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# Timer 555 Monostable, Astable - Output pulse duration calculator

Using this calculator, you will calculate the pulse duration of the output pulse of the NE555 IC in monostable or astable mode of operation.

## Timer 555 Monostable, Astable - Output pulse duration calculator - information

555 (also known as NE 555) - an integrated circuit (chip) that allows the implementation of many functions, e.g. a timer or multivibrator (square wave generator).

The 555 timer is one of the most popular and versatile chips ever produced. Consists of 23 transistors, 2 diodes and 16 resistors on a silicon wafer, housed in an 8-pin housing.

555 ma trzy tryby działania:
- monostable : 555 functions as a triggered single pulse generator. Applications of this mode include e.g. timing circuits, missing impulse detectors, elimination of switch contacts reflections, tactile switches, frequency dividers, capacitance measurement systems, generation of waveforms with a given pulse width (when stimulating from an astable system), etc.
- astable : 555 can act as a pulse generator or square wave. This mode is used for all kinds of blinkers (with LEDs or bulbs), for generating acoustic waveforms etc.
- bistable : 555 works as a flip-flop. In this operating mode, the DIS pin is not used and no capacitor is used. It is used, for example, to eliminate the effects of contact reflections in switches, or as memory elements.

Monostable system
The duration of the output pulse is set with one capacitor and one resistor.

Duration of the output impulse in the monostable plane:
$${\displaystyle t=ln(3)\cdot R\cdot C\approx 1.0986\cdot R\cdot C\approx 1.1\cdot R\cdot C}$$
R – in ohms (multiples of 1 kΩ = 1000 Ω, 1 MΩ = 1000 kΩ = 1 000 000 Ω)
C – in farads (aliquots of 1 μF =0,000001 F = 10^(-6)F, 1nF = 0,000000001 F = 10^(-9)F)

Astable system

In astable mode, the duration of the high state at the output is given by the formula:
$${\displaystyle t_{1}=\ln(2)\cdot (R1+R2)\cdot C}$$ duration of the low state
$${\displaystyle t_{2}=\ln(2)\cdot R2\cdot C}$$ Total time $${\displaystyle T=\ln 2\cdot (R1+2*R2)\cdot C=0,693\cdot (R1+2*R2)\cdot C}$$ The frequency of the output signal is given by the formula: $${\displaystyle f={\frac {1}{\ln(2)\cdot C\cdot (R_{1}+2R_{2})}}}$$

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