555 Basic Monostable Circuit

Basic monostable oscilator circuit can be deginhed by fallowing circuit schema.

Circuit trigger in from pin number 2 and output from pin 3.

The period can be calculated  T= R1 x C1

T is, time in seconds

R is, resistence in Ohms

C is, capacitanse in Farads

A negative trigger pulse at Pin 2 turns off a transistor that otherwise shorts C1 to ground, the output then goes high as C1 charges through R1. When the Vharge on C1 is 2/3 Vcc the 555 Discharges C1 to Ground. The output then goes low