Sensing Temperature Using AVR


In this new tutorial, we will be interfacing an LM35 based temperature sensor with ATMEGA32. The three main types are thermometers, resistance temperature detectors, and thermocouples. All three of these sensors measure a physical property (i.e., the volume of a liquid, current through a wire), which changes as a function of temperature. In addition to the three main types of temperature sensors, there are numerous other temperature sensors available for use. However, the LM35 based sensors are precision-integrated temperature sensors, with an output voltage linearly proportional to the Centigrade temperature. The main advantage is these types of sensors don’t require any external calibration. They are internally calibrated and simply generate the output to the temperature they detect. The device is used with single power supplies, or with plus and minus supplies. As the LM35 draws only 60 μA from the supply, it has very low self-heating of less than 0.1°C in still air. The LM35 is rated to operate over a −55°C to +150°C temperature range, while the LM35C is rated for a −40°C to +110°C range (−10° with improved… Continue reading

Temperature sensor with LCD

This is an 8051 based project with AT89C51AC2 microcontroller that reads temperature sensor LM35 value and displays it on standard LCD screen. As LM35 scale factor is 10mV per 1ºC there is a fixed gain amplifier used that pulls the voltage to 2.5V (VREF=2.5V) limit for 100ºC instead of 1V. This gives better accuracy of readings. Code is written in C and ASM languages – this gives quite some clue of working internals. Project is nicely documented and put in to Google doc. Continue reading