555 Timer Tutorial - The Monostable Multivibrator

The 555 timer chip is extremely robust and stable 8-pin device that can be operated either as a very accurate Monostable, Bistable or Astable Multivibrator to produce a variety of applications such as one-shot or delay timers, pulse generation, LED and lamp flashers, alarms and tone generation, logic clocks, frequency division, power supplies and converters etc, in fact any circuit that requires some form of time control as the list is endless.

555 Timer - Instructables

By wiring the 555 timer with resistors and capacitors in various ways, you can get it to operate in three different modes: Monostable Mode is great for creating time delays. In this mode an external trigger causes the 555 timer to output a pulse of an adjustable duration. Jump straight to an example circuit for monostable mode here.