this code has no input from the sensor?

The posted code takes input from the sensor on Digital pin 2 and reads it with an interrupt.

what is the meaning of the attachIntterupt?

At the top of the web page where the forum appears, there is a tab "Learning". Undee it you will find "Reference" where answers to basic syntax questions can be found.

4

Bad code. You should never, ever print within an interrupt.

void magnet_detect()//This function is called whenever a magnet/interrupt is detected by the arduino
 {
   half_revolutions++;
   Serial.println("detect");
 }