Alcohol Tester Kit MQ-3 Detection Sensor Module Welding Training DIY parts

Feature When alcohol vapor exists in the environment where the sensor MQ 3 is located the conductivity of the sensor will increase as the alcohol vapor concentration increases By measuring the series partial pressure between the sensor and the fixed resistor the alcohol content in the environment can be determined Working voltage 5 7 5V DCPCB size 6 2 3 6cmCircuit description This circuit can be powered by a 5 7 5 volt DC power supply The switch S1 is a power switch The resistor R1 and the light emitting diode D1 are used for power indication The sensor MQ 3 needs to be heated to a certain temperature during operation so there is a section of electric heating installed inside it The wire and resistor R4 are the current limiting resistance of the heating wire It is normal for the MQ 3 to generate heat after being energized When MQ 3 does not detect alcohol vapor its internal resistance is very large the voltage drop of R3 and RW is very low the voltage of pin 2 of NE555 is lower than the trigger voltage VCC 3 its pin 3 outputs high level D2 goes out The buzzer does not sound and the relay does not operate When MQ 3 detects alcohol vapor the internal resistance drops the voltage of R3 and RW rises the voltage of pin 2 of NE555 is higher than the trigger voltage pin 3 becomes low level D2 turns on and emits light and the buzzer flows The current starts to sound and the electromagnetic coil in the relay is energized to attract the switching action In