Circuit principle: The circuit is mainly composed of a pulse generator and a decade counter circuit. The pulse generator consists of NE555 and peripheral components to form a multivibrator. When the button S1 is pressed, Q1 is turned on, pin 3 of NE555 outputs pulses, and 10 output terminals of CD4017 output high level in turn to drive 10 LEDs to emit light in turn. After the button is released, Q1 will not be cut off immediately due to the presence of capacitor C1. As the voltage across C1 drops, the conduction process of Q1 will gradually weaken, the frequency of output pulses at pin 3 will slow down, and the frequency of LED movement will also follow. slow down. When C1 is discharged, Q1 is cut off, pin 3 of NE555 no longer outputs pulses, and LED stops moving. A ‘drawing’ process is thus completed.
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