Editing 555 Timers

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The 8-pin 555 timer is one of the most popular [[Integrated Circuits]] (ICs) ever made.
It is also one of the cheapest chips on the market, costing anywhere from $0.20 to $1.20 depending on the quantity and distributor.

The 555 timer will operate from a power supply of 4 V (some versions even less) to about 16 V.
The 14-pin 556 timer contains two 555 timers in a single package -- the two timers (A and B) share the same power supply pins.

Astable - producing a square wave
Monostable - producing a single pulse when triggered
Bistable - a simple memory which can be set and reset
Buffer - an inverting buffer (Schmitt trigger) 

For more details on a variety of circuits that can be built using a 555 timer, see
* http://www.555-timer-circuits.com/
* http://en.wikipedia.org/wiki/555_timer_IC

[[Category:Components]]


== Example ==
555 timer is an analog integrated circuit based on voltage comparison. If on '''pin 2''' there is a voltage which is lower than 1/3 power supply, the output ('''pin 3''') takes the high level. The circuit keeps that condition until the voltage on '''pin 6''' goes over 2/3 power supply.
'''Pin 7''' is an electronic switch, and we use it on delay applications, to discharge the capacitor.  When the output takes the low level, pin 7 closes to the ground.
In the following diagram you can see a possible application, based on 555.
This simple circuit can be utilized to drive a monostable relay, using a single button switch.
When I press the button IC output (pin3) assumes the high level, but Q1 transistor swithces
off. So when I release it the relay is energized (now the exchange switch is closed on 5 and 9).
 When I press the button again IC output assumes the low level, but Q3 transistor switches
on: when I release the button the circuit goes to the start condition.
*[http://docs.google.com/leaf?id=0B7LPpongh6DzOTZlNjc3MDUtMzYwMy00ODQ2LWFmODItYmJiZTUyN2IzZDRj&hl=it Schematic]
*[http://sites.google.com/site/plcandcircuitdiagram/home Related resources]
*[http://www.mykoncept.com Related resources]