Physics

555 Timer Calculator

Find the frequency and duty cycle of an astable 555 timer.

Calculated Output

Frequency (Hz) 68.571

Duty cycle (%) 52.381

Formula: f = 1.44 ÷ ((R₁ + 2R₂)·C)

Step-by-Step Breakdown

1. Values used:

2. R₁ = 1,000 Ω

3. R₂ = 10,000 Ω

4. Capacitance = 1 µF

6. Frequency = 68.571Hz

7. Duty cycle = 52.381%

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The math behind it

f = 1.44 ÷ ((R₁ + 2R₂)·C). Duty cycle = (R₁ + R₂) ÷ (R₁ + 2R₂).

R₁ = 1 kΩ, R₂ = 10 kΩ, C = 1 µF → about 68.6 Hz, 52% duty.

Why can't duty go below 50%?

In the standard astable circuit the charge path is always longer; a diode mod fixes this.