555 timer IC oscillate frequency online calculator

The 555 timer works in astable mode as shown in Figure 1, The capacitor charges through resistor RA and RB, and discharges through RB.

Figure 1

Figure 2 is the waveform of the output and the voltagge of the capacitor where Ra=5k ohm, Rb=10k ohm, and capacitor=0.01uF.

Figure 2

So the high time (charging the capacitor) is given by:

Where Ln(2)=0.693, And the low time (discharging the capacitor) is given by:

Total period is:

The frequency is:

Input RA, RB C to calculated frequency and period:

Capacitor C		pFnFuF
Resistor Ra		mOhmOhmKOhmMOhm
Resistor Rb		mOhmOhmKOhmMOhm
Output high time T1		smsusps
Output low time T2		smsusps
Total period T		smsusps
Oscillate frequency f		HzKHzMHz
Wave duty cycle D

More Related Pages