Somewhat OT: Long term design

[Sylvia Else]

They don't have to. The cast all read their scripts, and know what
to do. ;-)

And the aliens in many cases not only speak English, but do so with an
American accent.

Sylvia.

 

[Tim Williams]

Don't you get tired of being probed? ;-)

All the ones he's met used lube. ;-)

Tim

 

[D Yuniskis]

Evidently you haven't been watching Dr Who.

Or HHGTTG! (though they don't speak *real* english! :> )

 

[Tim Williams]

How can your DNA tell them what's in your mind?

How can your anus?

(Except for those with slomanitis. ;-) )

Tim

 

[krw]

Or a mind wipe? ;-)

Do that on DimBulb and it'll come back brown.

 

[Joerg]

Your part of Europe was obviously quieter than most.

Well, I meant the real serious wars where vast stretches of land go up
in flames or wild hordes destroy everything in their path. They always
had the little spats between individual fiefdoms. For example, Germany
wasn't really a country until "recently".

 

[Sylvia Else]

<grumble>.."functional"..guess one better start to define (nominal)
capabilities of that computer first.

That's a problem, in as much as the TV show had the computer (which
wasn't actually mentioned, or was referred to as a "core drive"),
housing a human personality. I wouldn't know where to start in terms of
defining its capabilities in a way that would make engineering sense.
Indeed, it may not be possible, even in principle.

Sylvia.

 

[Sylvia Else]

Noting wrong using a solar cell using your condition that the device
"be secreted from human tampering" for that 1000 years.

If it's hidden away, and only exposed to the sun after the time is up,
then we need a mechanism to do the exposing, and that mechanism will
require a power source.

Sylvia.

 

[Sylvia Else]

Good cells are fairly klunky monocrystalline silicon PN junctions.
They'd probably work fairly well after a million years if stored
properly.

This is where I wonder about difusion. Will those doping atoms stay put
over those sorts of time scales, or would we end up with a piece of
silicon pretty much equally doped throughout with both doping materials?

Sylvia.

 

[Sylvia Else]

Sine i am a baer, may i growl and say "Gurr-avity"?

Back to needing a mechanical mechanism that will work.

Sylvia.

 

[JosephKK]

What does the machine have to do? Mechanical stuff (gears, cams,
punch cards) lasts a long time. It could be powered by gravity.

George H.

Indeed, consider the traps in ancient tombs.

 

[Nico Coesel]

* Sorry, NASA has seen whisker growth in their satellites..

If it needs to be reliable solder is out of the question. Just look at
automotive electronics. The really reliable stuff is (sort of) spot
welded and covered with some sort of goo. Other ways are wire-wrap,
press-fit and crimping.

 

[Nico Coesel]

Al Po's?

Generally considered as good as tantalum and fairly indestructible, aren't
they? Kind of new to use for millenium hardware though.

Tantalums are very prone to failure. I avoid them if I can. Even
electrolytics are better because they don't cause a short. Nowadays I
use the MLCC capacitors where I can.

 

[JosephKK]

Yeah, even worse! I was probably thinking of this toy

I guess an artillery shell leaves in even bigger of a hurry, but
doesn't *keep* accelerating... More of a "jerk" situation?

Well an 8 inch 58 military cannon accelerates an approx 100 lb
projectile to about 3000 ft/s in some 22 feet. The acceleration
curve looks kind of like a truncated "F" distribution.

 

[Spehro Pefhany]

Not if you use them right

Wot mostly consists of leaving them safely on the reel.


Best regards,
Spehro Pefhany

 

[krw]

;-)

Well, then they still may fail ;-)
Just that you won't know about it.
s/know/care/

But on the more serious side, I have never had one go kaput,

I certainly have. We have a huge fallout on 220uF 35V tantalums;
right off the reel. They're better than aluminums, though. The
aluminums didn't make it through the RoHS process. :-(

I like them because of low ESR and small size.
They do not dry out, some have been on for 20 years...

Some light bulbs have made it 50 years, others have cause somewhat
more problems.

I have seen exploded ones cause damage in equipment, most likely because they were put in in reverse...
I put one in (actually a whole series) in reverse myself one day, because the + was marked with a big --
That came out when the first one was tested, and the resistor in series with it burned a hole in the PCB.
That was supposed to be a fusible resistor, I have now learned that metal film resistors do not fuse very well.

That too. Even ones inserted the right direction tend to short,
taking out the series resistor. We're seeing a lot of charred
resistors next to those 220uF caps.

Many years ago, it we found that no matter what we did, 1% got
inserted backwards. ...even if the manufacturer had to put them in
the tube backwards to meet the target. ;-) The solution was a fuse
in the cap, non-polarized cases (+-+ or +--+ pinouts), or big/little
pin, though the latter still could be force fit.

 

[Tim Williams]

They'll pretty well stay put. Diffusion is an exponential thing, so where
it's happening at say 800K, it's down by exp(800K/300K) = 14.4 times at room
temperature. Wait, that's not so impressive.

References.... ah, diffusion follows the Arrhenius equation, which puts it
in terms of exp(Eo/k_B*T), so the ratio between temperatures is
exp(-(Eo/k_B*T) * (1/T1 - 1/T2)). That requires knowing what the activation
energy is, though. Can't find it.

Tim

 

[Fred Abse]

A number of the original Tek tube scopes (517? do not remember
numbers it has been too long) still work only needing capacitor forming
via slow increase of AC via triac.

Didn't you mean "Variac"

;-)

 

[Fred Abse]

It's all about maintenance. Wonder how often the bellows had to be
replaced/rebuilt? Probably even some pipes?

There are some recorded instances of "tin plague" in organ pipes in
unusually cold weather.

 

[JosephKK]

The original 'lint' traps? ;-)

I think they predated even 'lint' by quite a bit. :)