Description
This kit composes of a clock generation circuit and a decimal counter circuit. It is a self-excited multivibrator with NE555 as the core. The power supply charges the capacitor C1 through R11, R12, and R13. When C1 just starts to charge, the 2 pin of NE555 is still in low level, so the output pin 3 is high. When the power supply charges C1 to 2/3 of the power supply voltage through R11, R12, R13, the output pin 3 level changes from high to low, and the internal discharge tube of NE555 turns on , The capacitor C1 is discharged through R12, R13, and the 7 pins of NE555, until the voltage across C1 is lower than 1/3 of the power supply voltage, the level of the 3 pins of NE555 changes from low to high again. C1 is charged again, This cycle forms an oscillation. The charging time is 0.695(R11+R12+R13)C1, and the discharging time is: 0.695(R12+R13)C1. Adjusting R13 can control the output frequency of the oscillator. The clock oscillation signal of NE555 is continuously added to the 14th pin of CD4017. 10 LEDs are connected to the 10 output terminals of the CD4017. When the 10 output terminals of the CD4017 generate a high level in turn under the action of the clock signal, D1–D10 will be lit in turn to form a water lamp effect.
