KitsGuru Piezo Electric Heat Sensor LGKT109 Educational Electronic Hobby Kit

Here is an Ultrasensitive Heat Sensor to monitor high temperature in Electronic devices. It can be placed inside the electronic gadget that usually generates heat during its operation. The circuit also functions as a sensitive Fire Alarm. This heat sensor uses the piezoelectric property to sense heatThe sensor element is the ordinary piezo disc found in buzzer. The middle part of the piezo disc is coated with a layer of piezo electric material. A high gain type OP-Amp is used to sense the electrical signals from the piezo disc. The inverting pin2 and non-inverting pin3 inputs of the Op-Amp IC CA3140 are shorted through the capacitor, so that both the inputs will be in a balanced state. When this happens, output of CA3140 remains low. When the piezo disc is subjected to heat stress, it generates a very small current that is enough for upsetting the balance of the inputs of IC CA3140. This changes the output of IC CA3140 from low to high. This high output is used to activate the alarm circuit based on the ROM IC UM3561.