555 Timer Calculator

Calculate timing parameters for astable, monostable, and PWM modes

Astable Mode Calculator

Calculates output frequency, duty cycle, and time periods for oscillator circuits.

About Astable Mode

The 555 timer in astable mode acts as a free-running oscillator. It continuously switches between high and low states without any external trigger, producing a square wave output.

Results

Frequency: 0 Hz

Period: 0 seconds

Duty Cycle: 0%

Time High (TON): 0 seconds

Time Low (TOFF): 0 seconds

Astable Mode Circuit Diagram

Current values: R1 = 10 kΩ, R2 = 10 kΩ, C1 = 10 nF

Monostable Mode Calculator

Calculates pulse width for one-shot timer circuits.

About Monostable Mode

The 555 timer in monostable mode produces a single pulse of a fixed duration when triggered. It returns to its stable state after the pulse duration completes.

Results

Pulse Width (T): 0 seconds

Monostable Mode Circuit Diagram

Current values: R1 = 10 kΩ, C1 = 10 nF

PWM Mode Calculator

Calculates pulse width modulation parameters.

About PWM Mode

Pulse Width Modulation (PWM) is a technique to encode a message into a pulsing signal. The 555 timer can generate PWM signals by varying the control voltage.

Results

Frequency: 0 Hz

Duty Cycle Range: 0% to 0%

Current Duty Cycle: 0%

Pulse Width: 0 seconds

PWM Mode Circuit Diagram

Current values: R1 = 10 kΩ, R2 = 10 kΩ, C1 = 10 nF

Reverse Calculation

Calculate resistor and capacitor values from desired frequency.

About Reverse Calculation

This tool helps you find suitable resistor and capacitor values to achieve a specific frequency in astable mode.

Hz
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Results

R1: 0 kΩ

R2: 0 kΩ

Actual Frequency: 0 Hz

Actual Duty Cycle: 0%

Help & Guide

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element.

This calculator helps you design circuits using the 555 timer in its three common modes:

  • Astable mode: The 555 operates as an oscillator, generating a square wave output.
  • Monostable mode: The 555 produces a single pulse when triggered.
  • PWM mode: The 555 generates pulse width modulated signals by varying the control voltage.

Astable Mode Formulas

Frequency: f = 1.44 / ((R1 + 2 × R2) × C1)

Duty Cycle: D = (R1 + R2) / (R1 + 2 × R2) × 100%

Time High (TON): 0.693 × (R1 + R2) × C1

Time Low (TOFF): 0.693 × R2 × C1

Monostable Mode Formulas

Pulse Width (T): 1.1 × R1 × C1

PWM Mode Formulas

Frequency: Same as Astable mode

Duty Cycle: Varies with control voltage (0-Vcc)

Astable Mode Applications
  • LED flashers and blinkers
  • Pulse generation
  • Clock generation for digital circuits
  • Tone generation
Monostable Mode Applications
  • Timers
  • Touch switches
  • Missing pulse detection
  • Debounce circuits
PWM Mode Applications
  • Motor speed control
  • LED dimming
  • Power control
  • Analog signal generation

  • For stable operation, use resistor values between 1kΩ and 1MΩ.
  • Use ceramic or electrolytic capacitors for timing circuits.
  • Add a 0.01μF decoupling capacitor between Vcc and GND close to the IC.
  • For precise timing, use 1% tolerance resistors and capacitors.
  • In astable mode, duty cycle can never reach 50% - it's always greater.
  • For lower frequencies, use larger capacitor values.
  • Keep leads short to minimize stray capacitance.