Wiring Diagram

In the monostable mode, the timer 555 acts as a "one-shot" pulse generator. The pulse Begins Pls the 555 timer receives a signal at the trigger input That falls below a third of the voltage supply. The width of the output pulse is determined by the time constant of an RC network, the which consists of a capacitor (C) and a resistor (R). The output pulse ends Pls the charge on the C equals 2 / 3 of the supply voltage. The output pulse width cans be lengthened or shortened to the need of the specific application by adjusting the values of R and C.