Variable frequency square wave generator based on IC 555 calculator

Square wave generator based on IC 555 online calculator allows you to easily determine pulse frequency and other parameters of a circuit.

A square pulse generator built on the basis of the popular 555 microcircuit works as a multivibrator i.e. in self-oscillating (astable) mode. This is a mode in which impulses arise themselves, without any external influences. Adding a variable resistor R₃ to the circuit allows to get variable pulse frequency.

To calculate the min (f₁) and max (f₂) pulse frequencies, you can use the following equations:

f₁ = 1 / (0.693 * C₁ * (R₁ + 2 * (R₂ + R₃))),
t_{1_1} = 0.693 * (R₁ + (R₂ + R₃)) * C₁,
t_{1_2} = 0.693 * (R₂ + R₃) * C₁,
f₂ = 1 / (0.693 * C₁ * (R₁ + 2 * R₂)),
t_{2_1} = 0.693 * (R₁ + R₂) * C₁,
t_{2_2} = 0.693 * R₂ * C₁
T = t₁ + t₂ = 1 / f,
D = (t₁ / T) * 100%

where:

f₁ – min vibration frequency
f₂ – max vibration frequency
t_{1_1} – pulse duration at min frequency
t_{1_2} – pause duration at min frequency
t_{2_1} – pulse duration at max frequency
t_{2_2} – pause duration at max frequency
T – period
D – duty cycle (%)

As follows from the calculation, in such a generator circuit it is impossible to obtain an exact filling of 50%, that is, a clear meander.

Learn more about square wave generator using IC 555.

This tool also allows you to share and print calculation results.

Learn more about SMD resistor code.