Design of a microcontroller based alcohol detector device

This book is about designing a microcontroller based alcohol detector device, also known as a breathalyzer device. The designed device basically consists of an alcohol sensor chip, a microcontroller development system, a text based LCD display, 3 coloured LEDs, and a speech processor module. The user blows onto the alcohol sensor through a small plastic tube. The alcohol sensor generates a voltage proportional to the measured alcohol level. This analog voltage is fed to the A/D converter input of a PIC16F887 microcontroller. The microcontroller processes the signal and calculates the actual alcohol level of the subject. The result is displayed in mg/L on the text LCD. In addition, one of the LEDs is turned ON to indicate whether or not the user is legally allowed to drive a vehicle. If the green LED is turned ON then the alcohol level is below the legal limit. If the orange LED is turned ON the user is legally at the border level. If on the other hand the green LED is turned ON then the alcohol level of the user is above the legal limit and the user should not drive a vehicle. In addition to visual outputs, the designed alcohol sensor also provides speech output through a speec