The 555 timer IC is an integrated circuit used in a variety of timer, delay, pulse generation, and oscillator applications. Derivatives provide two or four timing circuits in one package. The design was first marketed in 1972 by Signetics. [Wikipedia]
The 555 timer IC is an 8-pin dip plastic packaging chip. Many electronic component makers now manufacture it in significant quantities. Because it is a flexible IC that can be used to create a wide range of applications, it is highly popular among electronic design engineers, workers, students, and hobbyists.
Around 27 transistors and 10 to 15 resistors are found in each 555 timer IC. To create a useful project, the IC just requires a few external components. The IC has three modes of operation: oscillator, timer, and one-shot.
The IC has first launched 41 years ago and is still in use today. Its updated CMOS variant, designated 7555 and TLC555, is also available. The previous 555 was a loud chip, but the CMOS version has improved noise reduction circuitry as well as a slew of other new capabilities. The updated version also uses less power in terms of microamperes (uA), making it appropriate for battery-powered applications. In most cases, the 7555 may be used as a straight replacement for the 555.