How to change my incriment value from 1 to a decimal place

Projects Programming
1

Hi all

Ive got a state change detection sketch going on with my arduino uno. It works well and counts each time I close the contacts, and prints it in the serial.

But I now want it to count in 0.2 incriments, but I am stumped on how to do this, is there any way I can define the increment value to something different from 1??

thanks

2

Hello,

Use a float instead of an int.

Or, use an int, add 2, and divide by 10 only when needed, because it's more efficient to use int rather than floats.

3

Without posting your sketch all I can say is:

 x += 0.2
4

Post the code that you are using.

What you want sounds easy. A float variable, let's call it floatVariable then, at it's most explicit

floatVariable = floatVariable + 0.2;
5 
float myval;

void loop() {
  if (...) {
    myval += 0.2;
  }
}
6

/*
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 = 4; // 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

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(9600);
}

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) {
// if the current state is HIGH then the button
// wend from off to on:
buttonPushCounter++;
Serial.print("Rainfall: ");
Serial.print(buttonPushCounter);
Serial.println("mm");
}
else {
// if the current state is LOW then the button
// wend from on to off:
}
// Delay a little bit to avoid bouncing
delay(50);
}
// 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);
}

}

7

Read the advice offered and change buttonPushCounter to a float and

      buttonPushCounter++;

to

      buttonPushCounter += 0.2;

For the sake of sanity I suggest that you change the name of the variable too !

8

It is not a good idea to use a float as an index in a for loop because of rounding errors. It is possible to add 1.8 and 0.2 and get a number greater than or less than 2.0!

It is much better to do as suggested in post #1 and use an int index and divide when you need the float value.

9

great I'll give both of them a try. Thanks a lot!

10

Why do you want 0.2 ?

What are you trying to count?

11

Make your integer variable ten times bigger then increment by 2