Monitoring temperature of a particular place directly is difficult and sometimes impossible (ex: places where humans cannot be). So there is a necessity for wireless monitoring system which enables the user to track the temperature from a remote location. In this article we’ll learn how to build a wireless temperature indicator which sends the temperature value to a PC/Laptop through Bluetooth. The Temperature sensor LM35 produces an output voltage which is directly proportional to its surrounding temperature. For every 1°C of rise/fall in temperature, the output voltage of the sensor varies by 10mV. The output of this sensor is analog in nature which needs to be converted into a digital value using an Analog to Digital Converter (ADC) so it is fed into 37th pin of PORT A of the ATmega16 microcontroller. ATmega16 consists of 8 channels ADC (PA0-PA7) with a maximum resolution of 10 bits.