Temperature Sensor with Display: Measure and Show Room Temperature

What You’ll Learn

In this project, you’ll learn how to read data from a TMP36 temperature sensor and display the temperature on an LCD screen. This will help you understand how to interface with analog sensors and output data to a display, a common requirement in IoT and automation projects.

Components Needed

• 1 x Arduino Uno (or compatible board)
• 1 x TMP36 Temperature Sensor
• 1 x 16x2 LCD Display
• 1 x 10k ohm Potentiometer (for adjusting LCD contrast)
• Jumper wires
• Breadboard

The Concept

The TMP36 is an analog temperature sensor that provides a voltage output corresponding to the temperature. The sensor outputs a voltage of 500 mV at 0°C, and each 10 mV corresponds to a 1°C increase in temperature. We’ll use the Arduino to read the analog voltage, calculate the temperature, and display it on a 16x2 LCD in real-time.

Circuit Diagram

1. LCD Display:

   • Connect the VSS pin of the LCD to GND.
   • Connect the VDD pin to 5V.
   • Connect the V0 pin (contrast control) to the middle pin of the potentiometer, and the other two pins to 5V and GND.
   • Connect the RS pin to pin 12 of the Arduino.
   • Connect the RW pin to GND.
   • Connect the EN pin to pin 11 of the Arduino.
   • Connect D4, D5, D6, and D7 pins of the LCD to pins 5, 4, 3, and 2 of the Arduino, respectively.

2. TMP36 Temperature Sensor:

   • Connect the VCC pin of the TMP36 to 5V.
   • Connect the GND pin to GND.
   • Connect the Analog Out pin (middle pin) to the A0 analog input pin of the Arduino.

The Code for TMP36

#include <LiquidCrystal.h>

// Initialize the library with the LCD pin numbers
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int tempPin = A0;  // Analog pin for TMP36

void setup() {
  lcd.begin(16, 2);  // Set up the LCD with 16 columns and 2 rows
  lcd.print("Temp:");  // Print a label on the LCD
}

void loop() {
  int analogValue = analogRead(tempPin);  // Read the TMP36 sensor
  float voltage = analogValue * (5.0 / 1023.0);  // Convert the analog reading to voltage (0-5V)
  float temperatureC = (voltage - 0.5) * 100;  // Convert the voltage to Celsius

  // Print the temperature to the LCD
  lcd.setCursor(6, 0);  // Move the cursor to the position to start printing
  lcd.print(temperatureC);
  lcd.print(" C");

  delay(1000);  // Update the temperature every second
}

How the Code Works for TMP36

1. Reading Analog Data:
   The TMP36 outputs an analog voltage proportional to the temperature. The analogRead() function reads the sensor’s output from the analog pin (A0), returning a value between 0 and 1023, which corresponds to a voltage between 0 and 5V.

2. Converting to Temperature:
   The TMP36 sensor outputs 500 mV at 0°C, and the temperature increases by 1°C for every 10 mV. To convert the voltage to temperature in Celsius, we use the formula:

   
   float temperatureC = (voltage - 0.5) * 100;
   

   This adjusts for the 500 mV offset and scales the result to degrees Celsius.

3. Displaying on LCD:
   The temperature is displayed on the 16x2 LCD screen. The lcd.setCursor() function positions the cursor before printing the temperature. The display updates every second to show the current room temperature.

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Customizing the Project

• Fahrenheit Conversion: To display the temperature in Fahrenheit, you can modify the code as follows:

  
  float temperatureF = (temperatureC * 9.0 / 5.0) + 32;
  lcd.print(temperatureF);
  lcd.print(" F");
  

• Temperature Logging: You can expand the project to log temperature data over time by storing readings in an array or sending the data to your computer via serial communication for further analysis.

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Conclusion

In this project, you’ve learned how to read analog data from the TMP36 temperature sensor and display the temperature on a 16x2 LCD screen. You now understand how to handle analog sensor data, convert it into a meaningful temperature value, and output it to a display. This foundational knowledge can be applied to a wide range of sensor-based projects.