Digital circuit production 02-adjustable digital running water lamp

1. Circuit simulation and principle explanation

       NE555 and peripheral circuits form a multivibrator. When the power is turned on, the initial state of pin 3 of the 555 chip is high level. When the C2 capacitor begins to charge to 2/3 of the power supply, the voltage of pin 3 becomes low level, and the 555 The discharge tube inside the chip is turned on, and when the C2 capacitor slowly discharges to 1/3 of the power supply, pin 3 changes from low level to high level again. Continuously cycle the charging and discharging process of the capacitor, changing the resistance of R13 changes the output frequency of pin 3, thereby affecting the speed of LED flow.
CD4017 is internally composed of a counter and a sequential one-code circuit. Pin 14 CP is the pulse signal input terminal and is connected to pin 3 of the 555 chip. As the pulse is input, the ten output pins from Q0 to Q9 output high level in sequence. After completing ten times of output, it will automatically reset and continue output.

2. Precautions

(1) If the water lamp part does not light up, check whether the LED light is welded correctly and distinguish the positive and negative poles;
(2) If the LED12 power indicator light does not light up after powering on, you need to check whether the USB is welded well and troubleshoot the problem;