LCD Thermometer

Part of the Displays and Sensors section of Coddy's Arduino journey. Lesson 24 of 24.

A thermometer shows its unit with a degree sign: 24.5°C. The LCD draws letters from its own table of characters, and in that table the degree sign is number 223. Send it with (char)223: (char) tells print() to draw character 223 instead of printing the digits 2, 2, 3.

lcd.print(celsius, 1);   // one decimal: 24.5
lcd.print((char)223);    // the degree sign
lcd.print("C    ");      // spaces cover old characters

A ° typed in your text does not work: the editor stores it as two other numbers, and the screen draws the two symbols it keeps at those places.

As with Serial.println(x, 3), a second number in lcd.print(value, 1) sets how many decimals a float shows.

Challenge

Medium

The sketch works out celsius and the top row says Temperature. Show it on the bottom row like 24.5°C:

the temperature with one decimal
then the degree sign, (char)223, then C
with spaces after, so a shorter value leaves nothing behind

Press Run, change the temperature, then Check.

Try it yourself

#include <LiquidCrystal.h>

// RS, E, D4, D5, D6, D7
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const float BETA = 3950;

void setup() {
  lcd.begin(16, 2);
  lcd.print("Temperature");
}

void loop() {
  int reading = analogRead(A0);
  float celsius = 1 / (log(1 / (1023.0 / reading - 1)) / BETA + 1.0 / 298.15) - 273.15;

  // show it on the bottom row with one decimal and the degree sign, like 24.5°C
  delay(500);
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Displays and Sensors

Practice on your own: Arduino playground