Which Wireless Is Right Wireless?

October 19, 2018 by Kerry Scharfglass 24 Comments

Back in the early days of Arduino proliferation (and before you ask, yes we realize there was a time before that too), wireless was a strange and foreign beast. IR communication was definitely a thing. And if you had the funds there was this cool technology called ZigBee that was available, often in funny blue house-shaped XBee boards. With even more funds and a stomach for AT commands you could even bolt on a 2G cell radio for unlimited range. WiFi existed too, but connecting it to a hobbyist ecosystem of boards was a little hairier (though maybe not for our readership).

But as cell phones pushed demand for low power wireless forward and the progression of what would become the Internet of marking Terms (the IoT, of course) began, a proliferation of options appeared for wireless communication. Earlier this week we came across a great primer on some of the major wireless technologies which was put together by Digikey earlier in the year. Let’s not bury the lede. This table is the crux of the piece:

There are some neat entries here that are a little less common (and our old friend, the oft-maligned and never market-penetrating ZigBee). It’s actually even missing some entries. Let’s break it down:

Extremely short range: Just NFC. Very useful for transferring small amount of sensitive information slowly, or things with high location-relevance (like between phones that are touching).
Short range: BLE, Zigbee, Z-Wave, etc. Handy for so-called Personal Area Networks and home-scale systems.
Medium/long range: Wifi, Bluetooth, Zigbee, Z-Wave, LoRaWAN: Sometimes stretching for a kilometer or more in open spaces. Useful for everything from emitting tweets to stitching together a mesh network across a forrest, as long as there are enough nodes. Some of these are also useful at shorter range.
Very Long range/rangeless: Sigfox, NB-IoT, LTE Category-0. Connect anywhere, usually with some sort of subscription for network access. Rangeless in the sense that range is so long you use infrastructure instead of hooking a radio up to a Raspberry Pi under your desk. Though LoRa can be a fun exception to that.

You’re unlikely to go from zero to custom wireless solution without getting down into the mud with the available dev boards for a few different common protocols, but which ones? The landscape has changed so rapidly over the years, it’s easy to get stuck in one comfortable technology and miss the appearance of the next big thing (like how LoRaWAN is becoming new cool kid these days). This guide is a good overview to help catch you up and help decide which dev kits are worth a further look. But of course we still want to hear from you below about your favorite wireless gems — past, present, and future — that didn’t make it into the list (we’re looking at you 433 MHz).

Fully 3D Printed And Metalized Horn Antennas Are Shiny And Chrome

October 4, 2018 by Brian Boucheron 19 Comments

We’ve seen our share of 3D printed antennas before, but none as well documented and professionally tested as [Glenn]’s 3D printed and metalized horn antennas. It certainly helps that [Glenn] is the principal engineer at an antenna testing company, with access to an RF anechoic chamber and other test equipment.

Horn antennas are a fairly simple affair, structurally speaking, with a straight-sided horn-shaped “cone” and a receptacle for standardized waveguide or with an appropriate feed, coaxial adapters. They are moderately directional and can cover a wide range of frequencies. These horns are often used in radar guns and as feedhorns for parabolic dishes or other types of larger antenna. They are also used to discover the cosmic microwave background radiation of our universe and win Nobel Prizes.

[Glenn]’s antennas were modeled in Sketchup Make, and those files plus standard STL files are available for download. To create your own horn, print the appropriate file on a normal consumer-grade fused deposition printer. For antennas that perform well in WiFi frequency ranges you may need to use a large-format printer, as the prints can be “the size of a salad bowl”. Higher frequency horns can easily fit on most print beds.

After printing, [Glenn] settled on a process of solvent smoothing the prints, then metalizing them with commonly available conductive spray paints. The smoothing was found to be necessary to achieve the expected performance. Two different paints were tested, with a silver-based coating being the clear winner.

The full write-up has graphs of test results and more details on the process that led to these cheap, printed antenna that rival the performance of more expensive commercial products.

If you’re interested in other types of 3D printed antenna, we’ve previously covered a helical satcom feed, a large discone antenna, and an aluminum-taped smaller discone antenna.

SENSEation Shows The Importance Of Good Physical Design

October 4, 2018 by Donald Papp 1 Comment

Sensor network projects often focus primarily on electronic design elements, such as architecture and wireless transmission methods for sensors and gateways. Equally important, however, are physical and practical design elements such as installation, usability, and maintainability. The SENSEation project by [Mario Frei] is a sensor network intended for use indoors in a variety of buildings, and it showcases the deep importance of physical design elements in order to create hardware that is easy to install, easy to maintain, and effective. The project logs have an excellent overview of past versions and an analysis of what worked well, and where they fell short.

One example is the power supply for the sensor nodes. Past designs used wall adapters to provide constant and reliable power, but there are practical considerations around doing so. Not only do power adapters mean each sensor requires some amount of cable management, but one never really knows what one will find when installing a node somewhere in a building; a power outlet may not be nearby, or it may not have any unoccupied sockets. [Mario] found that installations could take up to 45 minutes per node as a result of these issues. The solution was to move to battery power for the sensor nodes. With careful power management, a node can operate for almost a year before needing a recharge, and removing any cable management or power adapter meant that installation time dropped to an average of only seven minutes.

That’s just one example of the practical issues discovered in the deployment of a sensor network in a real-world situation, and the positive impact of some thoughtful design changes in response. The GitHub repository for SENSEation has all the details needed to reproduce the modular design, so check it out.

WebSockets Embedded With The ESP8266

October 3, 2018 by Al Williams 15 Comments

It used to be that Web browsing was simple. You asked a server for some text, which was duly sent, and then formatted by your browser. Now a web page is as likely to be a full-blown application that is reading mail, editing text, or lots of other things and may use WebSockets to create a back channel to the server. Thanks to affordable hardware like the ESP8266 one of those things a modern web browser can do is sense and control the real world. [Acrobotic] has an interesting video about using WebSockets to allow a browser to talk to an ESP8266 web server in real time. You can see his simple demo in the video below.

Of course, you’ll use the usual language you use on the ESP8266 — [Acrobotic] uses C++ in the Arduino IDE. On the browser side you’ll use JavaScript, although that will be embedded in your C++ program which acts as a web server.

Continue reading “WebSockets Embedded With The ESP8266” →

Putting M5Stack On LoRa And The Things Network

September 29, 2018 by Eric Evenchick 4 Comments

LoRa is the new hotness in low-power, long-range communications. Wanting to let the packets fly, [Xose] was faced with a frequecny problem and ended up developing a Europe-friendly LoRa module for the M5Stack system. The hardware is aimed at getting onto The Things Network, a LoRa based network that provides connectivity for IoT devices. While there was an existing M5Stack module for LoRa, it only supported 433 MHz. Since [Xose] is in Europe, an 868 MHz or 915 MHz radio was needed. To solve this, a custom board was built to connect the HopeRF RFM69 series of modules to the M5Stack.

If you haven’t heard of it before, the M5Stack platform is a stackable development board platform. Like Arduino, you can add functionality by stacking PCBs using a standard header. Unlike Arduino, M5Stack fits in a case nicely and is designed for building devices with user interfaces. For $35, you get an ESP32 based system with WiFi, Bluetooth, a color LCD, battery, buttons, a speaker, and IO connectors.

With the hardware in place, [Xose] 3D printed a custom case to hold the board and added it to the stack. The firmware acts as a monitor for The Things Network, showing live coverage. The final product looks very clean for a prototype, maintaining the finished look of M5Stack.

The firmware, board design, and case design files for the project are all available on Github.

Antennas That You Install With A Spray-Can

September 27, 2018 by Al Williams 30 Comments

With the explosion in cell phones, WiFi, Bluetooth, and other radio technologies, the demand for antennas is increasing. Everything is getting smaller and even wearable, so traditional antennas are less practical than ever. You’ve probably seen PCB antennas on things like ESP8266s, but Drexel University researchers are now studying using titanium carbide — known as MXene — to build thin, light, and even transparent antennas that outperform copper antennas. Bucking the trend for 3D printing, these antennas are sprayed like ink or paint onto a surface.

A traditional antenna that uses metal carries most of the current at the skin (something we’ve discussed before). For example, at WiFi frequencies, a copper antenna’s skin depth is about 1.33 micrometers. That means that antennas have to be at least thick enough to carry current at that depth from all surfaces –practically 5 micrometers is about the thinnest you can reasonably go. That doesn’t sound like a lot, but when you are trying to make something thin and flexible, it is pretty thick. Using MXene, the researchers made antennas as thin as 100 nanometers thick — that’s 10% of a micrometer and only 2% of a conventional antenna.

Continue reading “Antennas That You Install With A Spray-Can” →

RTL-SDR Paves Way To Alexa Controlled Blinds

September 27, 2018 by Tom Nardi 11 Comments

You’d be forgiven for occasionally looking at a project, especially one that involves reverse engineering an unknown communication protocol, and thinking it might be out of your league. We’ve all been there. But as more and more of the devices that we use are becoming wireless black boxes, we’re all going to have to get a bit more comfortable with jumping into the deep end from time to time. Luckily, there are no shortage of success stories out there that we can look at for inspiration.

A case in point are the wireless blinds that [Stuart Hinson] decided would be a lot more useful if he could control them with his Amazon Alexa. There’s plenty of documentation on how to get Alexa to do your bidding, so he wasn’t worried about that. The tricky part was commanding the wireless blinds, as all he had to go on was the frequency printed on the back of the remote.

Luckily, in the era of cheap RTL-SDR devices, that’s often all you need. [Stuart] plugged in his receiver and fired up the incredibly handy Universal Radio Hacker. Since he knew the frequency, it was just a matter of tuning in and hitting the button on the remote a couple times to get a good capture. The software then broke it down to the binary sequence the remote was sending out.

Now here’s where [Stuart] lucked out. The manufacturers took the easy way out and didn’t include any sort of security features, or even bother with acknowledging that the signal had been received. All he needed to do was parrot out the binary sequence with a standard 433MHz transmitter hooked up to an ESP8266, and the blinds took the bait. This does mean that anyone close enough can take control of these particular blinds, but that’s a story for another time.

We took a look at the Universal Radio Hacker a year or so back, and it’s good to see it picking up steam. We’ve also covered the ins and outs of creating your own Alexa skills, if you want to get a jump on that side of the project.