The 555 Timer IC

August 22, 2012 2:19 PM

The simple but powerful 555 timer IC can be rigged to produce a timed pulse or a square-waveform oscillation up to 68kHz. It later came in dual-timer (556), quad-timer (558), military-grade (SE555), and low-power (7555) configurations. Although it's largely obsolete in commercial electronics, it became beloved of amateurs wanting an easy and cheap way to make things buzz or blink. In memory of the recent passing of its inventor, Hans Camenzind, Make Magazine offers a retrospective of 555 contest winners. Here's a tutorial on chip function from instructables. How to build a toy piano. The morse code practice circuit. Miniature beeping circuit prank to baffle your friends and co-workers and a screaming altoids tin. (Previously on metafilter, the 555 footstool.)
posted by CBrachyrhynchos (43 comments total)

I love the 555!
posted by scose at 2:27 PM on August 22, 2012

While not in the DIY, 555 buzzer spirit, annoy-a-tron is annoying!
posted by lalochezia at 2:30 PM on August 22, 2012 [1 favorite]

I am fascinated by electronics, although am not a builder of electronic stuff, just can't seem to get my head round the practical side of things. Still, this is fascinating stuff, the 555 is a seminal peice of semiconductor architecture. RIP Hans Camenzind.

.
posted by marienbad at 2:31 PM on August 22, 2012

Aren't all ICs that aren't fabbed to order for the device at hand (and, more often than not, contain a CPU core of some sort and some firmware) obsolete in commercial electronics? Or is there still some valid commercial reason for someone to build production circuits out of discrete ICs?
posted by acb at 2:32 PM on August 22, 2012 [1 favorite]

I remember discovering the 555 on one of my older electronic projects when looking for some kind of "clock" to run a LED counter on a protoboard. I'm glad I picked it over a quartz clock...it was a lot of fun to put together and taught me a lot about resistors and capacitors (used a 10k potentiometer to adjust frequency)
posted by samsara at 2:32 PM on August 22, 2012

Definitely check out this interview with Camenzind from the website Semiconductor Museum. He talks about the old-school process of designing silicon with an X-Acto knife!

There was an Exacto knife attached to a parallel arm. You used this to cut out the “runs” (in the rubylith), and peel off very carefully the plastic material from the area that’s not supposed to be there. Next, you photograph that, reduce it in size. The rubylith mask is about 300X. You had a table that was calibrated in hundredths of millimeters, still, it was almost impossible - if you had two resistors that had to match, to make them absolutely identical. It depends on how much patience you had with that arm.
posted by scose at 2:36 PM on August 22, 2012 [1 favorite]

My favorite 555 project was to use it to create a PWM adjustable power supply for a simple heater to keep the dew off my telescope's eyepiece, finder, and telrad glass. A simple and elegant chip that wasn't too complicated to comprehend.
posted by jclarkin at 2:37 PM on August 22, 2012

The 555 is absolutely NOT obsolete in commercial products. National Semiconductor sells them in die form. Those are not being sold to hobbyists.
posted by ryanrs at 2:40 PM on August 22, 2012 [1 favorite]

Aren't all ICs that aren't fabbed to order for the device at hand (and, more often than not, contain a CPU core of some sort and some firmware) obsolete in commercial electronics?

Huh? It is a very, very rare product that justifies custom chips. For example, I doubt your PC has any custom chips.
posted by ryanrs at 2:44 PM on August 22, 2012

Thanks for the tutorials! I'm pissed off I can't figure out how to wire up the Atari Punk Console (a.k.a. Forrest Mim's stepped-tone generator) and hopefully some of these links will set me straight.
posted by griphus at 2:45 PM on August 22, 2012 [1 favorite]

Forrest Mims'
posted by griphus at 2:46 PM on August 22, 2012 [1 favorite]

Something that got left out of my edit is that the 555 was invented in 1972 (months after I was born.)

ryanrs: I'm happy to be corrected, thank you.
posted by CBrachyrhynchos at 2:47 PM on August 22, 2012

The 555: the 6502 of DIP8s. . for you, mister inventor.
posted by BeeDo at 2:51 PM on August 22, 2012 [1 favorite]

First place winner in the minimalist category.
posted by deo rei at 2:52 PM on August 22, 2012 [2 favorites]

Aren't all ICs that aren't fabbed to order for the device at hand ... obsolete in commercial electronics?

You'd be amazed. On one project I've worked on (that you've probably seen in stores), it was cheaper to build the motor driver circuitry out of discrete resistors, transistors and resistors than it was to use an off-the-shelf motor driving chip that was built for doing exactly this operation. The incremental cost of placing the extra [/me does some mental calculation] yeesh, must have been 27 off-the-shelf discrete parts on the board was cheaper than using one off-the-shelf IC.

Custom ASICs are even more expensive to design, and even devices that sell a half-a-million units are sometimes designed for a market of a ten or two thousand, which means that with 20/20 hindsight you might have squeezed some more dollars out of the device, but nobody can predict that well...

So, nope: TIP120, 2n2222, 2n3904, 555, all of these parts that you might have stumbled across in the '70s are still alive and kicking in new designs.

And this is awesome and there are some things I need to go home and breadboard, 'cause I'm normally a software guy and need to generate more smoke.
posted by straw at 2:54 PM on August 22, 2012 [1 favorite]

Also the time to design and fab a custom chip is likely to be longer than the rest of your product.
posted by ryanrs at 3:00 PM on August 22, 2012

Huh? It is a very, very rare product that justifies custom chips. For example, I doubt your PC has any custom chips.

Aren't the large chips on the underside of hard drives dedicated hard-drive controllers of some sort?
posted by acb at 3:07 PM on August 22, 2012

Yeah, but they're not designed for a specific hard drive model or even disk manufacturer.
posted by ryanrs at 3:08 PM on August 22, 2012

Aren't the large chips on the underside of hard drives dedicated hard-drive controllers of some sort?

Well, one of them is just DRAM.
posted by eriko at 3:09 PM on August 22, 2012

Cool.

Now how do you make it in Minecraft?!
posted by markkraft at 3:42 PM on August 22, 2012

Oh... nevermind.
posted by markkraft at 3:43 PM on August 22, 2012

I never thought I'd see those shoes again!

Favorited

posted by mmrtnt at 4:00 PM on August 22, 2012

When I was a teenager, I combined two circuits from a Radio Shack project book to use a 555 to make an electronic Dungeons and Dragons percentile dice roller. The 555 pulsed at about a hundred times a second, a bcd-to-seven-segment display keep track, when you hit the switch the display would freeze on the last number counted.
posted by Nyrath at 4:09 PM on August 22, 2012

Let me guess, were the other chips a 7490 and a 7447?
posted by ryanrs at 4:27 PM on August 22, 2012

It's hard to overstate just how much a fundamental building block the 555 is to everyone from amateurs to the largest of commercial concerns, to this very day. This chip inspired my hardware hacker side, as with countless others. While I never progressed past the hack level, I'm still amazed to see truly creative applications of the chip popping up all the time.
posted by 2N2222 at 4:35 PM on August 22, 2012

> I'm pissed off I can't figure out how to wire up the Atari Punk Console

griphus, Jimmie P Rodgers makes a very nice little kit board that makes this trivial. He's travelling at the moment, so delivery might be slow.

I have a couple of boards spare, so might be able to send you one. Might even be able to build you one if you are not of the soldering type.
posted by scruss at 4:37 PM on August 22, 2012

In the past I was a big user of 555s, but these days if I need a waveform out of an 8-pin DIP, I'll use an ATTiny85 as a C programable function generator. Working with analog electronics has a certain charm, but it is so much easier to code up whatever outputs I need as a program rather than digging through my parts draws for the right 1% resistor or random capacitor. Tiny85's are $1.29 at digikey, while 555's are only $0.49, but that doesn't include the additional passives that are required to configure the 555.
posted by autopilot at 4:49 PM on August 22, 2012 [1 favorite]

Discretes are for real engineers!

The number and variety of things that can be accomplished with analog ICs, including the 555 is enormous. It's limited often by engineer experience more than technology.

Not everything has to be LSI and digital. Any competent engineer has a pile of analog parts (op amps, instrumentation amps, timers, etc. ) in his/her tool kit. There are still a lot of problems to solve with basics and not 200 pin ICs.

That said, the real issue most of the time is not tech, but economics. Sometimes, it's easier to do a circuit because the non-recurring engineering is shorter with an 8-pin DIP, so you use it. Other times, if you're going to build 1,000,000 of something, it warrants a lot of NRE to get rid of a few pennies of component or labor cost.

The 555 is in a lot of stuff. It's in a lot of parts cabinets and solution lists. It's a go-to for timing, delays, oscillators, missing pulse detectors, level controls, test signals, yada yada. It's the 6GH8A of SSI.

Great idea, it was.

(I do like to use MSP430's for complicated stuff, though. Cheap, uber flexible, small, algorithmic, decision making, precise, software reconfigurable, etc. Did I mention cheap?)
posted by FauxScot at 5:19 PM on August 22, 2012

Man, the old 555 timer. One of my earliest experiences with it is with Craig Anderton's "Electronic Projects for Musicians". What a great IC chip. Simple yet indispensable. Of course now everything is digital, and somehow it just doesn't seem as much fun...
posted by Eekacat at 6:00 PM on August 22, 2012

The 555 does have its problems, though, or at least it did when I was using them in anger. It's bipolar and thus thirstier than one might like, and it does spike a bit when switching. (That one nearly sank me once through power-line coupling; a set of 555s which were supposed to be free-running at slightly different frequencies to generate a pseudorandom sequence of twinkling lights on a display board wandered into sync over a few minutes longer than I'd tested it for before handing it over to the client. Ahem. Cured by the traditional BFC.)

The CMOS version, 7555, is better on both those points and has been quite a success in its own right. The original designers of that for - ah, was it TI? - had been pushing it as a project internally but were told to lay off by their boss. They did it anyway, sneaking the die through test on wafers containing other circuits, and had just pinned out their first working parts when said boss came crashing in saying that they should drop everything and do the darn design as a client was begging...

Skunk works FTW.
posted by Devonian at 6:05 PM on August 22, 2012 [2 favorites]

(And I should say that I have a design for a new thing, which is basically a kind of decorative spectrum analyser to describe domestic RF environments in an aestheticaly pleasing way, that controls anything from 1 to 1000 LEDs without a single digital part or signal. But it does have a 555.. possibly two, if I'm feeling too lazy to get creative about sorting out a particular state transition)
posted by Devonian at 6:11 PM on August 22, 2012

I saw this topic come up a few days on RetroThing.com. They noted that the 555 was on the IEEE Spectrum Magazine's list of 25 Microchips That Shook The World. I checked it out, it is number one on the list. Of course.
posted by charlie don't surf at 6:22 PM on August 22, 2012

MILSPEC beep prank would be pretty awesome.
posted by clvrmnky at 6:28 PM on August 22, 2012

I love the 555. (I love it almost as much as the 741, the universal op-amp.) I hoard a stash of ICs that I'm afraid will never be available again (like audio-quality current buffers), but I'm sure they'll be making 555s and 741s long after I'm gone.
posted by phliar at 6:35 PM on August 22, 2012

We had a rack mounted mini-fridge in our computer room, we disguised it by tacking the front panel of another computer to its door. A few 555s and a 5 volt power supply had the front panel LEDs winking on and off like a busy little box. Back in the day we kept beer in our computer lab as we often pulled all nighters and more coding debugging and testing. We lived on pizza and beer. It was always fun to ask a visitor if they wanted a beer and then walk over to the rack grab the front panel open up "the computer" and extract some frosty bottles. It was always good for a WTF and a laugh. The good old 555 came in real handy for goofball projects.
posted by pdxpogo at 7:05 PM on August 22, 2012 [2 favorites]

The 555 was the second chip I ever used in my discovery of electronics. The first was a very odd op-amp in a RS 150-in-1 kit which was a single inline package.

Quite some time later, I drifted from hardware and stuck in software for a couple of decades, but the arduino has brought me back to the fold.

The 555 was a wonderful chip.
posted by Bovine Love at 7:16 PM on August 22, 2012

scose: "Definitely check out this interview with Camenzind from the website Semiconductor Museum. "

I see you beat me to posting that link. I'll point out the interview comes with audio as well, if you hate the web format or comic sans. The 555 is probably super popular for some reasons pretty relevant to today's court cases in Apple v Samsung (etc):

There are no patents on the 555. Signetics did not want to apply for a patent. You see, the situation with patents in Silicon Valley in 1970 was entirely different than it is now. Everybody was stealing from everybody else. I designed the 555 Signetics produced it, and six months, or before a year later, National had it, Fairchild had it, and nobody paid any attention to patents. The people at Signetics told me they didn’t want to apply for a patent, because what would happen if they tried to enforce that patent, is the people from Fairchild would come back with a Manhattan-sized telephone book and say “These are our patents, now let’s see what you’re violating”. It was a house of cards – if you blew on it, the whole thing collapsed.

The more things change...
posted by pwnguin at 8:54 PM on August 22, 2012

I still have my copy of the Engineer’s Mini-Notebook - 555 Timer IC Circuits, by Forrest M. Mims III
posted by stp123 at 9:03 PM on August 22, 2012

As much kudos as the original 555 deserves, the CMOS versions are almost always superior, unless the design relies on a quirk of the bipolar 555. And I've seen a few that exploit such weird quirky behaviors in novel ways. Even then, I was likely to use a CMOS Schmitt trigger chip in place of the 555 of any type.

As software based chips became more popular, I kind of lost interest. Just doesn't have the same draw for me. I do have some solace sometimes when I occasionally see DIY projects using PICs or Arduinos performing some function, and thinking, "I can totally make that circuit with a 555".
posted by 2N2222 at 10:31 PM on August 22, 2012

I love the 555. (I love it almost as much as the 741, the universal op-amp.)

I spent years at the beginning of my career building test fixtures and then testing 741s because TI had a fab problem with the ceramic package version. My memories are bittersweet. But the 555 was always fun to play with, since we only used it for lab work and not in products.
posted by tommasz at 5:53 AM on August 23, 2012

You can grab 555s for $0.13 and 556s for $0.25 at Tayda.

The analog silicon vendors are surprisingly profitable. Largely this is because they use decades old silicon fabs and processes that are practically free because they were paid for and abandoned by the Intels and Microns of the world. Intel will spend a billion dollars to build a leading edge fab to put a billion transistors on a chip while the analog guys are only putting a few hundred or less on a chip. The analog vendors can use obsolete fab equipment that the digital vendors almost give away each time they move on to the next shrink in feature size.

The other interesting effect is that this often results in analog parts that are practically bomb proof in their ability to tolerate abuse. Where the latest digital parts can be destroyed by static electricity or a 10% over-voltage, many of the old analog parts will take about anything you can throw at them. This is because the feature sizes for the transistors are 100 times bigger than anything on the digital chips. It is like the difference between a carbon fiber racing bicycle and a bulldozer. The racing bike can be damaged by hitting a curb too hard but the bulldozer wouldn't be harmed by a sledgehammer.
posted by JackFlash at 7:23 AM on August 23, 2012 [2 favorites]

It was always fun to ask a visitor if they wanted a beer and then walk over to the rack grab the front panel open up "the computer" and extract some frosty bottles.

Thoroughly unrelated to the 555, but this story reminds me of another one told about an early University of Sydney computer.

SILLIAC was a large machine which generated a lot of heat; as a result it required a serious heat exchange system - one unit on each end of the machine. The cold side of the heat exchange provided a very useful chiller which held six bottles of beer!

posted by zamboni at 7:27 AM on August 23, 2012

@rynars: For example, I doubt your PC has any custom chips.

You'd be surprised; it's becoming more and more common. For example, if you're using a MacBook Air, you're using a custom chip Intel produced specifically for it. But even if you're not, there are likely tons of custom chips in everything that supports your PC. Cisco & Brocade, for example, use large numbers in essentially every product they make.

@ryanrs: Yeah, but they're not designed for a specific hard drive model or even disk manufacturer.

*looks* I'm pretty sure the chips on my Seagate disks with a "Seagate" logo and part number are specific to Seagate. (P.S. - I cheated there...I went to school with an ASIC designer at Seagate and we caught up a couple of months ago. There's custom, in-house designed chips on every drive).

Oh...and great post. I've quick-wired up some 555+LED blinky things recently to hook my daughter on electronics.
posted by kjs3 at 7:52 AM on August 23, 2012