beeping signal and flashes the LED in the gap of few seconds. But as the temperature or heat increases near the thermistor the number of beeping signal and LED flashing rate will also increase which will indicate the rise in the temperature.

The circuit is built around a 555 timer IC. The 1Meg Ohm NTC thermistor is used to sense the temperature. The 1K variable resistor is used to adjust the volume of the peizo buzzer. The circuit can be operated from 9V to 12V DC. 

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Here is a simple and easy to make heat or temperature sensor alarm circuit. A good feature of this circuit is that it will produce beep-beep sound and flashes an LED according to the temperature.
When the thermistor will receive low heat then the circuit will produces a

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Heat Or Temperature Sensor Alarm Circuit