3-LED Breathalyzer (breath alcohol tester)
(Reverse Engineered Schematics)
Schematic of a simple breathalyzer (electronic blood alcohol meter for breath tests) with an indication using three LEDs and with a flashlight. The sensor is probably MQ-303. It runs on 2 AAA alkaline batteries.
Schematic - For easier understanding of the function now drawn with the symbols of operational amplifiers (Op Amps) inside the LM324. LEDs indicate 3 levels of blood alcohol: less than 0.02%, above 0.02% and above 0.05%. The transistor controlled by the timing circuit will initially increase the heating voltage of the sensor for about 5 - 10s. Then you can take a breath test.
Breathalyser with a simple 3-LED indication.
3-LED breath tester opened.
Back to the list of reverse engineered schematics
Homepage