555 and 556 Timer ICs

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Datasheets[edit]

LM555, Texas Instruments

LM556, Texas Instruments

Oscillator Configurations[edit]

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[edit]

555-556 pinout.png

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[edit]

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.