# 555 Timer

The 555 timer is a very popular integrated circuit. It is often used in timers, pulse generation and oscillator applications.

### Astable

When the 555 timer is in astable mode, The timer will generate rectangular pulses with a specific frequency. An astable circuit can be connected as in the image below.

#### Formulas

The following formulas can be used to calculate the frequency, period, duty cycle, high time and low time of the 555 timer in astable mode.

f is the symbol for frequency and is measured in hertz (Hz).

C is the symbol for capacitance and is measured in farad (F).

R is the symbol for resistance and is measured in ohm (Ω).

T is the symbol for period and is measured in seconds (s).

DC is the duty cycle and is a percentage

#### Calculator

Enter the capacitance and resistances to calculate all other values.

### Monostable

When the 555 timer is in monostable mode, the generated pulse ends when the voltage on the capacitor is 2/3 of the supply voltage. The length of this pulse can be changed by changing the values of the resistor and capacitor. A monostable circuit is connected as in the image below.

#### Formulas

You can use the following formulas to calculate the capacitance, resistance, and output pulse width.

T is the symbol for period and is measured in seconds (s).

R is the symbol for resistance and is measured in ohm (Ω).

C is the symbol for capacitance and is measured in farad (F).

#### Calculator

Enter two values to calculate the third.