Raspberry Pi helps with 2.4GHz home automation

rpi-rf-server

Wanting to extend the capabilities of the radio frequency devices in his home [Kalle Löfgren] turned a Raspberry Pi into an RF control hub. We’ve seen some of his home automation work in the past. In his media room he built a universal remote base station which used the same RF board as in this project. The main difference is that before he went with an AVR microcontroller and this time he’s upgrade to a Raspberry Pi board.

The RPi brings a lot more to the table. Notably, the scripting (whose output is shown above) and networking features. His radio board is an nRF24L01 which he talks to via the SPI protocol. The Raspberry Pi has no problem talking to SPI devices through its GPIO header. [Kalle] just needed to do a bit of setup to configure the pin modes.

A Python script lets him sent commands using his keyboard, but this can also be automated. Combine that with the TCP server script he wrote and it opens up the a wide range of configurations to switch or talk to any device operating on the 2.4 GHz band.

IR Based Augmented Reality

ARUCI

For a final design project, [Frank] and his group took on an augmented reality project. The goal was to make objects interactively controllable by pointing a smartphone at them. Their solution was Augmented Reality Universal Controller and Identifier (ARUCI).

The system locates controllable objects by sensing IR beacons that contain identifiers for each object. The IR is received by a Wiimote sensor, which has been integrated into a custom PCB. This board sits in a 3D printed enclosure, and mounts to the back of a smartphone. The electronics are powered by tapping off of the phone’s battery.

Commands are sent to devices using a custom 2.4 GHz protocol which was implemented using the ATmega128RFA1. Each device has another ATmega to receive the signal and control the real world object. In their demo, the group shows the system controlling devices including a TV, a radio, and an RC car.

The system provides an interesting way to interact with objects, and the hardware integration is quite impressive. After the break, watch [Frank] give a demo.

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Wireless base station eavesdrops on robot communications

wireless-base-station-evesdrops-on-robot-communications

The good [Doctor Iguana] has been working on a pair of robots which communicate with each other using mRF24J40MA wireless transceivers. This presents a challenge in debugging, as he really didn’t have an easy way of monitoring those communications. His solution was to build his own base station which lets him use a computer to monitor what each robot is saying.

He spun his own board for the project. USB connectivity is provided by an FTDI chip, the FT232RL. This converts the USB communications in to serial for the dsPIC33 microcontroller. The FTDI chip comes with a fairly fine-pitch, but the footprint can still be fabricated using toner transfer if you’re fairly familiar with the process. [Dr. Iguana] took some close-up images of the unpopulated board which might make you a little nervous with the soldering iron. The other end of the board hosts the same Microchip wireless module as he used in his robots.

After a bit of rework (noted on the photo labels) he got this up and running. Now he can capture all of the wireless communications and see if problems are due to the sender or the receiver.

Cheap biquad antenna extends LAN between apartments

[Danilo Larizza] is sharing a network connection between a couple of apartments. They are not far apart, but they are also not right next to each other so a set of external antennas is necessary. He built this 2.4 GHz biquad antenna on the cheap (translated) just to test if it improved the signal before he tried to buy a proper antenna. It turns out to work well enough that this is all that he needs.

The antenna itself is about one meter of thick wire bent into two squares which are 31mm on each side. The coaxial cable going to the router connects to the center portion of this antenna. For a bit better directional reception he added some tin foil as a reflector. Since this is outdoors he used a food storage container for protection (the antenna is mounted to the lid, the body has been removed for this picture). The whole things is perched on a stake in a flower pot with proper line of sight to the other antenna.

We’ve seen a very similar design used for an NRF 24L01+ radio. If you need more details that [Danilo] posted that would be a good project to study.

Wireless speaker made using Arduinos and 2.4 GHz tranceivers

[Texane] picked up a 2.4 GHz transmitter/receiver pair for transmitting sensor data wirelessly. After using them in a project he wanted to try pushing them a bit to see what the limits are when it comes to higher bandwidths. He ended up building a wireless speaker that transmits audio at about 90 KB/s. That link leads to a subfolder of his git repository. The code for this project is in the RX and TX folders, with images and video in the DOC folder.

The radio hardware that he’s using is a Nordic nRF24L01P chip which is available on a breakout board from Sparkfun. [Texane] mentioned to us that the chip includes error checking, packet ACK, and automatic retransmission. But these add overhead that can slow things down. The chip does offer the option to disable these features to get lower level access to the hardware. That’s exactly what he did and he mentions that the example code he wrote for the transmitter and receiver make every cycle count. This makes us wonder if it’s the speed of the ATmega328 chip that is the bottleneck, or the transceivers themselves?

Need a quadcopter transmitter? Use a PS2 controller!

After [Pyrofer] built a quadcopter, he purchased a cheap 6-channel transmitter made in China. Unfortunately, that transmitter was terrible so he took an old PS2 controller and built his own.

For his build, [Pyrofer] broke out the analog sticks and wired them to an AVR housed in the handle of the controller. The AVR sent commands to a 2.4 GHz radio transmitter powered by a small LiPo battery. With the addition of a few tact switches behind the shoulder buttons of the controller, [Pyrofer] has four axes of control with a few buttons for changing modes on his quadcopter.

This build really doesn’t hold a candle to some of the awesome DIY RC transmitters we’ve seen, but we’ve got to give [Pyrofer] credit for coming up with a very simple and easy build. Just about everyone has a PS2 or XBox controller lying around, and with a few extra hardware bits it’s easy to bodge up a decent remote control.

[Pyrofer] used a project called Funkenschlag to generate PPM signals, so if you feel the need to replicate this project send it in when you’re done.

Power Index Window Display turns buildings into LED matrices

What started off as a fun project using light bulbs picked up some sponsorship and is going on tour. This project now uses LED modules controlled on the 2.4 GHz band to turn buildings into full color displays. It’s the product of students at Wrocław University of Technology in Poland. The group is something of an extra-curricular club that has been doing this sort of thing for years. But now they’ve picked up some key sponsorships which not only allowed for upgraded hardware, but sent the group on a tour of Universities around Europe. Who would’ve thought you could go on tour with something like this?

Much like the MIT project we looked at in April, this lights up the dark rooms of a grid-like building. It does go well beyond playing Tetris though. The installation sets animations to music, with a custom animation editor so that you can submit your own wares for the next show. Don’t miss the lengthy performance after the break.

[Read more...]

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