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The 555 and How It Got That Way (hackaday.com)
174 points by sohkamyung 5 months ago | hide | past | web | favorite | 48 comments

The 555 was great.

These days I usually just drop in a 6 pin microcontroller though. Less external parts, cheaper, less environmental instability, much more operational flexibility, and often I can have it perform several circuit functions. If I go to 8 pins, woah, look out!

I do so much digitally now that I've "forgotten" 75 percent of my analog stuff... Once in a while I come upon a cool analog trick though. Sad part is, that usually the "super simple, bulletproof" analog solution with just 5 parts usually ends up being more expensive in qc, bom, and board space that throwing a million transistors at it.

It's a strange world we live in.

Is this for a production device or like a hobby type thing? Reason I ask is that I'm often resistant to adding auxiliary microcontrollers to things just due to the extra hassle of maintaining, building, and distributing the firmware for them. Like, even if it's a device with JTAG, that's still a program-once-in-the-factory affair, unless you go the trouble of also setting up an SPI bootloader or something on it.

I guess the counter argument is that a 555 circuit can't be reprogrammed either, but it also doesn't have to be programmed even the first time.

With analog solutions, the complexity gets pushed into designing the test rigs, validating your component supply, thermal compensation, etc. Dealing with firmware instead may or may not be a net win, but the bottom line is you can change the firmware but you can't change the board.

The 555 is already overkill if you want a simple oscillator with fixed parameters. You can build one with two transistors.

Transistors are essentially free nowadays. Packaging and assembly are the cost drivers.

I was wondering this, even the leads seem enormous and wasteful compared to the actual device.




Notice that the discrete transistors actually cost more than the microcontroller.

Wow, it's like the two extreme endpoints of "Powers of Ten".


Those two transistors had better be hella good to justify the price difference.

Those transistors can drive 60V and 1A; hardly any controller can do such things. You might expect some special controller pins to drive e.g. 100 mA at 5V; more often, something like 20 mA at 3.3V.

Very telling

If you're interested in these classic chips and know how to solder, you owe it to yourself to build a Three Fives Kit:


That seems totally useless. I gotta get one. Thanks for sharing that link.

Don't miss out on the plush 555 circuit that they also sell: https://shop.evilmadscientist.com/else/663

Don't miss the #555 Episode of EEVBlog where Dave Jones solders this kit and talks a lot about how the 555 works its history:


Oh man, I haven’t soldered anything in 10 years since my physics PhD, but damn, this thing is calling to me :-)

They missed an opportunity to give this product the id 555.

Direct link to Hans Camenzind's (designer of 555 timer) free to download book "Designing Analog Chips"


Note that while the 555 is definitely a classic, definitely an amazing and useful chip, it puts large current spikes on the power supply and you would probably want to use something else in new designs unless you’re feeling nostalgic.

The CMOS 555s draw 110 μA vs 3 mA for the original bipolar ones.

What’s the alternative? Is the Ne555 or is there better?

Dave Jones' EEVBlog recently posted a video on cheap microcontrollers (<0.03USD):


Replacing a 555 timer is a very common job for this type of part. It will typically have an internal oscillator, so it won't need the additional components the 555 needs, reducing cost further. Even if you use something more expensive like an ATtiny (cut down version of the microcontroller found in Arduinos, so very easy to develop for) it might still be competitive because of the reduced parts count and board space.

Hmm. The argument for using a microcontroller to replace a 555 is the increase complexity, and risk. There is code to be written, programming process install at manufacture etc. So it is not necessary cheaper if you at a level higher than the BOM cost.

There are a huge number of cheap timing parts. You can even get an entire waveform generator in a 10pin MSOP.


There are many better alternatives now.


Arduino boards have pwm signal built in and tons of "other" functionality, on top of being programmable. You can get them below one dollar now.

They are also much, much, much larger than a 3mm x 3mm VSSOP part.

Not denying it. It has more I/O pins (pwm incl.) and it's easy to prototype, design/tune, though.

This was the first IC I ever saw, when I was pulling apart busted electronics equipment in the early 1970s. I understood why transistors had three leads, but what the heck could possibly need eight leads?!?!?

And I thought the 7400 series with DIP socket were the odd ones...

And for a list of applications what better than Forrest Mims' handwritten Engineer's mini notebook: https://archive.org/details/Forrest_Mims-engineers_mini-note...

Does anyone know what font that is (on the blue image)? It reminds me of the one used on a Z80 book I have and I really like it.

EDIT: Found it! it looks like the bold parts are "microgramma" and the less bold looking parts are "eurostile."

I think it's all eurostile but different widths and weights?

How did people 'reserve' a chip name back then? It's pretty cool to get 555, but what if some other designer wanted to call their chip 555 too?

As far as I know they just used whatever number they wanted, leading to confusing situations where one producers ' 4736 (made up, no idea if this one exists) would be a totally different thing from another's 4736. You'd keep them apart by the manufacturer code, i.e. FOO4736 = 'double-width gizmotron' while BAR4736='confufabulator (4ch)'. I used to leaf through catalogues looking for 'interesting' circuits and came across quite a number of such confusingly-named parts.

I loved this part. It was the second chip my dad let me use as a kid (after the 741) and IMHO he should have given them to me in the opposite order since the 555 seemed more magical and fascinating for a child.

Amazing. I remember 555 monostable and astable multivibrator and PLL were classic school projects. First simulation in P-Spice followed by implementation on bread-board.

A "mere $0.75" in 1972 is worth $4.60 today, perhaps not quite the bargain the article implies.

Compared to other parts cost at the time, it certainly was.

THe very first circuit I built as a hobbyist was with the 555 and even managed to sell a fake car alarm, I think that was round 1990?

Anybody know if he got any royalties from Signetics?

You'll find some details in 'Camenzind Oral History'[0] around page 4 (seems he got paid and it was a good arrangement, but there was no patent on the 555).

*[0] http://www.semiconductormuseum.com/Transistors/LectureHall/C...

Hard to admit: people like Bob Pease and Hans Camenzind would not find any much employment in today's industry even if they were back in their prime.

Work culture in America has changed since sixties.

Actually, Hans Camenzind was pretty busy up until the day he passed away in 2012. He continued to do analog circuit design, among other things (like writing books). (Good) analog engineers are not that common these days. At one point in the mid-2000's he mentioned to me that of his 15 most recent circuit designs, not one had an issue post-initial design. I don't think a lot of analog engineers today could say that. I suspect if he was still around and looking for work, he would not have much trouble finding it.

Yes, and Bob Widlar too. That was the early days of integrated circuits though, and in the early days of any field it's often the mavericks and non-conformists who make the most progress.

why is that?

Along with what baybal2 says today they'd have to fit in to a corporate environment that rewards credentials over demonstrated skills, gladhanding and backslapping over geeking, financial engineering over the creation of tangible things.

A paradigm shift. How it was: "make the chip, sell it later." How it is now: "sell the chip first, find out how to make it later if you did."

Companies now trust marketing/sales boys to know the market better than the very people who made that industry.

In sixties, a CEO comes to an engineer and asks what will be the "next bug thing" in one year term.

Today, a CEO comes to an engineer and tells him what will be the "next bug thing" in one year term.

Well you also have to remember that companies came and went faster than startups did. And consolidation happened quite quickly as well. Engineers made cool things but only a handful of the companies found a hit, and rarely did the same company consistently find the best. What ended up happening is the bigger companies just started buying the small company that had the hit that year. The old model was no more sustainable than the current model.

How it is now: "sell the chip first, find out how to make it later if you did."

Taken to its logical extreme you get Theranos. Will lessons be learned? I’m not holding my breath.

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