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Yes, but ... When I was designing stuff for production, and we started using simulation, it became obvious that the simulated schematic really had to be the same schematic that we used for production documentation; one of the incidental advantages of simulation is that if you've made a drop-off on the schematic you are simulating, the simulation doesn't work, and you want to exploit that as a form of error-checking, the two documents have to be the same.

So stuff that "doesn't matter" in the simulation should still be included in the schematic data base. It may not matter now, but ti may matter when you have to go back through the documentation, years later, to find out why the hardware you are producing doesn't meet specification any more.

Obviously.

Much less insane - they document exactly what you thought you were doing, and how you were doing it. That can be less obvious a few years later.

Not just knowing and calculating, but also documenting - so you really can build the same thing again and again.

I'm not getting much done at the moment, but nobody is paying me to do stuff, or could give a shit when I get it done. When I was getting paid, and other people were relying on me to get stuff done, I was a lot more productive - unusually productive by U.K. standards, though there were times when I wasn't producing what my manager though that I ought to be producing (because he didn't know enough about what was going on, and was unwilling to be educated).

And sometimes those few seconds aren't long enough to comprehend everything that's actually going on. It's fine as long as you really are excluding stuff that really doesn't matter, but when you get it wrong it can be difficult to unblinker yourself and recognise that something small isn't always negligible.

Unsavoury rhetorical device. You couldn't care less if it's ever going to work, but pretending to speculate about it gives you an opportunity to say something unpleasant.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman
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The RLC can be critically damped, which makes it forget previous events better. There's still the RC tail from the finite diode drop.

A better circuit would charge the cap from a current source, and then quickly and completely discharge it. At these speeds, that might be a PHEMT. I guess I could do that. The current source gets tricky with only 5 volts available.

The RLC also has a faster slew rate around the logic threshold, which makes for a more repeatable delay and less jitter. It's the first step towards a lumped delay line.

This isn't real bad...

+V | | R | | logic in--------|
Reply to
John Larkin

ote:

They do, but they don't happen to be competing in your little niche market, so you don't notice.

Production get shirty about that sort of solution - not unreasonably.

I certainly don't ignore the parallel capacitance of my inductors - I do rely on the regular LTSpice library model of my ferrite beads, but when there isn't a built-in library model I put something together.

And I wasn't "whining about you ignoring parasitics" - the parallel capacitance of an inductor determines the frequency range over which it looks like an inductor. It's not a parasitic, but an absolutely fundamental feature of the device, which you can only rarely get away with setting to zero.

It's never good "for an accurate simulation" of any circuit. You may have got away with it on this particular circuit, but all you are saying its that you didn't need a particularly accurate simulation.

It didn't make very much difference, so it can't be said to be any worse than your mindless over-simplification.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

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Enamel isn't a great dielectric. My experience went the other way. I needed a transmission line transformer, and wound something small with Filotex 55R 1,2mm OD coaxial cable. It worked, but it wasn't all that cheap. As a reality check, I tried a twisted pair made with 38 swg enamelled wire - mainly because the coil winding shop stocked both 38 swg with both red and green enamel (one was self-fluxing and one wasn't (or something like that).

It worked just as well - because I had room for more twisted pair it fell over at 150MHz rather than 500MHz but that was entirely due to the extra length of the twisted pair winding, which put the low frequency end down at about 50kHz, rather lower than fewer turns of the Filotex could offer.

send Ethernet data

When I was knowledgeable about Ethernet, back in 1980, it used proper coax, and a single Ethernet might span a university campus. It's changed a bit since then, and nobody has been paying me to keep up.

Bifilar windings are a nightmare in production? Your production staff can't be up to much.

Enough to know that you are improvising.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

Got any open-drain parts? ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

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Interesting. I'd no idea at all, either way. But a quick search did turn this up:

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It says, "In 1988, the log, with the moth still taped by the entry, was in the Naval Surface Warfare Center Computer Museum at Dahlgren, Virginia."

Perhaps the book was transferred in the intervening period.

Jon

Reply to
Jon Kirwan

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Yes, now I find this:

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Jon

Reply to
Jon Kirwan

R is usually put across the diode, then you point the diode in the direction you want the delay.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply to
Tim Williams

I don't do that. I only simulate little snippets that I can't predict the behavior of, like this little RLC thing. I never simulate whole products. It takes too much time, isn't necessary, and the device models are usually bad enough that the sim doesn't prove much.

We don't prototype, either. It's too complex and wastes time. We only brassboard little snippets that we can't predict from data sheets or past experience. We lay out real boards, formally release the docs to production, and expect to be able to sell rev A.

That is production documentation. Entirely different.

When's the last time you said something pleasant?

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

won't

requirement

you

Ethernet data

I'm not going to ask them to measure and twist and strip and solder 42 ga wire. It's under 3 mils in diameter, practically invisible. And what do we do with a couple of feet of that, on a small PC board?

You've been winding one transformer for months, or years, and you're still not done.

I'm designing electronics that works and sells, and you're not.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

Usually? That causes the diode current to taper off to zero, which extends the discharge tail. Keeping the diode current flowing keeps the dynamic resistance low, which makes the discharge tau low.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

=3D30

I gave you the link to the Smithsonian site which shows they have possessio= n of it, assigned it an Object ID: 1994.0191.01, and have it on display the= re.

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Note also on the same page "American engineers have been calling small flaw= s in machines "bugs" for over a century. Thomas Edison talked about bugs in= electrical circuits in the 1870s." So the use of the term, bug, was three = quarters of a century old by the time of Hopper incident. The terminology p= robably predates Edison by 100 years too- referring to any small hard to fi= nd component of a complex machine causing the entirety to malfunction.

Reply to
bloggs.fredbloggs.fred

More fool you.

Hierachical circuit design lets you simulate snippets of a complete (and consistent) circuit design. Having the sim run right may not prove much, but it does prove that that part of the net-list hasn't been corrupted by the wires getting hooked up wrong (which is the kind of human error that happens often enough any automatic proof-reading mechanism is very helpful).

That strikes me as sensible, particularly with fast circuits where the actual printed circuit layout is a crucial part of the design. Again, simulating a snippet with estimated track lengths, track inductances and track capacitances provides a sanity check on the transfer of the design into the documentation.

Everybody wants to sell the first example of whatever it is they are producing. If your design process proceeds by such small increments that you can do a "new" design in a fortnight you really ought to be able to manage it most of the time.

It shouldn't be. Keeping them separate looses you a useful form of "proof-reading" check.

r.

.
t

It must have been last week. Some nitwit claimed that I thought that I was smarter than everybody else and I reminded them that there a few posters here whom I do treat with considerable respect - Joerg comes to mind, and Spehro Pefhany, amongst others.

More recently John Fields nailed krw for being the contemptible waste- of-space that he's always been and I posted a brief congratulation.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

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You wind it onto a small transformer coil former - I mentioned RM core coil formers, and EP cores coil formers tend to be even more compact. Here's the data sheet for the EP7 parts, which includes an surface- mounting coil former.

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People have been coping with 42 ga wire for years - it's not rocket science. And the wire is perfectly visible under a binocular microscope (which you've got to have for fine SMD work anyway) although I can't remember ever having trouble seeing it (though I am short-sighted and tended to take off my spectacles when I was working on SMD boards).

I got the transformer and two different inductors wound a couple of weeks ago. Finding someone who still has a small coil winding machine did take about a week, but it all went quickly once I found a local coil-winding firm. I still haven't got around to putting the double screen on the transformer and over-winding it with the last - single- layer - bifilar winding, but I will.

Not at the moment. but I've quite done enough of it to know that you aren't quite as "insanely good" at it as you like to think.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

$10

more

won't

requirement

sell you

leadtimes.

send Ethernet data

That's insane. You're talking about a 42 gage twisted-pair delay line, and you propose to wind it up, unshielded, onto a bobbin?

Try it and let us know how it works.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

$10

more

won't

requirement

sell you

leadtimes.

send Ethernet data

He'll get right to it, after he finishes his oscillator.

Reply to
krw

Do it thyself bifilar winding machine:

I usually use two different insulation colors. There are plenty of other plans and coil winding abominations found on the Internet.

Bifilar wire and trifler are commonly found in RF torid transformers, double balanced mixers, power dividers/combiners, etc. The first time I saw the insides of the cans, I was amazed that it could even be done by humans. At the time, the tiny torid were made by MCL in Brooklyn, New Yuck.

My guess(tm) is that the delay line would be simply wound flat onto a long rod. It won't be very small, but it also won't leak signal between multiple layers.

Some bifilar bonded wire suppliers:

42AWG is difficult. At a former employer, we had a production small RF coil winder that was worked with bifilar and trifilar wire. Then it worked, it could spit out a months worth of production coils in a few hours. When it didn't, we spend days trying to figure out why the tiny wire was breaking. Much of the moving mechanism was devoted to wire tension control.

However, if you don't like bifilar, maybe something like this:

but that brings us back to where we started. You can buy passive delay lines in a small package. Sigh.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

Everything considered, I'd rather pick-and-place a few cheap 0603 parts.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

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Even 48 awg is only recommended for 1.4MHz to 2.8MHz

Skin loss doesn't stop transmission lines from working as delay lines - it just makes them a bit lossier

Wind the twisted pair onto a surface mount EP core coil former. I've already posted a URL to the EP7 part. The EP13 part - CSHS-EP13-1S-10P-T

- may be a bit big for you, but see

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You don't seem to know much about what's possible in a serious production environment. Your clowns may not be able to wind 43 swg twisted pair onto a EP former, but you should be able to find a sub-contractor who could do it for you, and then your laughable excuse for a production facility should be able to reflow the surface mount former onto your printed circuit board.

--
Bill Sloman, Nijmegen
Reply to
Bill Sloman

Why not? Did you miss the undergraduate lecture where they told you that twisted pair transmission lines don't generate significant external fields?

Each twist does have an external field, but they alternate in sign and cancel pretty effectively.

I haven't got the test gear. My transmission line transformer worked fine using exactly that construction.

--
Bill Sloman, Nijmegen
Reply to
Bill Sloman

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