h a l f b a k e r yQuis custodiet the custard?
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The dreaded smoke alarm battery changing ritual performed every year - wouldn't it be nice to fix it once and for all?
Incorporate a suitably long lived isotope (tritium perhaps) with comparable lifetime to the smoke alarm's americium source. The clever part is that this then slowly recharges a
supercapacitor on the unit which caches power for when the alarm is needed (enough for a half hour of beeping)
This also means the source used can be very small (as the supercap charges over several days) . Unit has a beep function to warn of end-of-source-life in enough time to replace the module before it fails.
Americium in Smoke Detectors
http://www.uic.com.au/nip35.htm
For [dint] [Worldgineer, Oct 17 2004, last modified Oct 21 2004]
Nuclear Power Reactors
http://reactor.engr.wisc.edu/power.html
How they work [Detly, Oct 17 2004, last modified Oct 21 2004]
The Radioactive Boy Scout
http://www.dangerou...s.org/radscout.html
Sort of the oposite of this idea. This boy tried to build a nuclear reactor out of smoke detectors. [RobertKidney, Oct 17 2004, last modified Oct 21 2004]
[link]
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So you'll be saved from smoke inhalation only to die of lung cancer ten years later...? |
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I don't think people would like the idea of sleeping beneath radioactive isotopes.
My smoke detectors plug into the main power and use the battery just for backup. |
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People already do. See link. |
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Nuclear power involves more than radioactive decay -> electricity. It is, in fact, decay -> heat -> boiling water -> turn turbine -> generate EMF -> modify for general usage. |
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How would you fit a turbine into a smoke detector? :) |
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(Oh, also, tritium doesn't emit gamma radiation, only betas, which can be quite a hazard depending on the quanitites.) |
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There are already smoke detectors available that connect to the home's electricity, obviating the need for batteries. Seems like a simpler solution. |
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Is nuclear powered smoke a particular danger? |
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krelnik: that's all hunky dory until your home burns down during a power outage... |
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Nuclear powered smoke alarm + M80 firecracker = one dirty bomb! |
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What's Osama's address in Pakistan? |
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//home burns down during a power outage//
Rechargeable battery inside. |
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A normal ionization smoke detector needs power for two things: (1) it needs a tiny amount of power to keep a small amount of air ionized; this power comes from the americium inside; (2) it needs an even tinier amount of power to monitor things and ensure that the americium is still iolized. This typically comes from the battery, but could probably come from the Am if desired; (3) it needs a pretty big amount of power to go BLEEPBLEEPBLEEP when it detects that the iolization has fallen off. This is way too much power go get from any reasonable radioactive source. |
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The real issue in a smoke detector isn't the unit's current consumption--it's the self-discharge of most typical batteries. It wouldn't do much good for a radiation-powered detection circuit to detect smoke if the batteries couldn't deliver enough power to sound the alarm. |
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Pay no attention to most of those who are paranoid about radiation when it's all around them. Like one of the previous people mentioned, smoke alarms are ALREADY radioactive. The purpose of the nuclear radiation is to ionize the air. If only there were a way to catch the positive and negative ions before they recombine, then you would be able to utilize the power provided by the radioactive decay. |
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//If only there were a way to catch the positive and negative ions before they recombine, then you would be able to utilize the power provided by the radioactive decay.// |
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As noted, the difficulty would be that while such decay could provide enough power to feed the monitoring circuitry, it would provide nowhere near enough to go BLEEPBLEEPBLEEP when a fire was detected. |
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BTW, on one of the "funny warning label" sites, someone posted a smoke detector warning to the effect of "Do not use the silence button in case of an emergency; it will not extinguish a fire." |
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Nuclear "batteries" using plutonium have actually been used before in some pacemakers but the current produced by a unit of that size was very little. It is possible to make one big enough to power both the sensing electronics and the sound producing part but it would need a considerable amount of plutonium. |
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(search for radio-isotope generator) |
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I was just about to post this, but clearly someone beat me to it many years ago. |
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Nuclear power doesn't have to run on turbines. Atomic batteries don't work that way. A radioactive source can generate electricity through heat, through thermal radiation and photovoltaics or through beta decay, among other methods.
An electricity supply isn't good enough because it could be interrupted by a fire. The problem with the power for the beeper is soluble by trickling power into a rechargeable battery or capacitor over a long period. It doesn't have to come from the radioactive source in one quick burst. |
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Why not just power the smoke detector from the heat from the fire using thermopiles? (didn't the Greeks have battle there?)
After all, everyone knows there's no smoke without fire. |
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Because the fire might be in a completely
different part of the building, and if it's got that
bad it's too late. I suppose you could use
thermocouples all over the place as heat detectors
and to power the smoke alarm based on changes
in temperature. On the other hand, if you
happened to live in Thermopylæ, you could always
power it with a Stirling engine in the river, but
what about the Hydra venom? |
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Silly people. Why not use a rechargeable battery or
capacitor that's topped up by a solar cell? Even in a shady
spot indoors, the output of a solar cell will surely exceed the
current drain of the idle detector? |
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