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For Hobbyists & Makers · 555 Timer

555 Timer for an op-amp filter

Built for hobbyists & makers exploring it for fun. Play with real physics and math, no license and no setup — just open and tinker. Simulate an op-amp filter live below — adjust the inputs and watch it respond, right in your browser.

555 Timer (Astable)Live

the classic square-wave oscillator

Controls

Presets

R1 (kΩ)

R2 (kΩ)

C (µF)

In astable mode the 555 oscillates on its own, charging the capacitor through R1+R2 and discharging through R2. Frequency f = 1.44 / ((R1+2R2)·C), and the duty cycle always exceeds 50% for this classic circuit. Educational tool.

▶ Run in Python

Data Inspector

Frequency1.4 Hz

Duty cycle55%

High time395.01 ms

Low time325.71 ms

Governing equation

f = \frac{1.44}{( R _{1} + 2 R _{2} ) C} = 1.4 Hz, D = \frac{R _{1} + R _{2}}{R _{1} + 2 R _{2}} = 55%

Reading this result: A slow 1.38 Hz output (period 0.72 s) suits an LED blinker; the large 10 µF capacitor dominates the timing.

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Frequently asked questions

Is this good for hobbyists & makers?: Yes — this version of "555 Timer for an op-amp filter" is framed for hobbyists & makers exploring it for fun. Play with real physics and math, no license and no setup — just open and tinker.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.