Somewhat OT: Long term design
in [Design]
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From: John Larkin on 14 Jan 2010 01:13 On Thu, 14 Jan 2010 00:07:31 -0600, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message >news:2bctk593ta9olnh7k5roud0jg94cbpbno9(a)4ax.com... >> They are kind of new, so it's hard to tell. Apparently one failure >> mechanism is water vapor leaking *in* and wrecking the polymer. >> >> If it ain't one thing, it's something else. >> >> I've been using polymers lately and they seem fine. ESR is low, >> leakage is low. They seem to fail suddenly at ballpark 2x rated >> voltage or so with no "warning" leakage or anything like you'd see in >> a tantalum or regular 'lytic. They don't detonate like tantalums. > >That's interesting. Do they just 'tick' like films then? Not self-healing >yet I suppose. Mmm, that would be interesting, self-healing electrolytics. Regular aluminums pretty much are self-healing. Tantalums are self-abusive. > >I'd like to try a few, but when I see the price, I just think... meh, I'll >beef up my cans with some ceramics and call it a day. And e.g. Mouser's >available product line isn't nearly as diverse yet either. > >Gee, this sounds like something Joerg would say. I'm betting he's never >even touched one. ;-) > >Tim We're using a 180 uF 6.3 volt surface-mount alum polymer, 86 cents each. That's a lot more than a regular 'lytic, but a pretty good deal for that low an esr. John
From: Sylvia Else on 14 Jan 2010 01:36 John Larkin wrote: > On Thu, 14 Jan 2010 15:51:25 +1100, Sylvia Else > <sylvia(a)not.at.this.address> wrote: > >> Joerg wrote: >>> John Larkin wrote: >>>> On Thu, 14 Jan 2010 13:31:08 +1100, Sylvia Else >>>> <sylvia(a)not.at.this.address> wrote: >>>> >>>>> A recent episode of Stargate Atlantis prompted me to think about how >>>>> would could design equipment that's intended to function far into the >>>>> future. The episode required stuff to function 48,000 years after >>>>> construction, but perhaps we could be less optimistic. >>>>> >>>>> Say 1000 years. >>>>> >>>>> Note, the requirement is not that the equipment function *for* 1000 >>>>> years, but that when it is turned on, 1000 years from now, that it >>>>> will work. >>>>> >>>>> It seems to me that semiconductors are out due to effects of difusion >>>>> and radiation. >>>>> >>>>> But how about thermionic valves? They're not very reliable, but do >>>>> they age when not in use? Would they hold a vacuum over that time? >>>>> >>>>> Obviously electrolytic capacitors are a no-no, but can resistors and >>>>> capacitors be made stable enough that they'd work? >>>>> >>>>> Would it help to enclose the entire circuit in a vacuum tube? Again, >>>>> could the tube sustain the vacuum over such a period? >>>>> >>>>> An energy source is a problem. Perhaps a cell where acid is added >>>>> (how?) at the appropriate time? >>>>> >>>>> Sylvia. >>>> I'd expect that most semiconductors and passives would last 1000 >>>> years, given a conservative design. There's not much radiation around >>>> at sea level. The gadget could be stored in vacuum or dry nitrogen to >>>> prevent corrosion and wiskers and such. >>>> >>>> It shouldn't be hard to keep a vacuum tight for 1000 years. A decent >>>> flange-sealed vacuum vessel hardly leaks at all. If it can do 1e-12 >>>> torr for a minute, it leaks to atmosphere in (linear extrapolation) 2 >>>> billion years. >>>> >>>> I think solar cells would stand up well. I bet that a Casio solar >>>> calculator will work 1000 years from now if properly stored. The >>>> biggest hazard would probably be polymerization of the plastics in the >>>> keypad, or maybe leakage from a poorly sealed LCD. >>>> >>>> I still use my original HP35 calculator, purchased in 1972. >>>> >>> HP11C over here. I still use my grandpa's drill from around the 1920's. >>> Works fine. You just have to keep the grease reservoirs packed by >>> tightening the caps once in a while and refilling when at the peg. >>> >>> Oh, and the church we were married at goes back about 1200 years, the >>> organ in there is probably well past 500 years. I guess a pipe organ >>> fulfills the definition of "equipment". It can be done. >>> >> Well, I'm not sure the organ qualifies, even if it reaches 1000 years. >> Has it never been repaired? >> >> The requirement is that the equipment be built, be left untouched for >> 1000 years, and then work. >> >> Sylvia. > > Reliability folks generally assign component failure rates in FITs, > namely one failure per billion hours. Most passives have numbers near > 1 FIT, and lots of semiconductors are in the single digits. > > So a 100-part gadget that uses average 1 FIT parts will have an MTBF > of 1e7 hours, a bit over 1000 years. That assumes the parts have no > wearout mechanism. In practise, field failure rates can be quite a bit > better than specs like MIL-HBK-217 or Bellcore predict, ie better than > 1 FIT average per part. > > John > > However, there is a caveat that these rates apply during the design life. That is, a part with a failure rate of one per billion hours cannot be expected to function, on average, for one billion hours before it fails, unless the design life is itself a billion hours. Which it probably isn't. In the context of this thread, the issue is further complicated by the question of whether a component is using up its design life while doing nothing. It may, or may not, depending. Sylvia.
From: Sylvia Else on 14 Jan 2010 03:21 a7yvm109gf5d1(a)netzero.com wrote: > OR.... > > go all mechanical > > http://www.longnow.org/ > > (How long does a weight suspended in the air keeps its potential > energy? Makes a good battery, no?) Yes.... But now you have to design a mechanism to extract the energy that will work after 1000 years. Sylvia.
From: Raveninghorde on 14 Jan 2010 05:51 On Wed, 13 Jan 2010 19:06:46 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Thu, 14 Jan 2010 13:31:08 +1100, Sylvia Else ><sylvia(a)not.at.this.address> wrote: > >>A recent episode of Stargate Atlantis prompted me to think about how >>would could design equipment that's intended to function far into the >>future. The episode required stuff to function 48,000 years after >>construction, but perhaps we could be less optimistic. >> >>Say 1000 years. >> >>Note, the requirement is not that the equipment function *for* 1000 >>years, but that when it is turned on, 1000 years from now, that it will >>work. >> >>It seems to me that semiconductors are out due to effects of difusion >>and radiation. >> >>But how about thermionic valves? They're not very reliable, but do they >>age when not in use? Would they hold a vacuum over that time? >> >>Obviously electrolytic capacitors are a no-no, but can resistors and >>capacitors be made stable enough that they'd work? >> >>Would it help to enclose the entire circuit in a vacuum tube? Again, >>could the tube sustain the vacuum over such a period? >> >>An energy source is a problem. Perhaps a cell where acid is added (how?) >> at the appropriate time? >> >>Sylvia. > >I'd expect that most semiconductors and passives would last 1000 >years, given a conservative design. There's not much radiation around >at sea level. The gadget could be stored in vacuum or dry nitrogen to >prevent corrosion and wiskers and such. > >It shouldn't be hard to keep a vacuum tight for 1000 years. A decent >flange-sealed vacuum vessel hardly leaks at all. If it can do 1e-12 >torr for a minute, it leaks to atmosphere in (linear extrapolation) 2 >billion years. It's not that easy. My only real job was for STC, then part of ITT on undersea telephone systems. The amps had to sit at the bottom of the sea for 25 years without failure. One of the big concerns was outgassing of corrosive gases from components. All resistors were plain, no coating. By 1977 they were testing PCBs for long term reliablity but stuff was still built on tags rivited to perspex. They were also working on fibre optics for new projects. > >I think solar cells would stand up well. I bet that a Casio solar >calculator will work 1000 years from now if properly stored. The >biggest hazard would probably be polymerization of the plastics in the >keypad, or maybe leakage from a poorly sealed LCD. > >I still use my original HP35 calculator, purchased in 1972. > >John
From: Bitrex on 14 Jan 2010 06:36
John Larkin wrote: > On Wed, 13 Jan 2010 21:54:46 -0800 (PST), a7yvm109gf5d1(a)netzero.com > wrote: > >> On Jan 14, 12:45 am, John Larkin >> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>> On Wed, 13 Jan 2010 21:30:33 -0800 (PST), a7yvm109gf...(a)netzero.com >>> wrote: >>> >>> >>> >>>> On Jan 13, 9:31 pm, Sylvia Else <syl...(a)not.at.this.address> wrote: >>>>> A recent episode of Stargate Atlantis prompted me to think about how >>>>> would could design equipment that's intended to function far into the >>>>> future. The episode required stuff to function 48,000 years after >>>>> construction, but perhaps we could be less optimistic. >>>>> Say 1000 years. >>>>> Note, the requirement is not that the equipment function *for* 1000 >>>>> years, but that when it is turned on, 1000 years from now, that it will >>>>> work. >>>>> It seems to me that semiconductors are out due to effects of difusion >>>>> and radiation. >>>>> But how about thermionic valves? They're not very reliable, but do they >>>>> age when not in use? Would they hold a vacuum over that time? >>>> Oh, they can be made very reliable. They can be accelerated at 100Gs >>>> and used in proximity fuzes (note the spelling), as in WWII; >>> 20,000 Gs! >>> >>> John >> Yeah, even worse! I was probably thinking of this toy >> http://www.youtube.com/watch?v=nLpLEgAS574&feature=related >> >> I guess an artillery shell leaves in even bigger of a hurry, but >> doesn't *keep* accelerating... More of a "jerk" situation? > > Artillery shells accelerate *very* rapidly and then spin at insane > rates. > > Good book: The Deadly Fuze by Baldwin. > > I have a few tube-type prox fuze schematics if anybody is interested. > > John > I am! Something more obsolete than my TTL clock! :) |