This is a circuit which helps us in turning off the soldering iron automatically when it detects overheating and thereby avoids it from getting damaged.
This is a circuit which helps us in turning off the soldering iron automatically when it detects overheating and thereby avoids it from getting damaged.
The circuit uses a thermistor for detecting the temperature of the circuit. The resistance of the thermistor is inversely proportional to the temperature thereby the temperature of the thermistor decreases with increase of temperature and its resistance increases with decrease of temperature.
An NPN transistor is used as a switch to turn on or off the circuit depending on the temperature sensed. If the temperature reaches a threshold value, then the transistor operates in saturation mode and thereby provides low voltage at the output. The transistor circuit is arranged in common emitter mode.