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# 555 timer calculator

Astable frequency and duty from RC values, resistors for a target, or a monostable pulse width.

Choose a mode and enter the timing components.

Timing follows the standard bipolar-555 equations: the astable charges through R1+R2 and discharges through R2 alone, so its duty cycle always sits above 50%, and the monostable pulse is 1.1 times R times C. Findings flag the component choices that tend not to work in real hardware: discharge resistance under 1 kΩ, timing resistance past 10 MΩ, capacitors under 500 pF or deep into electrolytic territory, frequencies past a bipolar NE555, and monostable pulses under 10 µs.
Options

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