Timer 555 astable

The classic oscillator! With the use of two resistors a 10kOhm and a 100kOhm resistor and a capacitor of 10uF the 555 can control its output oscillation with an amplitude ranging from 0V to the maximum power supply voltage. During charging of the capacitor via the two resistors, the timer 555 provides supply voltage at the output. If the capacitor is charged, the discharging process starts via the 100kΩ resistor. When the capacitor is discharged completely, the process starts again. The oscillation generated is a square signal, because the timer 555 switches between supply voltage and ground. The red LED flashes as long as the timer 555 is connected to the power-supply, that’s why this mode is called astable. The lighting period is 10 percent higher than the dark phase of the LED. Both phases together determine the period.
The time period can be calculated with the following equation:

T = (R1+2*R2 )*C*ln(2) = (10kΩ+2*100kΩ)*10μF*ln(2) = ca. 1.5s