Keyestudio ARDUINO maker learning kit, Manual

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As shown in the picture, the 555 integrated circuit is dual in-line with the 8-pin package. Thus:
Pin 1 (GND): the ground;
Pin 2 (TRIGGER ): the input of lower comparator;
Pin 3 (OUTPUT): having two states of 0 and 1 decided by the input electrical level;
Pin 4 (RESET): output low level when supplied a low voltage level;
Pin 5 (CONTROL VOLTAGE): changing the upper and lower level trigger values;
Pin 6 (THRESHOLD): the input of upper comparator;
Pin 7 (DISCHARGE): having two states of suspension and ground connection also decided by
input, and the output of the internal discharge tube;
Pin 8 (VCC): the power supply;
Schematic diagram
Connection for R3: