Wireless networks have been reduced to a component, for most of us. We fit a device, maybe an ESP8266 module or similar, and as if by magic a network exists. The underlying technology has been abstracted into the firmware of the device, and we never encounter it directly. This is no bad thing, because using wireless communication without having to worry about its mechanics gives us the freedom to get on with the rest of our work.
It is however interesting once in a while to take a look at the operation of a real wireless network, and [Alex Wong], [Brian Clark], and [Raghava Kumar] have given us a project with the opportunity to do just that. Their PIC Mesh university project is a distributed wireless mesh network using 2.4GHz NRF24L01 transceiver modules and PIC32 microcontrollers. They have it configured for demonstration purposes with a home automation system at the application layer, however it could be applied to many other applications.
The real value in this project is in its comprehensive but easy to read write-up of the kind you’d expect from a university project. The front page linked above has an overview of how the mesh works, but there are also pages taking us through the hardware, the networking software layer, and the home automation application layer. If you have ever wanted to understand a simple mesh networking system, this is a good place to start.
[Markus Gritsch] and his son had a fun Sunday putting together a little toy airboat from a kit. They fired it up and it occurred to [Markus] that it was pretty lame. It went forward and sometimes sideward when a stray current influenced its trajectory, but it had no will of its own.
The boat was extracted from water before it could wander off and find itself lost forever. [Markus] did a mental inventory of his hacker bench and decided this was a quickly rectified design shortcoming. He applied a cheap knock-off arduino, equally cheap nRF24L01+ chip of dubious parentage, and their equivalent hobby servo to the problem.
Some quick coding later, assisted by prior work from other RC enthusiasts, the little boat was significantly upgraded. Now the boat could be brought back to shore using any R/C controller that supported the, “Bayang,” protocol. He wouldn’t have to face the future in which he’d have to explain to his son that the boat, like treacherous helium balloons, was just gone. Video after the break.
To tackle the difficulty of discriminating between the different sounds from different sources, [Alex’s] wants to attach little sound sensors directly to the sound emitting devices. The sensors wirelessly communicate with the wristband. If the wristband receives a trigger signal from one of the sensors, it alerts the wearer by vibrating. It also shows which device triggered the alert by flashing an RGB LED in a certain color. A first breadboard prototype of his idea confirmed the feasibility of the concept.
After solving a few minor problems with the sensitivity of the sensors, [Alex] now has a working prototype. The wristband features a pager motor and is controlled by an ATMEGA168. Two NRF24L01+ 2.4 GHz wireless transceiver modules take care of the communication. The sound sensors run on the smaller ATTiny85 and use a piezo disc as microphone. Check out the video below, where Alex demonstrates his build:
A robot to explore the unknown and automate tomorrow’s tasks and the ones after them needs to be extremely versatile. Ideally, it was capable of being any size, any shape, and any functionality, shapeless like water, flexible and smart. For his Hackaday Prize entry, [Alberto] is building such a modular, self-reconfiguring robot: Dtto.
To achieve the highest possible reconfigurability, [Alberto’s] robot is designed to be the building block of a larger, mechanical organism. Inspired by the similar MTRAN III, individual robots feature two actuated hinges that give them flexibility and the ability to move on their own. A coupling mechanism on both ends of the robot allows the little crawlers to self-assemble in various configurations and carry out complex tasks together. They can chain together to form a snake, turn into a wheel and even become four (or more) legged walkers. With six coupling faces on each robot, that allow for connections in four orientations, virtually any topology is possible.
Each robot contains two strong servos for the hinges and three smaller ones for the coupling mechanism. Alignment magnets help the robots to index against each other before a latch locks them in place. The clever mechanism doubles as an ejector, so connections can be undone against the force of the alignment magnets. Most of the electronics, including an Arduino Nano, a Bluetooth and a NRF24L01+ module, are densely mounted inside one end of the robot, while the other end can be used to add additional features, such as a camera module, an accelerometer and more. The following video shows four Dtto robots in a snake configuration crawling through a tube.
While faking BLE advertising beacons using an nRF24L01+ module is nothing new, it’s become a heck of a lot easier now that [Pranav Gulati] has written some library code and a few examples for it.
[Pranav]’s work is based on [Dmitry Grinberg]’s epic bit-banging BLE research that we featured way back in 2013. And while the advertisement channel in BLE is limited in the amount of data it can send, a $1 nRF24 module and a power-thrifty microcontroller would be great for a battery-powered device that needs to send small amount of data infrequently for a really long time.
We’re not 100% sure where [Pranav] is going to take this project. Honestly, the library looks like it’s ready to use right now. If you’ve been holding off on making your own BLE-enabled flock of birds, or even if you just want to mess around with the protocol, your life has gotten a lot easier.
nRF24L01+ PA/LNA module specs look great on paper. Wireless communication up to 1000m in a small package readily available from a variety of cheap sources in China? The hard work of software connectivity already done by a variety of open source projects? Sounds great! But if you mashed BUY and are getting maybe 1% of that range, don’t worry because thanks to these clear directions, they can be fixed.
[Oitzu] in Germany wrote in to let us know about a series of short but very informative blog posts in which he describes building a series of solar-powered, networked birdhouses with the purpose of spying on the life that goes on within them. He made just one at first, then expanded to a small network of them. They work wonderfully, and [Oitzu]’s documentation will be a big help to anyone looking to implement any of the same elements – which include a Raspberry Pi in one unit as a main gateway, multiple remote units in other birdhouses taking pictures and sending those to the Pi over an nRF24L01+ based radio network, and having the Pi manage uploading those images using access to the mobile network. All with solar power.