Temperature Sensor Using Arduino and LM35

LM35 is a temperature sensor from National Semiconductor that have a high accuracy. The output of analog voltage and has a measurement range of -55 º C to +150 º C with an accuracy of ± 0.5 º C. Output voltage is 10mV / º C. Output ports can be directly connected to Arduino, because Arduino has 6 ADC ports (analog input).


Analog inputs on the Arduino has a 10-bit resolution, which can provide output 2 ^ 10 = 1024 discrete values. When used 5V supply, the resulting resolution is 5000mV/1024 = 4.8mV. Because the LM35 has a resolution output of 10mV / º C, then the resolution of the thermometer are made with Arduino is 10mV/4.8mV ~ 0.5 º C.

So, let make a simple temperature sensor with Arduino and LM35. After we connect the LM35 with the Arduino as in the picture above, we can start write the program.

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// variable declare float tempC; int tempPin = 0; void setup() {     Serial.begin(9600); // Open serial port, set baud rate 9600 bps } void loop() {     tempC = analogRead(tempPin);           // Read data from sensor     tempC = (5.0 * tempC * 100.0)/1024.0;  // convert from analog to temperature     Serial.println((int)tempC,DEC);        // send data via serial     delay(1000);                           // delay }

This program will read temperature data from LM35 and conversion the analog data to digital and write it to PC in celcius through Serial port.