# 555 and 556 Timer ICs

## Oscillator Configurations

Dublin Institute of Technology has a history and detailed explanation of the 555 pinout. ElectronicsTutorials has an excellent 555 oscillator tutorial that describes the ways a timer oscillator can be configured. Beavis Audio Research also has some very simple schematics that illustrate these configurations, and Williamson Labs has a cute animation.

## Timer IC Pinouts

555 pinout

1	GND
2	TRIG
3	OUT
4	RESET
5	CTRL
6	THR
7	DIS
8	V+/Vcc


556 pinout

14	Vcc
13	DIS
12	THR
11	CTRL
10	RESET
9	OUTPUT
8	TRIG
7	GND


555 → 556 Correspondence

1 => 7
2 => 8
3 => 9
4 => 10
5 => 11
6 => 12
7 => 13
8 => 14


## Applications

In astable mode, the 555 timer can be used as a simple pulse generator; this pulse generator can be modulated via the control pin, e.g. to construct an audio-modulated driver for a Plasma Speaker. It may also be used to construct a simple overload protection circuit.