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555 timer (pack of 5) £1.35

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IC 555 timer

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element.

The IC 555 has three operating modes:

  • Bistable mode or Schmitt trigger - the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches.
  • Monostable mode - in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.
  • Astable (free-running) mode - the 555 can operate as an electronic oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. The 555 can be used as a simple ADC, converting an analog value to a pulse length (e.g., selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor and the period of the output pulse is determined by the temperature). The use of a microprocessor-based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.


Tech Tin Files: Hans R. Camenzind Inventor of the 555 timer circuit

  • Hans R. Camenzind (1934 - August 8, 2012) was a Swiss electronics engineer best known for designing the 555 timer IC in 1970. He was an inventor on 20 US patents. Hans wrote numerous books and technical articles and lectured at the University of Santa Clara.
  • Hans Camenzind was born and raised in Switzerland. After college there in 1960 Camenzind moved to the United States. He received an MSEE from Northeastern University and an MBA from the University of Santa Clara. After several years doing research in the Boston area, he moved to the West Coast to join Signetics (acquired by Philips Semiconductors, now NXP Semiconductors) and later started his own company, Interdesign. After heading it for seven years he sold Interdesign to Ferranti. Following the sale of Interdesign, Hans was an independent design consultant in analog IC design.
  • During his career he wrote three textbooks, designed the first integrated class D amplifier, introduced the phase-locked loop concept to ICs, invented the semicustom IC and created the 555 timer. He had designed 140 standard and custom ICs as of 2006.
  • Camenzind's last book, Much Ado About Almost Nothing, a general audience book on the history of electronics, was published in February 2007. Other books in publication include Designing Analog Chips.