Portable alcohol tester circuit diagram

 As long as the subject blows a breath through the sensor probe composed of a gas sensor, the tester can display the depth of the subject's intoxication and determine whether the subject is still fit to drive a vehicle. The circuit of a practical alcohol tester is shown in the figure, which is the ideal gas for a practical alcohol tester. The gas sensor is an MQ-Jl alcohol sensor, which is particularly sensitive to ethanol gas, so it is an ideal gas sensor for practical alcohol testing.

When the gas sensor cannot detect alcohol, the level applied to pin I⑤ is low; when the gas sensor detects alcohol, its internal resistance becomes low, causing the level of pin IC⑤ to become high. The IC is a display driver with a total of 10 output terminals, each of which can drive a light-emitting diode. The display driver IC determines the number of stages of lighting the LEDs based on the potential of pin ⑤. The higher the alcohol content, the greater the number of stages of lighting the diodes. The upper 5 LEDs are red, indicating that the safety level has been exceeded; the lower 5 LEDs are green, indicating the safety level, and the alcohol content does not exceed 0.05%.

Figure: Alcohol tester circuit