Low cost, long range, or low power — when it comes to wireless connectivity, historically you’ve only been able to pick two. But a group at the University of Washington appears to have made a breakthrough in backscatter communications that allows reliable data transfer over 2.8 kilometers using only microwatts, and for pennies apiece.
For those unfamiliar with backscatter, it’s a very cool technology that modulates data onto RF energy incident from some local source, like an FM broadcast station or nearby WiFi router. Since the backscatter device doesn’t need to power local oscillators or other hungry components, it has negligible power requirements. Traditionally, though, that has given backscatter devices a range of a few hundred meters at most. The UW team, led by [Shyamnath Gollokota], describe a new backscatter technique (PDF link) that blows away previous records. By combining the spread-spectrum modulation of LoRa with the switched attenuation of incident RF energy that forms the basis for backscatter, the UW team was able to cover 2800 meters for under 10 microwatts. What’s more, with printable batteries or cheap button cells, the backscatter tags can be made for as little as 10 cents a piece. The possibilities for cheap agricultural sensors, ultracompact and low power wearable sensors, or even just deploy-and-forget IoT devices are endless.
We’ve covered backscatter before, both for agricultural uses and for pirate broadcasting stations. Backscatter also has also seen more cloak and dagger duty.
Continue reading “Hybrid Technique Breaks Backscatter Distance Barrier”
The world is dealing with a serious refugee crisis, and with that comes a problem: finding people. The Refugee Reuniter, a project entered into this year’s Hackaday Prize, is a possible solution to this problem. It’s a device that allows people to reconnect with their family, whether it’s children lost in transit to destination countries, or mothers and fathers reuniting.
The basic problem the Refugee Reuniter is trying to solve is tracking people. This is a whole ball of wax that involves privacy and technological concerns. Ideas put forward so far include GPS trackers, implantable RFID tags, and other such draconian measures. The Refugee Reuniter puts another spin on this, while still assigning a unique, electronic ID to every name.
The basic hardware for the Refugee Reuniter is simply an RFID wristband or token, carried with the refugee at all times. This token is mapped to a name that can be looked up in a small terminal, tied to a specific location. If a refugee logs into one of these terminals, their location is logged and they can search for their relatives. It’s a simple technological solution to what is basically a gigantic dead-tree logbook, only backed up into an online database.
If it’s been a few years since you’ve been to Disney World, you’re in for a surprise on your next visit. It seems the Happiest Place on Earth has become the Trackiest Place on Earth thanks to the Disney MagicBand, a multipurpose wristband that acts as your pass to all the Disney magic.
[Adam] recently returned from a Disney vacation and brought back his MagicBand, which quickly went under the knife for a peek at the magic inside. It turns out the technology is fairly mundane — a couple of flex PCBs with trace antennas and the usual trappings of an RFID transponder. But there’s also another antenna and a chip identified in a separate teardown as an NRF24LE1 2.4 GHz transceiver and microcontroller. The whole thing is powered by a coin cell, meaning the band isn’t just being interrogated by RFID – it’s actively transmitting and receiving.
What exactly it’s doing isn’t clear; Disney was characteristically cagey about specifics when [Adam] looked into the details, saying only that the bands “provide information that helps us improve the overall experience in our parks”. If you put aside the privacy concerns, it’s truly mind-boggling to think about the systems that must be in place to track thousands of these MagicBands around the enormous Disney property. And we can’t help but wonder if some of Disney R&D’s EM-Sense technology is at work in these wearables.
Thanks to [JohnU] for the tip.
If you live in a city, you’re constantly swimming in a thick soup of radio-frequency energy. FM radio stations put out hundreds of kilowatts
each into the air. Students at the University of Washington, [Anran Wang] and [Vikram Iyer], asked themselves if they could harness this background radiation to transmit their own FM radio station, if only locally. The answer was an amazing yes.
The trailer video, embedded below, demos a couple of potential applications, but the paper (PDF) has more detail for the interested. Basically, they turn on and off an absorbing antenna at a frequency that’s picked so that it modulates a strong FM signal up to another adjacent channel. Frequency-modulating this backscatter carrier frequency adds audio (or data) to the product station.
One of the cooler tricks that they pull off with this system is to inject a second (stereo) channel into a mono FM station. Since FM radio is broadcast as a mono signal, with a left-minus-right signal sent alongside, they can make a two-channel stereo station by recreating the stereo pilot carrier and then adding in their own difference channel. Pretty slick. Of course, they could send data using this technique as well.
Why do this? A small radio station using backscatter doesn’t have to spend its power budget on the carrier. Instead, the device can operate on microwatts. Granted, it’s only for a few feet in any given direction, but the station broadcasts to existing FM radios, rather than requiring the purchase of an RFID reader or similar device. It’s a great hack that piggybacks on existing infrastructure in two ways. If this seems vaguely familiar, here’s a similar idea out of the very same lab that’s pulling off essentially the same trick indoors with WiFi signals.
So who’s up for local reflected pirate radio stations?
Continue reading “Backscatter Your Own FM Pirate Radio Station”
You’d think that with as many sick people as there are in the world, it wouldn’t be too difficult for a doctor in training to get practice. It’s easy to get experience treating common complaints like colds and the flu, but it might take the young doctor a while to run across a dissecting abdominal aortic aneurysm, and that won’t be the time for on the job training.
Enter the SP, or standardized patient – people trained to deliver information to medical students to simulate a particular case. There’s a problem with SPs, though. While it’s easy enough to coach someone to deliver an oral history reflecting a medical condition, the student eventually needs to examine the SP, which will reveal none of the signs and symptoms associated with the simulated case. To remedy this, [Chris Sanders] and [J Scott Christianson] from the University of Missouri developed an open-source RFID stethoscope to simulate patient findings.
This is one of those “why didn’t I think of that?” ideas. A cheap stethoscope is fitted with an Arduino, and RFID reader, and a small audio board. RFID tags are placed at diagnostic points over an SP’s chest and abdomen. When the stethoscope is placed over a tag, a specific sound file is fetched from an SD card and played over earbuds. The student doesn’t have to ask, “What am I hearing?” anymore – the actual sound of bruits or borborygmi are heard.
We can easily see expanding this system – RFID tags that trigger a faux ultrasound machine to display diagnostic images, or tiny OLED screens displaying tagged images into an otoscope. A good place to start expanding this idea might be this digital stethoscope recorder and analyzer.
Continue reading “RFID Stethoscope Wheezes and Murmurs for Medical Training”
Give kids some responsible and challenging tasks, and you’d be surprised at the results. The “Anything Goes” exhibit at the National Museum in Warsaw was aimed as a museological and educational experiment. A group of 69 children aged 6–14 was divided into teams responsible for preparing the main temporary exhibition at the museum. Over six months, they worked on preparing the exhibition during weekly four-hour meetings. They prepared scripts, provided ideas for multimedia presentations, and curated almost 300 works for display. One of those was [Robert Mordzon]’s Giant Interactive Crossword.
The build is in two parts. The letter tiles, which have embedded RFID tags, obviously look like the easiest part of the build. The table, looking at the video (after the break), probably needed a lot more effort and labour. It is built in two halves to make construction easier. There are a 130 boxes that need to be filled in with the right letters to complete the crossword. Each box contains a bunch of electronics consisting of an Arduino Nano, a RFID Reader and a bunch of sixteen WS2812B LEDs, all assembled on a custom PCB. Do the math, and you’ll figure out that there’s 2080 LEDs, each capable of sipping 60 mA at full brightness. That’s a total current requirement of almost 125 amps at 5 V. Add in all the Arduino’s, and [Robert] needed a beefy 750 W of power, supplied via four switch mode power supplies.
Each Arduino Nano is a slave on the I²C bus. The I²C master is an Arduino Mega 2560, which in turn communicates with a computer over serial. When a box is empty, the LEDs are dim, when a wrong letter is placed, they turn Red, and when the right letter is placed, they turn Green. If a word gets completed, a special word animation is played. This information is also passed on to the computer, which then projects an animation related to the word on a giant wall screen. Upon the crossword getting completed, the table erupts in to a sound (via the computer) and light “disco” show and also reveals the main motto of this section of the exhibit – “Playing the Hero”.
Continue reading “Huge Interactive Crossword”
How often do you see problems that need fixing? How often do you design your own solutions to them — even if they won’t be implemented at scale? Seeing that many of the municipal parking lots in his native Sri Lanka use a paper ticketing system which is prone to failure, [Shazin Sadakath] whipped up his own solution: an efficient RFID tag logging system.
Continue reading “Faulty Parking Meter Tracking System? RFID To The Rescue!”