Alcohol tester kit drunk driving tester MQ-3 module alcohol sensor DIY parts

Alcohol concentration alarm circuit This circuit is mainly composed of an alarm control circuit composed of a gas sensor group mq-3. When there is alcohol vapor in the environment where the sensor mq-3 is located, the conductivity of the sensor will increase with the increase of the alcohol vapor concentration. The alcohol content in the environment can be determined by measuring the series voltage between the sensor and the fixed resistor.

This circuit can be powered by a 5-7.5 volt DC power supply. Switch S1 is the power switch. Resistor R1 and light-emitting diode are used for power indication. The sensor MQ-3 needs to be heated to a certain temperature when working, so a heating wire is installed inside it. Resistor R4 is the current limiting resistor of the heating wire. It is normal for MQ-3 to heat up after power is turned on. When MQ-3 does not detect alcohol vapor, its internal resistance is large, the voltage drop of R3 and RW is very low, the voltage of NE555's 2nd pin is lower than the trigger voltage (VCC/3), its 3rd pin outputs a high level, D2 goes out, the buzzer does not sound, and the relay does not work. When MQ-3 detects alcohol vapor, the internal resistance decreases, the voltage of R3 and RW increases, the voltage of pin 2 of NE555 is higher than the trigger voltage, pin 3 becomes low level, D2 turns on and lights up, the buzzer starts to sound through current, and the electromagnetic coil in the relay is energized to attract the switch. Thus, the detection alarm function is realized. The adjustable resistor RW is used to adjust the detection sensitivity. This circuit uses the second comparator inside NE555 to detect voltage changes and uses its internal trigger to eliminate jitter. Pins 7 and 5 of NE555 are not used and are in a suspended state. The output terminal J3 of the relay can be used to control other electrical appliances, such as exhaust fans. When the alcohol concentration exceeds the standard, the exhaust fan is started, and when the concentration drops, the exhaust fan is turned off to achieve automatic control. Diode D3 is used to eliminate the induced electromotive force generated when the relay coil is turned on and off. The power supply interface can be a DC , or it can be directly connected to the J2 position with a wire. Pay attention to the positive and negative poles. The DC supplies power with positive inside and negative outside.

Specifications:

Product Name: Alcohol Tester Kit

Material: PCB

Color: Green

Working Voltage: 5-7.5V DC

Size: PCB 60*36mm

Package Content:

1*Alcohol Tester Kit

Note:

1. The real color of the item may be slightly different from the pictures shown on the website caused by many factors such as brightness of your monitor and light brightness.