Help With LED Fading And Switch

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hi All,

I got my first arduino on Monday and have been learning ever since. I bought the MAKE "Getting Started With Arduino" book and have completed most of the exercises.

I have written a sketch which fades a single LED in and out, simple enough and it works. I have since combined this with a switch and can get it to switch on fine. However I cannot understand the correct logic to successfully see if the switch has been turned off. My sketch code is as follows:

#define LED 9
#define BUTTON 7

int i = 0;
int state = 0;
int val = 0;
int old_val = 0;

void setup()
{
  pinMode(LED, OUTPUT);
  pinMode(BUTTON, INPUT);
}

void loop()
{ 
  
    val = digitalRead(BUTTON);
    if ((val == HIGH) && (old_val == LOW))
    {
      state = 1 - state;
      delay(10);
    }
    
    if (state == 1)
    {
        
      for (i = 0; i < 255; i++) 
      {
        analogWrite(LED, i);
        delay(10);
      }
  
      for (i = 255; i > 0; i--)
      {
        analogWrite(LED, i);
        delay(10);
      }
    } 
}

Any help on the correct code would be most appreciated as I really am stuck.

Many Thanks

2

Where do you ever change the value of old_val?

That variable should be set at the end of loop, to val.

3

Oh sorry, I have been messing with the code. I have tried it with the old_val = val at the end and it still doesnt work :frowning:

4

Does this code work??

I mean..does that fade out and fade in with the button operation work with this code?

5

The fade in and fade out works fine, I just cant get it to stop fading mid fade.

6

I got a bad server..my page is loading late..I never intended to post that...Sorry

you have mentioned state==1 for turning on the switch rite..

the if statement before that will need a else statement before the turn off.

#define..:D..u can simply put that in int. increasing values from 0-255 1 by 1 is kinda laggy.

7

I got a bad server..my page is loading late..I never intended to post that...Sorry

you have mentioned state==1 for turning on the switch rite..

the if statement before that will need a else statement before the turn off.

#define..:D..u can simply put that in int. increasing values from 0-255 1 by 1 is kinda laggy.

8

I have this working now. I just got confused about the state of a button when it is pressed and not pressed. Needed to include a function during the fading to check whether the button had been pressed.

Here is my code as it is now working:

#define LED 9
#define BUTTON 7

int i = 0;
int state = 0;
int val = 0;

//A function to see if the button has been pressed, returns an int
int CheckButton()
{
  return(digitalRead(BUTTON) == HIGH);
}      

void setup()
{
  pinMode(LED, OUTPUT);
  pinMode(BUTTON, INPUT);
}

void loop()
{   
  
    //Check to see if the button has been pressed.
    if(digitalRead(BUTTON) == HIGH)
    {
      //While the digital read statement is true (high) continue the loop
      while(digitalRead(BUTTON) == HIGH)
            continue; 

      //state is true as state is 0 and if we do !state then it is 1
      state = !state;  
    }
    
    //If state is 1 which it will be as we wont make it 0. If we dont use state then we have to keep pressing the button
    if(state)
    {
          for (i = 0; i < 255; i++) 
            {
           //If checkbutton is true it means the button has been pressed
        if(CheckButton())
        {
            //Turn off the LED and break the loop
          analogWrite(LED, 0);
            break;
        }

          //Continue fading
          analogWrite(LED, i);
          delay(10);
            }
  
            for (i = 255; i > 0; i--)
            {
          //If the checkbutton is true it means the button has been pressed
          if(CheckButton())
          {
            //Turn off the LED and break the loop
            analogWrite(LED, 0);
            break;
        }

          //Continue fading
          analogWrite(LED, i);
          delay(10);
            }
     }
}

Thanks for all the help.