The 555 timer is a popular integrated circuit that can do a whole lot in a very small package. Integrated circuits like the 555 hide their complex internal circuits behind a plastic case and have small metal leads to let you hook components up to them.
All ICs have a tiny notch on one side which indicates where pin 1 is on the chip. Pin order is then ascends counter clockwise. Each pin on the IC has a specific function which is exhaustively documented in the IC's datasheet.
- Astable — has, well, no stable state and the output continually switches between HIGH and LOW.
- Monostable — output stays in a LOW state until there is a trigger input.
- Bistable (aka Schmitt Trigger) —
Learn the ins and outs of the 555 timer with the new Patchr: 555 Timer Deep Dive.
Hans Camenzind invented the 555 timer in 1971 for the American company Signetics Corporation, now a part of Philips.