Thank you Paul!!!
Finally it works.At first I tried with 10 ms, but it wasn't enough.After calcualting it , I tried with 20 ms and it works fine!Taking in account the wheel diameter I can use up to 200 km/h speed without problems.
MAy I put another question?...
I have my arduino project connect through usb to the computer to an excel file using netcomm.
I'm worried if I have a problem , for example ,if I lose the connection ( power failure of the laptop,mementary disconnection of the usb cable).I'm thinking to add additional DC current to Arduino if this happens, but....
when I run the excel file again, how can I recover the counted pulses of the arduino project?
here, the code:
/*
State change detection (edge detection)
Often, you don't need to know the state of a digital input all the time,
but you just need to know when the input changes from one state to another.
For example, you want to know when a button goes from OFF to ON. This is called
state change detection, or edge detection.
This example shows how to detect when a button or button changes from off to on
and on to off.
The circuit:
- pushbutton attached to pin 2 from +5V
- 10K resistor attached to pin 2 from ground
- LED attached from pin 13 to ground (or use the built-in LED on
most Arduino boards)
created 27 Sep 2005
modified 30 Aug 2011
by Tom Igoe
This example code is in the public domain.
*/
// this constant won't change:
const int buttonPin = 2; // the pin that the pushbutton is attached to
const int ledPin = 13; // the pin that the LED is attached to
// Variables will change:
int buttonPushCounter = 0; // counter for the number of button presses
int buttonState = 0; // current state of the button
int lastButtonState = 0; // previous state of the button
// the following variables are long's because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long lastEvent = 0; // the last time the output pin was toggled
long interval = 20; // the debounce time; increase if the output flickers
void setup() {
// initialize the button pin as a input:
pinMode(buttonPin, INPUT);
// initialize the LED as an output:
pinMode(ledPin, OUTPUT);
// initialize serial communication:
Serial.begin(19200);
}
void loop() {
// read the pushbutton input pin:
buttonState = digitalRead(buttonPin);
// compare the buttonState to its previous state
if (buttonState != lastButtonState)
{
// if the state has changed, increment the counter
if (buttonState == HIGH && millis() - lastEvent > interval) // <-- Ignore this press if it is too close to the last one
{
lastEvent = millis(); // <-- record when the last good event occurred
buttonPushCounter++;
// Serial.println("on");
// Serial.print("n pulsos: ");
Serial.println(buttonPushCounter);
}
else {
// if the current state is LOW then the button
// wend from on to off:
// Serial.println("off");
}
}
// save the current state as the last state,
//for next time through the loop
lastButtonState = buttonState;
// turns on the LED every four button pushes by
// checking the modulo of the button push counter.
// the modulo function gives you the remainder of
// the division of two numbers:
if (buttonPushCounter % 4 == 0) {
digitalWrite(ledPin, HIGH);
} else {
digitalWrite(ledPin, LOW);
}
}