Zener diode below-threshold reverse current

--- Birds of a feather, but OK; if you want to play some more I'm happy to re-engage.

The point is that you continually and relentlessly demean the 555 as if it were unfit for any use just because it didn't happen to fit into the niche you expected it to back in your salad days.

Now, in the autumn of your life, you seem to be clinging to its denunciation in the hope that you won't die with an A+ for vanity on your report card.

As for applications beyond your grasp, the automotive, consumer, and hobby markets seem to have eluded you as vast sinks for 555s.

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--- "could have done better" is a prejudiced value judgement on your part, made without the slightest knowledge of the circumstances surrounding my choice and - guess what? If my client - who got a lot of bang for his buck - should send me back a broken widget 30 years downstream, It'll be easy to bring it back to life since the 555 product stream/river is still viable.

Further, if repair of legacy designs, as you seem to be so fond of stating, is a reason for the brisk sales of 555s, you won't find me in that arena

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--- That's pretty nasty since "dirty" and "excuse" are chosen as masking pejoratives.

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--- Tell me about it in 20 years or so.

Can you say "74" or "4000"?

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And yet, you carry on?

ns I considered it for.

tuff than you do, and the 555 wasn't something that any of my colleagues we re all that enthusiastic about either.

I don't relentlessly demean the 555, though I do observe that it's an old d esign - 1971 - and that since about 1980 the niches it turned out to fill h ave been progressively taken over by approaches that weren't practical in 1

Back in the 1970's I did look at the part a couple of times, and it didn't do what I needed it to. Since then it hasn't been even potentially useful.

I say stuff about it these days when legacy designers go to trouble of clai ming that it's still worth using. This doesn't happen often enough for my r eactions to look like any kind of "relentless campaign" - you are pretty mu ch the only 555 enthusiast around here, so you do tend to be the target of most of these reactions.

I do spend more time being rude about John Larkin's gullible passion for cl imate change denial, but you wouldn't notice that.

The hobby market is also enthusiastic about the 741 op amp.

aren't going to be guilty about having used something that more or less wo rked.

If the 555 was the answer, your client probably wasn't asking the right que stion.

Second sourcing and readily available replacement parts are nice, but desig ning something that won't break is nicer.

No. You are a legacy designer, reiterating what more or less worked thirty years ago, because it is easier than working how you should be doing the jo b now.

The phrase "quick and dirty" has a long history. It's pejorative, but doing stuff faster than you should isn't a great idea, even if it can be necessa ry from time to time.

s a bit easier to make the case that it shouldn't, and it does give the lie to your proposition that selling in large numbers means that a part isn't obsolete.

ng that is out of date or superseded can also be obsolete. The 741 is defin itely obsolete, and the 555 is very close to the same state.

It won't be any less obsolete then.

I once shoe-horned some ECLinPS logic into a TTL circuit to get rid of a na sty - if sub-nanosecond - edge-jitter that the users didn't like, but it wa s supposed to be a stop-gap solution while we gone on with designing someth ing a whole lot better. The design did get completed, but the users weren't in a position to pay to have it built by then - quicker and dirtier might have been nice there, had it been possible.

The failure was more in the marketing area - I regularly succeeded in giving them what they asked for, but it tended to happen that what they asked for was something they couldn't sell when they got it.

You and John Larkin are closer to your customers than I was to mine - one of the consequences of working on more complicated products.

John Larkin has been known to describe his products as "insanely good" so he may have a conveniently inflated idea of their quality.

John Fields

Just this morning I was working on a repairing an acquisition board in an Agilent 54831B manufactured in 2004. Low and behold, I noted an SO8 555 chip!

What do those guys know, anyway!?

;^)

e:

signing something that won't break is nicer.

The 555 is cheap - if somewhat less than bulletproof - but anything that it can do there are almost always other jellybean parts that can do it better .

ty years ago, because it is easier than working how you should be doing the job now.

I don't have to know much to realise that if you think that the 555 is the solution, it's because you haven't explored the alternative.

ing stuff faster than you should isn't a great idea, even if it can be nece ssary from time to time.

You did seem to be in need of the clarification.

this can be very handy.

The 4000 series is a logic family, not a single device. Some parts of the f amily have lasted better than others. The 555 is a single device, with quit e a few applications when it was first introduced, but most of those applic ations are now better served by other solutions.

As logic families go, it's obsolescent, but today any significant chunk of logic is realised in a programmable logic device, so the parts that are sol d today are essentially sold as peripherals of one sort or another, much li ke the 555.

What sells them now isn't what sold them when they were introduced. I can s till remember designing 50 pound's worth of CMOS into a product (around 197

good design which doesn't seem to show up in any of the later versions of T TL, but it's really an analog part that sneaked into a digital logic family .

Which makes it relatively expensive.

How to recycle old designs, or bits of them. Not everything that came out of HP was absolutely perfect, though they did come closer than most.

I do remember being critical about an aspect of the design of the Hewlett-Packard laser interferometer, and being told that that particular feature was responsible for 90% of the returns for repair.

They didn't offer to take me on as a consultant ...

e:

rote:

designing something that won't break is nicer.

it can do there are almost always other jellybean parts that can do it bet ter.

Perhaps.

Your claim is the the 555 is remarkably flexible, so there are a lot of pla ces where it's a viable, but - almost always - a sub-optimal choice.

Enumerating (note the spelling) all them is almost certainly impossible, be cause by the time you'd gone through the process, another possibility would have emergfed.

in

hirty years ago, because it is easier than working how you should be doing the job now.

he solution, it's because you haven't explored the alternative.

Since my argument is that there are a lot of alternatives to the 555 across the myriad applications that you seem to think it's still suitable for, na ming one or two isn't exactly a useful exercise, and in fact looks like a t otal waste of time.

doing stuff faster than you should isn't a great idea, even if it can be n ecessary from time to time.

I'm not the clown that thinks the 555 is still a universal solution.

re this can be very handy.

e family have lasted better than others. The 555 is a single device, with q uite a few applications when it was first introduced, but most of those app lications are now better served by other solutions.

Most of us who used RCA's 4000 series were well aware that Motorola 14000 s eries were a viable second source for most parts, and did include some usef ul parts that RCA didn't offer.

The competition between the two companies was what drove the initial fall i n price that brought them into contention for commercial electronics.

If I were a god in my universe, I'd have a job. Knowing more than you do ab out the electronic universe beyond the 555 doesn't actually need god-like o mniscience.

I don't rail against its existence - I merely suggest that nowadays it's ra rely a viable component for new designs, and really ought to be designed ou t of most the places it is currently used..

Why are your still trying to persuade us that the 555 is worth considering in new designs (or worth leaving in when sorting out old designs)?

It does reveal a depressing ignorance of what's currently available.

You did snip the bit where I recalled identifying a design error in a Hewlett-Packard Laser Interferometer, and being told that it was responsible for 90% of their returns for repair on the unit.

Most design errors reflect failures of attention, rather than outright ignorance, and you don't have to be particularly clever to find them.

That's why design reviews are such a good idea. A fresh pair of eyes sees stuff that you've glossed over. It's like proof-reading, where those not skilled in proof-reading find about 30% of the errors, and skilled proof-readers still miss about 10%.

emerged (note the spelling).

As I seem to have mentioned before, we all make typos and proof-reading isn't 100% reliable.