555 Timer Astable Circuit Calculator

555 Timer Astable Circuit Calculator

555 Timer Astable Circuit Calculator

Output

Theory of Operation

555 Timer Astable Circuit Diagram

The 555 timer in astable mode is a multivibrator circuit that oscillates between high and low states continuously, producing a square wave output. The frequency and duty cycle of this output waveform depend on the resistor and capacitor values in the circuit.

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

  • R1: External resistor connected to the discharge pin (in Ohms).
  • R2: External resistor connected to the threshold pin (in Ohms).
  • C: Capacitor connected to the timing network (in Farads).

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

The high and low time durations of the output waveform are given by:

  • Time High (TH): 0.693 × (R1 + R2) × C
  • Time Low (TL): 0.693 × R2 × C

Applications

  • Waveform Generators: Used to generate square waves for timing and control applications.
  • PWM Circuits: Pulse width modulation for motor speed control.
  • Flashing Lights: Ideal for creating blinking LEDs or other oscillatory circuits.

Example Calculations

Example 1: Basic Calculation

Given:

  • Resistor R1 = 10kΩ (10,000 Ω)
  • Resistor R2 = 100kΩ (100,000 Ω)
  • Capacitor C = 10µF (0.00001 F)

Formula:

  • f = 1.44 / ((R1 + 2 × R2) × C)
  • D = ((R1 + R2) / (R1 + 2 × R2)) × 100%

Calculation:

  • f = 1.44 / ((10,000 + 2 × 100,000) × 0.00001) = 0.69 Hz
  • D = ((10,000 + 100,000) / (10,000 + 2 × 100,000)) × 100% = 35%

Result: Frequency is 0.69 Hz, and Duty Cycle is 35%.