-
So, first post here, never designed a project from idea to pcb to mini-production. (never design anything actually, i buy "starter kit".
i got a gift idea for a birth : let's offer a clock that will count day from birth to infinity and beyond.
That's around a 100 year lifetime, and it need to need a stability of 1 day per century.
it need to be rock solid, it need power, it need some kind of super simple display, it need to be switched on.
after a few minute of thinking about it ... doh! is it even possible ?
I'm stuck at the very first problem : power !
Battery :
does a battery that last 100y exist ?
solar panel ? can a solar panel live for 100y ? and it still need some kind of battery anyway
replaceable battery ? who know what kind of battery will be available in 100y ? Perhaps lead-acid battery will be forbidden in 50y, who know ?
Rust/moisture/oxydation :
i tought about sealing the project in a glass cube. Well not glass because the melting temperature is too hot for the electronic to survive, but some kind of transparent plastic ?
Transparent so the solar panel can be sealed, and the display is still readable but not exposed to the elements.
But if it's sealed, how to switch it on ? i switch it on before sealing it ? (there is no need to switch it off)
human interface :
What kind of display ?
It can't be always on, to save power.
But if it's sealed : no push button. perhaps an IR receiver ?
Power again :
i know it's hated but : "energy harvesting" ?
i mean... this think will probably need a few picoAmps (random prefix, i like pico... will it be nano ? femto ? micro ? dunno...), isn't it ?
Any random tought ? some "very important" stuff i didn't mention and forgot about it because i'm a noob ?
Perhaps it shouldn't be on a PCB, i don't know...
Thank you
Code: [Select]EDIT (where are we now) :
Mechanic :
- pure mechanical solution (eg : good old clock) is out of topic
- Mechanical part may be introduced if it improve the lifespan and do not require regular servicing (eg : lubrication). But it may greatly increase the manufacturing complexity & cost
Battery :
- no solution found yet
- battery self discharge is a major problem
- super/ultra capacitor are given for < 20 years
Display :
- LED (green one apparently have a better lifespan than red one)
- Electromechanical counter may be a viable option ( [url]https://www.google.com/search?q=electromechanical+counter[/url] )
Oscillator :
- Apparently, aging is not a problem.
- stability may be a problem
- frequency ?
Eprom/flash :
- 100 year doesn't seems to be a problem
- but we need redondancy/error detection
Microcontroller :
- it can be done.
Enclosure :
- need protection from rust/oxidation/moist
- http://en.wikipedia.org/wiki/Poly(methyl_methacrylate)#Acrylate_resin_casting ?
TODO :
- A lot :)
- Grab/post/archive datasheet for future reference
- Power is the main topic. -
Interesting...
I'm sure there are countless issues involved in keeping something running for 100 years.
Solvable of course, but so many traps, and how do you test it?
I think a mechanical clock is probably the best way to go here?
and there is 10,000 year clock project that cost a measly $42M:
http://www.10000yearclock.net/learnmore.html
http://mashable.com/2012/11/30/jeff-bezos-10000-year-clock/ -
IR emitter (like a remote command) may not be easily available in 100y. (we don't use it anymore in 2014
)
It need something as simple as possible.
no code or anything : if any kind of IR is received : display days for 1 second.
I think about engraving the instruction manual in the transparent sealing :
- how to read (eg : if it's a binary display. but 36500 (100years) is 16bit, it may be difficult to read but good for 179.5 years)
- how to switch on the display
Perhaps something about battery too
- eg : need 1h of light per day
- Which is by the way, not practicable. what if it's traveling on a boat for 4 days, it need to survive in dark for some time.
-
Interesting...
I'm sure there are countless issues involved in keeping something running for 100 years.
Solvable of course, but so many traps, and how do you test it?
I think a mechanical clock is probably the best way to go here?
and there is 10,000 year clock project:
http://www.10000yearclock.net/learnmore.html
This is the project that gave me this idea
About testing ... i don't know... probably can't. But the project need to provide as much warranty as possible, which may lead to something super expensive.
Priority :
- Reliability. of course, it's the ultimate priority.
- Cost : not as important, but don't be silly. Let's forget about gold, saphire, diamond. Well... not sure about gold. Considering the power usage, and considering it will be sealed, ultra thin gold wire, gold plated button, ... may be a possible option
- design : let's make it beautifull enough, it should be a gift
EDIT : $100 doesn't look overpriced, it's (literally) a lifetime gift. -
I would use an epaper display:
http://www.frank-buss.de/raspberrypi/epaper/index.html
Needs only power to change the image, but no power to show it. But no idea about the lifetime of it, 100 year is a lot. Same for a microcontroller: the flash might not hold the charges so long, maybe use some old school CPU with an EPROM, but then it needs more power and you would need a big solar cell area. Maybe a smart algorithm which refreshs the flash every some years might work.
And then there are the problems when someone moves to a Mars colony. On mars the solar day is 24 hours and 39 minutes. So you should add some buttons to adjust the length of the day, and to adjust the time if someone just moves to another timezone, because it could display the time as well, and I think it should increase the day count always on midnight.
Accuracy should be no problem, because 100 years are 36,500 days. A 10 ppm crystal (for less than 2 dollar at Digikey) would have an error of 1/3 day after 100 years. But maybe worse after 100 years? Probably a good idea to add an IR sensor to do some day light synchronisation.
Please report back in 2114 in this thread how it did go
-
a solar panel and a supercap may give you 20 years.
a primary lithium battery also may give you 25-30 years.
100years.... hmmmmmmPlease report back in 2114 in this thread how it did go
Let's hope Sagan keep this forum alive until 2114! -
And then there are the problems when someone moves to a Mars colony. On mars the solar day is 24 hours and 39 minutes. So you should add some buttons to adjust the length of the day, and to adjust the time if someone just moves to another timezone, because it could display the time as well, and I think it should increase the day count always on midnight.
Let's plan this feature for the version 2, when the v1 will reach its EOL
-
Most electronics engineers have the attitude that getting rid of moving parts is generally getting rid of wear and tear, and increases reliability and life expectancy. The reality is its easy to make a mechanical timer than will run for 100 years, and really really really hard to make an electronic one do the same thing. You would need to develop new components for almost every part of the device, as off the shelf ones have something that will chemically degrade over 100 years.
-
For a 100 year plus battery life you would more than likely need a radio isotope thermal battery, the sort of thing NASA uses on some space probes and rovers.
http://www.technologyreview.com/view/428751/nuclear-generator-powers-curiosity-mars-mission/
Mechanical clocks would certainly last a 100 years plus, I have worked on some clocks in the past that were 150 years old, but they only kept going due to regular servicing and they needed winding once a week or so cant see hou you would provide spring or weight power in one wind for so long. -
Yes, mechanical solution is out of topic.
Perhaps changing a battery every 20 years may be an acceptable solution, but it won't be sealed anymore and may lead to aging problem.
It could be a wearable product with kinetic energy harvesting. But who would want to wear a product all his life ?
-
You would need to develop new components for almost every part of the device, as off the shelf ones have something that will chemically degrade over 100 years.
If you seal it from air/moisture/light what exactly is supposed to happen to dry components in 100 years? (Lets ignore electrolytics, they aren't necessary any way.) There are plenty of electronic devices which already have passed the halfway mark. -
Maybe use only low-tech components, like this mechanical dot matrix display:
And no highly integrated components, only components with big structures where the chemical degration don't influence it (Commodore had some problems with electromigration in some of there chips, which causes them to fail sometimes after 30 years). Only a lot of transistors to build a counter, and a simple RC oscillator, synchronized to an IR sensor.
Solar cells should work 100 years. One of the first solar cell from 60 years ago is still working:
http://inhabitat.com/worlds-first-modern-solar-panel-still-works-after-60-years/
But there might be a loss of power of 0.5% per year, so only half the power after 100 years. -
Why battery? Make it working on mains power, store the start time in non volatile memory, user atomic clock radio signals and you are done. If the clock break, have a way to clone it with the same start time. Piece of cake. ;-)
-
Your "Life time" is just the current time minus the time you were born.
Realistically, someone is going to have to set your birth time into the unit (i think mum and dad are going to be a bit busy at your actual birth to worry about pressing a few buttons on a clock!!) That means you will need some form of "user input" unless you let people specific the "birth time" on ordering, and you write that into the firmware before the unit is sealed.
Current time is more complex. It could be set by the user, or returned from another souce (GPS, radiodata, internet over wifi etc) but you will have to ensure those sources remain "live" for the duration of the lifetime. I guess a combination of all four might be necessary. That means an onboard realtime clock, that can be set by the user or by input from GPS/radio data etc
If you want it to display simply "days alive" that only obviously changes once a day, then a epaper display makes a lot of sense, otherwise, the device may have to only show the "lifetime" when prompted by the user.
Any of those methods would perhaps be easiest with a wireless access (no plugs/sockets, and the device can be fully sealed), and you could use a "local" webpage to set it up and a remote webpage to supply it with the current time/date etc
Using an inductive charging loop means you could use an internal capacitor, and then give options for the "power supply", like, mains powered, solar powered, even "wind up" etc
interesting project, but very difficult to test over it's (your) lifetime ;-) -
Why battery? Make it working on mains power, store the start time in non volatile memory, user atomic clock radio signals and you are done. If the clock break, have a way to clone it with the same start time. Piece of cake. ;-)
Do you think a compatible atomic clock radio signal will be there in 100 years? -
OP, you want to check the movie In Time on Netflix. Every person there has a count down clock projected on his arm. When your clock get to zero you die. Lifetime is the currency and you can transfer lifetime between people as you would do with bitcoins (e.g. 1 year for a HP SMU).
-
GPS, radiodata, internet over wifi etc
... webpage ...
None of those will be around in the same, compatible form in 100 years (except maaaaybe GPS, or at least one of the newer GNSS coming up now). 802.11b will be gone in 25 years tops, and the newer wifi standards are lasting a shorter and shorter time before they get superseded. And the WWVB signal that radio clocks in the USA use just changed formats a few years back, which while it did not affect the cheap receivers did break a bunch of precision instruments. You never know which you can rely on. And in any case you don't need radio signals to keep time to 27ppm (1 day in 100 years) in the first place, let alone a web interface. -
There are indeed a few challenges with a project like this.
One of them is indeed the power. Maybe a thermoelectric solution can turn on the display when you hold it.
And maybe use an energy harvester from whatever source to keep an rtc on. The main disadvantage of batteries will be their chemicals.
You cannot have it work on any external time source since timezones and daylight savings will be unknown.
Not to mention the protocols or mediums involved.
It's like those ancient devices found in several sci-fi movies. After 10000 years the power modules/generators still work! -
Why battery? Make it working on mains power, store the start time in non volatile memory, user atomic clock radio signals and you are done. If the clock break, have a way to clone it with the same start time. Piece of cake. ;-)
First I thought data retention time of flash memory would be too short. But this application note says on page 4 that 100 years at 25°C is no problem at all and extremely conservative, it might work as long as 1324 years. I don't know if this is true, there might be other problems for this time, like bit flipping because of cosmic rays etc., but 100 years should be possible for a microcontroller with flash memory. Maybe save the program and data multiple times and add some error correction algorithm, for bit flips or broken bits. -
Thank you for all the ideas.
I have no definitive answers because i'm not the expert here, but :
- date set at build time : so yes, you buy it after the birth, which is not the best idea to sell a product. i'm not planning to sell it, i would if i could, but it's unlikely
perhaps build one product per day and sell it on auction ?
- But if you sell it after the birth, and you only one per day. you can also engrave the name
- make it an openhardware project sound like a better idea
- no external timekeeping dependency. I don't believe stuff like DCF77 will still be here in 100 year
- ultra-low-tech : no firmware, no flash, only 7400 TTL logic ? the size will probably be a problem.
- what about rad-hard low-tech IC ? are they expected to have a huge lifetime ? or is it only about radiation ? i have no idea bout the price of this kind of stuff but it's probably insane.
- i think LED have a huge lifetime, it need to be confirmed. But if you put 16 leds and engrave (in decimal) the value of each bit ... everybody know how to make an addition and i'm pretty sure we'll still use decimal in 100y. And even if we don't... we still know how to read roman numbers so it should be ok and we're good for 65535 days
- if solar panel can survive 100 year in a sealed environment (just pour plexiglass all over the circuit and make it a nice cube or something) that would be awesome. But it still need some kind of battery at night
- external battery : if we can find a way to have an external battery (gold plated contact ? it will probably wear out after 100y of battery switch) then we could have 2 battery.
At every birthday, on odd year : change the left battery. on even year : change the right battery. Instruction engraved, of course. and it still need to be able to survive a lot of years without battery switch, just in case.
But we don't know what battery will still exist in 100 year
I'm pretty sure it should be kept as lowtech as possible, no memory/MCU/... so no e-ink, even if it's an awesome idea.
Perhaps i underestimate their lifetime, dunno. -
Long life flash is only possible with old Eprom OTP packages, as these use a large cell size, so the stored charge is large. Current memory is getting down to the point where the stored charge can be counted in numbers of electrons in the floating gate. That is statistically going to lose charge at a rate that might do a decade or two. An old 2716 will likely still retain data after a dozen centuries if it is programmed using the slow method of a 50ms pulse per location. Fast programming will reduce the stored charge somewhat as it uses 1ms pulses until it verifies then gives a small extra charge.
If using eprom verify at 4V and again at 6V to ensure the voltage is over the threshold for it to be reliably read. -
it's pretty hard to keep time with 74xxx logic chip. possible but require at least 15+ different gates/chips.
you can use a device like DS1307 and a button to power up an MCU to show the date and then power off.... with a simple C/D size primary battery you have to change battery every 25 years.
the problem is flash based MCUs don't last that long. -
Sounds more like simple app.
-
Long life flash is only possible with old Eprom OTP packages, as these use a large cell size, so the stored charge is large. Current memory is getting down to the point where the stored charge can be counted in numbers of electrons in the floating gate. That is statistically going to lose charge at a rate that might do a decade or two. An old 2716 will likely still retain data after a dozen centuries if it is programmed using the slow method of a 50ms pulse per location. Fast programming will reduce the stored charge somewhat as it uses 1ms pulses until it verifies then gives a small extra charge.
If using eprom verify at 4V and again at 6V to ensure the voltage is over the threshold for it to be reliably read.
Good to know.
16 bit for the day storage, or we could go crazy and store a few more bit. 19 bit = 1436 years
If we can find a MCU that can survive more than a century, the firmware would be ultrasupertiny. Which mean we can store the time at different place in the eprom for redundancy. (and have a display a bit more complex than N leds) -
Sounds more like simple app.
it never was the problem. the problem is the lifetime.
What's your oldest electronic device ?
Mine is probably my FRG-7700 HF receiver : http://en.wikipedia.org/wiki/Yaesu_FRG-7700
it was in production from 78 to 82, the analog part is still working but the digital memory died a long time ago.