This circuit uses a LM35 temperature sensor along with a LM339 comparator. Interfaced to LM339 are the following components:
This project about fire alarm circuit is based around LM35 which is a temperature sensor and could be used to switch an alarm when temperature goes beyond a preset value. In this circuit the output of LM35 is fed to the negative pin of comparator of LM339. The positive input is connected to a preset VR1 of value 10K. This preset is used to set the reference temperature. If output of LM 35 is less than V reference than the output of comparator is low. The IC LM339 has four inbuilt comparators.
Filed Under: 555 Timers, Electronic Projects