temperature sensor circuit

The schematic presented is a project for a simple temperature sensor circuit, also referred to as a heat sensor circuit, which activates an LED in response to heat. The circuit is straightforward to construct and requires only a few components. Two BC547B transistors are configured as a Darlington pair to enhance the circuit's sensitivity. Additional components include an LED, a current-limiting resistor for the LED, a 20K variable resistor, and a thermistor. A thermistor is a type of resistor whose resistance varies with temperature; it exhibits higher resistance at lower temperatures and rapidly decreases in resistance when exposed to heat, allowing current to flow. The operation of the circuit is simple: when the thermistor detects heat, its resistance decreases, causing the transistors to turn on and allowing voltage to flow through them, which activates the LED. The 20K variable resistor is used to calibrate the circuit to activate the LED at the desired temperature threshold.

The temperature sensor circuit utilizes a thermistor, which is a critical component that responds to temperature changes by altering its resistance. This property allows it to function effectively in detecting thermal variations. The BC547B transistors, arranged in a Darlington configuration, provide a significant amplification of the current, thereby increasing the circuit's sensitivity to small changes in temperature. The Darlington pair is particularly advantageous in applications where a higher gain is required, enabling the circuit to respond to subtle temperature shifts.

The LED serves as a visual indicator, illuminating when the circuit detects a sufficient increase in temperature. The current-limiting resistor is essential to prevent excess current from damaging the LED, ensuring longevity and reliable operation. The inclusion of a 20K variable resistor allows for fine-tuning of the circuit's response, enabling the user to set the desired activation temperature for the LED.

In summary, this simple temperature sensor circuit is an effective solution for heat detection, leveraging the properties of a thermistor and the amplification capabilities of a Darlington pair to provide a reliable output in the form of an illuminated LED. The design is user-friendly and can be easily assembled with minimal components, making it suitable for various applications in temperature monitoring and alarm systems.The schematic shown here is a project of a simple temperature sensor circuit or we can also say it a heat sensor circuit, which will activate an LED when receive heat. The circuit is easy to make and using only few components. The two BC547B transistors are connected as a darlington pair to increase the sensitivity of the circuit.

Other components of the circuit are an LED, a current limiting resistor for LED, a 20K variable resistor and a thermistor. A thermistor is a device that limits the passing of current through it according to the temperature. In the condition of low temperature they have higher resistance and in the opposite condition when they receive heat their resistance starts decreasing rapidly and current starts to flow.

Working of the circuit is simple when the thermistor will receive heat its resistance will decrease due to which the transistors will become switched on and the voltage will starts passing through the transistors which will activate the LED. The 20K resistor is used to adjust the circuit to activate the LED on the required heat or temperature.

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