Description

• The 555 timer IC is an 8-pin electronic pulse generator. Its general-purpose design lets you configure it for different modes of operation, such as astable (free-running oscillator) or monostable (one-shot). It has a frequency range of less than one pulse per minute up to about 500 kilohertz.
  
  

Clock

• Many digital circuits need a centralized pulse source, called a clock, to synchronize signals and events. The 555 IC's astable mode produces a steady pulse waveform suitable for clocking digital circuits.
  
  

Tone Source

• The same astable mode that generates pulses can be used in the audio range to create tones in a speaker. You can use a 555 as a beeper, buzzer or siren.
  
  

One-Shot

• The 555 can be configured in monostable, or one-shot, mode. When it receives a trigger pulse, it produces a single, precisely timed pulse of its own. You can, for example, use this to open an automatic door for ten seconds, then close it.
  
  

Light Flasher

• You can use a 555 to directly drive a light-emitting diode (LED). Running as a pulse generator, it will flash the LED at any speed you wish. Several 555s flashing LEDs can create a colorful, twinkling display.