Talk:555 timer IC/Archive 1

Archive 1

Gutted article

Unless anybody objects, I'm bringing back the wealth of data that was here before 124.7.82.96 removed it without giving a reason (called me biased, but since it's just an IP I'm guessing the reason was "petty vandalism"). Kolbasz 23:58, 20 October 2006 (UTC)

I object that you asked for permission before fixing it.  :) But thanks for pointing it out; I was watching this article and didn't notice the vandalism wasn't properly reverted. Pfalstad 22:25, 23 October 2006 (UTC)

Great!. That saves me the trouble of going through the later edits and checking if any of them had added anything of value. ;) Kolbasz 17:44, 24 October 2006 (UTC)

Equations

Would it be worth adding the (rearranged) equation, to calculate the required R, given C and T? It is an equation I have used a lot when designing 555 circuits, and have found it very helpful. It is much easier (and cheaper!), to vary R (pots/ combinations of fixed resistors), than to change the capacitance. Jdedmond (talk) 17:40, 17 April 2008 (UTC)

Sorry

I've made the alterations, but forgot to login. I had to undo them and redo them again, so the contribution could be attributed to me. Samuel Lourenço (talk) 11:04, 7 June 2008 (UTC)

the circuit diagram?

is it correct? where's R1 and R2? 59.92.134.43 18:18, 21 December 2006 (UTC).

I believe that the resistor pictured is R1 and that R2 would be between DIS and THR in place of that wire. --129.65.98.192 20:01, 20 February 2007 (UTC)

 Done - The circuit is correct for the monostable mode. The picture was not captioned correctly, but now it is fixed. Samuel Lourenço (talk) 14:16, 7 June 2008 (UTC)

universal analog circuit

Most digital designers learn that sufficient quantities of NOR gates can be used to build any possible digital circuit -- such as the Apollo Guidance Computer.

Recently I have seen this claim for a universal analog circuit:

"It is a truth universally acknowledged, that any single circuit worthy of construction can be built with 555 timers." -- Cypress Application Note 2286 by Dave Van Ess 2005

If this "truth" is really so "universally acknowledged", then it would be good to mention this "truth" in the article, with a few of the top references.

-- DavidCary --70.189.73.224 04:37, 18 August 2006 (UTC)

I'm not an expert in analogs, but if this idea is true, I would reformulate it as "any analog circuit can be made using [Amplifiers, comparators and whatever I forget], and all these elements are available in the 555 IC", because a 555 has limitations (frequency, power...) that makes it unsuitable for many analog applications. We might compare a 555 to an elementary cell of an analog system on chip. CyrilB 12:12, 18 August 2006 (UTC)

It's a joke. The quote up until the word "circuit" is a reference to the opening sentence of "Pride and Prejudice"; it's witty because 555s have been put to a ridiculous number of uses way beyond their original purpose, but they certainly don't serve as some kind of basic element from which all other circuits can be built. —Preceding unsigned comment added by 92.234.123.8 (talk) 15:27, 2 March 2009 (UTC)

Table of derivatives

There is an incorrection in the table of derivatives. The LM555 and LM555C are different denominations for the same chip, the TTL version from National. These versions are not CMOS. Only the LMC555 is CMOS.

I shall correct it now. Whoever edited that pabe should have confirmed this in the National Semiconductor web site. 89.180.20.247 (talk) 10:25, 7 June 2008 (UTC)

The Sanyo LC7555 is not a 555 timer IC. —Preceding unsigned comment added by 66.66.197.121 (talk) 19:52, 3 March 2009 (UTC)

 Done - Indeed, seems to be a (long-discontinued) "Level Meter with Peak Hold Function". Removed from table. Hqb (talk) 20:06, 3 March 2009 (UTC)

Name derivation

Write somewhere that its name derives from the 3 resistors of 5kohm inside the IC. see http://www.uoguelph.ca/~antoon/gadgets/555/555block.gif for the internal scheme. —The preceding unsigned comment was added by 84.222.77.102 (talk • contribs) 22:32, 9 August 2005 (UTC)

Oh God. I have fond memories of this one! `Trollderella 04:41, 28 October 2005 (UTC)

Hans R. Camenzind does not say that the name derives from the 3 resistors, see there: http://www.semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzind_Page2.htm —Preceding unsigned comment added by 159.50.249.149 (talk) 16:21, 7 January 2009 (UTC)

 Done - Intro edited to clarify this issue Nkendrick (talk) 22:47, 6 August 2009 (UTC)

bad image in "Example Applications" section?

It looks like reusing the same illustration that's used earlier in the "Monostable mode" section in the "Example Applications" section doesn't make sense. The illustration isn't great to begin with (poorly labeled y-axis doesn't clearly show that there are three different 0 points in that axis) but reusing it in this fashion just seems unuseful. Shouldn't anyone who's wondering how the monostable mode looks just scroll back up the page?

-Bobby in the UChicago library 128.135.96.101 (talk) 02:15, 28 May 2009 (UTC)

I don't think the same picture should appear twice in one article. Is there a better picture to go with the example?--Segal'sLaw (talk) 05:22, 28 August 2009 (UTC)

Orders of magnitude

"Many" orders of magnitude, to me, would mean at least 5 or 6. I very much doubt you're going to see a lonely 555 driving a power transistor handling 50 kilowatts. Or 500 kilowatts. --Wtshymanski (talk) 05:07, 24 July 2010 (UTC)

Wait, what?

The connections of the pins explanation make no sense at all to me. Yeah, Vcc and GND I understand, but what's this? "Reset; Purpose: A timing interval may be interrupted by driving this input to GND." What's that supposed to mean? Timing interval? May be interrupted by driving this input to ground. Oh, so it may also not be interrupted under the same condition? What Is It For? That question is not answered.

Or this: "Trig; Purpose: OUT rises, and interval starts, when this input falls below 1/3 Vcc." Hm, makes half sense. I understand that if I connect less than 1/3 Vcc to this input, something happens to Out. But what? It rises. Does that mean it slowly rises, like, it takes one second for it to reach Vcc? Or is it instantly? In that case, wouldn't it easier to say, when Trig input < 1/3 Vcc, Out switches to high?

Other things not making sense: ""Control" access to the internal voltage divider (by default, 2/3 Vcc)." - doesn't say how that works. I can control the internal voltage divider? What is a voltage divider to begin with? And how do I access it and why would I want to?

"Open collector output; may discharge a capacitor between intervals." May (or may not?) discharge a capacitor. What capacitor? Do I need to connect one to this output? Or wait, is it an input? I have no idea. What's the reason for the chip to decide to discharge it? May discharge between intervals, that sounds like it's just a random occurance. Does the capacitor have anything to say in this process or should it just follow the chip's orders? 555 says: Discharge, slave! And the capacitor goes: Yes, oh Great Chip, I will do so instantly!

So, this needs way more explanation. It seems like a useful chip, but I have no clue how I could use it. There is no explanation anywhere that just tells me how to use this thing and how it works. I've read and re-read the explanations so many times, but it never makes any sense, I keep referring back to the pin explanation, and since they are not clear, I can not see what happens in a circuit. Just write something so it's actually understandable, please. nftaDaedalus (talk) 21:31, 31 July 2010 (UTC)

• Yes, the article is sketchy, but you made a mistake in the very beginning: don't rely on wikipedia as a textbook. It's not a textbook, it's not a how-to book, nor a circuit repository. It cannot come close even to a datasheet (and those datasheets from the 1960s and 70s were superb, they don't write stuff like that anymore). Some of your question ("May (or may not?) discharge a capacitor. What capacitor?"), if they are genuine (and not a figure of speech), give away misunderstanding of the basics. And article on the 555 cannot address these basics - rather, it should address the significance of the product, its role in the industry etc. - social, rather than technical, matters. Going back to your specific question,
  • Q: What capacitor?
  • A: Any capacitor, provided that the energy dissipated by the discharge transistor (which drives pin 7) is within SOAR specified by the manufacturer (derated for ambient temperature when necessary), and that the potentials of its "cold" (not necessarily grounded) and "hot" terminals are within safe limits that ARE NOT explicitly specified. This is a straight answer to a simple question, but does it really help? East of Borschov 07:14, 1 August 2010 (UTC)

Thank you for your reply. I know Wikipedia is not a textbook, but that doesn't mean it can be unclear. The questions I put up are questions any reader will ask, simply by looking at the explanation. The Discharge explanation is about discharging a capacitor, but a reader might ask himself, what capacitor? There's been no mention of a capacitor before. Wouldn't it be better to explain the pin as it being (internally connected to) a transistor's collector, thus when a specific action occurs (between intervals? aren't intervals usually seamless, is there a thing as being 'between intervals'?), it essentially connects whatever is connected to the pin to the ground. That usually/often/normally is a capacitor, which would then discharge (hence the pin name), but couldn't you also connect, for example an LED to it? This is what I mean, it is unclear. And that goes for the other pins too, why does it use seemingly incomprehensible wording to explain the Out pin? "Can be driven to Vcc or Ground", why not just say, Outputs Vcc when high, at which point it can be used as source or connects to Ground when low, and so can be used as sink. The problem: explanations are not understandable. They don't need to be overly specialistic, after all, Wikipedia is no textbook. But a simple explanation should be the least on here anyway, I think. Unfortunately I haven't enough knowledge of this thing to write it myself. nftaDaedalus (talk) 16:00, 1 August 2010 (UTC)

The table entry for pin 7 has a blue link to open collector, which should have the answers. But even this article cannot list all possible loads - it could be a LED, or a whole system powered through pin 7. East of Borschov 17:16, 1 August 2010 (UTC)

Yes, ok. But the fact that the pin is named 'discharge' and its purpose is (on here anyway) specifically explained with a capacitor, any beginner hobbyist amateur will draw the conclusion it is used for capacitors only. But anyway, even that blue link doesn't make this article so much more understandable. Well I suppose the only way to get to know it is to experiment with one. nftaDaedalus (talk) 22:58, 1 August 2010 (UTC)

Equation Simplification

Am I right in thinking that the frequency calculation for astable mode could be simplified? it would be nice to see an equation just below the frequency equation that is the same but simplified (1.44/(C*(R1 + R2))) this way there is no ln(2) needed. Also the reverse equations would be handy (in agreement with Jdedmond). And perhaps the Shmitt trigger function could be at least mentioned? Danieljabailey (talk) 13:04, 11 December 2011 (UTC)

Bistable Image

I've added an image of the 555 in bistable mode based on the images for mono- and astable modes. I've removed the imagereq in line with this. Abstract 01:44, 15 April 2012 (UTC)

Popularity

How come this IC is so popular while monostable or bistable circuits that use schmitt triggers (e.g. 4093 and 40106) use one component less and the circuits are so much easier to remember? SvenPB (talk) 13:47, 3 February 2009 (UTC)

I'll make 2 guesses: much higher output current capability and the timing does not change if you decide to use a different supply voltage. In other words: analog applications. Ywaz (talk) 18:30, 4 March 2013 (UTC)

Incorrect Image

The picture in the "Monostabel Mode" section shows a capacitor who's voltage changes instantly. This is impossible for capacitors. Potatoj316 (talk) 13:15, 9 March 2011 (UTC)

It also shows the output pulse starting instantly with the trigger signal, with no propagation delay. Is it permissible to say that the graph shows the approximate behaviour of the circuit, and that in most cases, the capacitor discharges much faster than it charges ? For the purposes of a technical encyclopedia article, does the image provide a useful indication of a typical circuit's typical behaviour ? Darkman101 (talk) 17:27, 10 April 2013 (UTC)

Astable frequency error?

Perhaps I am mistaken, but given the equation for frequency(f), Period T would equal 1/f. Since high and low time for a full cycle are approximately equal, period(high)≈1/(2f). Instead of high== ln(2)*C*(R1+R2), would this not yield high== 2*(ln(2)*C*(R1+2R2))? Perhaps I am missing something internally however — Preceding unsigned comment added by 173.12.43.145 (talk) 20:32, 20 October 2013 (UTC)

1N

Hi,

I see 1N throughout, in the some of the formulas as in the bistable formula....what does the 1N represent ?

Thanks — Preceding unsigned comment added by 170.215.57.166 (talk) 18:59, 17 March 2014 (UTC)

bistable/schmitt incorrect?

I don't think the description regarding the threshold pin in the bistable description is correct. The article has this to say, "The trigger and reset inputs (pins 2 and 4 respectively on a 555) are held high via Pull-up resistors while the threshold input (pin 6) is simply floating." I'm a preschooler with electronics but I've never left the thr pin floating in bistable configuration and the diagram confirms this. Can a more experienced EE confirm and edit? 66.87.118.72 (talk) 16:59, 1 July 2014 (UTC)

GND Connection

The pin marked GND which is a common negative for Vcc, Vtrigger and Vthreshold surely should be marked COMMON. I don't think there is any requirement for a ground connection, despite the liberal sprinkling of earth symbols in the circuits? — Preceding unsigned comment added by 86.190.208.60 (talk) 16:41, 25 March 2015 (UTC)

Comments and question

1. This article and the article on Hans R. Camenzind are inconsistent in terms of the year of the design of the IC.

2. The section on bistable operation sasy "The threshold input (pin 6) is simply floating". The image on the right does not show this and pin 6 is grounded. Pin 7 is floating and this is mentioned in the same section. Also, if TRIG is active high, why is the signal connected to it active low? Ideally, the signals should not be marked as active high or low but the pins of the devices.

3. This fragment needs to be revised: "where Vdiode is when the diode's "on" current is 1/2 of Vcc/R1 which can be determined from its datasheet or by testing"

4. Does anybody know why they went from 555 to 556 to 558 and they skipped 557?

ICE77 (talk) 07:04, 1 August 2015 (UTC)

4) I've always assumed the part numbering was based on the following concept. The reason of why no parts with 3 timers is similar reasons why you can only get opamp ICs with 1, 2, 4 per package. I don't have an official answer, though these guesses came from deductive reasoning. • Sbmeirow • Talk • 00:11, 14 August 2015 (UTC)

• 555 = 1 timer
• 556 = 2 timers
• 557 = 3 timers (no such part exists)
• 558 = 4 timers

Sbmeirow, that's an excellent explanation! Thanks for the input.

ICE77 (talk) 22:11, 15 August 2015 (UTC)

555 timer IC

Thanks for the history addition. I'd like to do some copyediting on it, but there are parts that I don't quite understand. If you can send me the original Japanese text and the English translation of the reference you used, maybe I can work from those to help figure it out. You can email me at my same account name at acm.org. Dicklyon (talk) 15:07, 27 December 2016 (UTC)

@Dicklyon: I wrote it as much as possible while I took care avoiding copyright violation. Could you tell me what a lack of explanation in the text? I borrowed the magazine from a public library, and I'll return it within a few days. Thank you. Darklanlan (talk) 15:51, 27 December 2016 (UTC)

OK, when I work on it I'll let you know what questions I have. To start: "Camenzind did its design with other two design works at the same time." might mean "Camenzind did his design while working on two other designs at the same time." or maybe "Camenzind did his design for several companies at the same time." or maybe something else? Dicklyon (talk) 17:04, 27 December 2016 (UTC)

I made some copyedits. Please review and see if I captured the intent correctly. Dicklyon (talk) 17:32, 27 December 2016 (UTC)

@Dicklyon: According to the article, during the development of the 555, he rented an apartment for his office and hired an engineer while he had a wife and four children when he was thirty six years old. He said he made two contracts about the IC design. However, it is unclear who contracted with him. Darklanlan (talk) 17:39, 27 December 2016 (UTC)

I took that out; then noticed that this oral history says basically that he got two other contracts. Not really very relevant to the 555, just that he was working as an independent contractor. Also, that interview says he was at PR Mallory before Signetics, not Fairchild. Please review your article and see if it really says he worked for Fairchild; and if so, is it credible? Seems wrong. Dicklyon (talk) 05:56, 28 December 2016 (UTC)

@Dicklyon: As you say, he seems to have been an independent contractor and got two conracts. The article doesn't mention them, but I agree with you they are not relevant to the 555. In the article, he says he worked at the Fairchild's research laboratory near Boston(?) I couldn't find the source that Fairchild founded a laboratory in Boston. Anyway, here I put the original translated text with its color. Darklanlan (talk) 07:13, 28 December 2016 (UTC)

スイスで生まれ育った私がボストン近郊のフェアチャイルド研究所に入ったのは1962年で、同僚のロバート・J・ワイドラーによるOPアンプ誕生前夜でした。(...)マサチューセッツ工科大学の図書館で数日間過ごし1935年の予稿集にPLL(Phase Locked Loop)を見つけましたが、フェアチャイルド社は研究所の閉鎖を決めたため、試す機会を逃してしまいました。ICの活動の中心はシリコンバレーへと移ったのです。1968年初頭、PLLの仕事をすることへの同意の下、4人の元フェアチャイルド社員が作ったサニーベイルにあるシグネティックス社へ移籍しました。

— Carmenzind, Hans (2010). "タイマIC 555 誕生秘話" [The birth of the 555 timer IC]. トランジスタ技術 (Transistor Technology) (in Japanese). 47 (12). Translated by 三宅, 和司. CQ Publishing: 73. ISSN 0040-9413.

It's confusing. I can't find evidence of either Fairchild or PR Mallory have an electronics laboratory in the Boston area. Maybe someone else can figure this out. Dicklyon (talk) 18:11, 28 December 2016 (UTC)

Found it. Definitely Mallory's "Laboratory for Physical Science" in Burlington Mass. See this paper and this book search. Not Fairchild; that might have been an error in translating to the Japanese version somehow? Dicklyon (talk) 20:58, 28 December 2016 (UTC)

@Dicklyon: You're probably right. Thank you for discovering evidence. I'll ask the publisher there is a mistranslation. They only accept questions via the post, so it will take weeks. Darklanlan (talk) 01:43, 29 December 2016 (UTC)

I finally received the response. Carmenzind only said he workd at a research laboratory. The author mistook his work place for Fairchild. It was wrong. Also, the author was surprised that PR Mallory was developing integrated circuits. That's all. Darklanlan (talk) 11:14, 30 January 2017 (UTC)

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Nomenclature

What does the NE in NE555 stand for? How come they gave it the number 555?

In general, it would be great if there was a article that explained the nomenclature of semiconductors and ICs devices.

Thanks, --Abdull 11:53, 19 Jun 2005 (UTC)

 Done - 555 number reason added at some point in the past. NE and SE were temperature range for Signetics linear chips (I added text to article). • Sbmeirow • Talk • 19:52, 30 June 2017 (UTC)

The article should be expanded

The article should really be expanded. It should have a schematic depicting the astable configuration, which is more popular. Also, the use as a Schmitt trigger should be mentioned. Samuel Lourenço (talk) 10:56, 7 June 2008 (UTC)

Maybe also (1) adding diodes to get a duty cycle below 50%, and (2) how to use two 555s (or one 556) to do PWM with fixed frequency ? — Preceding unsigned comment added by Jcpbr (talk • contribs) 12:32, 24 August 2018 (UTC)

(1) For diodes & below 50% duty cycle, it is already discussed in the article, search for "1N4148" in this article. The article does needs a schematic near that text. (2) Agree, it's been on my TODO list for a while, as well as a few other useful circuits, and some other cool things. I'll try to push it higher on my list. • Sbmeirow • Talk • 01:59, 25 August 2018 (UTC)

The NE 558

the NE558 (Philips / Fairchild) use only 1/2 UCC to detect the voltage of the C. The IC is simpler then four NE555 or two NE556. So the NE558 is not realy the same as four NE555! The 556 (ICM7556) has two NE555 (ICM7555) inside. see http://www.datasheetcatalog.com/datasheets_pdf/N/E/5/5/NE558.shtml —Preceding unsigned comment added by 79.230.140.84 (talk) 16:06, 30 December 2009 (UTC)

 Done - I overhauled the 558 section a while back. • Sbmeirow • Talk • 02:01, 25 August 2018 (UTC)

And what about the Shmitt trigger?

I'm pleased to see that some of my changes prevail, but the Shmitt trigger mode of operation of the 555 is not discussed here. Was it taken out? Why? Shouldn't Wikipedia be a comprehensive encyclopedia? —Preceding unsigned comment added by SLourenco (talk • contribs) 15:46, 7 November 2009 (UTC)

It is discussed in the Bistable section at 555_timer_IC#Bistable, though a schematic is missing. • Sbmeirow • Talk • 02:04, 25 August 2018 (UTC)

Frequency Range?

This page should mention, preferably in the specifications section, the frequency range these devices can operate over. My web browser could not find the string "Hz" anywhere in the article. 109.154.64.228 (talk) 12:47, 17 July 2012 (UTC)

 Done - I fixed this a while back. It varies by part. Look at 555_timer_IC#Derivatives section. • Sbmeirow • Talk • 02:06, 25 August 2018 (UTC)

Claim of popularity and quantity made

To say this is the most popular component is a drastic claim needs better sources than some dude's website, per WP:EXCEPTIONAL Graywalls (talk) 21:19, 1 August 2020 (UTC)

Other issues

I became introduced to this article through the article Atari Punk Console that has since been moved to Forrest Mims. I'm seeing some due weight issues that are referencing user manuals and user generated contents to support inclusion. Graywalls (talk) 21:29, 1 August 2020 (UTC)

most popular ever produced

I replaced a homepage source that was used to reference it was "the most popular ever replaced" with For Dummies, a reliably published book by Wiley. The book says "probably the most popular" with some hint of doubt, so I quoted the sentence as said. Graywalls (talk) 08:10, 10 August 2020 (UTC)

Thanks for working on that. Even if "For Dummies" got it from Wikipedia, it's at least an opinion of probability that has been reviewed by an editor now. I don't know if it's true; maybe some dram chip ships more per year, but probably not more cumulatively since they tend to have lives of only a few years. Dicklyon (talk) 18:29, 10 August 2020 (UTC)

Game controller/pads/joysticks as examples

There are likely untold number of applications for this component and the references to the component for these items in the article is only referenced to the products' circuit diagram in the users' or repair manual for the product and is an undue representation of these specific examples and I think they should be omitted unless there's a reliable secondary source that discusses these products with respect to the 555. The book sources used in that section don't talk about the use of 555 in these products. Graywalls (talk) 06:01, 11 August 2020 (UTC)

Example Application (removed from article)

I removed the following content from the article. Though it is USEFUL, it doesn't have any references, nor does it have any schematics or drawings (which are important). • Sbmeirow • Talk • 03:29, 7 November 2017 (UTC)

Missing pulse detector

This circuit will detect a missing pulse in a train of pulses. The timer is connected in the monostable mode. A PNP transistor is connected across the capacitor and the input trigger pulse train is given to the base terminal of the transistor as well as the pin 2 trigger input of the IC 555. The train of trigger pulses will continuously reset the timing cycle. Hence the output is always high. If any trigger pulse is missing, the device detects this missing pulse and the output goes low. The detailed working is as follows. When the input is 0, the PNP transistor is turned ON and the voltage across the capacitor is clamped to 0.7 V and the output is HIGH. When the input trigger voltage is high, the transistor is cut-off generator can be used as a athe capacitor will start charging.

If the input trigger signal goes low again before the completion of the timing cycle, the voltage across the capacitor falls to 0.7 V before reaching the threshold voltage (2/3 VCC) and the output continues to remain HIGH. If the input trigger signal doesn’t go low before the completion of the timing cycle due to a missing pulse, it allows the capacitor to charge to the threshold voltage and the output will become LOW.

In order to make this circuit work as a Missing Pulse Detector, the time period of the input trigger signal should be slightly lesser than the timing interval. Because of this, the continuous negative going input pulses will not allow the capacitor to charge till the threshold voltage. And the output continues to stay high. In case of change of input frequency or a missing pulse, the capacitor will charge to the threshold voltage and the output falls low.This type of circuit can be used to detect missing heartbeat.

Frequency divider

When the IC 555 is used as a mono-stable multivibrator, a positive going rectangular pulse is available at the output when a negative going pulse of short duration is applied at the trigger input. By adjusting the time interval t of the charging or timing circuit the device can be made to work as a frequency Divider circuit.

A continuously triggered mono-stable circuit when triggered by a square wave generator can be used as a frequency divider, if the timing interval is adjusted to be longer than the period of the triggering square wave input signal. The mono-stable multivibrator will be triggered by the first negative going edge of the square wave input but the output will remain HIGH (because of greater timing interval) for next negative going edge of the input square wave. The mono-shot will however be triggered on the third negative going input, depending on the choice of the delay. In this way, the output can be made integral fractions of the frequency of the input triggering square wave.

If the timing interval t is made slightly larger than the time period of the input pulse (trigger pulse), the device can act as a Divide – by – two circuit. The timing interval can be controlled by appropriately choosing the values of the resistor R and the capacitor C in the timing circuit.

So the circuit will trigger on every alternate negative going trigger pulse i.e. there is one output pulse for every two input pulses and hence it is a divide–by–two circuit. By adjusting the timing interval, a mono-stable circuit can be made to produce integral fractions of the input frequency.

Frequency shift keying

In digital communication, binary code is transmitted by shifting a carrier frequency between two preset frequencies called Frequency-shift keying (FSK). A 555 timer in astable mode can be used to generate FSK signal.

Pulse-position modulator

A pulse-position modulator can be constructed by applying a modulating signal to pin 5 of a 555 timer connected for astable operation. The output pulse position in time varies with the modulating signal, and hence the time delay is varied.

---

In mid-2020, another editor removed the following subsections. • Sbmeirow • Talk • 03:48, 2 October 2020 (UTC)

Joystick and game paddles

IBM PC Game Control Adapter
(8-bit ISA card) with 558 quad timer

The Apple II microcomputer used a quad timer 558 in monostable (or "one-shot") mode to interface up to four "game paddles" or two joysticks to the host computer. It also used a single 555 for flashing the display cursor.

The original IBM PC used a similar circuit for the game port on the "Game Control Adapter" 8-bit ISA card (IBM part number 1501300). In this joystick interface circuit, the capacitor of the RC network (see Monostable Mode above) was generally a 10 nF capacitor to ground with a series 2.2 KΩ resistor to the game port connector. The external joystick was plugged into the adapter card. Internally it had two potentiometers (100 to 150 KΩ each), one for X and other for Y direction. The center wiper pin of the potentiometer was connected to an Axis wire in the cord and one end of the potentiometer was connected to the 5 Volt wire in the cord. The joystick potentiometer acted as a variable resistor in the RC network. By moving the joystick, the resistance of the joystick increased from a small value up to about 100 kΩ.

Software running in the IBM PC computer started the process of determining the joystick position by writing to a special address (ISA bus I/O address 201h). This would result in a trigger signal to the quad timer, which would cause the capacitor of the RC network to begin charging and cause the quad timer to output a pulse. The width of the pulse was determined by how long it took the capacitor to charge up to 2⁄3 of 5 V (or about 3.33 V), which was in turn determined by the joystick position. The software then measured the pulse width to determine the joystick position. A wide pulse represented the full-right joystick position, for example, while a narrow pulse represented the full-left joystick position.

Stepped-tone generator

Atari Punk Console board with 556 dual timer and ear buds

Schematic of the stepped-tone generator. A series resistor must be added inline with R4 to prevent the timer discharge pin from shorting power to ground.

The Stepped-Tone Generator, known as the "Atari Punk Console" (APC) in the DIY audio synthesizer community, is a simple noise making circuit that utilizes two 555 timer ICs (or one 556 dual timer IC). The circuit is an astable square wave oscillator driving a monostable oscillator that creates a single (square) pulse. There are two controls, one for the frequency of the oscillator and one to control the pulse width. The controls are usually potentiometers but the circuit can also be controlled by light, temperature, pressure etc. by replacing a potentiometer with a suitable sensor (e.g., photoresistor for light sensitivity).

The circuit was created by book author Forrest Mims, who first called it a "Sound Synthesizer" on page 101 of 1982 booklet "Engineer's Notebook II: A Handbook of Integrated Circuit Applications", then later called it a "Stepped-Tone Geneator" on page 22 of 1984 booklet "Engineer's Mini-Notebook: 555 Timer IC Circuits". The circuit was renamed "Atari Punk Console" (APC) by Kaustic Machines because its "low-fi" sounds resemble classic Atari console games from the 1980s, with a square wave output similar to the Atari 2600. Their design changed the speaker output to a -4dB line level output.

References

The number 555 came from

Someone added a citation that "The 555 gets its name from the three 5-kW +VCC R1 discharging path 555 R 2 C 6 resistors...". I don't have that book, but I know these things:

1. Hans Camenzind denied the name 555 came from the three 5 k ohm resistors.
2. Signetics assigned 500 numbers for analogue ICs.
3. The Marketing Manager chose the 555 because he thought the circuit was gonna sell big who picked the special number.

I wrote it,(revision 2020-03-29) but it was removed. Does that book have more relevant mention of the name 555? Which is true? Anyway, the present article has a conflict between the history section and the internal schematic section. Darklanlan (talk) 12:46, 7 August 2020 (UTC)

References

@Darklanlan:, "The 555 gets its name from the three 5-kΩ +VCC R1 discharging path 555 R 2 C 6 resistors shown in the block diagram. These resistors act as a three-step voltage divider 8 between the supply voltage (VCC) and ground. The top of the lower..." on page 687 of Scherz's book and this book is definitely reliably published. I am not sure if webmaster who says he interviewed the inventor who said the name was because marketing manager said... makes a cut as a reliable source. I couldn't tell you about the foreign source, but if it is a reliable source, we could include both versions. We're not truth finders. If we find two differing information from reliable sources, then we report all versions. It seems like the foreign sources might be a translation of the webmaster dude's interview though. WP:VNT WP:SOURCETYPES WP:V Graywalls (talk) 15:51, 7 August 2020 (UTC)

@Graywalls: The Japanese source (ref.2 and 3) was not a translation of the web (ref.4). It was a 2010 interview, as the publisher uploaded videos. These videos don't mention the topic I cite, but according to the interview in the magazine, Hans Camenzind said "There is a view that the number 555 comes from three 5kΩ resistors, but it is incorrect.". Well, I agree that editors themselves shouldn't make judgments as to what is true and what is false. Thanks. Darklanlan (talk) 17:06, 7 August 2020 (UTC)

@Darklanlan:, I removed the sentence "It is a false myth that the 555 IC got its name from these three 5 kΩ resistors." following the guidelines I referenced in my last response. If you have access to those journals yourself, you could simply paraphrase what the source says and summarize that they disagree with eachother. Graywalls (talk) 08:19, 10 August 2020 (UTC)

@Sbmeirow:, please have a look at the dialogue above and please see the guidelines verifiability, not truth. So we have McGraw Hill published book saying the above; and some self published website saying otherwise; and we don't just over ride it with the version you think is the correct one. If need to be, present BOTH versions, assuming they are both completely credible sources. Graywalls (talk) 09:48, 27 August 2020 (UTC)

While Hans Camenzind was the designer/inventor, he's not the absolute authority on Signetic's sales & marketing department's decisions on the marketing. So we could add something along the line that sources @Darklanlan: talked about was told that was that was incorrect in their interview with Hans Camenzind. Graywalls (talk) 10:03, 27 August 2020 (UTC)

I temporarily removed it. The book "Practical Electronics for Inventors 4ed" does not cite a reference to prove where it got the text "The 555 gets its name from the three 5K ohm resistors". The author seems to be repeating the myth without any proof. • Sbmeirow • Talk • 10:31, 27 August 2020 (UTC)

We're not dealing with information forensics and as far as I'm aware, there is no information chain of custody requirements in our WP:RS policy expecting to know each step of source of information within reliable sources.Hans Camenzind was not designated to speak for Signetics and his interview words can not be assumed as the authoritative source in naming. Graywalls (talk) 19:57, 27 August 2020 (UTC)

Just a reminder, Graywalls has NOT proven that Camenzind is wrong. • Sbmeirow • Talk • 06:20, 28 August 2020 (UTC)

Just a reminder, Graywalls has NOT proven that "555 gets its name from the three 5-kΩ resistors". • Sbmeirow • Talk • 06:18, 28 August 2020 (UTC)

@Sbmeirow:, Are you familiar with our WP:NOR policy? When we edit Wikipedia, we don't publish our own research. We report what reliable sources say. "If reliable sources disagree, then maintain a neutral point of view and present what the various sources say, giving each side its due weight." from WP:V, emphasis added by me. I don't have those foreign sources, but those of you who do, please feel free to add the present what those sources say. so both versions are presented. You're looking at the whole thing wrong. It's not up to Wiki editors to prove/disprove reliable sources. Graywalls (talk) 07:27, 28 August 2020 (UTC)

This has NOT been resolved, because 2 people disagree with Grayswalls. This is a warning to Grayswalls to remove that content. Neither book states where it got "the 555 gets its name from the three 5K ohm resistors", thus both books are unreliable sources for this issue. • Sbmeirow • Talk • 08:42, 28 August 2020 (UTC)

@Sbmeirow and Darklanlan:, That's not how it works. Policies are based on a broader consensus and it's not simply over ridden by "hey look, me and other person vs you" argument. See WP:CONLIMITED. I've even went beyond what's required and provided two solidly published books one by McGraw-Hill Professional, and another by Prentice Hall. So far, the alternate name roots have all been based on people that talk to Carmazind said.. he said Art Fury said.. https://spectrum.ieee.org/tech-history/silicon-revolution/chip-hall-of-fame-signetics-ne555 this doesn't talk about naming at all. I'm only pinging Darklanlan just so they can comment if they'd like. I think the version I have now, that includes both versions makes a well rounded, neutral presentation. Graywalls (talk) 16:30, 28 August 2020 (UTC)

@Sbmeirow:, the comment in parenthesis you left, and emphasis on "the inventor" suggests you have a credibility bias in favor of Carmazind. The books have been through editorial process. The interviews have not. Inventor is not in charge of corporate decision in marketing. Graywalls (talk) 00:07, 29 August 2020 (UTC)

The name section now says two books claim it and Camenzind denied it; sources for both. Seems OK. Dicklyon (talk) 00:26, 29 August 2020 (UTC)

I disagree with Sbmeirow's addition of "(without citation)" commentary. The way it's written paints the editor's doubt on credibility. Those publishers are known for creating text books and in the realm of Wikipedia, they're considered higher in the source credibility than parts collector's interview with the inventor. The dude did a recorded interview with the guy who designed the chip who says his client/employer's marketing manager said. This is only anecdotal evidence. Graywalls (talk) 01:00, 29 August 2020 (UTC)

I doubt the authors credibility on this subject matter, and I'm betting they repeated a myth from the internet. I stand by this statement until they prove their source. • Sbmeirow • Talk • 03:57, 2 October 2020 (UTC)

Monostable mode

Pulled uncited section from page due to conflicting information on the accuracy of the information. The series of edits here challenges what was present before wasn't correct, but it's not cited before or after the change. So, I have pulled it out. If someone knowledgeable on whatever this is saying and can provide sources supporting whatever version is actually correct, please re-insert with proper citations. Graywalls (talk) 23:36, 20 October 2020 (UTC)

Assume initially the output of the monostable is zero, the output of flip-flop(Q bar) is 1 so that the discharging transistor is on and the voltage across the capacitor is zero. The negative input of the upper comparator (as shown in the internal block diagram above) is at 2/3 of supply voltage and the other (THR pin) is connected to the capacitor. For the lower comparator, the negative input is the TRIG pin (trigger input of the monostable) and the other is connected at 1/3 of the supply voltage. When the trigger input is applied, the output of the lower comparator become 1 while the upper comparator remains 0. The output of flip-flop (Q bar) becomes 0, while the output of the monostable becomes 1. Removal of trigger signal does not change this (R=0 and S=0 means 'hold' for SR flip-flops). Now, the 0 at the flip-flop output puts the discharging transistor in cut-off, allowing the capacitor to start charging through the resistor R.

When the voltage across the capacitor crosses 2/3 of VCC, the output of the upper comparator changes from 0 to 1, changing the state of the flip-flop and causing Q-bar to become 1 while the monostable output becomes 0 again. The discharging transistor is turned on, and the capacitor is eventually discharged again, putting the monostable back into the starting state. The charging and discharging of the capacitor depends on the time constant RC.

Accuracy level

Re "the natural log of 3 constant, which is 1.098612289" and "the natural log of 2 constant, which is 0.693147181":

It doesn't make any sense to operate with that many significant digits. The number "3" is sensitive to the tolerances of the three nominal equal internal resistors in the IC. I doubt it is much better than 1%.

From a sample datasheet the timing accuracy is on the order of 1-2%.

--Mortense (talk) 18:36, 30 December 2020 (UTC)

The text doesn't say anywhere that a person must use 9 digits for their 555 math calculations, instead it is meant to show the origin of the "0.7 or 0.69 or 0.693" and "1.1 or 1.099" constants that are typically found in books and datasheets. I shortened both constants to 6 digits. 07:01, 15 February 2021 (UTC)~

Improper Removal

My edit should not been removed. User:Graywalls hasn't proven just cause for removal!

• [1] - removed because lack of reference. First removal was only because there wasn't a reference.

• [2] - I added a reference to counter the first removal. See page 5.

• Sbmeirow • Talk • 22:36, 8 December 2021 (UTC)

The problem is that the characteristics described are generic to all CMOS devices, and not specific to their being timers. It's irrelevant, because it's implicit and explicit in being a low power CMOS design. Anastrophe (talk) 22:55, 8 December 2021 (UTC)

What is obvious to you isn't obvious to all readers, especially to electronics newbies. WP:OBVIOUS says "state facts that may be obvious to you". • Sbmeirow • Talk • 23:11, 8 December 2021 (UTC)

@Sbmeirow and Anastrophe:, it only referenced products' datasheets. Encyclopedia is not a guide book. It should also be comprehensive, but not exhaustive and every small details need not be included. Similarly, it is not necessary to rattle off advantages/disadvantages of plastic vs metal housing for every single semiconductor device offered in both package types. CMOS vs bipolar is more of generic attributes, not specific enough to 555. Sbmeirow, also I specifically referenced WP:ONUS but it appears you have not read it. The burden to establish a case is on those seeking to include, rather than those seeking to exclude. Graywalls (talk) 23:21, 8 December 2021 (UTC)

The output section of the NE555 has a known design flaw... that is the dang point of why it's important. Just a reminder that all bipolar output sections are NOT the same. • Sbmeirow • Talk • 23:32, 8 December 2021 (UTC)

In many uses, the bipolar NE555 timer output seciton design flaw is irrelevant, such as driving an LED / relay / speaker. On the other hand, when the bipolar NE555 timer drives some types of circuits, its sharp current spike is known to cause ground bounce and/or noise problems in sensitive circuits. The bipolar NE555 is known to cause false clocking when it drives some logic chips. If the bipolar NE555 ouput section was correctly designed, these types of problems wouldn't exist. • Sbmeirow • Talk • 23:55, 8 December 2021 (UTC)

"[...]known design flaw". That's interesting. The material you want to add does not describe this design flaw that you suggest addresses, nor does the article discuss the design flaw you mention. The argument is moot absent the information you claim supports its inclusion. To be clear: if you want to provide said details, sourced, then you might justifiably add the information in question, as then it becomes relevant. Anastrophe (talk) 00:00, 9 December 2021 (UTC)

I'll respond in the coming days. 07:10, 10 December 2021 (UTC)

There's no clock ticking, take what time is needed (article subject-related puns intended).Anastrophe (talk) 07:18, 10 December 2021 (UTC)

@Sbmeirow:, please see WP:VERIFYOR everything on Wikipedia is to be based on reliably published sources. Anything to be included must be cited to sources that meet Wikipedia's definition of reliable sources. However, per WP:NOTEVERYTHING not everything published should be included and if there is a disagreement as to what should be included, the editor wishing to include is the one that needs to establish consensus, which you can read about at WP:ONUS. The editorial decision to include excruciating details solely based on Wiki editors' compilation of information from datasheets would be a question of due weight. Also, in the 555 naming disagreement, you argued about a source that meets the requirements of WP:RS not citing sources. That's not really how it goes. What you know, and what you believe is to be true is solely relevant for navigating you to find types of sources that meet the Wikipedia definition of reliable sources. In this case, the "design flaw" needs to come from a source that meets WP:RS and the assertion of importance of this must come from the reliable source, not what you know. Graywalls (talk) 18:03, 14 December 2021 (UTC)

555 in computers

so i found a 555 inside my vic20. i feel like you guys should add that to the article. thats all. — Preceding unsigned comment added by 212.68.10.6 (talk) 10:40, 14 September 2015 (UTC)

No, the 555 is used in numerous products, and far too many for this article. • Sbmeirow • Talk • 03:42, 4 August 2018 (UTC)

Its use inside Commodore's computers is an interesting use-case, though. Despite MOS pretty much owning their own destiny with respect to the CPU and all the custom chips, they still added a single 555 to the reset circuit design. It's configured in a one-shot mode. When power is applied, it waits for a short amount of time to give the power time to set up, then triggers the reset line of the 6510. Without the humble 555, the 6510 would never be able to figure out how to start itself. Mdwyer (talk) 17:34, 10 January 2022 (UTC)