# NE555 Astable Circuit Calculator

In astable mode, the NE555 can be used to create an oscillating output between VCC and 0V. All that is needed is a setup like in the following schematic:

Capacitor $$(C)$$: nFμF ΩkΩMΩ ΩkΩMΩ

By selecting proper values for $$R_1, R_2$$ and $$C$$, we can determine the frequency and duty cycle of the oscillation:

Frequency: ▶

A period is the time for one full on/off cycle to repeat itself and the duty cycle is the percentage of time the signal was high in one period. In a NE555 astable circuit, the duty cycle can never be below 50%.

## Reverse Calculator

The following calculator presents possible resistor and capacitor values, based on a desired frequency and duty cycle.

Frequency $$(F)$$: Hz %

Possible set ups: