Ask Hackaday: Can Battery-Free Bluetooth Item Locating Tags Exist?

iFind Tag

[Vishak] tipped us about the iFind Kickstarter campaign, a 1.25×1.06×0.09″ (32x27x2.4mm) tag meant to be attached to anything you may lose in your daily life. This device communicates with Bluetooth Low Energy (BLE) enabled smartphones, has a 200ft (60m) detection range and a loud alarm. What is interesting to mention is that this device doesn’t need any battery to operate as it

recycles electromagnetic energy and stores it in a unique power bank.

As you can guess, this particular claim intrigued the Hackaday team given that we never featured so small energy harvesting devices. The ‘closest’ thing that comes to our minds is the Allsee project, a simple gesture recognition device that uses existing wireless signals (TV and RFID transmissions) to extract any movement that occur in front of it. However the antenna was quite big and very little power was extracted.

A quick Google search let us know that Bluetooth Low Energy solutions usually consume an idle current of around 10uA @ ~3V. The (very) successful Sticknfind campaign which promoted the same battery-enabled product claimed a one year autonomy with a CR2016 battery and a 100ft range, leading to a ~90mAh/24/30.5/12 = 10.2uA idle current. As we’re not expert on the subject, we would like to ask our readers if they ever came across such energy harvesting performances (3V*10.2uA = 30uW) in a normal home environment. Our very bad maths indicate that if one would like to extract power from a typical Wifi router located 2 meters from you emitting 0.5Watts of power (in a perfect vacuum environment) with a 32*27mm = 864mm = 0.000864m² tag you’d only be able to get 0.5 * (0.000864/(4*pi*2*2)) = 8.6uW.

It is therefore too bad that we can’t see in the presentation video what is inside the iFind, nor more details about the patent pending technologies involved. We hope that our dear readers will enlighten us in the comments section below.

220 thoughts on “Ask Hackaday: Can Battery-Free Bluetooth Item Locating Tags Exist?

    1. OK. I think I understand this enough to respond like so: Yes, it’s possible; no, I don’t think the amount of power required is feasible. Unless it also harnesses ambient sound for energy.

      Speaking of which, I’m really excited to wait for the first voice-POWERED bluetooth headset. Imagine never having to charge it up again, but only having to talk. The time is coming soon enough. Wish I could be a part of it, but I don’t have the time or skills.

      1. It is entirely possible:

        Those guys managed to get 220uW from a fairly large antenna. Okay, so these tags have a much smaller antenna but they also have lower energy requirements. The paper I linked shows running a clock/thermometer that requires 25uA/1.5V with occasional peaks of 50uA.

        So 10uA is the idle current for BTLE, but does it need to be idle the whole time? Since they don’t state how often they check if a tag is in range it might only pair once every five or 10 minutes. Between those times it could be unpaired and completely powered down.

        1. It’s interesting. I’m following the energy harvesting technology for a while, but not real EM/RF harvesting products in the real world for powering RF transceiver, especially for consumer.
          RF/EM harvesting is tough in the real world because of the environment various, EM field big different even in the same house, direction of wave and receiving antenna, limited antenna size and matching networks for wide-band, antenna gain and signal loss, etc.
          The energy storage is another issue due to size and density. Some new technology may not available for use with extra thin, and may causing cost too high. Current Cymbet CC3150 is 50uAH at 3V, it can’t power BLE for half day if you set BLE adverting to 1000mS.
          The lowest power BLE chip in the world should be Dialog, which avg sleeping current is about 1.9uA at 1000mS sleep interval. The TX/RX averaging over this period about 2uA, then you can calculate without any extra leakage and power consumption.
          So, I’m very interesting for iFind solution which can be used everywhere. Need lot of things to learn.
          Hope to share more from you all.

      2. Voice powered should be doable. Voice powered phone systems are still used as emergency comm systems on military ships. In the early days of telephone systems some quite long runs were done with voice power, then powered repeater amplifiers were added. Eventually centralized phone system power obsoleted the old tech.

        If you have an ordinary old phone that draws all its operating power from the phone line, you can still have phone service for a while after a power outage. Telcos have large battery banks to keep their systems running for several hours. If you have a cordless phone or a phone that does anything that requires it to also be plugged into a power outlet, it’ll be useless in a power outage.

        So if you’re a “prepper” and have kept your landline phone service, you’d best get yourself an “old school” phone.

  1. “stores it in a unique power bank” <- if i entered a meeting with an investor and dropped that line without further explanation on exactly how it works i would have been escorted out, don't even let me start with an employer … my guess is it simply uses NFC and pretends it uses BTLE and has a real range of 2" if it would ever be produced at all … and if they did come up with such a tech (im guessing using miniature quantum tophats) using it on something to help you find your remote seems like a waist of a clearly million+ dollar patent …

    1. ” if i entered a meeting with an investor and dropped that line without further explanation on exactly how it works i would have been escorted out, don’t even let me start with an employer” <- I'd personally be crucified as well

      1. That’s the thing, you’re neither to them. Give, for instance, LG a call and ask them for detailed info on how their LCD screens are manufactured, let us know what they say ;-)
        Tell them your thinking of pre-ordering their latest model but don’t believe it works, ask them for a schematic and a detailed report on how they wish to acheive 4k in a 1mm panel…let us know how it pans out :-)

        1. But LG would demo it in the store for you wouldn’t it?

          iFind’s kickstarter video seem to presents only a mockup prototype (Bluetooth wasn’t even enabled on the phones presented) ,and they don’t confirm that they have a working prototype (as of the current date on their comments) … this raises a lot of suspicion because kick-starter’s guidelines on hardware projects ( are very clear about No product simulations

          It’s the “dragon in my garage” problem…

          Now LG would gladly(and are required to) give the customers the power requirements of their TVs…Apple will also gladly specify the charger requirements for their products, or back in the day sony wouldn’t hide how many AA were needed for a walkman…
          Likewise is no big deal to ask for the Electromanetic Irradiance(W/m^2) or any apropriate radiometry units needed to power such a device indefinitely so that customers can check if this is realistic with their intended operating environment wouldn’t you agree stevetyson2014 ?

          As soon as they provide credible evidence I will personally get in line and endorse (as well as help spread the word in favor)… but for now the evidence just isn’t there…

          1. Ok, I agree, LG would be able to demo unless you pre-ordered an item which wasn’t yet ready for release (like pre-ordering a new ipad version).
            As for power requirements, I agree there too, yes they are obliged to publish these but they are generally quite useless when trying to reverse engineer a product or prove its viability. They give very little insight into what lies beneath.
            The thread is about whether it can work (and how), I believe it can, but, only under certain conditions. Their description seems to state it will work ad infinitum which is a little less believable.

            W/m^2 would be useful, not sure how many customers would be able to measure this though :-)

            Just to be clear, I haven’t found anything to totally dismiss their claims but, like you, would love to see a demo. If their claims are true then it could be a very long demo.

    2. I hate to be “that guy”, but I’m with you on this one… either they’re sitting on something faaar bigger or there are some magical unicorn farts in the mix. It will be interesting to see how this pans out.

      1. They don’t need unicorns, they figured out zero-point energy. It’s like a unicorn but less fun to pet.

        Although if we do have unlimited energy and the first use was to find a remote I’m hopping on the first super-shuttle off this galaxy

          1. I think the supercap capacities of graphene can be laid flat in a very small space with a huge capacity. I could envision radio waves, which are energy always available in the air ,being harvested as a voltage and stored in a supercap. Why not?

          2. There are supercaps that could do this and with very low leakage current (ie 1 μA loss / 120 hours). However putting them plus everything else on a device selling for $16 is… challenging..

          3. My money is on a small, rechargeable coin cell or LiPo cell.
            Either way they will be using a boost converter so the rechargeable battery tech is a moot point.

          4. Supercaps and (to a lesser extent) LiPols are considered ‘leaky’, but the leakage is proportional to capacity (internal surface area, more directly). This would most likely be using ambient RF harvesting of some kind (Google ‘WISP’), either assuming some signal of opportunity (HDTV, Wifi) or with the Tx device spamming the air with packets, and the tag responding every 1000th packet or so (whenever it has saved up enough juice for a single response packet). The internal power source would only need some mJ of energy, enough to cover one Tx packet and overcome any quiescent usage + self-discharge for the power-saving duration between replies.

        1. I think it’s the claims which are vague – yes, it may never need a battery replacement but that must only apply to their idea of ‘normal operating conditions’ which aren’t stated.
          Yes, it could harvest enough power to do ‘stuff’ a certain number of times per [insert time frame here!]. Without ‘normal operating conditions’ or some, published, assumed usage scenario then it could appear to be a ‘perpetual motion machine’ and we all know about those, right!

    3. Replying just to say I’m using ‘uses quantum top hats’ to explain unrealistic technology to people now.
      “A 16 ghz ten core processor that uses less than 5 watts of power, and will do your laundry for you? How did they make that work?”
      “Uses quantum top hats, obviously.”

  2. YAWN. The discrediting kickstarter thing is getting a bit tedious. We know it’s a cheap way of getting incoming links and page views for hackaday – but there IS NO HACK ELEMENT. Come on guys, get it sorted.

    1. This energy harvesting topic seems quite interesting, actually. And I’m sure a lot of hacking goes into designing something like that – if it actually works. Either way, it’s something to think about – but if you rather yawn, well..

      1. There are government imposed limits on the elecomagnetic field strength that the population should be exposed to, to avoid frying their brains and other more subtle problems. The limit is something like 1 mW/square cm so, just maybe, it’s possible to get enough power in populated areas (lots of transmitters of all types). The problem would be efficiently capturing the energy. If you attached a few tv antennas, a couple of fm antennas, a long wire and ground system plus a microwave dish or two it should work fine. In general, receiving antennas aren’t very efficient.

    2. B-but muh circlejerk!

      Speaking as someone just cutting their teeth in the hardware world, it’s actually a bit interesting to hear experienced electronics experts discuss How they might go about making this technology work, or why they think it’s totally impossible.

      You’re right, however, that there is no hack here. And this isn’t either. Maybe this sort of content is best left for the forum

    3. I must have missed all the other times HaD dismissed kickstarters as dubious. That’s quite impressive of me.

      I did notice a lot of very dubious projects on kickstarter though, things that get plenty of funding and then never anything is heard again. (or they make a billion from selling out to facebook..)

    4. But without HAD highlighting them, I wouldn’t know about these products. And if I don’t know about them, I can’t laugh at them. They are doing a public service here!

  3. The Dialog DA14580 BLE SoC runs on about 0.5 μA at 3V in deep-sleep mode.

    Granted transmit mode is 5 mA 3V (note the m), but I guess if they do it very very briefly and then go back to deep sleep it might be possible. Add a supercap and Bob’s your uncle.

    The device just needs to send an advertising packet anyway, nothing fancy.

    That said they sure look tiny for an RF harvester..

  4. May be a embedded coin cell baterry in the tag? This would give him some time to get the money until the people realized that doesn’t harvest anything except his money. ;) (in spanish we say “pelotazo”… maybe “shot” in english?)

    1. Sounds like the “shake lights” that – in the legitimate versions – use a supercap about the size of a coin cell battery. The fake ones use a battery, and consequently they work for a few days then *poof*. Also reminds me of the irritating motherboards with the CMOS battery soldered on. :\

  5. The answer is yes and no. Yes you can use ambient energy in the air to power your BT device, however you just need your ambient power to be high. IE near a radio-station, near a power line.

    Really you will not have enough power to actually do any real data passing, but if you harvest energy for several days, and only use it for a few seconds. I have no reason to believe it cant work.

    that being said there is not a big enough antenna to be broad band enough to actually harvest meaningful amounts of energy. The narrow band power an average device is around is so low you would never be able to gather meaningful amounts of energy, but the power across the spectrum may be enough. when collected over a few days.

    My opinion with respect to power the radio off BT power… Impossible, you are talking about using -40 to -80 dBm of BURST rf power at duty cycles of <10% (i am assuming that you will not be able to keep high traffic up) to power a device TRANSMITTING burst packets of 0 dBm at the same duty cycle.

        1. In the near field a transformer coil is sufficient. Even in the far field a tuned-loop can do. But I’m not sure there is actually that much noise energy down in this range in comparison to that which comes from intentional radiation.

        2. Impressive statement but any antenna picks up all frequencies it is only the filters that take unwanted frequency energy out and feed it back to ground while isolating the wanted group of frequencies. So with tuned circuitry this can be picked out and channeled to a cap quite easily.

          1. Wavelengths that are too long for the antenna will only pick up with greatly reduced power. Teeny antennas only pick up very high frequencies, on which nothing is transmitted at very high power.

          2. I always think of the antenna as a form of sympathetic resonance in tuning forks that if the length is close you will get near maximum power transfer ( I also think of an antenna as a filter as well, that attenuates signals that are either side of the right frequency, a bit like a swing ( Yes the signals are still there but at a much much attenuated power level.

          3. And if you had a tuneable filter (or filters) and could tune to highest RX sig strength and harvest from that then you’re onto a winner. With a wideband fractal antenna plus a bank of tuneable filters which are have their frequency pulled by a uC it could work.
            A uC can be extremely low power and you could have some passive signal strength monitors at common frequencies.
            Kind of like how antenna diversity is implemented but swap ‘antenna’ for frequency – ie. dynamically choose the frequency which has the highest rssi and use that for harvesting.

      1. I hope to god you are not using enough power to generate strong enough magnetic fields to be useful for this application. i am thinking that you would need several KV and and sever a huge amount of current to make this work… I am not saying it is feasible, what i am saying is it is possible to harness enough energy from the air to do things, if you are in a place that has a huge amount of energy in the air.

    1. Just a heads up of the latest comments of this project:

      “I purchased 3 of the StickNFind location stickers. They did not work very well. Many times the connection was lost and many times they could not be found. I am very disappointed in the product. ”

      “these StickNFind buttons do not work as advertised. They constantly make false ‘separation alarms’, even when the button is within 12 inches of the iPhone it is paired with.”

      “have never felt more robbed. this campaign is the reason i would never fund another tech indiegogo campaign.”

      nice work!

  6. The shape is too suspicious. It is begging for a CR-2032 inside. My guess is they put a CR-2032 inside and lied about the rest.

    It is possible to use NFC but many phones, including ALL iPhones I believe, has no NFC. And NFC range is very very poor.

    If the company can really pull energy through thin air and enough to power BT-LE, they would have solved A LOT of problems. Their technology could easily worth $Billions. Common sense says NO.

    1. Some of the people listed under “our core members” have strong pedigree. That is a reason to think the product will have the claimed features. Unless some of those people come out and distance themselves from the campaign.

    1. maybe 200ft in a vacuum, and the tranmitter is placed inside a parabolic dealybob to broadcast focused upon the reciever? these specs are like car stereos, that will say 10,000 watts! and have 25 amp fuses in them. with math, when you round all your numbers up, you reach 800 watts. then you jump that to a thousand because whatever, no one regulates it. and then you put your safety mechanisms in, and limit it to 300, if the fuse is faulty and doesn’t blow at quite 25 amps…

  7. regarding “Our apologies. At the moment we can’t offer free international shipping since we are a US based company and we have to pay both shipping fee and the export taxes to other countries outside of the continental USA”

    yes you can offer free international shipping by eating the costs like many ebayers do and just tack the cost onto the item cost.

    have you ever wondered why the same product can go for $100 with free shipping in 1 listing and the next listing from the same user has 1 penny for the item and $100 for shipping.

    1. Wow, those look very cool.It’s pretty impressive that they’re able to cram 1200 mF into a 3mm tall package. Shame they’re pretty limited to pretty much just dealing with power spikes and energy harvesters. Even so, very neat.

    2. Lithium thin film batteries still have much greater energy capacity. Based on the claimed lifetime, I’m fairly certain they arrived at-it having done a back-of-the-envelope calculation in reference to a lithium-thin-film battery datasheet.

      Unfortunately, Infinite Power Solutions (makers of the Thinergy batteries) is not doing so well and supply of the thinergy cells is scarce. ST has an EnFilm line, too, but this is not available yet. I suspect that the iFind creators have yet to realize this supply problem.

      1. I was just looking for a Thinergy battery solution but your above email has confirmed my suspicions. Do you know of another company that supports a similar battery? Do you have any contacts of any of the previous employees. I’m assuming this product line may have been picked up by another company, but if it has it’s not being marketed as Thinergy.

  8. On their KS page, they say they have some patents, so I looked for them.

    A quick google on Zhangyang “Atlas” Wang gives some patents (in China) but none related to the iFinder (

    The search is more successful with the co-founder of iFinder’s company, Dr. Paul McArthur. I found with the details of the patent on
    To summarize, the patent is on a RFID chip, not a Bluetooth chip. RFID doesn’t require a battery from what I remember :-)

    Also, another patent, (maybe the same?) says “The transceiver module can also include a battery that is operable to power the second memory unit, the second receiver, the second transmitter, the second timer, and the second control unit. In one embodiment, the transceiver module is powered by radio frequency energy.”

      1. Yes they are, but have a range limited to the magnetic filed of the reader. For most readers that is a few cm, but for some (IE 2 W with highly directive antennas) it can be a few meters

        1. NFC normally operates up to 10cm or so (having said that, you can create a device to listen in to a conversation between a tag and a reader a lot further away than that…)

          RFID gen 2 Tags/readers (there are a host of static and mobile. Think Impinj speedway, Alien Technologies, Zebra/Motorola MC319Z, Nordic ID merlin, and many others). They will pick passive tags up from several meters and typically run at 0.5W – 2W depending on local laws. While not industry standard, IPC RFID tags and readers can have pretty impressive performance as well.

          With all RFID, a lot depends on the tag and what the tag is attached to in addition to the reader. A tag designed to operate in free air (e.g. an apparel swing tag), will not be happy attached to a can of fizzy drink for example and will significantly under perform.

          RFID tags can also be active (with a power supply) or passive. Passive ones are cheaper, but in more challenging environments, powered tags are an option.

          1. This is all true, but doesn’t get to how they could develop a tag that could be read over UHF RFID using phones that don’t have UHF RFID readers. I work specifically with UHF RFID reader chips, and I am confident that there are no existing reader chips that are considered acceptable for smartphones, let alone in existing phones. Restrictions include size and power consumption.

            Even if we did have UHF RFID reader chips in our phones (and I hope that one day we will) they wouldn’t achieve BTLE read ranges, which the KS campaign promises. Moreover, they explicitly state they are using BTLE.

            My money is on overly optimistic designers or outright vaporware. I would give this project a 2% chance of meeting its promises, and yes, I’d be happy to put money on it.

          2. The following video seem to be a first draft of their kickstarter video:

            take a look at what the narrator says at 2:55 and compare it with the original kickstarter video:

            -“It utilizes a combination of rfid & bluetooth technology”
            -“It utilizes bluetooth technology”

            which would indicate a Gen2/BLE style hibrid (nonetheless it would only work as long as there were Impinj portals nearby to act as wireless charger for a battery that shouldn’t exist )…now this would make the whole thing a lot more plausible…

            Unfortunately …they are specific saying it’s not RFID either (on the comments)…

  9. My best guess is that they’re hoping the tag will normally live in your pocket next to your phone and be able to suck up the radio energy and store it in a battery/capacitor to tide it over when it’s away from a power source.
    “Pocket” energy is maybe up to 2W for GSM/3G only inches away from your tag device, brain, genitals, etc… So can be pretty helpful for charging your tag or making you infertile or stupid… (Do we really believe those claims any more?)
    (figures from random internet source that seems believable :

    I expect if you leave the tag in a field and expect it to work, you’ll be disappointed.

    1. Except the 2 Watts is only when you are in a call, and only when you are using low band GSM, and that is typically used only when you are using voice calling, AND it is designed to work at the minimum usable power, so you only will get 2W when you are at the edge of all cell towers in your area. So mostly this is a really really poor assumption.

  10. They mention shaking the tag to find your phone. Is it possible they’ve got a small kinetic energy generator in the device that’s harvesting energy? Everyone seems to be jumping straight to RF energy harvesting. If there is a small enough generator, and a supercap, I could see attaching the tag to stuff that’s always on the move, generating energy.

    1. From his patent:
      “III. Power Source:

      The basic circuit is connected to an onboard power source 116: a battery, such as a coin cell battery, a double layer capacitor, a lithium ion battery, or a thin film battery. Based on unique power conservation programming/algorithms, even the most basic device has an operating life in active mode of at least three months (six months for average use), This life is extendable using a power harvesting component 117 operating via a light sensitive component (e.g. a solar cell), a RF sensitive device (e.g. a coil, antenna), a mechanically sensitive device (e.g. a piezo-electric PZT, a bimorph, a ceramic, a coil with a magnet) or temperature sensitive device (e.g. a bimetal). “

      1. Using ambient vibrations picked up by the piezo buzzer as a power source. I wonder if anything has done that before?

        Prior art would involve going wayyyyy back to the early telephones that ran on voice power and used the speaker for a microphone.

      1. The idea is that you shake it if you _have_ a tag, but you’ve lost your phone… I’m deeply suspicious of this project’s claims of running on harvested energy. It’ll be interesting to go back well after the funding date and see what’s happening in the comments…

  11. The idle power consumption isn’t really relevant … it wouldn’t be running idle, it would simply be off most of the time. No need to listen all the time for a ping, if it listens once every couple of seconds that’s fine.

    It’s more a question of whether you can build a rectenna that small which can deal with the leakage currents in the threshold detection circuitry, power switch circuitry, rectifiers and whatever capacitor you use for storage (ultracaps seem right out).

      1. You wake up every 5 seconds, only long enough to recognize a signal (maybe a couple milliseconds). Your transmitter broadcasts for 6 seconds when pinging, no need for any synchronization.

  12. “The (very) successful Sticknfind campaign” It may have been successful, but from the reviews I’ve seen they are rather cheap and suck. Also Sticknfind has failed to deliver their other products they claimed where nearly complete over a year ago.

  13. It’s probably a rechargeable battery. Since the theory is that t will get recharged over and over the user will never have to replace it. As such its magic to the user and they can say, “look over here, user, there’s no battery (that you need to worry about) and its the coolest thing ever”.

  14. Considering that I build a device not too much different than iFind (at least from a basic perspective), and I know the state of the art for wireless energy harvesting as well as anyone does, I would be VERY hesitant to pre-order one of these. Let’s look at other BLE trackers, Stick ‘n Find and Tile, and then compare the state-of-the art to the pie-in-the-sky claims of the iFind.

    Stick ‘n Find:
    Stick ‘n Find has had a disastrous reception from its users. In my testing, it has about one or two months of charge in the 2016 cell, and it is basically impossible to replace it. The range is about 10-15m.

    Tile needed to enlarge their device substantially in order to accommodate a CR2032, needed to have one year battery life, and in order to enlarge the antenna to get a mere 30m range. Tile is now looking like 38 x 38 x 6mm or so.

    Looking more deeply into this iFind, the solution size of a rechargeable battery, the charge controller IC, and the energy harvesting element is too thick for their quoted dimensions. In 2012 when I was beginning the designing my product, I had even prototyped lithium-thin-film batteries, but these are still impractical for a bunch of reasons I won’t go into. If you pre-order this product, it will either never ship, or it will ship in a form completely different than the one that is promised.

  15. In the FAQ they have another suspicious claim:
    “Is there any Visual alerts for people with hearing issues?
    Yes, the iFind App does have a visual locating display showing the estimated direction and distance.”

    I’m not aware of any phone that has direction finding RF capability.

    And how about some image analysis!!!
    On the top image, the apple keys (15 x 15 mm) are very close to 15 pixels tall and wide. The tag is only 26×22 pixels, meaning it is smaller than the 32x27mm stated.
    Comparing the cat’s paws to the tag would mean the cat’s paws would be almost 2.5″ long… and it’s head close to 7″ across. That’s one big cat!

    Considering that Kickstarter prohibits renderings of final products, I’m throwing a flag there…

    1. Using the phone compass and RF strength while turning about with the phone will be able to give you a good approximation (ignoring multipathing etc) of RF direction, so there you go. Also the same thing with “distance” with regards to RF strenth received. All approximations but would be good enough to provide a showy app… if the tag works

        1. Sigh, no they are not, however, with a weak signal like low power bluetooth, and you in a room swinging a phone about, you will be an effective shield at the 2.4 ghz it operates at, turning yourself and the phone into a hokey approximation of a directional antenna. As I mentioned, mainly gimmick, but it does have a little basis to work with.

  16. Some of you mention that you don’t like the “can this kickstarter claim be for real” postings, but I, for one, find the discussion on these kind of topics very interesting. Clearly there are some very intelligent and resourceful posters on HaD and I always end up learning something new from the comments posted.

  17. The following is from the iFind FAQ:

    Is it possible that the “battery” of iFind tag dies?

    To begin with, iFind tag doesn’t have a battery. Instead, it uses our patent pending EM Harvesting technology and stores the energy in a uniquely designed power bank. In other words, iFind tag powers itself.
    ->> In the worst case scenario, let’s say you lost your tag in the middle of a remote desert, where there’s no EM wave at all, the tag will still hold power for days .<<-
    For more information about our EM Harvesting technology, please check our coming update on Kickstarter or go to our official blog (coming soon).

    1. Power bank… sounds like flim-flam for battery.
      “remote desert where there’s no EM wave at all” – Um, unless it was underground as well, there’s still light, which is EM. Not to mention the strange grammar of that sentence.

  18. The trouble with RF harvesting is that there just isn’t that much energy available. Assuming that the noise floor in the 2.45 GHz band is a consistent -90dBM / Hz, that is barely enough to power a BLE device assuming that the conversion to DC is near-perfect. The other problem is that the 2.45 GHz band, as noisy as it is, is only a consistent -90dBm/Hz in truly noisy environments.

    1. Agreed. Even if the conversion was 100% efficient, I don’t see how the device could harvest enough power to function. According to their FAQ, the “power bank” will last for days even without EM. They also indicate their app will display the charge level of any tag’s power bank.

      1. I’m almost 100% sure the “power bank” they are considering here is a Lithium Thin-Film battery.

        Anyway, I’m less skeptical that it’s possible than I am skeptical it can be done in the form factor they specify for the price they offer. With the 2.45 GHz band alone, it is *conceivable* to build a device in this form factor, but not for $14 and not reliable. Using multiple RF bands for input energy requires multiple antennas and multiple tuning circuits, though, in addition to a somewhat exotic semiconductor chemistry to pass multiple bands in far away spectrums. So high cost.

    2. Even with a really efficient horn, in a development environment running hundreds of devices on BT and with several wifi AP, i don’t think i have ever seen 90 dBm/ Hz using an efficient antenna. Typically i see 90 dBm/10KHz or less. And yes i have done the math one this one several times. Even adding moving to cell band, the bandwidth you would get a tiny amount of power.

    3. If it communicates at 2.4GHz, why would you limit the power-reception to that frequency? Why not make a very wide antenna/rectenna. From lets say 17~1800MHz, up till 100GHz?

      Using lower frequencies (88-108MHz transmitters for example) is not really useful for a ‘battery free small tag’, since your antenna construction would be larger. The trade-of is size/weight versus power.

      NFC tags can communicate at several meters. not centimeters. They actually do mass check-in/out for people at train stations in some countries, using big antennas above (for example) escalators.

      Oh. And take a look at CherrySwitches, they make/produce energy harvesting switches, and NXP the IC’s. Cherry even has 802.15.4 supportive switches. Through Cherry itn’t using RF. It’s a option. and commercially available.

      I’ll think those BLE “energy harvesting” tags could exist.

  19. Oh dear. Looks like at least 1500 backers, at time of writing, are all going to get ripped off. To what degree of ‘ripped off’ is yet to be seen.
    It’s all too good to be true and some people obviously don’t realise where the limits of current technology are to be able to compare this to. Their ignorance will be their undoing, quite right too, suckers!

  20. All very plausible:
    Antenna: Wideband fractal printed on their PCB substrate. Compact and can be very wideband.
    Low input V, low Iq, boost converter: Linear Tech do a few for energy harvesting apps.
    Energy storage:
    BLE silicon: Plenty around.

    I think it becomes unbelievable when they make out that it’s got an endless source of power. It does (kind of – there are EM waves everywhere) but that endless source of power is very very low. Their energy storage component will deplete pretty quick should that ‘loud beeper’ keep beeping for a few mins and you keep polling the BLE tag!
    In summary, it’s all possible but they need to ensure they include some caveats and manage expectations.
    Once the energy storage component is fully depleted I wonder how long it takes to charge it up again – say, to a point where it can communicate and power its beeper?

    1. VHF and UHF tv transmissions are consistent power sources, and I’ve seen videos a device powered off TV signals. But all it could do was flash an LED, and it had a dipole antenna that was about 20cm long.
      So I think given the size and power requirements, I’d say it’s bogus.

    1. Yeah, it’s a good brain workout, when those who know start explaining exactly why it won’t work. Gives some of us a bit of extra knowledge in a new area, which is always worth having.

  21. Interesting, it reminds me of the Lunacase, also on kick starter. It’s a case with a few LED notifications built in but no power source, rather claiming to rely on the elctromagnetic radiation from your phone.

    1. i remember five-ten years ago having a pen that had a LED at the back that would light up whenever there was an incoming call on my cellphone – or any phone within 5 meters running completely passive only on GSM harvested energy (yes, i did rip it apart eventually to verify, it was an awesome piece of chinese hackery). I see no reason why this shouldn’t work with BTLE.

      1. Oh yeah, those horrible little dongles were everywhere, every street-corner vendor of low-quality cellphone accessories at least. I thought they had a battery inside.

        1. Most did, but I also recall a device like this in the form of a sticker that one would place on the phone’s case near the antenna that seemed far to small to contain a battery. I could be wrong. I also seem to recall said device claiming to reduce harm to the user caused by the phone’s radiation…

      1. Stepping up from a few tens of mV is easily done and at good efficiency.
        Many manufacturers, such as Linear Tech, make these DC-DC boost converters.
        I really don’t see an issue with their claims TBH. What is suspect is that they aren’t giving any caveats with them.

    1. Dude! You stole my thunder! I was gonna recommend a joule thief!

      Of course it could be an orgone-energy RF joule thief…a jouluminous ether-thief, if you will.

  22. Even ignoring the battery (or lack of) the are also couple of other things a-miss here.

    Firstly the size. They mention it is 2.4mm thick, now assuming it’s injection moulded then there will be a minimum wall thickness of about 0.7mm reducing the internal space to a mere 1mm. I would be amazed if they could all the required circuitry and also a buzzer (at least a buzzer that’s louder than a flea’s fart) in that space. Especially considering the space which needs to be left around the BLE antenna for it to work properly.

    Secondly throughout the video the bluetooth icon never comes to life when they are demoing the app. May just be for video purposes but still odd.

    Thirdly the 200ft/60m range claim. Now in an open area it is definitely possible to achieve this distance with a standard spec BLE antenna with the TX power set around 5dbm, however it would be a very unstable connection, and would drop out if you looked it the wrong way. In the real world usage, like for example when you put your phone in your pocket, you would not really see more than 100ft/30m.

    1. Could be molded around the PCB instead… heat problems with that, of course, although maybe some thermosets would be tolerable.

      Could be vacuum formed. Rigid thin plastic makes a fairly good mechanical gain medium to make the beeper louder…

      Could be pressed metal… but is electrically conductive and would interfere with EM absorption … unless they’re being reeeeeally clever. (Funny diplane antenna with plastic spacer?)

  23. IN regards to “Quantum Tophats”, it seems that an Israeli battery research firm migth have done something in that general direction

    Their site

    Not saying that the Kickstarter has access to Israeli army research (because that would be highly unlikely), just pointing out that “Quantum Tophats” might be around sooner rather than later.

      1. Ah, you beat me to it! I was going to suggest the motion generator (a number of really small shake-activated generator projects out there). The little generator just needs to get bounced around regularly to pick up a little charge.

        I don’t see where the ‘awake’ vs ‘asleep’ times are specified for this. Could it be that they charge a small storage device (they say no battery – so maybe supercap)? During active, bouncy times the tag gets juice regularly, but as the cap discharges the cycle gets longer…. and longer…. and longer. Still wouldn’t be bad for something like tagging keys that get bounced around a lot.

        1. I am using EM harvesting in a product of my own. I use a special transducer that is 20% efficient, and it can harvest energy across a 500 Terahertz (!!!) patch of spectrum. The active surface area is 20x6mm, and it optimal conditions I’ve observed it to deliver a battery charge current of 4.5mA @ 4.2V.

          Yep, it’s a solar panel. If you want a cheap way to harvest a lot of energy, it’s really the best way to go. Even indoor lighting provides way more energy than virtually every other harvesting method there is.

          1. It can’t be only a solar cell, since the promotion video shows a tag being tucked into a compartment in a wallet. But maybe their device will rely on several different harvesting methods (wireless signals, solar, motion, …)

      1. Problem is, per the paper, this seems to generate about 460 mV, rather than the 3 volts used by the BLE. If the HAD math of 30uW listed above is the norm for idle draw, then the amount of current they would have to be able to harvest would seem even more unattainable. I think we’re talking 65 uA.

    1. I was thinking along the same lines. A crystal radio is a classic example of powering a device using only the signal itself. However, as you mention, they typically use a large antenna and only generate enough power to drive a tiny, very sensitive speaker.

  24. Maybe they use a printed battery, the capacity is very low (~2mAh 3V) for this size, but for being dormant 99.99% of the time that is good enough. RF energy harvesting seems unlikely to me with typical ambient fields in households.

  25. The fact that these guys are showing this SparkFun Electronics, Inc. Accelerometer BreakOut board as the only glimpse of their Engineering says much about their naiveness toward hardware development (or better yet…faking it)…

    And that’s not because of the 3uA they’re adding (while in sleep mode and 400uA when operating) , not because the current price of this accelerometer would be around 10% their SELLING PRICE…or even the EXTREMELY questionable choice of a 3 axis accelerometer given that they don’t need to detect orientation (just shaking) and are on such a tight power budget

    Coup de grâce:
    The component in question is on its EOL (EndOfLife)… no engineer in his right mind would use a EOL parts for a project like this… so my guess…they don’t have any engineers working on it…

    Tracking down the people responsible for this project:

    The people behind it:
    The Kickstarter Bio is VERY suspicious (names don’t match the credentials or linkedIn/Blog/Profiles)
    Domain uses anonimizer registrar
    Kickstarter username however “yuansong84” hints to the same yuansong84 (industrial designer) from and whose Fb profile is (yep it’s him)
    He is also friends with (From the kickstarter Bio) an Intern at Adobe (according to the kickstarter he’s the Co-founder of the company)
    The guy who shot the video : (he also apears on the video) and said ( ) that it was pretty good for a couple of idiots with a camera (on his timeline)

    none of them live in Texas…

    1. Also on KS Atlas Wang’s profile says “Atlas is a Ph.D. candidate”, however his webpage clearly articulates that he is only in his 2nd year and probably hasn’t even completed his qualifier. One only becomes a Ph.D. candidate (at least in the US) once you propose your thesis to the committee.

      Also his expertise doesn’t scream low-power RF, energy harvesting etc. at all. Something is fishy indeed.

    2. Dr Paul McArthur (first among equals at iFind) seems to have an extremely low net profile for someone who has taught at Univ of Utah in 1989-90

      (Jun 16th posting here: )

      and been in management positions at Freescale and Philips (according to his bio). Yet he declines to state where he did his undergrad and graduate degrees, and has no Linkedin profile. He claims to have had his identity stolen and is thus reluctant to divulge much online.

      I found a reference to Dr Paul McArthur at the Univ of Utah Hyperthermia Research Group in a 1990 Masters thesis (pg 15):

  26. Let’s say the device requires 10mA in active mode. A BLE announce transmission is <1ms. So that's 30uJ. Double that for a 2-way exchange and you have 60uJ. Assume that the device can harvest on average 1uW of power (beyond what it takes to keep the device in standby). Then it would be able to communicate only once every 60 seconds and that wouldn't allow for any excess power to recharge the battery. It doesn't seem like this would deliver acceptable performance based on the product category and the combined performance of power harvesting/consumption would have to increase by 50-100x to be usable. Since they publish only marketing/sales fluff and no numbers, one cannot say what improvements they are claiming. Overall it warrants a lot of skepticism and though operation in a lab setting is believable it would likely be disappointing in real world conditions.

  27. “How do I replace the battery?
    The top of the Stick-N-Find twists off just like bottle top. It is then a simple matter of removing the old battery and replacing it with a new one.”

  28. Dave jones couldn’t ship his uCurrent internationally with a cr2032 because it was in violation of some law (not sure which one, shipping lithium batteries by airfreight?) but if the ifind does have a battery then they will be in violation of that law.

  29. I always have been skeptical of anything with a cool name and an even cooler graphical presentation but accompanied by the absence of any technical detail.
    It usually indicates they’re spending the most money/time on presentation which is common practice among fraudsters.

  30. The FAQ on their website contains this:
    How long will my iFind last?
    TWO DECADES, as long as it is not subject to extraordinary physical abuse!

    I wonder if this is referring to physical wear and tear, or to the the power supply.

  31. They’re claiming they have received an email threatening one of their personnel. It doesn’t look like anything you would do, and I hope it is not from the Hackaday Team…

      1. I sent them an email asking for clarification on the math of the whole thing and asked them if this was a publicity stunt , a scam or if they really believed that this was possible
        And to give them a chance to Scientifically defend themselves (I try to always follow Carls Sagans scientific skepticism, meaning that if they convince me of that it is possible I would endorse them , I asked for evidence )

        according to them it’s for real! (I wasn’t even expecting a reply, so )

        When I pointed out that Sparkfun breakout board with that EOL accelerometer (on their video) and sent them the same calculations as I presented above in the comments at that point they said that I was threatening them :P , and that I wanted their device (Straw Man Fallacy)

        They did clarify however that the person who shot the video (and was stating on facebook that it was “not too shabby for a few idiots with a camera”) isn’t with them (is not part of their company) so they weren’t mocking their backers on facebook

        I then replied that I did not want to see their device nor was threatening anyone (I did say that if they couldn’t convince me I’d report their project to KickStarter, which in my mind is more than a reasonable action based on the total lack of evidence),
        And that what I want is the maths behind their amazing claims… (regarding psu and their theoretical supply current )

        1. Really, if I were involved in a commercial project, where my own financial well being was based upon it succeeding, then I wouldn’t tell anyone how it works either!
          Try asking Samsung how their HW achieves their claimed battery life…they won’t tell you.
          Again, their claims seem valid ie it can work. It’s not a new science and their theory of operation has been proven many times.
          What is dubious (and is a glaring omission) is the use cases and caveats. What I mean is details regarding what the tag can do and how often. If they claim it can operate in rope mode, flash it’s LED, beep its beeper etc continuously ad infinitum then that would appear to be a challenge and would require a consistent few mA which is unlikely from ambient RF. This would deplete the battery/energy store after a while as the RF harvesting is unlikely to replenish it quick enough.

          I think the devil is in their lack of detail :-)

          1. Exactly! The problem isn’t the energy harvesting technology itself (as you stated Linear has some very interesting regulators that could potentially be used to trickle charge low leak caps or even one of those Battery Life Extenders (LTC3330) )

            The problem is the claims that they don’t have any battery or supercap and just like you said they promise a highly responsive operation (rope) , a buzzer an accelerometer that would require quite a lot of power to be constantly harvested from the environment (without any special transmitter or RFID Gen2 style portal)

            A nice harvesting example can be found at Linear’s DN483 (appnote)
            “Two 12” × 24” copper panels are placed 6” from a 2’ × 4’
            fluorescent light fixture.” resulting in a 200uW @ 6 inches…

            Now if you had an antenna the size of a quarter that could vastly outmatch the performance of DN483 setup , capable of harvesting enough constant power (remember…no battery/supercap claim) to actually poll the BLE RX at a decent rate AND transmit at 60m (not just leave it in idle) along with the operation of a loud buzzer and accelerometer without any distance restriction from a transmitter (the only restriction would be for it to be anywhere in a urban environment )….basically the holy grail of RFID Would you:
            -Sell it to the highest bidder at probably several hundred million usd? This is THE holy grail in active tag business…
            -Start a Kickstarter initially asking for 25K and sell it at cost…

          1. It’s now $100k but hey, that’s chump change when taking to market a new product, trust me, I’ve done it many times before.
            Their project is plausible, as I have said, can be made from parts from Farnell, reasonably priced and there seems to be no cloak and dagger.
            Their unwillingness to tell the world how it works isn’t a sign that it doesn’t. It’s commercially sensible to keep quiet especially if there are patents pending (I know they may have filed applications but they don’t want a $h/t storm of objections and challenges!).
            Why not throw down $14 or whatever and get in line for a product, you will then be a customer and may get some response when asking about the project. Don’t expect too much though, you can buy any high-street electronics but its unlikely the manufacturer will let you have a schematic or ‘maths’!
            Again, just my 2c (or £0.015 over here)!

          2. Steve,
            You say it is plausible, but the majority of posters here appear to disagree.
            If these tags are plausible, wouldn’t it also be plausible to create a batteryless bluetooth mouse using the same technology and at about the same price ?
            That would obsolete almost all wireless mice currently in use, and make the inventor very wealthy I would imagine.

          3. Yes, Technight, it would be possible on a larger scale (for mice) and yes, I do think its plausible no matter what the masses say, I am fairly technical and can make my own mind up based on experience and research.

            I have designed a number of BT (not BT LE I might add) mice and the pwr consumption is much higher than this tag – check out Agilent (ADNS?) for mouse sensors, many mA required – the optical sensor is the dominant consumer of power.
            A mouse has much more space inside due to it being for a hand to clasp, much more space to employ a more sensible harvesting technique such as movement (ie moving magnet) or thermal etc. Actually, if it did employ EM harvesting, it could do quite well being located (typically) so close to electrical equipment!

            Problem is, as a consumer, would you rather pay $20 for a wireless mouse which takes 2x AA batteries and lasts a year (until you change them) or $50 for a mouse which has no batteries? Do bear in mind that the (imaginary) $30 differential buys 10 years worth of AA batteries. These are the types of things a business will consider before over-engineering a product.

            At the end of the day, the usage scenario for a mouse means its not as much of a pain to change the batteries (when was the last time you lost your mouse) as it is for something like a locating tag. For a tag you don’t want to have to remember to change the batts, you just need to rely on being able to find it.
            Mind you, if you had to check and replace the batteries on a tag you might not lose whatever it’s attached to so much!

          4. Steve,
            I am not sure where you come up with the $50 figure for a mouse using this technology.
            An iFind (if viable) is $14. A wired mouse can easily be gotten for $6. Throw in $5 for misc additional costs, which is more than generous and we are talking $25. I think you would find a lot of people willing to buy a $25 wireless mouse that will never need a battery.

          5. Also, it’s unlikely to make the ‘inventor’ (there’s lots of prior art, check the web) wealthy, the bom cost would present a cost barrier for the consumer vs traditional primary cell equivalents. For the consumer there is no financial incentive to buy one. There is, potentially, a ‘green’ environmental benefit but not a financial one….money in your pocket is what matters to what we would call the ‘masses’.

          6. To be honest, I would like this technology to prove viable, as it would serve as a gateway for all kinds of new batteryless gadgets, but the realist (skeptic) in me is far from convinced that it can work. Time will tell, as the iFinds are supposed to ship in October.

          7. I see what you’re saying.
            $50 seems to be a reasonable cost for a half decent BT mouse – my last one cost a lot more.
            Whether its a mouse or tag, the EM ambience is outside of your control, it’s much easier to power a tag at ??uW vs a mouse at (when I was making them) 140mW.
            I think a mouse may be able to be charged via EM harvesting (not operated) but, given the extra space in a mouse, it’s more suited to a more traditional energy harvesting techniques….or primary cells!

            Mice aside, I think a BTLE module is rechargeable via EM although operating from EM is another very different (and challenging) story. They claim no battery but I suspect there is one…or a bank of ceramic caps.

      1. Price negotiations and licensing legalities can take a while and it’s not something you want to take lightly. If taking a high (ish) volume product to market you should know this.
        Sounds like they are doing things right.

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