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| − | [[Image:Signetics NE555N.JPG|thumb|right|NE555 from [[Signetics]] in [[Dual in-line package|dual-in-line package]]]]
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| − | [[Image:555-schem.png|frame|right|Schematic symbol of the 555 timer]]
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| − | The '''555''' is an [[integrated circuit]] (chip) implementing a variety of [[timer]] and [[multivibrator]] applications. The IC was designed and invented by [[Hans R. Camenzind]]. It was designed in [[1970]] and introduced in [[1971]] by [[Signetics]] (later acquired by [[Philips]]). The original name was the SE555/'''NE555''' and was called "The IC Time Machine". It is still in wide use, thanks to its ease of use, low price and good stability. Even today, [[Samsung]] in [[Korea]] manufactures over 1 [[billion]] units per year ([[As of 2003|2003]]).
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| − | The 555 timer is one of the most popular and versatile integrated circuits ever produced. It includes 23 [[transistor]]s, 2 [[diode]]s and 16 [[resistor]]s on a silicon chip installed in an 8-pin mini dual-in-line package ([[Dual in-line package|DIP]]). The 556 is a 14-pin DIP that combines two 555s on a single chip. The 558 is a 16-pin DIP that combines four, slightly modified, 555s on a single chip (DIS & THR are connected internally, TR is falling edge sensitive instead of level sensitive). Also available are ultra-low power versions of the 555 such as the 7555. The 7555 requires slightly different wiring using fewer external components and less power.
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| − | The 555 has three operating modes:
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| − | *[[Monostable]] mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, etc.
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| − | *[[Astable]] mode: the 555 can operate as an [[oscillator]]. Uses include [[LED]] and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, etc.
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| − | *[[Bistable]] mode: the 555 can operate as a [[Flip-flop (electronics)|flip-flop]], if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.
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| − |
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| − | ==Usage==
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| − | The connection of the pins is as follows:
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| − | {| border=1
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| − | ! Nr. !! Name !! Purpose
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| − | |-
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| − | | 1 || GND || '''G'''rou'''nd''', low level
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| − | |-
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| − | | 2 || TR || A short pulse high->low on the '''tr'''igger starts the timer
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| − | |-
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| − | | 3 || Q || During a timing interval, the '''o'''utput stays at [[Vcc|+V<sub>CC</sub>]]
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| − | |-
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| − | | 4 || R || A timing interval can be interrupted by applying a '''r'''eset pulse to low (0V)
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| − | |-
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| − | | 5 || CV || '''C'''ontrol '''v'''oltage allows access to the internal voltage divider (2/3 V<sub>CC</sub>)
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| − | |-
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| − | | 6 || THR || The '''thr'''eshold at which the interval ends (it ends if U.thr > 2/3 V<sub>CC</sub>)
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| − | |-
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| − | | 7 || DIS || Connected to a capacitor whose '''dis'''charge time will influence the timing interval
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| − | |-
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| − | | 8 || V+, V<sub>CC</sub> || The positive supply '''v'''oltage which must be between 5 and 15 V, high level
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| − | |}
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| − | Using simply a [[capacitor]] and a [[resistor]], the timing interval, i.e. the time during which the output stays low, can be adjusted to the need of the specific application. An example configuration is shown below:
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| − | <center>[[Image:555-schem-2.png|Example 555 schematic]]<br />Example 555 schematic </center>
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| − | The interval time ''t'' is given by
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| − | :<math>t = RC</math>
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| − | which is the time it takes to charge C to 63% of the applied voltage (exact figure: ''(1-1/e)V''). See [[RC circuit]] for an explanation of this effect.
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| − | In the astable mode, the high time from each pulse is given by
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| − |
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| − | :<math>high = 0.69 \cdot (R1 + R2) \cdot C</math>
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| − | and the low time from each pulse is given by
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| − | :<math>low = 0.69 \cdot R2 \cdot C</math>
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| − |
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| − | where R1 and R2 are the values of the resistor in [[ohm]]s and C is the value of the capacitor in [[farad]]s.
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| − |
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| − | ==Specifications==
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| − | These specifications apply to the NE555. Other 555 timers can have better specifications depending on the grade (military, medical, etc).
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| − |
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| − | {| border=1 cellpadding=2
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| − | |Supply voltage (V<sub>CC</sub>)
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| − | |4.5 to 15 V
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| − | |-
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| − | |Supply current (V<sub>CC</sub> = +5 V)
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| − | |3 to 6 mA
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| − | |-
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| − | |Supply current (V<sub>CC</sub> = +15 V)
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| − | |10 to 15 mA
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| − | |-
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| − | |Output current (maximum)
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| − | |200 mA
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| − | |-
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| − | |Power dissipation
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| − | |600 mW
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| − | |-
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| − | |Operating temperature
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| − | |0 to 70° C
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| − | |}
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| − |
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| − | ==Derivatives==
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| − | Many pin-compatible variants, including [[CMOS]] versions, have been built by various companies. The 555 is also known under the following type numbers:
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| − |
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| − | {| border="1" cellpadding="2"
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| − | !Manufacturer
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| − | !Model
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| − | !Remark
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| − | |-
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| − | |ECG Philips
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| − | |ECG955M
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| − | |-
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| − | |Exar
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| − | |XR-555
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| − | |-
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| − | |Fairchild
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| − | |NE555/KA555
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| − | |-
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| − | |Harris
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| − | |HA555
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| − | |-
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| − | |Intersil
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| − | |SE555/NE555/ICM7555
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| − | |-
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| − | |Lithic Systems
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| − | |LC555
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| − | |-
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| − | |Maxim
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| − | |ICM7555
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| − | |-
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| − | |Motorola
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| − | |MC1455/MC1555
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| − | |-
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| − | |National
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| − | |LM1455/LM555C
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| − | |-
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| − | |NTE Sylvania
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| − | |NTE955M
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| − | |-
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| − | |Raytheon
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| − | |RM555/RC555
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| − | |-
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| − | |RCA
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| − | |CA555/CA555C
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| − | |-
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| − | |Sanyo
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| − | |LC7555
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| − | |-
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| − | |Texas Instruments
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| − | |SN52555/SN72555; TLC555
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| − | |-
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| − | |USSR
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| − | |K1006ВИ1
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| − | |-
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| − | |Zetex
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| − | |ZSCT1555
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| − | |down to 0.9V
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| − | |}
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| − | ==External links==
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| − | *[http://www.uoguelph.ca/~antoon/gadgets/555/555.html 555 Timer Tutorial]
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| − | *[http://www.fairchildsemi.com/ds/NE/NE555.pdf Data Sheet (Fairchild) (PDF)]
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| − | *[http://www.falstad.com/circuit/ex-555.html Java simulation] of 555 oscillator circuit
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| − | *[http://www.datasheetarchive.com/search.php?q=NE555&sType=part&ExactDS=Starts 1972 Signetics NE555 datasheet (PDF)]
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| − | [[Category:Integrated circuits]]
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| − | [[da:555 timer ic]]
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| − | [[de:NE555]]
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| − | [[es:Circuito integrado 555]]
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| − | [[it:NE555]]
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| − | [[lt:NE 555]]
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| − | [[nl:555 timer IC]]
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| − | [[pt:CI 555]]
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| − | [[sk:NE555]]
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| − | [[th:ไอซี 555]]
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