We are building a thermostat to control our furnace and A/C. We are using a DFRobot LCD / Keypad shield we received from Hacktronics.com to display the temperature, and to set the temperature ranges for both the heating and cooling modes. The following is a sketch that shows how the lcd and the buttons are utilized. Only one analog input is needed for the 6 buttons, as they are connected to resistors, and the resistance is measured to determine which button is being pushed. We will be customizing this with a Dallas DS18B20 temperature sensor, and MOSFET / SSR control over the Furnace and A/C. A video of how this works has been uploaded to YouTube.
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//Sample using LiquidCrystal library#include "LiquidCrystal.h"/*******************************************************This program will test the LCD panel and the buttonsMark Bramwell, July 2010********************************************************/// select the pins used on the LCD panelLiquidCrystal lcd(8, 9, 4, 5, 6, 7);// define some values used by the panel and buttonsint lcd_key    = 0;int adc_key_in = 0;#define btnRIGHT 0#define btnUP    1#define btnDOWN  2#define btnLEFT  3#define btnSELECT 4#define btnNONE  5// read the buttonsint read_LCD_buttons(){ adc_key_in = analogRead(0);     // read the value from the sensor  // my buttons when read are centered at these valies: 0, 144, 329, 504, 741 // we add approx 50 to those values and check to see if we are close if (adc_key_in > 1000) return btnNONE; // We make this the 1st option for speed reasons since it will be the most likely result if (adc_key_in < 50)  return btnRIGHT;  if (adc_key_in < 195) return btnUP;  if (adc_key_in < 380) return btnDOWN;  if (adc_key_in < 555) return btnLEFT;  if (adc_key_in < 790) return btnSELECT;   return btnNONE; // when all others fail, return this...}void setup(){ analogWrite(10, 50); // set brightness on pin 10 to 0-255 lcd.begin(16, 2);             // start the library lcd.setCursor(0,0); lcd.print("Push the buttons"); // print a simple message} void loop(){ lcd.setCursor(9,1);           // move cursor to second line "1" and 9 spaces over lcd.print(millis()/1000);     // display seconds elapsed since power-up lcd.setCursor(0,1);           // move to the begining of the second line lcd_key = read_LCD_buttons(); // read the buttons switch (lcd_key)              // depending on which button was pushed, we perform an action {   case btnRIGHT:     {     lcd.print("RIGHT ");     break;     }   case btnLEFT:     {     lcd.print("LEFT  ");     break;     }   case btnUP:     {     lcd.print("UP   ");     break;     }   case btnDOWN:     {     lcd.print("DOWN ");     break;     }   case btnSELECT:     {     lcd.print("SELECT");     break;     }     case btnNONE:     {     lcd.print("NONE ");     break;     } }}Become the Maker you were born to be. Try Arduino Academy for FREE!
I want to build one of these to run a small air conditioner. Could it be modified to read 2 or 3 temperature sensors and display the readings in f.
Turn on the device when sensor 1 (room temperature) is above the set point and turn off the device when sensor 2 (the coils on the AC) drop below a certain point.
Sensor 3 would just be informational, like outside temp.
That would be easy to do. Look at our DS18B20 projects we have posted here in the past. One had two sensors, 3 is just as easy.
Thanks for the reply. I found the other post "after" I submitted my question. Nice that the temp sensors are addressable. Ordered everything "I think I need" last night. Ordered a 4 line LCD so I can list set point, TS1, TS2 & TS3 all at the same time. Please don't tell me that can all be done with the 2 line LCD you used above as the LDC Shield would be easier to use and already has buttons.
I prefer 4 line lcd's, but even with a two line, you can have multiple "pages" for different functions.