IN the alcohol sensor interface we use alcohol sensor as a input logic. We attach one ic 555 as with this sensor . Here ic 555 work as a monostable timer. Sensor output is connected to the ic 555 pin no 2 via npn transistor. Pin no 2 is a negative trigger ic. When sensor activate then positive output is available and this positive output is converted into negative with the help of the NPN transistor. Output of the NPN transistor is now connected to the pin no 2 of the ic 555. Pinno 4 and 8 of the ic 555 is connected to the positive supply. Pin no 1 is connected to the ground pin. Pin no 7 is the output pin. Pin no 6 and 7 is the time constant pin. Pin no 6 and 7 provide a time constant option. When ic 555 works then output is available on the pin no 3 . Now this output is switching by the further NPN transistor.One led is also connected to the transistor circuit. Output of the npn transistor is available on the collector point. This output from the collector of NPN is now connected to the microcontroller pin no 1 which is port p1.0. Pin no 40 of the controller is connected to the positive supply. We supply a 5 volt regulated power supply on this pin. For regulated power supply we use one step down transformer . Step down transformer step down the voltage from 220 volt ac to 9 volt ac. This ac is converted into dc with the help of the rectifier circuit. Here we use two diode as a full wave rectifier. Output of the rectifier is now converted into 5 volt regulated supply with the help of 7805 regulator. IC 7805 regulator provide a 5 volt constant supply to pin no 40 of the ic. Pin no 20 is connected to the ground pin. LCD is connected to the port 0. Here we use 2 by 16 lcd for display. 2 by 16 means 2 line and 16 character.
Two output is available from the controller from port P2. One output is buzzer and second output to RF transmitter circuit. RF receiver circuit
To control a relay we use two transistor circuit. Output from the controller is drive the pnp transistor through 1 k ohm resistor. Collector of the pnp transistor is connected to the npn transistor through 1 k ohm resistor. Collector of the NPN transistor is connected to the relay coil directly. . Here relay is for the switching purpose only . As the transistor is on relay is on and relay break the contact of supply chain.
The systems will most likely have an alcohol sniffer or other sensors that can check a person’s odors, sweat, and awareness to see if they are capable of driving the car.
Here in this project we show that how we detect a alcohols then alarm is on and the same time lcd display shows the alcohol detection display. If the alcohol is detected then our system will switch on lights on vehicle.