Raspberry Pi as 433 MHz to MQTT Gateway

Many low-cost wireless temperature and humidity sensors use a 433 MHz transmitter to send data back to their base stations. This is a great choice for the manufacturer of said devices because it’s simple and the radios are cheap, but it does limit what we as the consumer can do with it a bit. Generally speaking, you won’t be reading data from these sensors on your computer unless you’ve got an SDR device and some experience with GNU Radio and reading the Nexus protocol.

But [Aquaticus] has developed a very comprehensive piece of software that should make integrating these type of sensors into your home automation system much easier, as long as you’ve got a spare Raspberry Pi lying around. Called nexus433, it uses a cheap 433 MHz receiver connected to the Pi’s GPIO pins to receive data from environmental sensors using the popular Nexus communication protocol. A few known compatible sensors are listed in the project documentation, one of which can be had for as little as $5 USD shipped.

In addition to publishing the temperature, humidity, and battery level values from the sensors to MQTT, it even tracks connection quality for each individual sensor and when they go on and offline. To be sure, this is no simple hack. In nexus433, [Aquaticus] has created a mature Linux service with enough flexibility that you shouldn’t have any problems working it into your automation setup, whether it’s Home Assistant or something you’ve put together yourself.

We’ve seen a number of home automation hacks using these ubiquitous 433 MHz radios,  from controlling them with an ESP8266 to hacking a popular TP-LINK router into a low-cost home automation hub.

Speaking the Same Language as a Wireless Thermometer

Temperature is a delicate thing. Our bodies have acclimated to a tight comfort band, so it is no wonder that we want to measure and control it accurately. Plus, heating and cooling are expensive. Measuring a single point in a dwelling may not be enough, especially if there are multiple controlled environments like a terrarium, pet enclosure, food storage, or just the garage in case the car needs to warm up. [Tim Leland] wanted to monitor commercially available sensors in several rooms of his house to track and send alerts.

The sensors of choice in this project are weather resistant and linked in his project page. Instead of connecting them to a black box, they are linked to a Raspberry Pi so your elaborate home automation schemes can commence. [Tim] learned how to speak the thermometer’s language from [Ray] who posted about it a few years ago.

The system worked well, but range from the receiver was only 10 feet. Thanks to some suggestions from his comments section, [Tim] switched the original 433MHz receiver for a superheterodyne version. Now the sensors can be a hundred feet from the hub. The upgraded receiver is also linked on his page.

We’ve delved into thermocouple reading recently, and we’ve featured [Tim Leland] and his 433MHz radios before.

Gamify Your Workout with this Wearable Console Controller

‘Tis soon to be the season when resolutions falter and exercise equipment purchased with the best of intentions is cast aside in frustration. But with a little motivation, like making your exercise machine a game console controller, you can maximize your exercise gear investment and get in some guilt-free gaming to boot.

Honestly, there is no better motivation for keeping up with exercise than taking classes, but not many people have the discipline — or the pocketbook — to keep going to the gym for the long haul. With this in mind, [Jason] looked for a way to control PS4  games like Mario Karts or TrackMania with his recumbent bike. In an attempt to avoid modifying the bike, [Jason] decided on a wearable motion sensor for his ankle. Consisting of an Uno, an MPU9250 accelerometer, and a transmitter for the 433-MHz ISM band, the wearable sends signals to a receiver whenever the feet are moving. This simulates pressing the up arrow controller key to set the game into action. Steering and other game actions are handled by a regular controller; we’d love to see this expanded to include strain gauges on the recumbent bike’s handles to allow left-right control by shifting weight in the seat. Talk about immersive gameplay!

While we like the simplicity of [Jason]’s build and the positive reinforcement it provides, it’s far from the first exercise machine hack we’ve seen. From making Google Street View bike-controlled to automatically logging workouts, exercise machines are ripe for the hacking.

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Attack Some Wireless Devices With A Raspberry Pi And An RTL-SDR

If you own one of the ubiquitous RTL-SDR software defined radio receivers derived from a USB digital TV receiver, one of the first things you may have done with it was to snoop on wide frequency bands using the waterfall view present in most SDR software. Since the VHF and UHF bands the RTL covers are sometimes a little devoid of signals, chances are you homed in upon one of the ISM bands as used by plenty of inexpensive wireless devices for all sorts of mundane control tasks. Unless you reside in the depths of the wilderness, ISM band sniffing will show a continuous procession of chirps; short bursts of digital data. It is surprising, the number of radio-controlled devices you weren’t aware were in your surroundings.

Some of these devices, such as car security keys, are protected by rolling encryption schemes to deter would-be attackers. But many of the more harmless devices simply send a command in the open without the barest of encryption. The folks at RTL-SDR.com put up a guide to recording these open data bursts on a Raspberry Pi and playing them back by transmitting them from the Pi itself.

It’s not the most refined of attack because all it does is take the recorded file and retransmit it with the [F5OEO] RPiTX software. But they do demonstrate it in action with a wireless lightbulb, a door bell, a wireless relay, and a remote-controlled switched socket. Since the data in question is transmitted as OOK, or on-off keying, the RPiTX AM mode stands in for the transmitter.

You can see it in action in the video below the break. Now, have you investigated the ISM band chirps in your locality?

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Long Range Wireless Internet

While most of you reading this have broadband in your home, there are still vast areas with little access to the Internet. Ham radio operator [emmynet] found himself in just such a situation recently, and needed to get a wireless connection over 1 km from his home. WiFi wouldn’t get the job done, so he turned to a 433 MHz serial link instead. (Alternate link)

[emmynet] used an inexpensive telemetry kit that operates in a frequency that travels long distances much more easily than WiFi can travel. The key here isn’t in the hardware, however, but in the software. He went old-school, implemending peer-to-peer TCP/IP connection using SLIP — serial line Internet protocol. All of the commands to set up the link are available on his project page. With higher gain antennas than came with the telemetry kit, a range much greater than 1 km could be achieved as well.

[Editor’s note: This is how we all got Internet, over phone lines, back in the early Nineties. Also, you kids get off my lawn! But also, seriously, SLIP is a good tool to have in your toolbox, especially for low-power devices where WiFi would burn up your batteries.]

While it didn’t suit [emmynet]’s needs, it is possible to achieve extremely long range with WiFi itself. However this generally requires directional antennas with very high gain and might not be as reliable as a lower-frequency connection. On the other hand, a WiFi link will (in theory) get a greater throughput, so it all depends on what your needs are. Also, be aware that using these frequencies outside of their intended use might require an amateur radio license.

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Radio Decoding Swiss Army Knife in a NES Controller

If you wanted to name a few things that hackers love, you couldn’t go wrong by listing off vintage console controllers, the ESP system-on-chip platform, and pocket tools for signal capture and analysis. Combine all of these, and you get the ESP32Thang.

At its heart, the ESP32Thang is based around a simple concept – take an ESP32, wire up a bunch of interesting sensors and modules, add an LCD, and cram it all in a NES controller which helpfully provides some buttons for input. [Mighty Breadboard] shows off the device’s basic functionality by using an RFM69HW module to allow the recording and replay of simple OOK signals on the 433 MHz band. This is a band typically used by all sorts of unlicenced radio gear – think home IoT devices, wireless doorbells and the like. If you want to debug these systems when you’re out and about, this is the tool for you.

This is a fairly straightforward build at the lower end of complexity, but it gets the job done with style. The next natural step up is a Raspberry Pi with a full software defined radio attached, built into a Nintendo DS. If you build one, be sure to let us know. This project might serve as some inspiration.

With the wide availability of SPI and I2C modules these days, combined with the ease of programming provided by the Arduino environment, this is a project that just about any hacker could tackle after passing the blinking LED stage. The fact that integrating such hardware is so simple these days is truly a testament to the fact that we are standing on the shoulders of giants.

Dumbing Down a Smart Switch

Internet of Everything is the way to go for home automation these days. ITEAD makes an ESP-8266 switch that IoT-ifies your appliances. If you still have an ancient, 433 MHz style radio switch system, they even make one that does WiFi and 433 MHz. But if you’re too cheap to shell out for the dual-mode version, you can always add a $1 433 MHz radio yourself. Or at least, that’s what [Tinkerman] did.

IMG_20160522_163814x_thumbnailAside from the teardown and reverse-engineering of the WiFi-enabled switch, [Tinkerman] also flashed custom firmware into the switch’s ESP-8266, and worked it all into his existing home Node-RED framework. Now he’s got more possible ways to turn on his living-room lights than any person could possibly hope for!

If you want to get into this whole WiFi-based home automation game, you could do worse than to have a look at the series we ran on MQTT just a little while ago. Seeing [Tinkerman]’s Node-RED demo makes us think that we’ll have to give that a look for our home system as well.