Sunday, May 12, 2019

Makerspace Project: LED Side-lit Acrylic Signs

One of my favorite projects over the last couple years to do in our maker-space classroom is side-lit acrylic signs. The project has evolved a bit as I have improved the design of the signs and workflow for students and it is now in a place I really like. 
Through this project 7th and 8th grade students learn the following skills and processes:
  • Simple conversion of graphics from bitmap to vector
  • Using Turtle Geometry to code a closed shape
  • Using hand tools such as hand saws and drills
  • LED circuitry, LED polarity and forward voltage, and soldering
  • Simple pocket milling

Choosing and Vectorizing A Sign Image

To settle on an effective image for their sign students have to find or draw something with a simple white background that does not rely on subtle shading for its clarity. That is to say, pictures of people such as themselves or family members don't work very well. The most effective graphics are text, shapes, cartoony or illustrated images, and line drawings. Once students find an image they upload or paste the URL into and see if they like the result. I used to have them use the Image Trace feature in Illustrator but I have since eliminated the need for them to use Illustrator as it opens many potential pitfalls that only I can fix, and one of my aims in this project is for them to move independently through the steps with support here and there. Students find creative ways to include their own text, such as combining an image and text on a Google Slide and taking a screenshot.
If they draw their own image or text they use a sharpie to bring clear definition to all lines. I photograph the drawing, crop and increase the contrast, import into Illustrator and run Image Trace, Expand, and delete the white background.

Coding a Closed Shape Cutout

In an earlier project students learn to code geometric shapes with TurtleArt, so it is easy for me to tell them to make a program that draws the shape they want their sign cut out with. This was something they had done in Illustrator in previous iterations but I like the freedom Turtle Geometry affords and they come up with some really neat shapes to frame their images that would only be possible to make in Illustrator with a more extensive learning process.
Once they settle on a shape they drop the file into Paula Bontá's TurtleArt Converter, with hairline mode selected. This downloads an svg path to place around the graphic they have chosen to etch.

Preparing For Laser In Illustrator

Students turn in their vectorized graphic and their vector hairline shape graphic in a Google Drive folder where I then combine the two in Illustrator to cut and etch on 3mm clear acrylic. I finally learned this time around that the LEDs illuminate the etching much better when looking from the back so I flip the images for etching.
The hairline path generated by the TurtleArt Converter comes in with these settings which are perfect for our Universal laser:

I size the pieces to 6.5 inches wide to fit the 7 inch pieces of wood students cut in the next section.

Cut Some Wood!

Earlier in the year students did some hand saw exploration, trying out rough cut saws (good), back saws (good), and hack saws (not so good for this) with various clamp arrangements to see what they found easiest to use. I do this so they see that rather than being told "the right way" to cut a piece of wood, they can discover what does and doesn't work for themselves and share those discoveries with each other. I give them tips when they ask or when it looks like they need it, and use women woodworkers to teach skills, like Anne of All Trades in this great back saw segment. So for this project when I tell them to cut a 7" piece of wood from the reclaimed bed slats we have in the materials rack they are very independent about it.

Milling a Pocket

I can't think of a good way to cut a 1/8" slot in the wood for the acrylic to sit in besides milling it with a CNC machine. The only other way I can think of would be using chisels but kids would have a hard time with it. So our Carvey comes in very handy here. And vacuuming up the sawdust is the best. For a 3/4" piece of wood I mill a pocket 1/8" wide and 3/8" deep.

Choosing LEDs

Here the students learn that an LED is a diode, what a diode is, refresh their memories about DC circuit polarity, and differences in voltage draw in different LED colors (AlInGaP vs InGaN). I don't teach much, just show these two short videos (here is a playlist) and have them take 15 minutes to explore placing LEDs on batteries and answer a few questions in a document as part of their own discovery research:
  • Make one LED light up. What do you have to do to make it light up?
  • Can you make more than one light up at once? How many can you get lit up at once?
  • Are there any LED colors that will not light up together? Which ones are not compatible?
  • Why do you think some colors will not light up together?
They know they have to understand these concepts about LEDs because they will have to align the positive and ground LED legs on the appropriate sides of their circuit and they will have to choose colors that will work together. Watching the above videos they see why red and yellow will work together but not with any other color.

Drilling LED Holes

Students test LEDs below their acrylic signs and make marks in their wood where they want the LEDs to shine from. They use a 7/32" drill bit to make their holes the right size for 5mm LEDs.

Laying Pos and Neg Rails

Students lay a strip of copper tape on either side of their LED holes and write a + next to one and a - next to the other. They place their LEDs in the holes and bend the legs to extend over the tape, make sure to put the long leg over the + rail. Then they solder the legs on the copper tape. If you are looking for a soldering iron recommendation I love these. And tip cleaner like this is essential with the irons sitting on for long stretches.

Completing the Circuit

To complete the LED circuit students do the following:

  • hot glue the battery holder to the end of the wood, with the opening facing away from where the switch will be. Here is the 3D printing model I devised for such projects.
  • hot glue the latching switch next to the battery holder. I recently found these and they work great. Latching press switch means you press once to close the switch, press again to open it. It's easier than using slide switches, which I had to solder leads to.
  • run copper tape from one rail to the bottom of the battery holder where it will contact the bottom side of the battery
  • run copper tape from under one metal end of the switch to over the top of the battery holder. It is important that the tape stick out a bit so when they slide the battery in the tape gets pulled in with it, but also that it isn't so long that it ends up shorting the battery.
  • run copper tape from under the other metal end of the switch down to the other LED rail.
  • Notice I didn't specify which rail was positive and which was negative. That is because it will be hard for them to plan out matching a positive and negative side of their battery and switch arrangement. Rather they just put in their battery positive up or positive down depending on which rail it lines up with in the circuit.
  • I devised a good way to get a battery out in case it goes in the wrong way. Press a piece of masking tape on the exposed part and it will slide out pretty easily!
This time around for a finishing touch I am giving them felt pads to put on the bottom because they don't sit flat very well. Extra laptop feet can work well, too!
It's a shame that the camera doesn't do these justice, but the kids love the result!

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