NE555. How does it work? Set and reset. This is the block diagram of the NE555 IC.

NE555. How does it work?

Set and reset. This is the block diagram of the NE555 IC. The first circuit analyzed is the voltage divider. The voltage at pin 8 is Vcc. Three 5K resistors are in series. Note the switch B connecting Vcc to pin 6 of the IC.

Voltage divider. Two-thirds of Vcc. Voltage divider. One-third of Vcc. The voltage of 1/3 of Vcc is compared with the voltage at pin 2. If it is less than 1/3 of Vcc, it activates the output at pin 3.

Switch A connects pin 2 to GND. Voltage at pin 2 = 0 Volts. The output at pin 3 goes to the voltage Vcc. You can connect a load. Switch B connects Vcc to pin 6. This is the Reset. It turns off pin 3.