This is a Thermistor Temperaturee detecting and warning circuit in one. When the temperature exceeds a certain threshold, the circuit sounds an alarm. Temperature monitoring is a critical and widely used application in businesses and a variety of other settings where the temperature must be kept below a certain limit. When a case like this develops, this circuit comes to our rescue.
The circuit is designed to be low-cost and dependable, allowing you to build it with fewer resources while maintaining high performance. Even though it is not an industry-standard calibrated circuit, it is adequate for non-mission-critical applications. Another benefit of this circuit is that it can modify the temperature level to which it is set. This means you can specify the temperature at which the circuit should sound an alarm if the temperature rises above a certain level.
Circuit Diagram of Thermistor Temperature Sensing Alarm:
A thermistor is an element in a circuit that senses the temperature of the environment. The meaning of the name is obvious. The term “thermistor” refers to a device that combines the terms “thermal” and “resistor.” It signifies that the thermistor’s resistance changes as the temperature changes. The resistance of the thermistor and the temperature have an inverse relationship. This means that as the temperature in the atmosphere rises, the thermistor’s resistance drops, and as the temperature outside falls, the thermistor’s resistance rises. The thermistor’s property allows us to utilise it to feel the temperature of the environment.
When the temperature exceeds the desired value, the circuit uses two BC547 NPN transistors to activate the alarm. The circuit uses the IC 4011, which is a quad NAND gate integrated circuit. It contains four NAND gates in a single integrated circuit. This decreases the circuit’s size and complexity.
An oscillator circuit is a combinational circuit that is made using NAND gates. Any combinational circuit, as we all know, has an inherent time delay between the input and output. This time delay is often regarded undesirable, but we’re using it to make it act as an oscillator in this case. As a square wave oscillator, the circuit turns on and off repeatedly with a time delay. The oscillator’s output is sent into a buzzer, which works at the audio frequency. The capacitors in the circuit operate as filters, removing undesired signal components and maintaining the circuit’s stability and appropriate operation.