Exercise 32 - Sensors on LCD
1. INTRODUCTION
Arduino can be used as a system of control and data acquisition. On this exercise, several sensors are going to be connected to an Arduino board to measure some parameter. You can choose any sensor, but this example uses the following sensors: Obstacle IR detector, potentiometer, Resistive force sensor. Furthermore, a simple menu is made using a LCD screen.
You can extrapolate this exercise to measure and control the parameters of a room or house to do a house automation system.
2. HOW TO CONNECT?
Materials:
· Arduino UNO board
· Protoboard
· Some wire Jumpers
· Button
· Force sensitive resistor
· Potentiometer
· IR obstacle sensor
· 2x 10K ohms resitors
Connections:
Pot: 5V, Pin A3, GND
Force sensor: 5V,Pin A2, 10K resistor, GND
Obstacle sensor: 5V, GND, Pin 3
Selection Button: 5V, Pin 2, 10K resistor, GND
EXERCISE_A
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3. PROGRAMMING
Do not forget to include necessary libraries!
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);
int antiReboundTime = 100;
int counter = 0; //Variable to increment the counter
boolean lastState = LOW; // Last state of the button
boolean currentState = LOW; // Current state of the button
const int buttonPin = 2;
int pot = A3;
int force = A2;
int obstacle = 3;
On setup the sensor has been declared as Inputs and the backlight on lcd is turned on. Also lcd and serial communication has been initialized.
void setup()
{
pinMode(buttonPin, INPUT);
pinMode(pot, INPUT);
pinMode(force, INPUT);
pinMode(obstacle, INPUT);
// initialize the LCD
lcd.begin();
// Turn on the blacklight and print a message.
lcd.backlight();
lcd.print("HELLO!");
delay(2000);
Serial.begin(9600); // Initialize Serial communication
}
debounce() function compares the current state of the button with the previous state and also return the value of the current state.
This function is adapted to use with a LCD screen if you use the anti rebound function on PUSH_BUTTON exercise, the characters will blink on LCD when they are printed.
boolean debounce(boolean last) // anti-rebound function
{
boolean current = digitalRead(buttonPin);
if (last != current)
{
current = digitalRead(buttonPin);
}
return current;
}
On loop, debounce function is called to eliminate rebound. On the other hand, if currentstate has a HIGH signal and lastState has a LOW signal the counter is incremented one by one because this condition means that the button is pressed.
Secondly, the condition changes when the counter is incremented, and it prints the value of the different sensors.
void loop()
{
currentState = debounce(lastState); // Eliminates rebound
if ( lastState == LOW && currentState == HIGH)
{
counter = counter + 1; //Increments counter
Serial.println(counter); //Prints the value on Serial monitor
}
lastState = currentState; // Update the state
This condition limits the counter to 1, 2 or 3.
if (counter < 1 || counter > 3) {
counter = 1;
lcd.setCursor(0, 1);
lcd.print(" ");//Print 16 spaces to Erase row
}
lcd.setCursor(0, 0);
lcd.print("Selection: ");
lcd.print(counter);
if (counter == 1) {
lcd.setCursor(0, 1);
lcd.print("Pot Value=");
lcd.print(analogRead(pot));
lcd.print(" ");
}
if (counter == 2) {
lcd.setCursor(0, 1);
lcd.print("force Value=");
lcd.print(analogRead(force));
lcd.print(" ");
}
if (counter == 3) {
lcd.setCursor(0, 1);
lcd.print("Obstacle?->");
if(digitalRead(obstacle)==0){
lcd.print("Yes");
}
else{
lcd.print("No");
}
lcd.print(" ");
}
}