How inaccurate is a 555 or 7555 REALLY?

On Wed, 06 Dec 2006 18:43:51 -0700, Jim Thompson Gave us:

He was the one that wouldn't give the explanation you asked for. Must be a BEAR for him. :-]

Of course. Unconfusing them takes time ande costs money. All other things being more or less equal, I'll go for the transparent design every time.

So you don't use programmable logic parts. Why am I not surprised.

If you say so John. But you do look a bit silly, bent over, with your head buried in the sand.

So quote a few. With 2173 to chose from, even you should be able to come up with a few examples.

I don't. I simply haven't seen much about RISC or DSP parts in the stuff you post,or anythihg about programmable logic, for that matter.

Quite a lot. Try doing the system design for an electron beam microfabricator sometime, or a stroboscopic electron microscope. Not a place for a 555-addict.

--- Forgot to mention...

This is USENET, Bill, and if you think anyone's going to be interested in learning PLD when what they really want is a one-off they can wire up themselves and get working with the least amount of hassle, then you're just f****ng insane.

Also, I just went over to the Xilinx site and looked up prices on their Cool-Runner stuff.

Pick me up off the floor, OK?

I'm laughing so hysterically it's all I can do to type this without meaking missteaks!

-- JF

to

Don't be silly. First you libel me, then you claim it is up to me to prove that your unsupported libel is false.

You haven't raised the stakes at all - the electron beam microfabricator included a laser driven inteferometric stage positioning system, and hardware to map arbitrarily scaled data defining the inegrated circuit masks to be written onto the interoferometer measurements. We did fall short of full generality by assuming that the wafer/mask to be written was within two degrees of being square to the interferometer designed grid, but our customers assured us that that was all the tolerance we needed.

Our electron beam provided better resolution than your photolithographuc system ever could, and was doing write on the fly. I think you have just een comprehensively trumped.

Not if you want 0.5nsec wide stroboscopic pulses (which required an electrostatic beam-blanking system - albeit the boss would not spring for the wide-voltage range version on which I'm named as the inventor. Magnetic beam blanking is nice - we used it on the old EBMF 10.5 electron microfabricator - but it won't go sub-nanosecond nor anywhere near it.

In fact the interesting part of that system, which I first proposed in

And we didn't need two detectors - a sing;e relatively fast Everhart-Thornley detector above the final lens did everything we needed. The fast-focussed photo-multiplier tube did need a fast output amplifier, which incorporated an analog finite-impulse response filter built around a lumped constant delay line - a trick I've recycled a few times since then.

Great fun, but I don't know anybody who would describe it as "duck soup" once they understood what was going on.

It never did what I wanted done.

That isn't exactly genius. Anyone whio can do enough calculus to find minimum sensitivity conditions can demonstrate the same genius on a wide variety of circuits. I spent a lot design time doing this on various resistor networks when I was younger and doing serious analog design.

Camenzind did come up with a great circuit for its time, but the combination of crummy timer and crummy saturating switch didn't have much to offer by 1974, when I might have used it, and has had even less appeal since (except to people who are bit slow to learn new tricks - when are you going to get into PLDs?).

I don't begrudge Hans Camenzind his success. Try to find some evidence to support that daft allegation.

I''ve also got no reason to suppose that I'm smarter than Hans Camenzind, nor have I ever made any such ridiculous claim.

You don't seem to have a particulary secure grasp of reality, do you.

--- If it is, you should be able to prove it.

The reason I don't want to go slogging through your stuff is because when I did present you with evidence you'd claim that what I found was taken out of context or that it wasn't what you meant, or any number of other excuses to try to get out of it.

The other reason I don't want to go slogging through your stuff is that I just don't have the stomach for it.

---

--- Actually, it sounds pretty much like what we were doing, which was writing patterns generated on a CAD system directly onto an alumina wafer by ablating its surface with a laser. We also used a laser interferometer to get the stage's position, which in our case was a shuttle driven pneumatically back and forth, with the interferometric data being used to get data from memory which was to be written at that position.

---

--- Yup, sounds neat.

---

--- I suspect that's because there was always some reason you could come up with why it was never satisfactory. Probably because you considered it to be so far beneath your lofty designs that you'd have nothing to do with it.

---

--- If you mean use them, then when I need to, if ever. They just don't excite me very much and I've always been able to do what I needed to without them using cheap, easily obtained parts, so what's the big deal. I notice from an earlier post that you're itching to get your hands on some of Xilinx's stuff but you're waiting for an "opportunity" to come along? Why not just buy what you need and get started.

---

--- Just a feeling...

---

--- How about the: "That isn't exactly genius."... paragraph above?

You seem to be setting yourself up as a judge of what constitutes genius and what doesn't, thereby putting yourself above him by declaring his work "not genius". Strangely, what I said was that it was "brilliant". The "genius" part was in a different context.

---

--- Not according to you, but then I always keep a saltshaker around whenever I read your stuff.

-- JF

I don't care *that* much about about your opinion.

Oh, come on - this exchange has been going on for a couple of days, and you seem to have read most of the stuff I've posted. If my posts did turn your stomach. you'd be too busy retching to respond.

Except that you were working at a larger scale, and slower - we had a shaped beam electron source, which could write a shape - a rectangle in the range 100nm to 10um -in less than a microsecond (I can't remember the exact number) if the area was less than 1 or two square microns. Part of the design was a gigaword random access memory with 72-bit words plus eight bits of error correction and detection information. We managed to publish the design

Dream on. The stuff I've worked on has included some very crude fixes - through we did try and get rid of the cruder stuff. I was never all that pleased with my driver for the magnetic blanking circuit on the EBMF 10.5 - it was (just) fast enough, and didn't blow up when the service engineers shorted the output to ground - but when I dropped in on Cambridge Instruments (by then renamed) in the late 1990's they were still using it, some 15 years later, with the lumped constant delay line, and the largely capacitatively coupled drive to the output MOSFET and all, none of which I was all that proud of, but hadn't been able to improve.

Fewer parts, less board space, and the facility to offer more complicated logic than you can reasonably cram in with standard parts. Back in 1975 I thought up a way of minimising the low frequency noise coming out of a PWM driver, and couldn't put it into a practical circuit until 1993 when it just fitted into an ICT 7024 - it is in figure 7 of my milli-degree controller paper in Measurement Science and Technology, volume 7 pages 1653-1664 published in 1996.

Motivation and time. I've actually got a stick of surface mount parts, but solder has probably already oxidised the point where they will be a swine to mount - the idea that I was working out ddn't work out quite the way I expected, and the next critical point involves doing a messy mechanical drawing with QCAD, which I've yet to get working.

The application is the thing. The technique he used to get the application to work is sort of routine for properly trained engineers.

The arguement is about where the ingenious innovation was made. You seem to be over impressed by elementary calculus, and insufficiently respectful of of the trick of finding the right combination of features for the time.

Nobody is asking you to believe the bits you don't understand. That would be unreasonable, though you'd profit by a less skeptical approach.

I know - anything you can't do by tacking diodes around a 555 is a hassle. Other people have learnt to master more than one or two devices.

Do keep in mind that the PLD handles all the logic - there isn't a lot left to wire up after you have programmed the PLD, and that saves a load of time, space, money and potential unreliability.

Pity that you couldn't remember the prices that brought on this hysteria. I got 15 XCR3032XL-10PCG44C for $1.70 each in June 2006. That doesn't strike me as expensive for use in a one-off. But then you do design and price everything as if it was going to manufacturered in thousands - one of those habits that "professional" designers develop and can't seem to lose, if you really are an example of this interesting breed.

Not according to the QA department. This stuff went into power stations and oli refineries and everybdy involved was rather picky.

Quite a lot. In particular, service engineers who are prepared to travel all over the globe are a rare breed, and both George Kent and Cambridge Instruments hired as many as they could find. They could afford to be too picky about the their trainability. The design engineers understood that keeping the service engineers happy was part of their job - if the service engineer got fractious, we were next in line to spend six weeks in Seoul.

The worst I copped was a week in Nice in the middle of winter, and that was sorting ot a mess that the marketing department had got us into, but we were all encouraged to be careful.

Final test was a different kind of problem. They worked down the corridor, and if they got stuck the good ones had a tendency to stick their head around the door and ask or advice, which used up design time. The bad ones invented their own solutions to what they perceived as the problem, which you'd find out about when it appeared in the "proposed modifications" file - usually some two hundred items long, which appeared on the desk of any design engineer when he (or she) was between projects.

If the design wasn't transparent to the final test technicians, you always ran the risk of the machine going out the door distinctly maladjusted, and the quality of the final test technicians was always a bit erratic - if we we doing well, we'd just hired a bunch of new technicians of variable quality who were still being trained,and if we were doing badly, the good technicians would get themselves a more secure job somwhere else.

One time I designed a circuit that used an un-trimmed - thus cheap - Analog Devices multiplier to do a job, and wrote a procedure that let me set up the two trimpots required in about ten minutes. I got called into final test when the first machine went through to find that the boss of final test and his star technician had been fiddling all day trying to do the adjustments that I then did in the usual ten minutes.

Total cost (in techniican time) was about $300. I promptly modified the circuit to use the more expensive laser trimmed multiplier, and did the offsets on the rest of that batch (about 5 electron microscopes) myself. We weren't expecting to sell more than about fifty of that model before we obsoleted it with the first fully computer controlled electron microscope, so my blunder with the cheap part cost us more than I could have saved over the whole production run by using the cheaper part.

On 7 Dec 2006 18:36:59 -0800, snipped-for-privacy@ieee.org Gave us:

You're an idiot. Anyone with half a brain can tell that it was the baretard that I was "after" in both cases.

hygroscopic.

It all depends on the voltage. Figure that one out, ditz.

Irrelevant. I figure Jim is in more serious need of stirring, and your semi-literate posts weren't doing the job I wanted done.

They are diffused resistors and thus voltage dependent, as I've mentioned before. Try doing some reading before you start slinging criticism.

The local theory was that the resistors could vibrate on the mounting wire and eventually the wire could fatigue through.

Life was a little too short to try and persuade QA any different - we had better things to do.

It takes time to make sense of a complex circuit diagram, and realising a digital function with analog components doesn't speed up the process. You are welcome to s*it on your service engineers as much as you like. We treated ours as colleagues. They weren't servicing just one machine, but a variety of different machines, so they did have to consult the circuit diagrams pretty frequently.

And - granting our QA department - using that particular trick wouldn't have saved us anything anyway.

Grow up. That sort of work is pretty boring, and if you try and get smart people to do it they get bored and find themselves another job.

It was iterative, and the final test guys didn't follow it. I could have rewritten it, but one go around had already cost more than using the untrimmed multiplier was ever going to save.

I've designed out a lot of pots in my time, but we knew how much they cost, and how long final test took to set them (and what that cost). In the application the untrimmed multiplier, two pots and a ten minute set-up procedure should have saved money - around $4 per machine.

It looked perfectly transparent to me and to my boss and to his procedure-reading side-kick(who was a very intelligent guy who was very good at "misunderstanding" ambiguous procedure descriptions). I still don't know what threw the technicians - it certainly wasn't worth spending the time to find out.

No, I don't - the cheaper part was some $10 cheaper than the trmmed multiplier. Maximum total savings was thus $500 over 50 machines, less $100 worth of pots and $200 worth of setting-up time, if the technicians could have set it up as fast as I did.

Hi all,

My name's ananth, from india, a novice hobby electronics enthusiast . a year back, i got a PSoC kit to play around with and i implemented a few of their app notes, including one about operation from 1.5AA battery as the PSoC includes an FET switch as an onchip peripheral which can be used to build a boost convertor. it requires some extra components. i did a simple project from 1.5 everready AA cell (i think some push buttons and led--sorry do not remember). the smallest of devices is an 8 pin one and all members of the family are available in very small packages (though i have not used anything other than dip). only some external discrete's are required which can be got in small packages. i used a few ic's from 27xxx series which i got as samples. cypress has a lot of app notes , including an2286 which talks of simulating 555 using psoc and an2097 which talks of using onchip fet as switched mode pump. a visit to

regards ananth

WildIrish wrote: