Die Photos Of A Runner’s RFID Chip

June 30, 2016 by Jenny List 17 Comments

A mass participation sporting event such as a road race presents a significant problem for its record keepers. It would be impossible to have ten thousand timekeepers hovering over stopwatches at the finish line, so how do they record each runner’s time? The answer lies in an RFID chip attached to the inside of the bib each runner wears, which is read as the runner crosses the line to ensure that their time is recorded among the hundreds of other participants.

[Ken Shirriff] got his hands on a bib from San Francisco’s “Bay to Breakers” race, and set about a teardown to lay bare its secrets.

Stripping away the foam covering of the RFID assembly revealed a foil antenna for the 860-960MHz UHF band with the tiny RFID chip at its centre. The antenna is interesting, it’s a rather simple wideband dipole folded over with what looks like a matching stub arrangement and an arrow device incorporated into the fold that is probably for aesthetic rather than practical purposes. He identified the chip as an Impinj Monza 4, whose data sheet contains reference designs for antennas we’d expect to deliver a better performance.

After some trial-by-fire epoxy removal the tiny chip was revealed and photographed. It’s a device of three parts, the power scavenging and analog radio section, the non-volatile memory that carries the payload, and a finite-state logic machine to do the work. This isn’t a proper processor, instead it contains only the logic required to do the one task of returning the payload.

He finishes off with a comparison photograph of the chip — which is about the size of a grain of salt — atop a 1980s 8051-series microcontroller to show both its tiny size and the density advancements achieved over those intervening decades.

Since RFID devices are becoming a ubiquitous part of everyday life it is interesting to learn more about them through teardowns like this one. The chip here is a bit different to those you’ll find in more mundane applications in that it uses a much higher frequency, we’d be interested to know the RF field strength required at the finish line to activate it. It would also be interesting to know how the system handles collisions, with many runners passing the reader at once there must be a lot of RFID chatter on the airwaves.

We’ve featured [Ken]’s work before, among many others in his reverse engineering of Clive Sinclair’s 1974 scientific calculator, and his explanation of the inner workings of the TL431 voltage reference. Though we’ve had many RFID projects on these pages, this appears to be the first teardown of one we’ve covered.

Reverse Engineering The OWON SDS7102 Oscilloscope

June 29, 2016 by Jenny List 23 Comments

It is something of a rite of passage for an electronics enthusiast, the acquisition of a first oscilloscope. In decades past that usually meant a relatively modest instrument, maybe a 20MHz bandwidth and dual trace if you were lucky. Higher spec devices were eye-wateringly expensive monsters, not for the Common People.

We are fortunate that like most other areas of technology the world of test equipment has benefited in the last few years both from developments in digital technology and from the growth in Chinese manufacturing. If your first ‘scope is that second-hand 20MHz CRT you will probably secure it for pennies, and the first ‘scope you buy new will probably have a spec closer to those unattainable super-scopes of yesteryear. Gone is the CRT and timebase generator, in its place a TFT, system-on-chip, and super-fast A to D converter.

[Christer Weinigel] has just such an entry-level modern digital ‘scope, an OWON SDS7102. He comments that it’s got an impressive spec for its price, though the input is noisier than you’d expect on a more expensive device, and the software has one or two annoying bugs. Having owned it for a while, he’s now subjected it to a lengthy teardown and reverse engineer, and he’s posted his findings in a succession of blog posts.

[Christer]’s interest lay mainly in the OWON’s digital section, it seems there is already a substantial community paying attention to its analog front end. He’s deduced how its internals are connected, ported Linux to its Samsung SoC in the scope, succeeded in getting its peripherals working, and set to work programming the Xilinx FPGA that’s responsible for signal processing.

The series of posts is a fascinating read as a run through the process of reverse engineering , but he points out that it’s quite a lot of information. If you are just interested in how a cheap modern oscilloscope works, he says, he suggests reading his post in which he recaps on all its different components.

He also makes a plea for help, he’s no slouch on the ‘scope’s software but admits he’s a bit out of his depth on some aspects of the FPGA. If you’re an FPGA wizard with an interest in ‘scopes, he’d like to hear from you.

This isn’t the first time we’ve featured ‘scope reverse engineering here at Hackaday, though it may be more in-depth than others. In the past we’ve seen a Uni-T screen grab protocol laid bare, and an investigation of a Rigol 1054Z.

Get Set For SAQ On Alexanderson Day With These Active Antennas

June 26, 2016 by Jenny List 32 Comments

If you need to generate a radio frequency electrical signal, you will make some form of electronic oscillator. We’ll probably all be used to oscillators using transistors, tubes, logic gates or a host of other electronic technologies. Similarly if you need to generate radio frequencies at high powers, you’ll couple your oscillator to an amplifier, a relatively simple task with today’s electronic parts bin.

If you needed to do the same thing with a high power radio signal in the early years of the 20th century, none of these options were open to you. There were no transistors or integrated circuits, and the tubes of the day could not produce high power outputs. Radio engineers back then had to employ other solutions to the problem, one of which was the Alexanderson alternator. It’s old news we’ve covered here before at Hackaday, a high frequency alternator capable of generating hundreds of kilowatts in the VLF radio frequency range.

There is one operational Alexanderson alternator remaining in the world at the Varberg radio station at Grimeton in Sweden. It is no longer in constant use, but as a World Heritage Site and museum it is put on air a few times a year including the Sunday closest to the 2nd of July, known as Alexanderson Day. We come now to the point of this article: this year’s 3rd of July Alexanderson Day transmission is fast approaching, and since last time we covered it we signed off with a plea for a good VLF antenna design we should post a solution in good time to allow our readers to receive this year’s signal.

G3XBM's e-field VLF antenna — G3XBM’s e-field VLF antenna

Fixing up a receiver is easy enough, we linked to the original SAQrx VLF Receiver and the extended version in our previous coverage. Both pieces of software use your computer’s sound card as the front end of a software defined radio to receive the 17.2kHz from Grimeton. The antenna though presents a problem. You might think that attaching a long piece of wire to the microphone input would be enough, but the problem is that due to the huge wavelength of the VLF signal any reasonable long wire you might be able to assemble simply wouldn’t be long enough to deliver a good result. Clearly a different antenna is required, and the solution comes courtesy of a high-impedance active e-field antenna. This uses a FET input and a surprisingly small patch antenna to deliver a low noise floor at VLF frequencies rather than to be the amplifier you might expect.

We’ve found a couple of designs for you to look at. The first is a two transistor version you will find in various different guises on many sites. This one uses an MPF102 FET, but you should be able to substitute a J310. The second design is a little more surprising, while it is the same idea of a FET input amplifier it uses a TL071 op-amp as its active device. This is in no way an IC you’d normally expect to find in an RF circuit, however the frequency in question is not that of your normal RF.

If you build either of these antennas we hope you’ll be able to hear the Alexanderson Day transmission. The point of a high power VLF transmitter is that it has a huge coverage area, so it should be possible to receive it across all of Europe and perhaps into the eastern United States. If you are out of range though, never fear. You can always try to pick it up through a handy webSDR receiver closer to the source.

Alexanderson alternator picture By Gunther Tschuch (Own work) [ CC BY 2.5 ], via Wikimedia Commons.

Effortlessly Send Antenna Wires Skywards With A Spud Gun

June 26, 2016 by Jenny List 29 Comments

The heroes of action films always make it look so easy. Need to climb a tall building? Simply fire a grapnel hook from a handy harpoon gun, it’ll always land exactly where you want it and gain a perfect purchase so you can shin up the rope and arrive at the top barely having raised a sweat. If Hackaday ran Q Branch, we can tell you, we’d make ’em work a bit harder. If only because nobody likes a smartass.

If you’ve ever had to get a real line over something tall, you’ll know it’s a lot more difficult than that. You can only make it work with the lightest of lines that you can then use to pull up something more substantial, and you would be amazed how poor a thrower you are when you’re trying to throw upwards. Try attaching fishing line to a weight, try a bow and arrow, and nine times out of ten you won’t make it. There’s a serious amount of skill and luck involved in this line-throwing game.

[WB5CXC] has an interesting solution to this problem, at least as far as the application of throwing antenna wires over tall obstacles. He’s made a spud gun from PVC pipe, powered by compressed air. It takes the form of a U-shaped tube with one side of the U being a pressure vessel separated from the other by a ball valve.. Place a close-fitting puck with your wire attached in the open side with the valve closed, pump the pressure vessel full of air with a bicycle pump, and open the valve to send both puck and wire skywards. He says it will clear 100′ trees, counsels the user not to go higher than 100psi, and warns that the speeding puck can be dangerous. We like it already.

We’ve covered many spud guns here at Hackaday in the past, but it seems this is the first wire launching one. We’ve had a steam one for example, or this bolt-action spud gun, but pride of place has to go to the spud gun to end all spud guns.

Via DXZone.

This Arduino Console Has 64 Bit Graphics

June 25, 2016 by Jenny List 6 Comments

Numbers are wonderful things when applied to technical specifications. Take [Bobricius]’ handheld Arduino-based game console. With an 8×8 LED matrix for a display it’s not going to win any prizes, but while he’s pushing the boundaries of dubious specification claims he’s not strictly telling any lies with his tongue-in-cheek statement that the graphics are 64-bit.

Jokes aside, it’s a neatly done build using a DIP version of the Arduino MCU and all through-hole components on a custom PCB. Power comes from a CR2032 cell, and it includes three buttons and a small piezoelectric speaker. He’s implemented a whole slew of games, including clones of Pong, Breakout, and Tetris, and judging by the video below it’s surprisingly playable.

Now you might look at this console and wonder what the big deal is. After all, there are plenty of similar designs to be found, and it’s nothing new. Of course, it’s a neat project for any hacker or maker, but we can see that this would make a great starter project for the younger person in your life who wants to try their hands at building something electronic. All through-hole construction for easy soldering, and a neat game at the end of it all.

He’s posted a full write-up of the design process as well as the hackaday.io page linked above, so if you fancy building one yourself there’s nothing to stop you too squeezing 64 bits of graphical goodness from an Arduino.

Continue reading “This Arduino Console Has 64 Bit Graphics” →

Capacitors Made Easy The Hackaday Way

June 21, 2016 by Jenny List 66 Comments

If you build electronic circuits on a regular basis the chances are you will have used capacitors many times. They are a standard component along with the resistor whose values are lifted off the shelf without a second thought. We use them for power supply smoothing and decoupling, DC blocking, timing circuits, and many more applications.

Different capacitor applications. By Elcap (Own work) [CC0], via Wikimedia Commons

A capacitor though is not simply a blob with two wires emerging from it and a couple of parameters: working voltage and capacitance. There is a huge array of capacitor technologies and materials with different properties. And while almost any capacitor with the right value can do the job in most cases, you’ll find that knowing more about these different devices can help you make something that doesn’t just do the job, but does the best possible job. If you’ve ever had to chase a thermal stability problem or seek out the source of those extra dBs of noise for example you will appreciate this.

Continue reading “Capacitors Made Easy The Hackaday Way” →

FCC To Investigate Raised RF Noise Floor

June 21, 2016 by Jenny List 90 Comments

If you stand outside on a clear night, can you see the Milky Way? If you live too close to a conurbation the chances are all you’ll see are a few of the brighter stars, the full picture is only seen by those who live in isolated places. The problem is light pollution, scattered light from street lighting and other sources hiding the stars.

The view of the Milky Way is a good analogy for the state of the radio spectrum. If you turn on a radio receiver and tune to a spot between stations, you’ll find a huge amount more noise in areas of human habitation than you will if you do the same thing in the middle of the countryside. The RF noise emitted by a significant amount of cheaper modern electronics is blanketing the airwaves and is in danger of rendering some frequencies unusable.

Can these logos really be trusted? By Moppet65535 (Own work) [CC BY-SA 3.0], via Wikimedia Commons

If you have ever designed a piece of electronics to comply with regulations for sale you might now point out that the requirements for RF interference imposed by codes from the FCC, CE mark etc. are very stringent, and therefore this should not be a significant problem. The unfortunate truth is though that a huge amount of equipment is finding its way into the hands of consumers which may bear an FCC logo or a CE mark but which has plainly had its bill-of-materials cost cut to the point at which its compliance with those rules is only notional. Next to the computer on which this is being written for example is a digital TV box from a well-known online retailer which has all the appropriate marks, but blankets tens of megahertz of spectrum with RF when it is in operation. It’s not faulty but badly designed, and if you pause to imagine hundreds or thousands of such devices across your city you may begin to see the scale of the problem.

This situation has prompted the FCC Technological Advisory Council to investigate any changes to the radio noise floor to determine the scale of the problem. To this end they have posted a public notice (PDF) in which they have invited interested parties to respond with any evidence they may have.

We hope that quantifying the scale of the RF noise problem will result in some action to reduce its ill-effects. It is also to be hoped though that the response will not be an ever-tighter set of regulations but greater enforcement of those that already exist. It has become too easy to make, import, or sell equipment made with scant regard to RF emissions, and simply making the requirements tougher for those designers who make the effort to comply will not change anything.

This is the first time we’ve raised the problem of the ever-rising radio noise floor here at Hackaday. We have covered a possible solution though, if stray RF is really getting to you perhaps you’d like to move to the National Radio Quiet Zone.

[via Southgate amateur radio news]