Strange behaviour with incrementing pushbutton

Projects Programming
1

Hi there, I'm running this code on my Uno, it's a thermostat. It all works fine except for one thing: when the set temperature(des) and the actual temperature are the same, or when the des is one point below the actual temperature, if I press the up button (to add one degree to des) the des reading will jump up in increments of anywhere between 2 and 6 points. I have de-bounced the switches, which seems to have worked for the down button, and for the up button so long as the des is below the actual temperature. Can anybody see why this might be happening?

/*
 
  The circuit:
 * LCD RS pin to digital pin 8
 * LCD Enable pin to digital pin 9
 * LCD D4 pin to digital pin 10
 * LCD D5 pin to digital pin 11
 * LCD D6 pin to digital pin 12
 * LCD D7 pin to digital pin 13
 * 10K resistor:
   * ends to +5V and ground
   * wiper to LCD VO pin (pin 3)
 
 *relay connected to D0 to control heating element
 *LED connected to D4 as quick visual indicator
 *LM35 temperature sensor to A0
 *up and down buttons to D1 and D2
 
 */

// include the library code:
#include <LiquidCrystal.h>

int des = 0;   //set temperature variable
int lastdes = 0;
int pin = 1;   //LM35 input
int tempc = 0; //temperature variable
int Counter1 = 0;   // counter for the number of button presses
int Counter2 = 0;   // counter for the number of button presses
int State1 = 0;         // current state of the button
int State2 = 0;         // current state of the button
int lastState1 = 0;     // previous state of the button
int lastState2 = 0;


long lastDebounceTime1 = 0;  // the last time the output pin was toggled
long debounceDelay1 = 50;    // the debounce time; increase if the output flickers
long lastDebounceTime2 = 0;  // the last time the output pin was toggled
long debounceDelay2 = 50;    // the debounce time; increase if the output flickers

int pot = 5;   //temperature adjust input
const int set1 = 1;
const int set2 = 2;
int heat = 0;
int indicate = 4;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(8, 9, 10, 11, 12, 13);

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  lcd.print("SET: ACT: HEAT?");  // Print headings the LCD.
  analogReference(INTERNAL);     
  pinMode(heat, OUTPUT);
  pinMode(indicate, OUTPUT);
  pinMode(set1, INPUT);
  pinMode(set2, INPUT);
  }

void loop()
{
  
  State1 = digitalRead(set1);
  State2 = digitalRead(set2);

  
  if (State1 != lastState1) {
        if (State1 == HIGH) {      //if up button is pressed, add 1 to des
        des++;
     } 
    State2 = digitalRead(set2);
  }
   else if (State2 != lastState2) {  //if down button is pressed, subtract 1 from des
       if (State2 == HIGH) {
       des--; 
    } 
    
    
  int reading1 = digitalRead(set1);        //debounce buttons 1 and 2 (up and down)
  if (reading1 != lastState1) {
     lastDebounceTime1 = millis();                             
  } 
  
  if ((millis() - lastDebounceTime1) > debounceDelay1) {  
      State1 = reading1;                                
  }
  int reading2 = digitalRead(set2);
  if (reading2 != lastState2) {
     lastDebounceTime2 = millis();                              
    
  } 
  if ((millis() - lastDebounceTime2) > debounceDelay2) {  
      State2 = reading2;                                
  }
  lastState1 = reading1;
  lastState2 = reading2;
  }
  
  
  
  
  
  
  
  analogRead(pin);
  delay(5);
  tempc = (100* (long)analogRead(pin)/1024.0);  //save temperature reading as 'tempc'
  delay(5);                                     //gives a range of about 30
  
  lcd.setCursor(1, 1);
  lcd.print("  ");     //clear field
  lcd.setCursor(1, 1);
  lcd.print(des);     //print set temperature
   
  lcd.setCursor(6,1);
  lcd.print("  ");    //clear field
  lcd.setCursor(6,1);
  lcd.print(tempc );  //print actual temperature

  if(tempc <= des){                 //if actual temperature is less than
    digitalWrite(heat, HIGH);       //or equal to the set temperature, turn the heater on
    digitalWrite(indicate, HIGH);
    lcd.setCursor(11,1);
    lcd.print("ON ");
}
  else  if(tempc > des){             //otherwise leave the heater off
    digitalWrite(heat, LOW);
    digitalWrite(indicate, LOW);
    lcd.setCursor(11,1);
    lcd.print("OFF");
  
  
delay(100);   
}
}

Thanks guys.

2

Why is this:

State1 = digitalRead(set1);
  State2 = digitalRead(set2);  
  if (State1 != lastState1) {
        if (State1 == HIGH) {      //if up button is pressed, add 1 to des
        des++;
     } 
    State2 = digitalRead(set2);
  }
   else if (State2 != lastState2) {  //if down button is pressed, subtract 1 from des
       if (State2 == HIGH) {
       des--; 
    }

Not this:

  State1 = digitalRead(set1);
  State2 = digitalRead(set2);  
  if (State1 != lastState1) {
        if (State1 == HIGH) {      //if up button is pressed, add 1 to des
        des++;
     } 
    
  }
  
  if (State2 != lastState2) {  //if down button is pressed, subtract 1 from des
       if (State2 == HIGH) {
       des--; 
    }
  }

?

3

There is a "Button " library that someone wrote that works great for this. I had the same problem with noisy switches and it fixed it.

4

You're using pin 1 which is part of the USB/Serial pin0&1 pair. It may the reason for spurious presses. In theory you can use them as normal IO but then you must not use Serial (you aren't) nor have the USB connected.

I do not understand your second question - the difference between the two code examples is obvious - you've got an [b]else[/b] in the first block. But I am sure that wasn't the question. Is the difference in behaviour: switch 2 will not be testet properly if switch 1 has changed state in the 1st example. Example 2 is better, testing independently for each switch.