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.
Astable Mode outputs an oscillating pulse signal/waveform. In this mode the output of the 555 timer is switching between high and low states at a tunable frequency and pulse width. Jump straight to an example circuit for astable mode here.
Bistable Mode causes the 555 timer to toggle its output between high and low states depending on the state of two inputs. Jump straight to an example circuit for bistable mode here.
Some applications that come to mind include:
- a steady clock/trigger to keep time in a circuit (astable mode)
- the core oscillator of an analog synthesizer, with the addition of some op amps and other components this pulse wave can be shaped into a triangle, saw, and even sine shapes
- a very basic chiptune style noise maker (see atari punk console)
- time delay for an incoming signal (monostable mode)
- very basic storage of input data/management of two button control system (bistable mode)
The 555 timer is flexible, cheap, and easy to find (you can even pick them up at Radioshack). It's also a great starting point for audio projects because its output can be wired directly to a speaker. Feel free to use any of the info or example circuits I've provided in this tutorial as a starting point for an entry in the DIY Audio Contest! We're giving away an HDTV, DSLR cameras and tons of other great stuff! (ends November 26)