Mainly composed of clock generation circuit and decimal counter circuit. The self-excited multivibrator with NE555 as the core, the power supply charges capacitor C1 through R2, R3, R. When C1 starts charging, the 2 pin of NE555 is still at low level, so the output pin 3 is high level. When the power supply is charged to the 2/3 power supply voltage through R2, R3, and R4, the output pin 3 level changes from high to low, and the NE555 internal discharge tube is turned on. The capacitor C1 is discharged through the 7-pin of R4, R3, and NE55 until the voltage across C1 is lower than 1/3 of the power supply voltage, the level of the 3 pin of the NE555 changes from low level to high level. C1 is charged again, and the cycle forms an oscillation. The charging time is: 0.695 (R2+R3+R4)C1, the discharge time is: 0.695 (R4+R3)C1, the R4 can be adjusted to control the output frequency of the oscillator, and the clock oscillation signal of NE555 is continuously added to the 14th pin of CD4017. Ten LEDs are connected to the 10 outputs of CD4017. When the 10 outputs of CD4017 alternately generate a high level under the action of the clock signal, D1--D10 are sequentially illuminated to form a water-light effect. Adjust the R4 to adjust the flow speed of the LED light. 2 x Module Item Type: Water Flowing Light Voltage: 2.5~14.5V Size: 5.4 x 2.1cm / 2.13 x 0.83in Thickness: 1.6mm