555 timer

Texas Instruments NE555 in DIP-8 and SO-8 packages

The 555 timer IC was designed in 1970 by Hans Camenzind. There are hundreds of applications for the 555. The 556 is two independent timers in the same package.

Operating modes

• Astable multivibrator, (free-running) mode – operates as an oscillator for uses such as tone generation, pulse generation, clock signal.
• Monostable multivibrator, (one-shot) mode – functions as a one-shot pulse generator. Applications include switch debouncing and pulse-width modulation.
• Bistable multivibrator, (flip-flop) mode – operates as an SR flip-flop. Uses include debounced latched switches.
• Schmitt trigger, (inverter) mode – operates as a logic gate to convert a noisy input into a clean digital output.

Further reading

• Electronics engineer's mini-notebook - 555 timer circuits by Forrest Mims, Radio Shack Electronics, 1996
• Integrated Circuit 555 Projects by E.A. Parr, Bernard Babani Publishing, 1978, ISBN 0859340473
• 555 Timer Applications Sourcebook With Experiments by Howard Berlin, Sams Publishing, 1979, ISBN 0672215381
• Timer/Generator Circuits Manual by Ray M. Marston, Newnes, 1995, ISBN 0750604093
• IC Timer Cookbook by Walt Jung, Howard W Sams, 1977, ISBN 0672214164
• 110 IC Timer Projects by Jules Gilder, Hayden Book Co, 1979, ISBN 0810456885
• Encyclopedia of electronic components by Charles Platt with Fredrik Jansson, Timers, Ch. 9, Vol. 2, pp. 69-88, Maker Media, 2015, ISBN 9781449334185

External links

• 555 timer IC, Wikipedia
• xx555 Precision Timers, Texas Instruments data sheet
• 555 timer circuits, Lessons in electric circuits, Volume VI, Chapter 8 by Tony R. Kuphaldt

Projects

• Atari Punk Console
• Thomas Henry 555 VCO
• The VCO-555 by Thomas Henry, Electro-music.com Forum, Aug 2012
  • VCO-TH555, Green online, GitLab
• An easy AD envelope generator by Thomas Henry, Electro-music.com Forum, Dec 2018