555 timer ic

Eksempel på et elektronisk kredsløb med en 555 ic.

Fotografi af en 556-mikrochip overflade (dobbel 555).

555 er et integreret kredsløb (ic-chip), som anvendes til at implementere en timer eller multivibrator.

Kredsen blev designet og opfundet af Hans R. Camenzind.^[1]^[2] Den blev designet i 1970 og introduceret i 1971 af Signetics (blev senere overtaget af Philips).^[3]^[4] Kredsens oprindelige produktkode er SE555/NE555 og er blevet kaldt "The IC Time Machine". Den anvendes stadig meget, takket være dens enkle brug, lave pris og gode stabilitet. Selv i dag fremstiller Samsung i Korea 1 milliard enheder per år (2003).

555-timeren er en af de mest populære og bredt anvendelige integrerede kredse produceret nogensinde. I dens bipolare udgave, indeholder den 23 transistorer, 2 dioder og 16 modstande i dens siliciumchip. Den er typisk indlejret i en 8-bens DIP "lakrids". 556 er en 14-bens DIP som indeholder to 555ere på en enkelt chip. 558 er en 16-bens DIP som kombinerer 4, let modificerede, 555'ere på en enkelt chip. DIS & THR er forbundet internt, TR er følsom overfor faldende-kant i stedet for niveau-følsom.

I dag findes den også i laveffektsudgaver med produktkoderne: ICM7555, TLC551, TLC555, ZSCT1555, LMC555CD, MC1455.

NE555 specifikationer[redigér | rediger kildetekst]

Disse specifikationer gælder for NE555. Andre 555-deriviater kan have bedre (eller andre) specifikationer.

Spændingsforsyning (V_CC)	4,5 til 15 V
Strømforbrug (V_CC = +5 V)	3 til 6 mA
Strømforbrug (V_CC = +15 V)	10 til 15 mA
Maksimal strøm-output pull-down	200 mA
Maksimal afsat effekt	600 mW
Anvendelsestemperaturinterval	0 to 70 °C

Utilsigtet forsyningsben RF-puls[redigér | rediger kildetekst]

Bipolare udgaver af 555 (fx NE555) laver kraftige forsyningsben strømpulser på mellem 100-400 mA i ca. 100-200 nSek. Hvis ikke IC-kredsen er afkoblet mellem forsyningsbenene (fx ben 8 og 1) falder denne spænding længere ned end V/2. Herudover spreder RF-pulserne sig via forsyningsbenene, så nærliggende hurtige kredsløb kan fejle. Løsningen er at sætte 10-100uF mellem forsyningsbenene på 555'eren - eller istedet vælge en CMOS-udgave, der har ikke denne støjuhensigtsmæssighed.^[5]^[6]^[7]^[8]

Derivater[redigér | rediger kildetekst]

Mange ben-kompatible varianter, inklusiv laveffekts CMOS versioner, er blevet lavet af forskellige firmaer. 555'eren er også kendt under følgende produktkoder:

Producent	Model	Bemærkning
ECG Philips	ECG955M
Exar	XR-555
Fairchild	NE555/KA555^[9]
Harris	HA555
IK Semicon	ILC555	laveffekt CMOS. Ned til 2V
Intersil	SE555/NE555
Lithic Systems	LC555
Intersil og Maxim	ICM7555	laveffekt CMOS. Ned til 2V
Motorola	MC1455/MC1555
National	LM1455/LM555C
National	LMC555	laveffekt CMOS. Ned til 1,5V
NTE Sylvania	NTE955M
Raytheon	RM555/RC555
RCA	CA555/CA555C
Sanyo	LC7555
STMicroelectronics	NE555N/ K3T647
Texas Instruments	SN52555/SN72555
Texas Instruments	TLC551	laveffekt CMOS. Ned til 1V. Fra 15uA(typ.@1V)-360uA(typ.@15V). Rail-to-rail output.
Texas Instruments	TLC555	laveffekt CMOS. Ned til 2V
USSR	K1006ВИ1
Zetex	ZSCT1555	laveffekt CMOS. Ned til 0,9V

Kilder/referencer[redigér | rediger kildetekst]

^ "The 555 Timer Was Just The Beginning For Hans Camenzind". electronicdesign.com. 28. november 2012. Arkiveret fra originalen den 25. april 2015. Hentet 6. juni 2015.{{cite web}}: CS1-vedligeholdelse: BOT: original-url status ukendt (link)
^ "blog: Long Live the 555 Timer IC". electronicdesign.com. 16. august 2012. Arkiveret fra originalen den 15. marts 2015. Hentet 6. juni 2015.{{cite web}}: CS1-vedligeholdelse: BOT: original-url status ukendt (link)
^ Web archive backup: 555 Timer Tutorial
^ Datablad: 1972 Signetics NE555 datasheet (PDF) Arkiveret 28. september 2011 hos Wayback Machine
^ nutsvolts.com: ‘555’ Monostable Circuits, backup Citat: "...Worst of all, it draws a brief (a fraction of a microsecond) but massive 400 mA spike of supply current as its output transitions from one state to the other, and this generates an RF noise burst that can play havoc with nearby digital circuits. In critical 555 applications, this RF burst can be suppressed by wiring an electrolytic capacitor (10 µF to 100 µF) directly between supply pins 8 and 1. The 7555 CMOS device suffers from none of these snags; it can use supplies in the range of 2V to 18V, draws only 100µA quiescent from a 15V supply, and draws a peak spike current of only 10 mA when its output transitions from one state to the other, thus generating negligible switching RFI..."
^ Mange referencer: March 11, 2022, edn.com: The NE555 current spike, backup Citat: "...The power supply went crazy, overcurrents pinning the meter, and so forth...The issue is well-documented. At first I didn’t know what to make of it, as it seemed to be a serious design flaw: Totem-pole outputs, connected directly to the positive rail and ground, without any kind of current limiting or special switch timing...Various people have posted scope traces and described the issue [3,4,5,6,11,14,15]. Typical reports are of a current spike that lasts 100-200 nsec and pulls about 300 mA...With no decoupling capacitors, power supply drops can be seen of more than half the supply voltage...But efforts at producing a “better” bipolar 555 have all succumbed to the overwhelming force of the original..."
^ sound-au.com: The 555 Timer. Rod Elliott - Copyright 2015, backup Citat: "...It's easily simulated, and my simulation showed a peak current of around 100mA, lasting for about 100ns (0.1µs). A bypass capacitor is always needed to handle this, and the minimum is 10µF. In the drawings below I used 47µF, which will usually mitigate supply voltage disturbances..."
^ talkingelectronics.com, SHOOT-THROUGH: 555 Circuits (more than 101 Circuits), backup Citat: "...The 555 (the TTL version, such as NE555, SE555) has a problem that both the output transistors turn ON when the output changes from HIGH to LOW or LOW to HIGH. This only occurs for a very short period of time...That's why you need a large-value electrolytic (100u) across the 555 and try to avoid using it with counting-chips and microcontrollers..."
^ "Data Sheet (Fairchild) (PDF)" (PDF). Arkiveret (PDF) fra originalen 26. oktober 2000. Hentet 9. juli 2006.

Eksterne henvisninger[redigér | rediger kildetekst]

Wikimedia Commons har flere filer relateret til 555 timer ic

[1] "The 555 Timer Was Just The Beginning For Hans Camenzind". electronicdesign.com. 28. november 2012. Arkiveret fra originalen den 25. april 2015. Hentet 6. juni 2015.{{cite web}}: CS1-vedligeholdelse: BOT: original-url status ukendt (link)

[2] "blog: Long Live the 555 Timer IC". electronicdesign.com. 16. august 2012. Arkiveret fra originalen den 15. marts 2015. Hentet 6. juni 2015.{{cite web}}: CS1-vedligeholdelse: BOT: original-url status ukendt (link)

[3] Web archive backup: 555 Timer Tutorial

[4] Datablad: 1972 Signetics NE555 datasheet (PDF) Arkiveret 28. september 2011 hos Wayback Machine

[5] utsvolts.com: ‘555’ Monostable Circuits, backup Citat: "...Worst of all, it draws a brief (a fraction of a microsecond) but massive 400 mA spike of supply current as its output transitions from one state to the other, and this generates an RF noise burst that can play havoc with nearby digital circuits. In critical 555 applications, this RF burst can be suppressed by wiring an electrolytic capacitor (10 µF to 100 µF) directly between supply pins 8 and 1. The 7555 CMOS device suffers from none of these snags; it can use supplies in the range of 2V to 18V, draws only 100µA quiescent from a 15V supply, and draws a peak spike current of only 10 mA when its output transitions from one state to the other, thus generating negligible switching RFI..."

[6] Mange referencer: March 11, 2022, edn.com: The NE555 current spike, backup Citat: "...The power supply went crazy, overcurrents pinning the meter, and so forth...The issue is well-documented. At first I didn’t know what to make of it, as it seemed to be a serious design flaw: Totem-pole outputs, connected directly to the positive rail and ground, without any kind of current limiting or special switch timing...Various people have posted scope traces and described the issue [3,4,5,6,11,14,15]. Typical reports are of a current spike that lasts 100-200 nsec and pulls about 300 mA...With no decoupling capacitors, power supply drops can be seen of more than half the supply voltage...But efforts at producing a “better” bipolar 555 have all succumbed to the overwhelming force of the original..."

[7] sound-au.com: The 555 Timer. Rod Elliott - Copyright 2015, backup Citat: "...It's easily simulated, and my simulation showed a peak current of around 100mA, lasting for about 100ns (0.1µs). A bypass capacitor is always needed to handle this, and the minimum is 10µF. In the drawings below I used 47µF, which will usually mitigate supply voltage disturbances..."

[8] talkingelectronics.com, SHOOT-THROUGH: 555 Circuits (more than 101 Circuits), backup Citat: "...The 555 (the TTL version, such as NE555, SE555) has a problem that both the output transistors turn ON when the output changes from HIGH to LOW or LOW to HIGH. This only occurs for a very short period of time...That's why you need a large-value electrolytic (100u) across the 555 and try to avoid using it with counting-chips and microcontrollers..."

[9] "Data Sheet (Fairchild) (PDF)" (PDF). Arkiveret (PDF) fra originalen 26. oktober 2000. Hentet 9. juli 2006.

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