Simple Extruded Aluminum Frame for LED Panels

We really like to use LED panels for making clocks, game timers and information boards. Our family has used a Raspberry Pi based "Weasley Clock" for the last five years. In a one minute cycle, it displays the time, weather, school information, and local train schedule. It will inform us of any delays or stoppages in the train through a scrolling message. It can also display alerts for internet outages. They have a Halloween mode that allows them to fill the room with a ghostly green glow or a fire effect. Our clocks are based on Raspberry Pi 3's and the Adafruit RGB LED hat. They would not have been possible without Henner Zeller's amazing libraries. ( https://github.com/hzeller/rpi-rgb-led-matrix )

With the introduction of the Adafruit Matrix Portal, we built a couple of smaller ones. Over the next year, we will try and migrate some of the code for the "Weasley Clock" over to them. For building a single application, they are great, and the kids program python.

That brings us back to the purpose for this Instructable, the point of which is due to my dear wife. She took one look at the Raspberry Pi, the Matrix Panels, power supplies, wires, lots of wires and said "No way is that monstrosity going on my kitchen counter." It has to look nice. Fortunately, she as a very generous definition of what "looking nice" entails.

Using some leftover extruded aluminum and steel bars, we have come up with a simple and easy to adjust design that looks nice, and with the addition of a piece of 35mm din rail, will be well organized and tidy. We present it here to you.

Figuring Out What You Want to Build.

There are a lot of choices here, and you need to figure out some things before you start. What are you going to use the display for? A display device such as a clock, message board, or timer? A light source for special effects or background lighting? A chess clock or scoreboard that needs buttons? Something else?

First, how many panels do you want to use, what density and what pitch? Where is the panel going to be viewed from? How far away will the viewer be? How many LEDs will be lit at a time? Go do some research, Adafruit has some excellent tutorials.

The most common configuration we built used 128x32 LEDs. Both of those were made with two panels of 64x32. The biggest one we made was 128x128 LEDs. It was made with four 64x64 panels. This is overkill for most projects, unless you are displaying train schedules or using LED Lab ( https://apps.apple.com/us/app/l-e-d-lab/id8320421...) with the most excellent pixelpusher. ( https://github.com/hzeller/rpi-matrix-pixelpusher ) . We would suggest starting with one panel of 64x32 to get started. (If you expand it later, you only have to replace two of the extrusions in the basic design.)

The next thing to consider is the pitch of the panels you want to use. Pitch is how close the LEDs are to each other on the panel. The smaller the pitch, the closer the LEDs, and the smaller the size of the panel. The smallest pitch we use is 2mm, the biggest is 6mm. The 2mm is great for desktop displays and the 6mm is good for when the display is on the other side of the room. Again, go do your research.

The second to the last thing to consider is what processor is going to drive the display. There are a lot of choices ranging from Arduino's, Adafruit Feathers, Raspberry Pi's and Adafruit's Matrix Portal. Go do your research and remember, the processor is the easiest (and cheapest) part to swap out.

Lastly the biggest thing to consider is the power supply. GO Do Your Research. We size the power supplies by figuring out the current required to light up every LED on the panel and then adding a fudge factor. (Remember that halloween mode.) The power supplies can run up to 80 amps at 5V. If you are not going to drive the panels that hard, you might get away with a smaller supply. GO DO YOUR RESEARCH.

Once you have decided what you wanted to build, and have the parts in hand, it is time to get started with the measuring. ( It as also best to the software that you intend to run, up and tested. )

This is a minor warning, depending on where you get your parts from there can be subtle differences in what the data sheet says and what is shipped to you. The differences are small, usually a millimeter or two, but measuring the actual parts (panels) is always best practice.

Pick Your Layout

Measure, Measure, Measure.

You will hopefully have built and tested your display system. This is great because you can measure actual components. So, layout the working system, test it, unplug it and grab a ruler.

A typical system will be comprised of the following components.

1. The LED panel or panels. This may be as few as one, to a maximum of "let your imagination run wild while draining your bank account." The biggest we have built using these techniques is eight by eight panels. The most common is two by one panels, which gives us 128 by 64 LEDS which is 8192 tri-color LEDs. Take special note of how close the magnets are on the back of each panel, this will determine how many steel strips you will need to secure the panels. Generally, a one inch wide pice of steel can support two panels next to each other. The panels will have shipped with magnetic feet.

2. The power supply. There are a lot of great articles on LED panels on Instructables and the Adafruit website that deal with how to correctly size your power supply. Go read them all. Next to panel selection, this is your most important selection. Our personal recipe is to calculate the current for the 'on' state for all colors, then add 20% extra. (Then go buy the next bigger level of power supply.) If you are going to make the sign portable, you need to compute or measure the actual draw of your application and size your battery accordingly. (Again, many good articles, go read them all.)

3. Microcontroller or microcomputer. This is a matter of religion, availability or skill level. The majority of these we have built have been controlled by raspberry pi 3s or 3Bs and the Adafruit LED board. There were some early experiments with Arduino's and some home built shields. Sitting on my son's desk is an Adafruit Matrix Portal for his next project.

4. Cables. This project is about making the LED panels have a nice compact package. So you should have some ideas about what the cables look like and how they get routed. (The one that kind of jumps out is the power supply cable. Look at the requirements for a line voltage cable going into an 80 amp 5 volt supply. )

The way we approach this step is to unplug the LED panels. Attach the little magnetic feet that hopefully came with your panels and attach them to a convenient metal surface (White boards work great). Arrange the panels in the configuration they will be used. When you have settled on a configuration, push them together as close as you can. (pushing them against a long piece of scrap 8020 or a carpenters framing level helps.) Measure the dimensions and write them down. Now go away and do something else for a couple of hours. When you come back measure it again. Write the numbers next to the first set. They should be the same. These are now the input set of numbers for our cut calculations. (Make sure that you use the same ruler, meter stick or tape measure for all your measurements. )

Picking Your Extrusion

There are a lot of possibilities for extrusion based on the final look you want. Everything we use is 8020 Series 10 or comparable. It is a standard one inch profile. It comes in a number of different configurations (four channel, three channel (8020-1003). two channel(8020-1004)), colors (natural, black anodized, yellow?) and surface finishes. Using a three channel stock extrusion allows the construction of a flat bezel around the panels.

The smallest frame we have built uses a single pice of 8020 1020 as the base with three pieces of 1010 to complete the frame.

There is even the possibility of 3D printing the beams. (But that is another instructable.)

Update: https://www.instructables.com/A-Simple-3D-Printed...

Making a Cut List for the Aluminum Extrusion

Ok, so now we measure everything again. Depending on your design, you will have a list of all the lengths of the extrusions you will have to cut in the next step. ( You can also use the list to order the extrusions pre-cut and taped from a manufacturer and skip the cutting yourself. )

You may wish to pre-mark the cut lines in order to compare them with your design before cutting. This dry fitting before cutting is a check on the overall measurements for your design. It may expose problems with your measurements before the extrusion is clamped into the saw.

If you are use re-cycled or scrap material, it is useful to lay the pieces out against the panel so you can see different possible configurations. You also want to check the ends of the extrusions to insure that you can make a flush connection.

In the example photos above we started with an intended build plan and modified it as we found pieces of extrusions in the scrap pile.

Cutting the Aluminum

Cut the extrusions to length. Good practice here is to dry fit the pieces as they come off the saw.

You may wish to read other Instructables to learn about how to cut Aluminum extrusions.

Ours can be found at: https://www.instructables.com/A-Simple-Method-to-...

Cutting the Steel

The steel bars exist as an attachment point for the magnetic feet on the LED panels. This is how the large display panels are constructed, so that individual sections can be swapped out for replacement. It this system, the bars are mounted to the back of the frame. The panel ( 0.6in) and the magnitude feet ( 0.4in) are the same combined height as a one inch aluminum extrusion.

Cutting the steel bar is a little more forgiving than cutting the aluminum extrusion. The length is determined by the direction you are going to mount the steel bar on the frame. Our normal practice is to mount the steel bars vertically. The example in the photos is the only time we have mounted the steel bars horizontally. We did this because the normal configuration would have blocked access to the connectors. ( Also, home depot was out of both 1-inch and 3/4-inch steel, so we were down to scraps. )

The other pictures or the rest of the pictures in the DIN Rail section that will illustrate the normal mounting confirmations.

Just measure the outside dimension in the direction that you are going to mount the bars.

DO NOT CUT THE STEEL WITH THE MITER SAW. Use a hacksaw, or other saw rated for mild steel.

3D Printing the Drill Guide and Drill the Holes in the Steel

Print a drill guide for the width of steel bar that you used. It will be used to guide or mark the drill spot for the ends of the steel bar. Mark both ends.

We use the guide to mark the steel and then drill a small pilot hole through the steel. We then come back with the correct size bit and expand the hole to the correct sized for the bolts we are using.

You can also print two of the T-nut spaces for each of the bars you cut.

Downloads

drill guide for 1-25 steel one hole 2 90 mm v2.stl

drill guide one hole 2 90 mm v2.stl

hole guide three hole 2 90mm v2.stl

Tnut spacer for universal v1.stl

Drill Some Holes Into the Aluminum Extrusion

Drilling the holes in the aluminum extrusion is a fairly precision operation. The drill must be centered on the beam 1/2 inch from the end, in the valley between two wings.

Fortunately there is a simple and precise fix. An access hole drill jig can make you life easy. It will allow you to drill the holes you need even with a hand drill. It will last nearly forever. So, unless you have access to a drill press and want to make your own jig.....

https://8020.net/6131.html

Tap the Ends of the Aluminum Extrusion

Tap the ends of cut extrusion where needed.

Assembly of the Frame and Mounting the Panels.

There are only three things to do in this step.

1. Screw the t-nut bolts into the taped extrusions.

2. Put the extrusions together and tighten the bolts.

3. Attach the steel support bars for the magnetic feet on the LED panels and tighten the bolts. It does help to use the panel as a guide when you are lining up the ends of the extrusions with the holes that allow access to the bolts.

Lets Print Some More 3D Parts to Mount the Electronics.

This is where we print the DIN rail mount.

You will need to print two brackets for the 35mm din rail. We use 35mm din rail because it is very rigid over short spans.

You may also wish to print the mounting brackets for components that will be attached to the din rail; such as the power supply, processor and any sensors you are going to use.

We have provided a few to get you started and your favorite 3D print repository will have dozens more.

Downloads

8020 Din Rail Standoff Standard bolt size v2.stl

RPI 4 din rail side mount work 1 v6.stl

RPI 4 din rail start v3.stl

meanwell 320 work mark3 v2.stl

The Strange Case of the Missing Magnetic Feet

https://www.thingiverse.com/thing:4728127

In a strange twist of fate, suppliers are not shipping the magnetic feet with the LED panels. The above link will allow you to print your own if you do not have them supplied with the panel or could not purchase them with the panel.

Cut a Section of DIN Rail

Cutting the DIN rail is best done with a hacksaw. (If you don't have access to a band saw with a metal cutting blade.)

It will be cut to the same length as the outside width as your frame. Pay attention to the hole pattern in the rail as you need exposed holes over the 3d printed bracket.

Mount the DIN Rail to the 8020

Attach the din rail to the brackets and insert the t-nut bolts through all the components. Attach the bracket to the aluminum extrusion and ensure that it does not block access to the connectors on the LED panel. Tighten everything up.

Hang Your Components

Attach the components to the din rail. Make sure that you are not making access to the connectors on the back of the panel(s) difficult. You should also check to see if the components are visible from the front of the panel and adjust the din rail mount accordingly.

A Special Case for Adafruits Matrix Portal

This step is only relevant if you are using an Adafruit Matrix Portal to drive your LED panel.

If you are working with a really big panel this step may not necessary.

If you test fit the Matrix portal and it does not touch the frame, you're done with this step. If it does, and you still want to use the Matrix Portal, you have a couple of options. They both require remote mounting the matrix portal. Here are links to mounting options for 8020 and din rails.

https://www.thingiverse.com/thing:4728088

https://www.thingiverse.com/thing:4728084

You will need an extension cable to remote mount the Matrix Postal.

Wire It Up

Attach the wires. Ensure that all the wires are properly insulated and not in danger of coming into contact with any metal surface over time. Be especially careful of anything attached to the power supply. Also be careful of power supplies that have built in fans, they will cause small vibrations the can chafe wire over time.

You're Done

Congratulations, you're done.

Time for the smoke test and then placing your project in its new home.

Next Steps

Add sensors, buttons, feet for the aluminum extrusion and other things.

Yes, those are cup holders. (although they hold pencils, dry erase markers and an eraser on that board. ) It can be found at: https://www.thingiverse.com/thing:3602413

The button holders can be found at:

https://www.thingiverse.com/thing:3172579

https://www.thingiverse.com/thing:3172570

https://www.thingiverse.com/thing:3172566

https://www.thingiverse.com/thing:3172573