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    element14's The Ben Heck Show

    Join Karen as she shares her enthusiasm for teaching STEM subjects, gives you what you need to know to get started on electronics projects, and more.

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    The Learning Circuit
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    In a previous segment, Karen showed you how to make a simple circuit using an LED.   Now, she’s going to apply that to a fun project by showing you how to make an edge lit sign.  To make an edge lit sign you add scratches to a piece of acrylic. Those scratches will interrupt a beam of light from an LED and show your design.



    Karen is using acrylic that is 0.1 inches thick.  You could also use 1/8 inch or a similar thickness.  You don’t want to go to thin, because then it might break.  You don’t want to go too thick because it’ll be difficult to deal with.  When deciding the size of your acrylic, you want to stick around two to three inches in either rectangular or square.  If you go too big, the light of your LED won’t reach your design, and it won’t light up very well.  For this particular application, if you’re only using one LED, then you want a smaller design.

    When drawing your design, you want to make sure that your lines are not going to be too thin because there will not be enough mass to catch the light significantly to really show off your design. When you make your design you want to make sure that you’re using nice, bold lines.  Karen draws extra lines within the border of the acrylic. This is because when it’s done, she’s going to be putting aluminum tape around the edges, and this is to make sure that the design isn’t covered up later.  When her design is done, she tapes the acrylic down so that it doesn’t shift, and so she can get good alignment between the acrylic and her design.

    Next, you’re going to want to etch your design. You can use an exacto blade or any kind of hobby knife that has a sharp pointy end. She suggests using electric etchers if you have a child doing this.  For her example, she etched in a few different techniques so she could show you the differences of direction of scratch and how it affects your design when you place your LED.  She goes over some of her different etching techniques.  She suggests doing cross hatching, if you don’t have a specific design in mind. Scratch in opposing directions so that no matter where you place the light, it’ll still catch it. She recommends, though it’s not required, cutting a little notch in the edge of your acrylic to hold your LED in place and to keep the light pointing exactly where you want.

    She cuts the acrylic and gives some advice on choosing your LEDs. A diffused LED doesn’t let as much light through, a colored LED is pretty good, but a clear one (red LED) is the best because it lets the most light through to get to your design.  When placing your LED against your acrylic, you want to make sure that the leads are on top of each other.  You’re going to be placing your battery in between them and you want to make sure that it’s going to be flat along with the acrylic.

    Placing aluminum tape around the edges not only holds the LED and battery in place, but the white on the inside of the tape helps to reflect the light back in towards the design, making the sign brighter.