Connecting the LM35 Temperature Sensor to Arduino: The Right Way

The LM35 is a temperature sensor that outputs an analog voltage directly proportional to the temperature in degrees Celsius. If you want to incorporate this sensor into your Arduino projects, you can't simply connect it to a digital pin. Instead, you should connect it to an analog pin, which is designed for handling such inputs. This article will guide you through the proper setup and provide you with a comprehensive understanding of how to use the LM35 with your Arduino.

Understanding the LM35 Sensor

The LM35 is widely used due to its simplicity and accuracy. It measures temperature in degrees Celsius without requiring any external components for calibration. However, its output is an analog voltage, meaning that it provides a continuous range of values corresponding to the temperature. This is in contrast to digital outputs, which provide discrete levels.

Connection Setup

Power (VCC): Connect the VCC pin of the LM35 to the 5V pin on the Arduino. Ground (GND): Connect the GND pin of the LM35 to the GND pin on the Arduino. Analog Output: Connect the output pin of the LM35 to one of the Arduino's analog input pins, such as A0, A1, or A2.

Reading the Temperature

Once connected, you can use the analogRead function in your Arduino code to read the output voltage from the LM35. However, the value returned by analogRead is an integer ranging from 0 to 1023, and you need to convert it to the actual temperature. The relationship between the analog reading and the temperature is linear and can be calculated using the following formula:

Temperature °C (analogRead / 1024) * 5 * 100 Temperature °C (analogRead / 1024) * 5 * 100

Example Code

const int lm35Pin  A0; // Analog pin for LM35void setup() {  (9600); // Initialize serial communication}void loop() {  int sensorValue  analogRead(lm35Pin); // Read the sensor value  float voltage  (float)sensorValue * (5.0 / 1024.0); // Convert to voltage  float temperature  voltage * 100; // Convert to temperature in Celsius  (Temperature  );  (temperature);  ( C);  delay(1000); // Wait for 1 second before next reading}

Conclusion

In summary, the LM35 temperature sensor should be connected to an analog pin on the Arduino, not a digital pin. The output voltage can be read using the analogRead function and then converted to temperature using the appropriate formula. This method ensures accurate and reliable temperature readings from the LM35 sensor. By following the steps outlined in this article, you can successfully integrate the LM35 into your Arduino projects and accurately measure temperature.