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CleanSpace CO Sensor Runs On Freevolt RF Harvesting
mspohr writes: A few years ago, a Kickstarter was set up to develop a locator tag powered by free radio frequency (RF) energy harvested from the environment. This was called a scam here on Slashdot and was shut down before it was funded on Kickstarter. However, it now appears that the concept is not as far-fetched as some predicted. A UK company CleanSpace has developed a carbon monoxide (CO) sensor which is powered by free RF. A review of the product has been posted on YouTube. It uses Freevolt technology to keep a battery charged and the CO sensor running. Since they have several thousand of these devices collecting data, they do appear to work and it seems to be in the 'not a scam' department.
You can run a CO detector on it. You might be able to run a smoke detector on it, although you'd think they'd be doing that if they could. Perhaps you could run a wireless keyboard or mouse over a very short range. Harvesting radio noise isn't a new idea.
It's not a general battery replacement. Their website says "RF Energy Harvesting For the Low Energy Internet of Things" which is a fairly ugh slogan, but it seems relatively accurate. I don't see any reason why you couldn't fire up a microcontroller, do a little bit of sampling, and report your results before going back to sleep until the next time your capacitor was full.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
"Curse you, thermodynamics! I'll get you next time." (jumps into perpetual motion flying machine and plummets to earth)
The world's burning. Moped Jesus spotted on I50. Details at 11.
Stolen? No. Settled law.
Back in the 80s a new 100kw FM transmitter was setup in Colorado right next to an EEs house. He couldn't get away from the noise, on the land line, TV etc etc.
He set up a 'faraday wall' (between 99 ft antenna towers) and inverter, harvested about 20% of the stations output, and sold it back to the power company. The FM station sued, they lost.
In the end they worked out an agreement, IIRC the EE got something like 2 or 3 times fair market value to go away.
John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
It's always fun hearing from disgruntled investors.
The world's burning. Moped Jesus spotted on I50. Details at 11.
I've worked on this project and it doesn't work.
Basically all it is is an antenna with a half bridge diode rectifier. This is pretty straightforward however the problem is that despite using 'zero drop' diodes the ambient RF energy does not produce a sufficient voltage (power out of the antenna with the line impedance at the diode) to switch the diode properly which causes a rapid drop off in efficiency. Basically the diode is still in the sloped part of the IV curve (zoom in on an IV curve at the knee). This combined with the fairly low amounts of power available means that the power output of these things is in the 10s of uW, which is less power than is consumed by the charge pump needed to top the battery up! So how does it work then? Check the tear down photos and you'll see a massive battery...
The other interesting thing about this 'technology' is that you can calculate the energy density of a harvester, it's simply the mean time till failure x power output / volume of device. When you do this calculation you quickly realise that due to the size of the antenna needed to see any appreciable power the device would have to last for 10-20 years to begin to approach the energy density of even coin cells (including the casing)!
Most rechargeable batteries have a substantial self discharge rate and will go to zero in a few months with charging.
This used to be the case, but for a decade or so now there are rechargeable 'ready to use'/'low self-discharge' (LSD) NiMH batteries on the market that can hold a significant amount of their charge for several years (for good ones, 75% after 3 years). LSD NiMH's do have a bit smaller capacity per volume but that is maybe a 10-20% difference, at the most.
But maybe these sensors have a rechargeable Li-Ion battery? I don't know about LSD types of those but Li-Ion have very bad charging characteristics when almost empty (high internal resistance - so it's harder to charge the emptier it is) so I don't think they are useful when recharging in these extremely low power conditions. And then there are supercapacitors, but they have a way too high self-discharge rate to be able to claim 5 years of operation on the 'battery' alone.
One of the side-effects of this device, implicit in its design, is that it will re-radiate mixing products of all received signals. This tends to interfere with nearby radio reception.
Bruce Perens.
If it notifies a powered device, the powered device can sound the alarm.
A lot of time, the benefit of wirefree power isn't power savings, it's the saving of installation cost of wires, or replacement labor on batteries.
You don't sell it to make money, you sell it to piss them off.
I built an AM radio – with no battery – that would audibly play local stations. This was in the 1970s.
Surely many slashdotters did the same. Heath-Kit.