This module is used for beginners to learn the principle of water level alarms through the practice and experiment.

The core of the the test board is HQS1315. Power, HQS1315 enters self-testing state, SPI buzzer sounds loudly, D5 LED turns on. Then begin to detect the potential of 8/9/10 feets, R1/R2/R3 are pull-down resistors, when the water is empty, 8/9/10 feets are at low level, at this moment, D1 indicator light is steady on, buzzer sounds intermittently and the module enters into lacking water alarm state; The third foot of HQS1315 outputting high level means now is filling with water, D5 indicator intermittently lit; When the water level rises, due to the conductivity of the water, the power supply VCC will firstly rise the potential of the 8th foot, then D2 LED is lit, the buzzer stop alarm, indicating that currently has exited water alarm and entered a low-level state; But the third foot of HQS1315 still outputs high level, D5 keeps flashing, indicating that it keeps filling with water; When the 9th foot of HQS1315 outputs high level, D3 LED is lit, indicating that the water level is in medium; When the 10th foot outputs high level, indicating that it has been fully filled with water, D5 LED stops flashing, the third foot of HQS1315 outputs low level, D4 LED is lit, indicating water is full; Until then, all the work process is finished.