計算機

555 Timer Calculator

Calculate 555 timer circuits — astable oscillator frequency, duty cycle, and monostable pulse width with component design, circuit diagrams, and waveform preview

Component Values

10 kΩ

47 kΩ

Frequency
138.750 Hz
Period: 7.207 ms · Duty: 54.8%
High Time
3.950 ms
Low Time
3.257 ms
Duty Cycle
54.8%
Period
7.207 ms

Astable Circuit

5558 Vcc7 DIS6 THR2 TRG1 GND4 RST3 OUT5 CV+VccR1R2C+VccOUT10nF

Output Waveform

555 Timer Formulas

Astable (Free-Running)

High Time
t_high = 0.693 × (R1 + R2) × C
Low Time
t_low = 0.693 × R2 × C
Frequency
f = 1.44 / ((R1 + 2×R2) × C)
Duty Cycle
D = (R1 + R2) / (R1 + 2×R2) × 100%

Monostable (One-Shot)

Pulse Width
t = 1.1 × R × C

Where R is in ohms and C is in farads. The 0.693 constant is ln(2) and 1.1 constant is approximately ln(3).

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