Kategorie: Linux

Reading Time: 3 minutes

“The project uses a Raspberry Pi 3B+, a Raspberry Pi Camera [Module], Python, 3D printing, and 576 NeoPixel LEDs to create an interactive art piece that shows you your reflection in ‘low resolution’ by lighting up a grid of LEDs,” says Alex.

In essence, it’s taking your picture using a Raspberry Pi Camera Module, converting it to a low‑resolution picture, and then setting the LEDs to the same colour as the individual pixels in the resulting image. Magic? Yes. Practical? No. Fun? Absolutely.

Make art with LED and Raspberry Pi

Where did such an idea come from, though? “I was inspired by the various ‘analogue mirrors’ made by Daniel Rozin,” Alex reveals.

“The Children’s Museum of Pittsburgh, where I built an exhibit for a Systems Engineer class that I took during graduate school, had one of Mr Rozin’s mirrors on display. The mirror at the Children’s Museum used blocks of wood and servo motors to display images of people who were standing in front of it in low resolution. Ever since then, I’ve been following Daniel’s work, and wanted to build one of his mirrors myself. I thought that such a project would be perfect for my YouTube channel, because it would allow me to put my own twist on the concept while simultaneously teaching people about programming, 3D printing, laser cutting, and more!”

The build itself has an impressive list of components. Alex created a custom prototype PCB, 3D-printed and laser-cut several parts, and connected 24 strips of 24 LEDs to make the magic 576 number. A Raspberry Pi was used to power it due to its size, ability to run Python and address all the LEDs, along with the Raspberry Pi Camera Module which makes it all possible.

On display

With such an unconventional project, you might expect some issues when it was finally unveiled. However, it went down very well.

“The project made its debut at the 2019 Cleveland Maker Faire, where it ran for over eight hours during the event without a single hiccup,” says Alex. “An advantage of being able to run everything via Python code is that I could adjust camera settings on the fly based on lighting conditions in the location where I was at, making sure that the mirror clearly displayed the reflections of visitors throughout the day.

Maker Faire attendees interacted with the mirror and stopped by the Super Make Something booth to learn more about the YouTube channel, Raspberry Pi, and Python programming. “One of my favourite observations I made during this event is that the mirror captured the interest of an audience with a broad age range – people between the ages of 5 and 65 were fascinated by the mirror and enjoyed moving their limbs and making faces in front of it, excited to see what would happen.”

If you’ve not managed to see the mirror in person, all is not lost. Alex has been in discussions to add the mirror to the Great Lakes Science Center, very hopefully with upgrades. Look out for more info on his YouTube channel.

How to make an mirror from LEDs

Reading Time: 6 minutes

Raspberry Shake is a great project for budding geologists and citizen scientists because it’s relatively simple to assemble (although you do need to be careful to handle and level the parts correctly).

Once built, it’s low maintenance, sitting in a quiet part of your home or office, waiting for the earth to move. And all that time, Raspberry Shake is gathering data, which you can investigate using the new web interface – or you can dive in and play around with the data directly.

We interviewed Branden Christensen, CEO of Raspberry Shake and seismologist, back in 2018. You can also find a tutorial in The MagPi issue 60.

In the last two years, Raspberry Shake has come along leaps-and-bounds and it now has a powerful web interface, app interface, and a thriving international community. We think it’s time to revisit Raspberry Shake.

This month we’re looking at assembling Raspberry Shake and sharing your data with the wider Shake community.

You can buy all the parts for Raspberry Shake separately (see the ‘You’ll Need’ info) or pick up a turnkey system with all the parts included. You can even buy a fully assembled system, but we think that takes all the fun out of things.

You’ll Need

Step 01: Wire up the geophone

Start by wiring up the RGI-4.5Hz geophone. Ours has two wires: grey and blue. Make sure the wires are twisted and connect the grey cable from the positive ‘+’ connection on the geophone to the ‘+’ pin on the RS1D Raspberry Shake board. Next, connect the blue wire to the ‘-’ connection. Take care not not over-tighten the screws, otherwise you may damage the wires.

Step 02: Put Raspberry Pi in the enclosure

Take the bottom of the enclosure and attach the four shorter stand-offs. Tighten them by hand. Place your Raspberry Pi board on top of the four stand-offs using the holes in the Raspberry Pi.

On top of three of the holes, you need to place a washer and the longer stand-offs (the hole in the middle has just a washer and screw). Take a look at the assembled Raspberry Shake (Figure 1) to see which one doesn’t need the large stand-off. Now insert your microSD card. If you bought it from Raspberry Shake, it will be pre-installed with Raspberry Shake software. Otherwise, flash a card with the image file.

Step 03: Attach the geophone

Place the geophone in the hole on the bottom of the enclosure with the wires on the top. Separate the two wires so there is a gap between them. Now place the plastic strap on top of the geophone to hold it in place. Use two washers and two screws to fix the clear plastic strap to the bottom of the enclosure.

Step 04: Attach Raspberry Shake

Connect the RS1D Raspberry Shake board to Raspberry Pi’s GPIO pins. The board has only a 26-pin header (like the original Raspberry Pi Model A and B); most Raspberry Pi boards have 40-pin GPIO, so you’ll need to make sure you are connecting the RS1D Raspberry Shake to the correct pins. The board connects to the end of the GPIO pins where the microSD card is (leaving those pins towards the USB sockets free).

Make sure the Raspberry Shake board orientation is correct (the wires to the geophone should be near to the USB ports). If in doubt, take a close look at Figure 1 below.

Now clip in the sides of the enclosure. Look carefully at the holes in each side: the small hole is for the microSD card, the medium hole is for the HDMI port and power, and the large hole is for the Ethernet and USB sockets.

The lid of the enclosure has three holes in it, which will line up with the long stand-offs (from Step 02). Use three screws to hold the lid in place. It’s recommended to ensure the Raspberry Pi Shake is fully enclosed to prevent any wandering of the results.

Step 05: Levelling Raspberry Shake

The Raspberry Shake enclosure comes with three holes protruding from the sides. These are used to level the device with the levelling feet. If you bought an official enclosure, it will come with a small spirit level on the base. Use a screwdriver with the levelling feet to ensure that the bubble in the spirit level is inside the black circle.

Step 06: Position the Raspberry Shake

The device is designed to be left running 24 hours a day, monitoring for earth tremors. So you’ll want to find somewhere out of the way. With the Raspberry Pi 3B included in the kit, you should use an Ethernet connection to the router, to avoid possible wireless LAN interference to the geophone (this is not an issue if using a Raspberry Pi Zero or 3B+).

You’ll need to run an Ethernet wire directly from Raspberry Shake to your router. We used Devolo DLAN Powerline adapters to extend our Ethernet connection across the electrical wiring. We positioned our Raspberry Shake in the conservatory to the rear of our home.

According to the makers of Shake: “For best results, install your Raspberry Shake on a bare floor (no carpet) and not on top of your desk. A good location for the Shake would likely be on the concrete slab of the lowest floor, near a foundation wall and away from furnaces, washing machines, air conditioners, and such.”

Step 07: Power up

With Raspberry Shake in position and connected to your router, use the power adapter to turn on Raspberry Pi. A blue light will appear on top of the Raspberry Shake board. You don’t access Raspberry Pi directly with a keyboard and screen – instead, it is set up for remote connection over your network. Open a web browser from another computer on the network, and go http://rs.local (don’t forget the ‘http://’ part. (Note that ‘rs.local’ replaces the former ‘raspberryshake.local’)). You will see the Raspberry Shake web interface.

Step 08: Change SSH and setup

The default SSH username and password are ‘myshake’ and ‘shakeme’. Default SSH passwords are a security risk, so we’re going to change it. Click the Actions icon near the top of the interface, then click on the Actions tab. Now click Change SSH Password. Enter the current password ‘shakeme’ and then your new password. Press ENTER to save the new password.

See ‘Ready, Set, Get Hacked!’ on the Raspberry Shake website for more information on security.

Step 09: Join the team

With your Raspberry Shake password changed, you can turn on data sharing and join the Raspberry Shake community. This enables you to share your data with the citizen science project.

Click Home and Settings. Fill out your details in the General section and click Set Location. The location data is randomised by a couple of hundred yards to preserve privacy.

Finally, enter the floor that the device is on – this is zero-indexed, so 0 is the ground floor – and how many floors you have in the house.

Now click the Data tab and tick the box marked ‘Forward Data’. Read the licensing information and click Save and Restart. Raspberry Shake will restart (you may be prompted to enter your new SSH password from Step 08).

Step 10: Earthquake and Station View

Now that you’re part of the wider Raspberry Shake community, it’s time to take a look at earthquake activity around the world. Click Raspberry Shake Earthquake View to see a global map. The circles indicate earthquake activity. The colour of the circle corresponds to its depth, with red circles showing it’s closer to the Earth’s surface. The size of the circle indicates its severity. Click on any circle to see more information.

If you want to see all the Raspberry Shake devices (including your own), make a note of your station number and click on the Station View icon. Here you will see all the devices running in the world. Click any device to view its data.

Reading Time: 3 minutes

Warning! Electricity & water: Take extra care when combining electricity and water in a project: the two should be kept well apart!

Pump it up

A pump pushes water from a reservoir (children’s paddling pool) through PVC piping attached to water solenoids connected to sprinkler tubing pointed up in the air. A Raspberry Pi controls the solenoids, creating the effect of water jetting out in sync with the music being played.

“A total of eight solenoids were connected back to a mechanical relay, which in turn was controlled by Raspberry Pi,” says Nick. Seven out of the eight solenoids were connected to brass reducers to fit into garden sprinkler tubing. The eighth solenoid was a pressure control (relief) valve, which was used to control back pressure in the system.

“When I wanted to ‘fire’ one of the seven solenoids to shoot water, Raspberry Pi would close the pressure solenoid,” explains Nick. This built up pressure in the PVC pipe, at which time Raspberry Pi would trigger a relay to open the desired solenoid so a jet of water would shoot out. “This was required to get any distance with very little water. I also didn’t want to burn out the pump, so the relief valve was open when no other solenoid was open.”

Water music

The music is synchronised to the solenoid firing by using FFT (fast Fourier transform) analysis performed on the audio in real-time. “I wrote a sequencer in Python to perform the analysis and determine which solenoids to turn on and off, based on a config file which maps high fidelity signals (bass, mid-range, etc.) to particular solenoids or solenoid groups,” says Nick. “In summary, you just put WAV files in a songs directory and start the Python code, which did all the heavy lifting in real-time.”

One technical challenge was solving the timing discrepancy between the solenoid firing water and the musical note being heard by the audience. “The water had to be shot out of the jets approximately 600 ms ahead of the audio for the water to appear to be in sync with the music.”

Another issue was safety, as mixing water and electricity can be hazardous. “The power for the system was a 12 V automotive battery,” reveals Nick, “so I used fuses to protect things, just as you would find in a family vehicle. I also tried to keep the dangerous gear out of reach of the general public.”

Everything went well on the day, albeit with a few bugs: “There were certain sequences of musical notes where the FFT analysis would produce changes too rapidly for the back pressure and corresponding solenoid firing to produce much of a water jetting effect.” The result was a variance in water height from song to song.

“I rode on the float during the parade, so the public reaction was the most rewarding part of the project for me,” he adds. “After people figured out what they were looking at, the responses ranged from laughter to astonishment. The public response made my day and all the efforts of the team worthwhile!”

Reading Time: < 1 minute

Save 37% off the cover price with a subscription to The MagPi magazine. Try three issues for just £5, then pay £25 every six issues. You’ll save money and get a regular supply of in-depth reviews, features, guides and other PC enthusiast goodness delivered directly to your door every month.

Subscribe

Reading Time: 5 minutes

Magic mirrors have to be one of the most popular projects out there. Initially created by combining old laptops and semi-reflective observation glass, they appear as normal mirrors but with text and images that appear to float in mid-air. The information displayed is typically what you need as you’re preparing to leave the house: weather, news headlines, and transit information. Although they come across as advanced builds, the community behind the projects have made significant advances in making magic mirrors accessible to all. Let’s take a look at one of these makers and then have a go at building our own mirror.

Creating a good magic mirror requires experience in many disciplines including carpentry, electronics, programming, and graphic design. Fortunately, the team at MagicMirror2, headed by Michael Teeuw (see The MagPi issue 54), have not only compiled tutorials and fostered a great community, they’ve also built their own open-source application. This modular system takes away all the programming and design pain. Best of all, you can expand the capabilities of your mirror through the hundreds of community plug-ins available and, if you wish, you can write your own. It’s no wonder it won the number one slot in our best projects feature for The MagPi issue 50.

Assembling a simple magic mirror

Would you like a magic mirror, but don’t fancy all that carpentry? Here’s a first project to ease you in without having to reach for the band-saw

To build a magic mirror, you’ll need:

Tip! Not for Raspberry Pi Zero

A Raspberry Pi Zero would seem ideal for this project, but MagicMirror2 is incompatible with that model and the original Raspberry Pi 1.

There have been some impressive magic mirror projects as makers around the globe challenge each other to improve on previous designs. Although the results are undoubtedly impressive, it can make the hobby look a little daunting to the beginner, especially if you don’t have access to the necessary equipment to build a custom frame. In this tutorial, we’ll assemble a simple magic mirror using off-the-shelf parts. This can be built in an afternoon and is a great way to find out whether you want to take it to the next step and get working on something a bit bigger.

Prepare the frame

To create our magic mirror, we will create a ‘sandwich’ of the frame, a piece of observation mirror acrylic, and the screen. It’s vital that all these are kept as clean as possible during assembly as any dust will get trapped and leave an irritating mark on your lovely mirror. Unpack the frame, remove the mount, and then remove the plastic clear sheet. You’ll need to carefully peel back the two protective layers and then replace the clear sheet in the frame. This is statically charged and will start to attract dust, so lots of cleaning is required. Return the mount to the frame.

Mount the mirror

The big ‘trick’ of a magic mirror is the use of two-way material, also known as ‘observation glass’. This material is the same that is used in police interview rooms and as privacy screening. It’s only semi-reflective, so the output from your screen can be seen ‘through’ the glass but it’s still effective as a mirror (if a little darker than a regular mirror). This material is cheapest when bought by the roll, so it’s ideal for custom-build or larger mirror projects. Ours is a £5 A5 acrylic sheet. Remove the protective sheeting and place in the frame, making sure it covers the open area. Secure with sticky tape.

Add the screen

We’re using the official 7-inch touchscreen for this project to make power requirements easier; we only need one cable to drive both Raspberry Pi and the display. It also happens to be a perfect size for this project. The touchscreen needs to be carefully placed so it’s in parallel with the frame and central. Secure with sticky tape.

Secure in place

The combined weight of a Raspberry Pi computer and the touchscreen doesn’t come to much, so rather than getting into complicated mounting solutions, we will apply generous amounts of gaffer (or duct) tape to hold everything in place. This is of course a very lo-fi solution – if you want to go for something more refined, you can consider making use of the mounting points on the screen that can be used with horizontal or vertical bars to attach to the inner edge of the frame. Check for any trapped dust or marks in our ‘sandwich’ before proceeding.

Just add Raspberry Pi

Normally, you would mount a Raspberry Pi computer on top of the screen’s PCB on the provided standoffs. If you want to mount your completed mirror on the wall, this poses a problem, as the computer now sits quite a way proud of the frame. Your options are: 1) don’t care (not advisable), 2) buy a second frame and fix it to the original to double its depth, or 3) mount the Raspberry Pi computer on the side. We’ve gone with option three and it just fits, even with the supplied display cable. Make sure you line the back of the screen with insulation tape to avoid any electrical shorts and secure in place with a Velcro pad to allow for future access to the microSD card.

Check and test

With a microSD card with Raspbian installed, mount the Raspberry Pi 4 into place. Check the display ribbon cable hasn’t been stretched too much and the four jumper cables that connect the display to the GPIO are in the correct position. You should now be able to boot and see the Raspbian boot sequence through the display. It will probably look disappointingly dull. Don’t worry, we’ll address that in the next tutorial. If everything is free of dust, secured, and the display is working, shut everything down (you may need to connect a keyboard and mouse to do this).

Professional magic mirror builds

We’ve created a simple project for you here that requires no cutting or mains electricity. However, it would be remiss of us not to admire the work of those who have dedicated hours and hours to making the ultimate magic mirror. One of those is MagicMirror2 creator Michael Teeuw, who has created several mirrors completely from scratch, building his own frames and carefully mounting large monitors – all powered by Raspberry Pi computers, of course! The great thing about magic mirrors is you can start small and work up to masterpieces like this, learning as you go.