[electronic scheme design] PCBA solution for alcohol tester

　　 According to statistics, about 50% of traffic accidents in the world are related to drinking , And want to increase the punishment for drunk driving , The first thing to be solved is how to measure the alcohol content of human body efficiently , Alcohol tester came into being . The following is an alcohol tester developed by the solution provider PCBA programme .
　　
　　 How the alcohol tester works ：
　　
　　 When the gas sensor cannot detect alcohol , Add to A Of the 5 Pin level is low , When the gas sensor detects alcohol , Its internal resistance becomes low , So that A Of 5 The pin level becomes high .A To display the pusher , It has 10 Outputs , Each output can drive a light-emitting diode , Show pusher A According to the first 5 The pin level determines the number of light-emitting diodes that are lit in turn , The higher the alcohol content, the greater the number of stages of lighting the diode . above 5 The LEDs are red , It means that the safety level is exceeded . below 5 LEDs are green , Indicates the safety level , The alcohol content does not exceed 0.05%.
　　
　　 Function is introduced
　　
　　1. Turn it on ： Press and hold the key 2 Second power on , Buzzer “ di ” A sound ,LCD Full display 1 second .
　　
　　2. preheating ： Buzzer “ di ” A sound , Start 10 Seconds to warm up , Show at the same time ① Warm up sign ② battery level ③ Sensor life indicator ④10 Second countdown display ⑤ arc .
　　
　　3. measurement ： Buzzer “ di ” A sound , Start 10 Second measurement , Show at the same time ① Blowing sign ② battery level ③ Sensor life indicator ④10 Second countdown display ⑤ arc .
　　
　　4. result ： Buzzer “ di ” A sound , Start 10 The second result shows , Show at the same time ① Result flag ② battery level ③ Sensor life indicator ④ Measurement value and unit ⑤ arc ⑥ Warning level sign , The buzzer will sound when the result is out of range “ Diddiddidi ” Continuous alarm ; Press and hold the key in this state 2 Seconds to enter the history display .
　　
　　5. Historical record ： Buzzer “ di ” A sound , Display record number 1 second （1~50）, Then the history and units are displayed 9 second , Show at the same time ① Result flag ② battery level ③ Sensor life indicator ④ Warning level sign ; In this state , Short press the key to record the number increasing circularly , And restart the display timing ; In this state, the arc around the value is not displayed .
　　
　　6. To turn it off ： Buzzer “ di ” A sound , Display the sensor life indicator 1 Seconds later , The screen is turned off .
　　
　　 Sensor life indicator
　　
　　1. Number of tests ≤500 when , green
　　
　　2. Number of tests ＞500 And ≤1000 when , yellow
　　
　　3. Number of tests ＞1000 when , Red
　　
　　4. Number of tests ＞2000 when , Flashing red
　　
　　5. Number of tests ＞2500 when , Jump straight to 【 To turn it off 】
　　
　　 battery level
　　
　　1. Battery voltage ≥3.7V when , The battery logo is displayed in full cells
　　
　　2. Battery voltage 3.3V~3.6V when , The battery logo is displayed in half space
　　
　　3. Battery voltage 3.2V when , The battery flag space displays
　　
　　4. Battery voltage 3.1V when , The battery flag space flashes
　　
　　5. Battery voltage 3.0V when , The battery flag space flashes , Jump straight to 【 To turn it off 】

　　 Warning level sign
　　
　　1. Measurement results ＜0.15mg/L when , Show green sign （ Security ）
　　
　　2. Measurement results ≥0.15mg/L And ＜0.25mg/L when , Show yellow sign （ Warning ）
　　
　　3. Measurement results ≥0.25mg/L when , Show red sign （ dangerous ）