is only 500uA, due to which it is ideal for battery operated projects.
The heart of the circuit is a LM358 IC that is working as a comparator in the circuit. A 100K NTC thermistor is used to sense the heat or temperature. The desired level of heat to activate the relay switch can be selected with the 20K variable resistor. The circuit can be adjusted to achieve any specific level of heat by experimenting the values of 20K variable resistor, 100K resistor and thermistor. The operating voltage of the circuit is 9V to 12V DC. The circuit can also be operated with lower voltages like 5V or 6V. The relay should be used according to the operating voltage.
This is a simple circuit of a heat sensor using lm358 IC. The circuit can be adjusted to activate a relay switch on a desired level of heat. Any AC or DC appliance could be connected to the relay switch to switch it ON at a desired level of heat. In standby the current consumption of the circuit
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