Build an Alcohol Detection Engine Lock System

Depending on the country, as many as 25 to 35% of motor vehicle accidents happen because of drunk driving every year. When drivers consume alcohol, they not only put themselves at risk but others on the road. Fortunately, such accidents are preventable with a combination of education, personal responsibility, and community efforts.

There are also systems that can provide additional support. We’ll build one in this project.

This circuit design includes an alcohol detection device with an engine locking system. It uses the property of conductivity in an MQ3 alcohol gas sensor.

Working principle

The MQ3 alcohol gas sensor is developed from a material called SnO2, which detects alcohol gas. Connecting it to a microcontroller makes it possible to register the SnO2’s change in voltage output in the presence of alcohol. Thanks to a relay, a vehicle’s motor will automatically shut off based on the data from this sensor.

Block diagram

Figure 1. Block diagram

Materials

Arduino UNO (or a similar microcontroller board)
MQ-3 alcohol sensor
5V relay
LED
Buzzer
BC547 transistor
Dual-shaft dc geared Mmotor 100 RPM
Pushbutton switch
Power supply (9-V battery or dc adapter)
Breadboard and jumper wires
Connecting cables

Circuit diagram

Figure 2. The circuit diagram of the alcohol detection system using an MQ3 gas sensor.

Step-by-step guide

Step 1. The components
First gather all of the required materials and components. Set up the Arduino UNO on a breadboard and connect the MQ-3 alcohol sensor, the relay module, and the switch according to the circuit diagram.

Figure 3. The alcohol sensor connections.

Figure 4. The LED and buzzer connections.

Figure 5. The transistor circuit connections.

Step 2. Program Arduino

Ensure Arduino IDE is installed on your computer.
Write the code for the alcohol levels from the MQ-3 sensor and display them on the LCD.
Implement the logic to compare the alcohol levels with a predefined threshold.
Program Arduino to control the relay module, which acts as the engine lock mechanism.

Step 3. Calibrate the sensor

Power on Arduino and the alcohol sensor.
Allow the sensor to warm up and then calibrate it by exposing it to clean air and recording the baseline value.
Test the sensor with an alcohol source to ensure accurate readings.

This is a cost-effective sensor with many uses, including alcohol alarms, portable detectors, and breathalyzers. It’s quite sensitive and typically offers a long lifespan.

Step 4: demonstration
If no alcohol is detected, the vehicle’s motor will run normally. However, if the MQ3 sensor detects alcohol, it sends a signal to Arduino, which activates the buzzer and the LED. This alerts the motor via a circuit with a transistor and relay and will prevent the vehicle from turning on.

Figure 6. The demonstration.

Conclusion

Following the above steps, you can create an Arduino-based alcohol detector with an engine lock, promoting safe driving practices. Remember to use this device responsibly and encourage others to do the same to stop preventable car accidents.