Analog pin value keep fluctuating in Arduino

Hello,

I think that the reason of the fluctuation is just the switch. When you press the switch, the analog input receives a value, that is the highest and you see that it decreases if you put a resistor in series. Instead when the switch is not pressed, the analog input does not receives signals and - exactly as we can expect, the internal DA converter fluctuates. You get the same result if you try to read another analog pin with nothing connected.

If you need read a switch on / off from the analog pin, I suggest to send the Vref to both the switch sides but to one of the two (e.g. the off position) you can put a resistor, e.g. 5K or more. So, then the switch is off, you receive a fixed value while then the switch is pressed the resistor is bypassed and you receive the highest value (1023, that you can assume it is the digital "1")

Just a note: as you write you are already using a 20K resistor it is better if you put the scheme so it is possible to have an idea of what should be expected.

Enrico

Hi Enrico,

Thanks for your reply..

I am not from Electronics background...I could not understand the setup you have mentioned for noise reduction..

Could you please show in circuit diagram or in anyother format so that I can buy necessary components and try the configuration..?

Thanks,

Radha

Hello,

what I have asked is the circuit that you have done. Please put the drawing of the circuit so I figure out what you are doing. Else it is almost impossible.

Thank you. Enrico

generk4

     Hello, there is a problem of reading a switch which should have a value of high or low with analog which is like a variable resistor. If the values are changing, you do not have the leg of the switch pulled to ground. In other words the switch is floating. You claimed it is 20K. Here is code and a picture of connecting a switch from arduino.cc:

Code

/* switch

*

* Each time the input pin goes from LOW to HIGH (e.g. because of a push-button

* press), the output pin is toggled from LOW to HIGH or HIGH to LOW. There's

* a minimum delay between toggles to debounce the circuit (i.e. to ignore

* noise). 

*

* David A. Mellis

* 21 November 2006

*/

int inPin = 2;      // the number of the input pin

int outPin = 13; // the number of the output pi

int state = HIGH; // the current state of the output pin

int reading; // the current reading from the input pin

int previous = LOW; // the previous reading from the input pin

// the follow variables are long's because the time, measured in milliseconds

// will quickly become a bigger number than can be stored in an int.

long time = 0;                   // the last time the output pin was toggled

long debounce = 200;      // the debounce time, increase if the output flickers

void setup()

{

  pinMode(inPin, INPUT);

  pinMode(outPin, OUTPUT);

}

void loop()

{

     reading = digitalRead(inPin);

  // if the input just went from LOW and HIGH and we've waited long enough

  // to ignore any noise on the circuit, toggle the output pin and remember

  // the time

  if (reading == HIGH && previous == LOW && millis() - time > debounce) {

    if (state == HIGH)

      state = LOW;

    else

      state = HIGH;

    time = millis(); 

  }

  digitalWrite(outPin, state);

  previous = reading;

}

Hi Enrico,

This is what I have done for the analog input,

Thanks Clem.You have given me digital input code.I will try and update the status..

This looks wired incorrect.  The Analog line while the button is open, is floating unless you are using a internal pull up resistor.  The schematic should be like this.    Your Analog line is HELD high until you push the button. I did not change the resistor value, but 10K will work just fine.

This looks wired incorrect.  The Analog line while the button is open, is floating unless you are using a internal pull up resistor.  The schematic should be like this.    Your Analog line is HELD high until you push the button. I did not change the resistor value, but 10K will work just fine.