http://www.opencircuits.com/api.php?action=feedcontributions&feedformat=atom&user=AndreapgOpenCircuits - User contributions [en]2026-04-22T15:05:01ZUser contributionsMediaWiki 1.34.2http://www.opencircuits.com/index.php?title=555_Timers&diff=19249555 Timers2010-02-17T00:11:20Z<p>Andreapg: </p>
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<div>The 8-pin 555 timer is one of the most popular [[Integrated Circuits]] (ICs) ever made.<br />
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.<br />
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The 555 timer will operate from a power supply of 4 V (some versions even less) to about 16 V.<br />
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.<br />
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Most 555 timers are connected to a couple of resistors and capacitors in one of these 4 configurations:<br />
* Astable - producing a square wave<br />
* Monostable - producing a single pulse when triggered<br />
* Bistable - a simple memory which can be set and reset<br />
* Buffer - an inverting buffer (Schmitt trigger) <br />
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For more details on variety of circuits that can be built using a 555 timer, see<br />
* http://www.555-timer-circuits.com/<br />
* http://en.wikipedia.org/wiki/555_timer_IC<br />
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[[Category:Components]]<br />
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== Example ==<br />
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.<br />
'''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.<br />
In the following diagram you can see a possible application, based on 555.<br />
This simple circuit can be utilized to drive a monostable relay, using a single button switch.<br />
When I press the button IC output (pin3) assumes the high level, but Q1 transistor swithces<br />
off. So when I release it the relay is energized (now the exchange switch is closed on 5 and 9).<br />
When I press the button again IC output assumes the low level, but Q3 transistor switches<br />
on: when I release the button the circuit goes to the start condition.<br />
*[http://docs.google.com/leaf?id=0B7LPpongh6DzOTZlNjc3MDUtMzYwMy00ODQ2LWFmODItYmJiZTUyN2IzZDRj&hl=it Schematic]<br />
*[http://sites.google.com/site/plcandcircuitdiagram/home Related resources]</div>Andreapg