trying to print line once instead of everytime analog sensor is read

Projects Programming
1

i'm totally new to this stuff so i'm sure this is a really simple question but i'm trying to make a light dimmer with a pot that displays a sentence once when the brightness is in a certain range. Right now it only works for when my analogRead(pot) is zero...

const int pot = 0;
int volt = 0;
const int Rled = 9;
const int Gled = 10;
const int Bled = 11;
int oldVal = 0;

void setup()
{
Serial.begin(9600);
pinMode(Rled, OUTPUT);
pinMode(Gled, OUTPUT);
pinMode(Bled, OUTPUT);
}

void loop()
{
volt = analogRead(pot);

if (volt != oldVal)
{
if (volt == 0)
{
Serial.println("Light is Off.");
}

else if (volt > 0 && volt <= 341)
{
Serial.println("Light is dim.");
}

else if (volt >= 682)
{
Serial.println("Light is Bright!");
}

else
{
Serial.println("Light is medium.");
}

oldVal=volt;
}

analogWrite(Rled, analogRead(pot)(255/1023.0));
analogWrite(Gled, analogRead(pot)(255/1023.0));
analogWrite(Bled, analogRead(pot)*(255/1023.0));

}

2

Put a "Serial.println(volt) ;" after "volt = analogRead(pot) ;"
what is printed?

3

doint that gives me a line that continuously prints an update of the analog pin reading even it it doesnt change

i.e
0
0
0
0
23
23

but what i want is for my text line to print only when i move the potentiometer

4

how is your POT wired!

Change
const int pot = 0;
To
#define pot A0

5

my pot has 5V coming in from the arduino and then going to ground with the middle being wired to the A0 pin

6

LarryD:
how is your POT wired!

Change
const int pot = 0;
To
#define pot A0

Do this, As Larry said, should fix your problem.

7

I tried that and it did not work, am I resetting oldVal to volt in the wrong part of the loop or something?

8

but what i want is for my text line to print only when i move the potentiometer

The below is for controlling servos with pots, but it contains code to limit continuous printing when a pot value is not significantly changed.

//zoomkat multi pot/servo test 3-23-13
//includes dead band for testing and limit servo hunting
//view output using the serial monitor

#include <Servo.h> 
Servo myservo1;  //declare servos
Servo myservo2;
Servo myservo3;
Servo myservo4;
Servo myservo5;

int potpin1 = 0;  //analog input pin A0
int potpin2 = 1;
int potpin3 = 2;
int potpin4 = 3;
int potpin5 = 4;

int newval1, oldval1;  //pot input values
int newval2, oldval2;
int newval3, oldval3;
int newval4, oldval4;
int newval5, oldval5;

void setup() 
{
  Serial.begin(9600);  
  myservo1.attach(2);  
  myservo2.attach(3);
  myservo3.attach(4);
  myservo4.attach(5);
  myservo5.attach(6);
  Serial.println("testing multi pot servo");  
}

void loop()
{ 
  newval1 = analogRead(potpin1);           
  newval1 = map(newval1, 0, 1023, 0, 179); 
  if (newval1 < (oldval1-2) || newval1 > (oldval1+2)){ //dead band 
    myservo1.write(newval1); //position the servo
    Serial.print(newval1); //print the new value for testing 
    Serial.print("a,");
    oldval1=newval1; //set the current old value
  }

  newval2 = analogRead(potpin2);
  newval2 = map(newval2, 0, 1023, 0, 179);
  if (newval2 < (oldval2-2) || newval2 > (oldval2+2)){  
    myservo2.write(newval2);
    Serial.print(newval2);
    Serial.print("b,");
    oldval2=newval2;
  }

  newval3 = analogRead(potpin3);           
  newval3 = map(newval3, 0, 1023, 0, 179); 
  if (newval1 < (oldval1-2) || newval3 > (oldval3+2)){  
    myservo1.write(newval3);
    Serial.print(newval3);
    Serial.print("c,");
    oldval3=newval3;
  }

  newval4 = analogRead(potpin4);           
  newval4 = map(newval4, 0, 1023, 0, 179); 
  if (newval1 < (oldval1-2) || newval4 > (oldval4+2)){  
    myservo1.write(newval4);
    Serial.print(newval4);
    Serial.print("d,");
    oldval4=newval4;
  }

  newval5 = analogRead(potpin5);           
  newval5 = map(newval5, 0, 1023, 0, 179); 
  if (newval1 < (oldval5-2) || newval5 > (oldval5+2)){  
    myservo1.write(newval5);
    Serial.print(newval5);
    Serial.print("e,");
    oldval5=newval5;
  } 
  delay(50);  //to slow loop for testing, adjust as needed
}
9

Light is dim.
Light is dim.
Light is dim.
Light is dim.
Light is dim.
Light is dim.
Light is dim.
Light is dim.
Light is dim.
Light is Off.

This is what i get when the pot starts at full resistance, i turn the light on and then turn it off again. All the conditions fail to print one update line except for light is off.

void loop()
{
volt = analogRead(pot);

if (volt != oldVal)
{

if (volt == 0)
{
Serial.println("Light is Off.");
oldVal = volt;
}

else if (volt > 0 && volt <= 341)
{
Serial.println("Light is dim.");
oldVal = volt;
}

else if (volt >= 682)
{
Serial.println("Light is Bright!");
oldVal = volt;
}

else
{
Serial.println("Light is medium.");
oldVal = volt;
}
oldVal = volt;

}

this is my loop

10

if (volt == 0)
This will more than likely never be 0 as there is always some noise in the system.
Try
if (volt < 10) // or some other low value.

11

Change
const int pot = 0;
To
#define pot A0

Why?

If anything, change it to const byte pot = A0; but I cannot see any logic in your approach.

12

IMO it adds to the readability.
But
const byte pot = A0;
is better