An unpainted art canvas can make a great diffusion screen for RGB matrix panels. In this guide I'll show how to use art canvases to construct wall-hanging matrix panel enclosures for several different sizes of RGB matrix panels.
This guide will help you to build one of these wall-hanging canvas displays.
Parts
The most crucial part - the one that makes this a relatively easy build - is the Matrix Portal. This will attach to the RGB panel that you choose and allow for it to be programmed easily (in CircuitPython).
The 3 amp Raspberry Pi 4 power supply is a good way to power the canvas when it's hanging on the wall. Note that you can get these in white from DigiKey.
Below are a number of USB-C parts that will probably come in handy on a project like this.
Related to the above, there is such a thing as a USB-C extension cable. They have a plug on one end and a socket connector on the other. I don't believe Adafruit carries any, but you can find them on Amazon and elsewhere.
I'm finding that it works great to have one of these extension cables plugged into the Matrix Portal. Then it can easily be swapped between a computer (for re-programming) and a wall power adapter (for normal usage).
Another thing to look for on the wider internet is right angle USB-C adapters. Adafruit carries one (linked above), but I was able to find a more svelte example. Also, note that some of the extension cables come with a right-angle plug end.
In addition to the electronic parts and cables, you will need some hardware for securing the matrix panel inside the canvas and for hanging the canvas on the wall. Most of these parts can be found at an art supply store (like Michaels), or a hardware store.
Pieces of foam board will be used for securing the matrix panel inside the canvas.
The 9x12 inch foam board was a good size for the 64x32 pixel, 4mm pitch panel. For the smaller panels, the 8x10 inch foam board may be a better starting point.
The matrix panels have M3 screw mounts, so these nylon screws and standoffs will be helpful in attaching matrix panels to things like foam board.
The items show below will be attached to the back of the canvas. The hanging wire and D-rings are used to hang the canvas on the wall. The offset clips will hold foam board in place behind the canvas.
I use these plastic spacers from Pololu to add a little distance between the back of the canvas and the hanging wire, allowing space for the foam board in between. If that doesn't make sense, don't worry, it will be explained better in pictures to follow.
Any of the spacer lengths shown below (2mm, 4mm, 6mm and 8mm) could turn out to be useful in building a compu-canvas project, and sometimes I start with one length and realize later a longer or shorter spacer will work better.
The D-rings (shown above) come with screws, but often I find they are too long, short or wide for what I need.
I have found that #4 and #5 screws work great with the Pololu spacers shown above (and #6 is too big). I got several different lengths to try, but for this project the 0.75 inch #4 or #5 screws are perfect in most cases.
Make sure to double-check that the screws selected are not too long, or they will puncture through the front of the canvas!
The last set of pictures here show how the spacers and screws will be used with the D-rings to create a little space between the D-rings and the back of the canvas.
The last picture also shows roughly how the D-rings, hanging wire and offset clips will be placed behind the canvas. In this example the offset clips are on the side, but often it makes more sense to put them on the bottom. You'll see examples of both in the builds covered in this guide.
In several of the builds I used a pair of 8-pin Arduino stacking headers to extend the distance between the Matrix Portal and the matrix panel by a few millimeters. I think these could come in handy in a lot of situations where the canvas is just a little bit too deep for the Matrix Portal.
You'll only need the two 8-pin headers from this kit:
There was also one build (the final one) where I used these extra long break-away headers:
Tools
You'll need a few tools for this project, shown below. I used the pencil and measuring tape to mark places to cut on the foam board.
Use the "x-acto" type blade for cutting the foam board along a line or curve.
Use an awl for making holes in the foam board to run cables or screws through. If you don't have an awl, a nail will work instead. The foam board is not difficult to puncture.
And the Phillips screwdriver will be used with the nylon and the metal screws shown above.
The only other things you need are one of the RGB matrix panels and an art canvas that the panel fits inside. The next 4 sections of this guide show how to construct wall-hanging canvases for 4 different matrix panels. The Adafruit product link for each panel is at the beginning of the section devoted to that panel.
SPOILER ALERT:
If you are looking for the best fit - with the least amount of unused space inside the canvas, and the thinnest 'bezel' of unlit canvas as seen from the front, and the most pixels - then the 64x64 pixel, 3mm pitch panel with a 10x10 inch, low-profile canvas is the best pairing I have found.
The canvases you will find at a typical art supply store come in standard sizes. It is possible to get custom made canvases (here is another example), but it will be more expensive.
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