You don't need to connect C1 and R10 first. When you tap the toggle switch once, it is equivalent to getting an oscillating working voltage waveform from 0V to 6V on pin 14 of IC1, which is in line with the rising edge waveform standard. Ideally, every With one tap, the LEDs are illuminated successively from LED0 in a cyclic system. But when operating, why is it not illuminated successively, but only at will? To know the reason for this, you also need to learn the professional knowledge of training function key debounce.

Because the inside of the toggle switch is a metal shrapnel, when the toggle switch is pressed or released, due to the elastic effect of the metal shrapnel, the power switch cannot be connected immediately and smoothly when it is turned off. When the toggle switch is released, the metal shrapnel is released. It also cannot be disconnected immediately, that is, at the moment of closing and disconnecting, a series of unstable vibrations occur. The method of eliminating vibration can use the characteristics of capacitor battery charging to develop the current formed in the whole process of function key vibration. Smooth edges.

Connect the capacitor C1 and the resistor R10, and carry out the experiment again. Each time the toggle switch is tapped, does the LED light up in turn? How to design a book that can automatically illuminate LEDs successively? In the front, we will introduce in detail the unstable situation of 555, which can receive the data signal output by 555 to the input terminal of CD4017, and complete the actual effect of LED automatic water flow.

In order to make the layout more reasonable and beautiful, the LED and the corresponding power resistor can be replaced, and the electronic counter can first connect the LED from the power resistor to the negative level of the switching power supply.