Power supply voltage: 3-5V This kit is mainly composed of a clock generation circuit and a decimal counter circuit. Self-excited multivibrator with NE555 as the core Charging time is: 0.695 (R2+R1+VR1)C2, The discharge time is: 0.695 (VR1 + R1) C2 Adjusting VR1 can control the output frequency of the oscillator. The clock oscillation signal of U1 is continuously applied to pin 14 of U2. Ten LEDs of U2 are connected with 10 LEDs. When 10 outputs of U2 are under the action of clock signal When a high level is generated in turn, D1--D10 are sequentially illuminated to form a water light effect. The power supply charges the capacitor C2 through R2, R1, and VR1. When C2 starts charging, the 2 pin of U1 is still at a low level, so the output terminal 3 is at a high level, when the power supply is charged to R2 through R2, R1, and VR1. When the 2/ supply voltage is reached, the output pin 3 level changes from high to low, U1 internal discharge tube is turned on, and capacitor C2 is discharged through VR1, R1, and U1 pins until the voltage across C2 is lower than 1/3. At the voltage, the level of the 3 pin of U1 changes from low level to high level. C1 is charged again, and the cycle forms an oscillation. Specification: PCB size: 88x25 mm / 3.46x0.98 inch Package Includes: 1x NE555+CD4017 kit