Pyro Electric Fire Alarm
Here is an ultra-sensitive fire sensor that exploits the direct piezoelectric property of an ordinary piezo element to detect fire. The lead zircon ate titan ate crystals in the piezo element have the property to deform and generate an electric gate protected p-channel MOSFETs in the inputs. It has high speed of performance and low input current requirements.There are two inputs—the non-inverting input (pin 3) connected to the piezo element through diode D7 (OA71) that carries the voltage signal from the piezo element and the inverting input (pin 2) that gets a preset voltage momentarily changes the voltage level at pin 3 of IC1 and its output swings high. Transistor T1 conducts taking the reset pin 12 of IC2 to ground. IC2 is now enabled and starts oscillating. With the shown values of the oscillating components C3 (0.22μ) and R6 potential when heated, thus converting the piezo element into a heat sensor. The circuit described here is very sensitive. It gives a warning alarm if ...