
555 timer teardown: inside the world's most popular IC - dezgeg
http://www.righto.com/2016/02/555-timer-teardown-inside-worlds-most.html
======
vardump
Probably a coincidence, but 0x555 == 0b010101010101. Just like the flip flop
output signal.

~~~
vinodc
Cool!

I was curious and looked this up on Wikipedia [0]:

> It has been hypothesized that the 555 got its name from the three 5 kΩ
> resistors used within, but Hans Camenzind has stated that the number was
> arbitrary. [1]

[0]
[https://en.wikipedia.org/wiki/555_timer_IC#Design](https://en.wikipedia.org/wiki/555_timer_IC#Design)
[1]
[http://www.semiconductormuseum.com/Transistors/LectureHall/C...](http://www.semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzind_Page2.htm)

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xt00
Maybe was the most popular chip for a while until the 90s, but these days they
are not in very many things that sell in high quantities unless it is like a
really cheap toy or something.. smartphones for example don't have 555 timers
in them. Battery charger IC's probably are the biggest total seller.. but many
companies sell similar types under different names, so not sure if you could
call them all "one chip" like you can call the 555 timer and all of its
clones..

~~~
swamp40
The cheapest ones at Digikey are going for 10 cents (compared to 35 cents for
the cheapest small microcontrollers [PSOC or a 10F200]).

So I guess they still have some use.

Probably sell mostly to hobbyists, universities and old designs though.

~~~
dheera
Hobbyists hardly use these things anymore, because they require all that
external stuff -- resistors, capacitors -- before you get what you want out of
them. They're not self-contained.

These days you can just program a PIC or something, drop it on your
broadboard, and you get whatever signal you want out of them with software,
without any components besides the chip itself, and maybe a quartz crystal if
you want better accuracy (although I really wish they'd package a crystal
inside the DIP as well to make it even more self-contained).

~~~
beeforpork
The DS3231 RTC clock chip indeed has an accurate crystal oscilator inside the
package, so, yeah, put em in an AVR why not!

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mafuyu
Chris Gammell (of Contextual Electronics) and Jeri Ellsworth (of Technical
Illusions) held a really neat 555 timer contest a few years ago. You can see
some of the results here:

[http://makezine.com/2011/04/21/555-contest-winners-
announced...](http://makezine.com/2011/04/21/555-contest-winners-announced/)

[http://makezine.com/2012/08/22/555-timer-contest-
highlights/](http://makezine.com/2012/08/22/555-timer-contest-highlights/)

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Jugurtha
I started writing a sort of tutorial for the NE 555. Most documents give you
just the formula to have the values (multiply the value by Ln2 and stuff), not
_how_ we got there.

It's not finished yet, but here are the first few pages:

[http://j.mp/ne555calc](http://j.mp/ne555calc)

It will also deal with duty cycle and things like that.

Here's the French version (old lab report when I was in college):

[http://j.mp/ne555fr](http://j.mp/ne555fr)

~~~
HeyLaughingBoy
This one of the reasons I hang on to old databooks and app note books. The
National Semiconductor, Motorola and Signetics appnote collections in
particular are very good for delving into the theory of how the devices work.

I may never _need_ them again for real work, but are they ever fun to read!

~~~
Jugurtha
Right on! Well since you seem to like that, I've shared a link once here on HN
but it went unnoticed. It's about Analog Design and it has a _ton_ of
information. Don't get lost:

[http://www.wisewarthog.com/](http://www.wisewarthog.com/)

It give recommendations depending on what you want to do, discusses books and
application notes, gives links to treasures, advice, pointers, and insights.

You might know the site; otherwise, I hope you'll enjoy it.

~~~
HeyLaughingBoy
Thanks! Bookmarked.

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pdkl95
If you want to play with a simulated 555 - and are willing run an old java
applet - my favorite (educational) circuit simulator includes several 555
circuits (and an implementation of the 555's internals).

[http://www.falstad.com/circuit/e-555pulsemod.html](http://www.falstad.com/circuit/e-555pulsemod.html)

~~~
gluelogic
Paul Falstad's Java applets were my biggest regret about deciding to uninstall
it.

~~~
haddr
Wow, I didn't know them before. Cool stuff!!

PS. I entered with my android mobile and to my surprise it works... Another
thing I was not aware is that I have Java applets on by default...

~~~
randomchars
Android doesn't support Java applets. The site uses JS.

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davidgerard
There was a project in Elektor a few years ago to program some cheap 8-bit
microcontroller to emulate a 555.
[https://www.elektormagazine.com/magazine/elektor-201511/2819...](https://www.elektormagazine.com/magazine/elektor-201511/28192)

They also did a kit to build your own 555 from discrete transistors.
[https://www.elektor.com/the-three-fives-555-discrete-
timer-k...](https://www.elektor.com/the-three-fives-555-discrete-timer-kit)

~~~
Stratoscope
I have that kit! It was great fun to build it, make some simple circuits, and
trace the voltages through the "chip". The kit is really nice quality and
thoughtfully designed.

This kit is actually from Evil Mad Scientist [1], the same people who make the
EggBot and other nifty stuff. Their own site has a lot more information about
it, and they sell it cheaper than Elektor. [2] They also have a similar μA741
op-amp kit. [3]

Back in the '70s I used to make blue boxes [4] with a bunch of 555s in them.
This was probably not the best way to design a DTMF box - I remember I had a
heck of a time keeping the frequencies stable. Woz's blue boxes probably
worked a lot better!

[1] [http://shop.evilmadscientist.com/](http://shop.evilmadscientist.com/)

[2]
[http://shop.evilmadscientist.com/tinykitlist/652](http://shop.evilmadscientist.com/tinykitlist/652)

[3]
[http://shop.evilmadscientist.com/tinykitlist/762](http://shop.evilmadscientist.com/tinykitlist/762)

[4]
[https://en.wikipedia.org/wiki/Blue_box](https://en.wikipedia.org/wiki/Blue_box)

~~~
davidgerard
Yep. Those links were nostalgia for me, 'cos I remember first using the 555
when I was a kid building projects from Elektor and ETI ...

~~~
jacquesm
The old elektor magazine was super good. Every issue had something on just
about every level of competence in it. I learned so much from those. The most
complex thing I built from them was the 2D graphics accelerator, hooked that
up to the Beeb and wrote a fully functional vdu driver for it.

------
paulgerhardt
HN readers: what products do you know of that used the 555 IC?

I'm working of a catalog of popular consumer electronic devices that used this
chip. Anything you know of that used this chip would be helpful.

~~~
craigjb
It's actually incredibly rare in consumer products. Especially since an 8-bit
micro controller can cost much much less in bulk today.

Edit: and 8-bit micros come much cheaper than Digikey when you buy consumer
product volumes directly.

~~~
paulgerhardt
Do you know what it is was used for in non-consumer products?

~~~
HeyLaughingBoy
It's in a number of ancient DC time-delay relays.

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chillingeffect
I've found this related IC to be useful in modern circuits:
[http://www.ti.com/lit/ds/symlink/tlc551.pdf](http://www.ti.com/lit/ds/symlink/tlc551.pdf)

It's a low-power version of the 555. It runs down to 1.0V!

I've used it in inductor circuits to chop-boost small voltages.

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capex
Link to the original chip designer's free book:

[http://www.designinganalogchips.com/](http://www.designinganalogchips.com/)

~~~
de_Selby
Thanks for this, I've got a few pages in and I really like his writing style.

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ghshephard
I had no idea the 555 chip that we use today, is the same as it was in 1970. I
would have (incorrectly) guessed that as time went on, that it would have
undergone improvements/revisions as technology improved.

~~~
kens
Well, there are lower power CMOS versions of the 555 available.

~~~
Animats
A 555 timer chip can deliver 200mA at the output, so it can drive small lamps
and relays directly. The output load usually dwarfs the current used for
timing. So, for most applications, a lower power version is pointless.

~~~
ajnin
I doubt that most applications of the 555 are driving relays and lamps, it
probably is mainly used to generate timing signals. But that's besides the
point, the low power versions can function with low voltages, allowing to
power the chip with a single 1.5V battery, which would be impossible with the
standard version, so it's far from pointless.

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readams
I just about died when I saw "banana for scale" on the photo near the bottom.

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DonHopkins
I wonder if they make a giant expensive high voltage/amperage/speed EMP proof
military space hardened version of the 555, for use in LED atomic bomb count-
down clocks, etc.

Here's a cool DIY project: Make a drop-in replacement kit for the 555
integrated circuit with discrete transistors and resistors [1]

[1] [http://spectrum.ieee.org/geek-life/hands-on/build-your-
own-g...](http://spectrum.ieee.org/geek-life/hands-on/build-your-own-
giant-555-timer-chip)

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madengr
Who actually makes the 555 these days? Or is everything old stock?

~~~
VLM
digikey hardly sells everything, but they do sell various 555 chips from 12
manufacturers, at least per the parametric search.

Its fun to look at the weird options available. A UFBGA-8 package is
available... weird, never used one of those before. TI sells chips that go up
to 3 MHz. TI will also sell bare dies if you have a wire bonder. Supply
currents are available down to 30 uA.

~~~
kens
Buying bare dies would be really convenient for my die photos / analysis, but
unfortunately with the Digikey minimum quantities, I'd need to buy 25 @ $4
each which isn't worthwhile.

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spydum
this is a super cool write up of something plenty of us neglect. I wasn't
expecting the excellent interactive explorer at the bottom! Click on the
component diagram and see the component highlighted in the actual image!

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k0stas
For those interested in understanding the general operation, this type of
circuit is called a relaxation oscillator.

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electronicsguy
feel so nostalgic reading this! I remember my first contact with the 555 was
through the Chip-chap electronics kit when I was 10. good times making LED
timers, metronome, etc.

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poseid
cool to see the mix of images, schematics, interactive graphics

