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:

NE555 Astable Circuit Schematic

Capacitor \((C)\):
Resistor \((R_1)\):
Resistor \((R_2)\):

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

Period \((T)\):
Duty Cycle:
Time High \((T_1)\):
Time Low \((T_0)\):

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%.

NE555 Period description

Reverse Calculator

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

Frequency \((F)\): Hz
Duty Cycle: %

Possible set ups: