Magnets4you

1. The bending control was provided by a magnetic field from a 1 mm × 1 mm neodymium magnet of maximum energy product of BH max 342–358 kJ/m 3 (Magnet-shop SM-01x01-N, grade N45, pull force 25 g, Magnets4you GmbH, Lohr a.
2. Please email me at rhonda@magnets4you.com with location, specifics and asking price. From Wood, 10:27 PM. Looking for Lexington Regency.

In today's magnet application, we present you an alternative to wall decoration; a bottle cap wall.
This magnet application comes from one of our employees today.

Bottle cap wall

In his previous job as a bartender, he collected an enormous number of bottle caps.
These colorfully mixed bottle caps gave him the idea to equip his living room wall with them.

The implementation:

Our self-adhesive magnetic film – can be trimmt to size with a thickness of 1 mm – was used here.
Our employee decided not to stick the film on. He nailed it directly to the wall.
Alternatively, you can use the Magnetic foil, self-adhesive on one side, width 610 x 1.0 mm x meter.
Please keep in mind; this film is stored and sold on rolls. At the beginning, this can curl up again.

The bottle caps adhere to the magnetic foil by themselves. The use of an adhesive or magnet is not necessary here.

Magnets4you GmbH, Bgm.-Dr.-Nebel-Str. 15a, 97816 Lohr a. Main +49 9352-604386-0 +49 9352-604386-20. Bottle cap wall.

Countless projects can be implemented with bottle caps. Equipping a complete living room wall with it is also an absolute novelty for us.

There was absolutely no limit to creativity. Visually, this wall became an absolute eye-catcher in his living room.
The effort that was made here was very great. Attaching each individual bottle cap took a lot of time and took several days.

We would like to praise and share the result of this arduous work with you.

A very original idea!

Many thanks to our employee for this great application.

Project, result, summary

Mainly inspired by Michael K. Castor awesome PiPad project, I built a homemade tablet. It is powered by a Raspberry Pi (model B), connected to a 10 inch touch screen by ChalkElec. The main technical difficulties are: building an enclosure strong enough to hold the board, yet light enough that it is still portable, and sending power to the electronic boards (it takes lots of soldering).

I have since then updated the tablet into a Mark 2, with a different architecture (PixelQi screen, Raspberry Pi 1B+, new enclosure).

The final product looks like this:

Inside

What does it look like inside?

How do you do it?

• Making the hardware work (that's the easy bit)
• Carry electric power to the different boards (trickier)
• Making an enclosure (trickier)
• Making sure everything fits inside the box

The hardware

The electronic hardware itself is the easiest part: connect the screen to the video converter, plug the video converter into the HDMI port of the Raspberry Pi, connect the input from the touchscreen to a USB port, and you're set.

Now, the real problem is to send electricity to the different parts.

Magnets 4 Media

Carrying electricity

To power the tablet, you need an external battery. And you need to transport electricity from the battery to a power button, and from the power button to the different boards: the Pi itself, the video converter and the USB hub.

Once you're done, you connect all these to your power button:

(to power the USB hub, I just cut its original cable)Now, all should be working together, and you can check by booting the Pi.

The enclosure

Magnets4you Shop

There are several methods to build the enclosure: Michael K. Castor used Birch Plywood with a CNC machine. Harrison Holbrook used a 3D printer. I only had access to a laser cutter, so I used that.

I cut three layers in a plate of 8mm of plexiglas, giving a total height of 2.4 cm (roughly an inch):

The hole at the bottom left is for the light sensor from the screen. It is slightly larger in diameter for the bottom two layers, because the sensor is larger at the bottom. All layers are available as Adobe Illustrator files.

I changed a few things with Michael design, because I wanted to reduce the amount of soldering (not my area of expertise). So the audio out (blue square) goes directly out of the enclosure. That means I had to remove the RCA out (yellow square next to it, visible in earlier pictures) because you can't have two holes next to each other. I also decided I didn't need the GPIO out (one less hole to drill).

Once you've done all that, you place the three layers together, and you drill your biggest hole yet: the 16mm hole for the power button. That's the scary part.Finally, I added rare-earth magnets all around the enclosure to stick the top layer (with the screen glued to it) to the bottom of the case.

Making sure everything fits

Even with careful design, 3D CAD software and (in my case) a cardboard mockup, things are a bit tight inside the enclosure. To make things worse, the touch screen reacts strangely to pressure on its back, so anything above the height limit has to go.

If I had to do it again?

I retrospect, if I was to restart the project again, I would:

• Replace, as much as possible, the right angles in the plexiglas cuts with rounded angles. All these right angles are introducing extra constraints in the plexiglas, and making it more likely to crack.
• Use a smaller power button. Or rather, on that does not require such a large hole in the enclosure. Not sure which one, though.
• Keep the plexiglas (having a semi-transparent enclosure is kind of cool). But it isn't fully transparent in the end: simply because you have to glue, drill... you have to sand it, even slightly. The laser cutter also introduces imperfections that have to be sanded as well.
• Use a more accurate drilling machine.
• Use a different material for the bottom. I used a 0.2 mm carbon fiber plate. It works, but it feels a bit too thin.
• Try to find shorter cables. In the end, all these cables take a lot of room inside the box. But I couldn't find cables in 10-15 cm lengths.
• Probably use a different board. The Pi doesn't have wifi nor bluetooth included, which means you must use 2 USB dongles, which means you must have a USB hub, which adds more cables. Also, the range of a small wifi dongle is not too good. And a more powerful processor would be nice.
• Rotate the screen so the USB plug for the touchscreen doesn't touch the board.

Full costs

How much did the whole project cost?

These are just the parts. I'm not counting the tools (soldering gun) and the glue... It's certainly not cost-competitive: for that amount of money, you could have a brand tablet. But it's definitely interesting to build your own tablet.