Wireless sensor networks are nothing new to Hackaday, but [Felix]’s wireless PIR sensor node is something else entirely. Rarely do we see something so well put together that’s also so well designed for mass production.
For his sensor, [Felix] is using a Moteino, a very tiny Arduino compatible board with solder pads for an RFM12B and RFM69 radio transceivers. These very inexpensive radios – about $4 each – are able to transmit about half a kilometer at 38.4 kbps, an impressive amount of bandwidth and an exceptional range for a very inexpensive system.
The important bit on this wireless sensor, the PIR sensor, connects with three pins – power, ground, and out. When the PIR sensor sees something it transmits a code the base station where the ‘motion’ alert message is displayed.
The entire device is powered by a 9V battery and stuffed inside a beautiful acrylic case. With everything, each sensor node should cost about $15; very cheap for something that if built by a proper security system company would cost much, much more.
Getting a device on the internet is great – but what if you want to monitor multiple wireless sensors? The [WickedDevice] crew have been publishing a tutorial series focusing on just that. Their weapon of choice is the Nanode, an Arduino based wireless sensor system we’ve seen a few times in the past. So far the first and second parts have been posted up. Part one starts with an explanation of the Arduino and Nanode platform, and takes us through connecting the Nanode to a wireless temperature sensor. Part two walks through the hardware and code changes to add multiple wireless sensors to the system. Part three will focus on getting the entire network up on the internet, and piping data onto the Xively data hosting site.
This tutorial does begin a bit on the basic side, covering the installation of the Arduino software environment. This may seem a bit simplistic for some of our readers, but we think this type of tutorial is necessary. It helps ‘newbies’ get started down what could otherwise be a difficult path. For more advanced readers, it’s easier to skip past steps you already know than it is to try to hunt down information that isn’t there.
nRF24L01+ modules like the one shown above are a great way to send data wirelessly between your projects. They can be found on many websites for less than $1.50
a piece and many libraries exist for them. After having thoroughly looked at the Bluetooth Low Energy (BLE) specifications, [Dimitry] managed to find a way to broadcast BLE data with an nRF24L01+.
Luckily enough, BLE and nRF24L01+ data packets have the same preambles. However, the latter can’t send more than 32bytes in a packet and can’t hop between frequencies as fast as the BLE specification wants. [Dimitry] found the solution when he discovered that he could send unsolicited advertisements on three specific channels. In the end, considering the 32 bytes the nRF24L01+ can send, you’ll need to use 3 bytes for the CRC, 2 for the packet header, 6 for the MAC address and 5 for devices attributes. This leaves us with 16 bytes of pure data or 14 bytes to split between data and name if you want your project to have one.
When we hear reports of radioactive water leaking into the ocean from the [Fukushima Dai-Ichi] plant in Japan we literally have to keep ourselves from grinding our teeth. Surly the world contains enough brain power to overcome these hazards. Instead of letting it gnaw at him, [Akiba] is directing his skills at one solution that could help with the issue. There are a number of storage tanks on site which hold radioactive water and are prone to leaking. After hearing that they are checked manually each day, with no automated level monitoring, he got to work. Above is the wireless non-contact tank level sensor rig he built to test out his idea.
A couple of things made this a quick project for him. First off, he just happened to have a MaxSonar MB7389 waterproof sonar sensor on hand. Think of this as a really fancy PING sensor that is water tight and can measure distance up to five meters. [Akiba’s] assumption is that the tanks have a hatch at the top into which this sensor would be positioned. The box next to it contains a Freakduino of his own design which includes hardware for wireless communications at 900 MHz. This is the same hardware he used for that wireless toilet monitor.
We really like seeing hacker solutions to environmental problems. A prime example is some of the cleanup hacks we saw around the time of the BP Gulf of Mexico oil spill.
If you want to mess around with your Xbox 360 controllers on a computer Microsoft would be happy to sell you a USB dongle to do so. But [Tino] went a different route. The board that drives the Xbox 360’s status light ring also includes the RF module that wirelessly connects the controllers. He wired this up to his Raspberry Pi using the GPIO header.
The module connects via an internal cable and is treated much like a USB device by the Xbox motherboard. The problem is that it won’t actually handle the 5V rail found on a USB connector; it wants 3.3V. But this is no problem for the RPi’s pin header. Once a few connections have been made the lights are controlled via
SPI I2C and [Tino] posted some example code up on Github to work with the RF module. He plans to post a follow-up that interfaces the module with a simple microcontroller rather than an RPi board. If you can’t wait for that we’re sure you can figure out the details you need by digging through his example code.
Linux users now have a simple option for controlling the Modlet smart outlet. Hacklet is a Ruby script that can switch and read status information from Modlet.
This is the first we remember hearing about Modlet. It’s another take on controlling your appliances remotely. Unlike WeMo, which puts control of one outlet on WiFi, the Modlet uses a USB dongle to control two outlets wirelessly. It has the additional benefit of reading how much current is being used by each plug. This does mean that you need a running computer with the USB dongle to control it. But cheap embedded systems like the Raspberry Pi make this less of an issue both in up-front cost, and the price to keep it running all the time.
[Matt Colyer’s] demo video includes an unboxing of the $60 starter kit. The screen seen above shows his script pairing with the outlet. It goes on to demonstrate commands to switch it, and to pull the data from the device. He even provides an example of how to use IFTTT with the script.
Continue reading “Hacklet adds Linux control for the Modlet smart outlet”
Like all good tinkerers, [Andrew] decided to figure out how his wireless security system worked. Yes, it’s an exercise in reverse engineering, and one of the best we’ve seen to date.
After breaking out the handheld spectrum analyzer and TV tuner SDR, [Andrew] cracked open a few devices and had a gander at the circuit boards. The keypad, PIR sensor, and base station all used a TI radio chip – the CC11xx series – that uses SPI to communicate with a microcontroller.
Attaching a logic analyzer directly to the radio chip and reading the bits directly, [Andrew] started getting some very good, if hard to understand data. From the security system specs, he knew it used a ’20-bit code’, but the packets he was reading off the SPI bus were 48 bits long. The part of this code was probably the system’s address, but how exactly does the system read its sensors?
The easiest way to figure this out was to toggle a few of the sensors and look at the data being transmitted. With a good bit of reasoning, [Andrew] figured out how the alarm system’s code worked. This theory was tested by connecting one of the radios up to an Arduino and having his suspicions confirmed.
While [Andrew]’s adventure in reverse engineering is only a benefit for people with this model of security system, it’s a wonderful insight into how to tear things apart and understand them.