555 Timer: What is this, How it works and Its Modes of Operation

555 Timer is an IC which is used to create timed pulses with regular intervals. In this post you’ll learn what is 555 Timer, how it works and its operations modes.

What is 555 Timer and How it works

A 555 timer is an eight terminal integrated circuit which emits timer pulses. The IC has three 5 ㏀ resistors which are connected in series between the pin 1 & 8, due to which it is named as 555. The 555 timer operates in two modes:

  1. Monostable mode
  2. Astable mode
In mostable mode a change in voltage state (from low to high) creates a timed pulse. Whereas in astable mode the timer itself triggers when the power source is connected. Let’s watch the 555 timer IC in action:

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