Do you ever need a cheap, quick way to make an impressive display? Do ever want to show more than a blinking LED but want something easier to use than a LCD? Do you want to make light appear to hover in mid-air? Then give some thought to edge lighting.
At the last Maker Faire I had a bunch of interactive gizmos for people to play with, but one question I was asked more than any other was "How did you make those displays?" On the Rock Paper Scissors Playing Glove one small display showed three different images and text while on the Secret Knock Detecting Gumball Machine the light just seemed to float in the clear plastic without an obvious source. The answer is edge lighting.
Edge lighting exploits a fun property of light called internal reflection where light can get trapped inside a transparent material. It's the same concept that makes both a diamond sparkle and optical fibers work. But we’re going to use it to make light come out of a sheet of plastic.
Simply put we shine a light in the edge* of a clear piece of plastic and etch it where we want the light to come out. With this simple, cheap method you can use a single LED to display words or images. Because it's etched into a transparent surface the images can seem to float in mid air or you can layer several of them to make a single display with more than one image or color.
Keep reading to see how easy and quick it is to get this effect.
*And thus the name "Edge Lighting"
At the last Maker Faire I had a bunch of interactive gizmos for people to play with, but one question I was asked more than any other was "How did you make those displays?" On the Rock Paper Scissors Playing Glove one small display showed three different images and text while on the Secret Knock Detecting Gumball Machine the light just seemed to float in the clear plastic without an obvious source. The answer is edge lighting.
Edge lighting exploits a fun property of light called internal reflection where light can get trapped inside a transparent material. It's the same concept that makes both a diamond sparkle and optical fibers work. But we’re going to use it to make light come out of a sheet of plastic.
Simply put we shine a light in the edge* of a clear piece of plastic and etch it where we want the light to come out. With this simple, cheap method you can use a single LED to display words or images. Because it's etched into a transparent surface the images can seem to float in mid air or you can layer several of them to make a single display with more than one image or color.
Keep reading to see how easy and quick it is to get this effect.
*And thus the name "Edge Lighting"
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Signing UpStep 1: Credits And Theory
Please check out all the annotations on the images. There is useful information in them.
Credit:
First I need to give credit where it's due. This idea is not new or original. At very least it was used in calculators in the 60's. I was turned on to it by the always creative Evil Mad Scientist Labs and their great Christmas cards. They also did the research and found great materials which make the whole process easier
Theory:
When light passes between two different materials (like plastic and air) at a very high angle it will get reflected back rather than passing through. You can see this in a glass of water. Look at it from above and you can see right through it. Looking at it almost edge on and it will be very reflective. This means that if we shine a light into the edge of clear plastic the light will bounce around inside until it finds a way out. By etching and/or carving the surface of the plastic we control where it escapes.
Credit:
First I need to give credit where it's due. This idea is not new or original. At very least it was used in calculators in the 60's. I was turned on to it by the always creative Evil Mad Scientist Labs and their great Christmas cards. They also did the research and found great materials which make the whole process easier
Theory:
When light passes between two different materials (like plastic and air) at a very high angle it will get reflected back rather than passing through. You can see this in a glass of water. Look at it from above and you can see right through it. Looking at it almost edge on and it will be very reflective. This means that if we shine a light into the edge of clear plastic the light will bounce around inside until it finds a way out. By etching and/or carving the surface of the plastic we control where it escapes.
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Again thanks for the great instructable!
Looks awesome! I did one for my daughter too, however mine doesnt have a frame around it as I engraved the design a bit too close to the edge, so I made a stand instead. On the base of the display is beading that goes around the edge of laminate flooring just to tidy it up a bit. This is my 1st attempt, I may do another one later on sometime to improve on the flaws.
Thanks again to Grathio for this amazing instructable!
Here's a pic of the one I did yesterday. It's roughly 12 inches by 9 inches and took a total of 4 hours to complete. 2 1/2 hours of engraving with my dremel VERY slowly so I wouldn't screw up!
Thank you!
I just had a query about the engraving tool. There is a special tool by dremel called the 'engraver'. does it work on acrylic?
I dont have the rotary tool by dremel either.. So planning to buy the right tool..
Kindly comment on what tool should work well...
Thnx!
but can plain glass be used instead of plexi-glass to make these signs?
or maybe coz the glass wasnt polished..
and i will try to make it
thx man
The Evil Mad Scientists did a bunch of research on this kind of circuit, you can read about it here.
THANKS
I would probably just go with an EL sheet. If you're in the US you can find it for around $1 a square inch on eBay.
Any gap between the LED plastic and the display plastic will cause reflection at the interfaces. The air gap has a refractive index of 1 (n = 1) while the plastics are about 1.5.
Not the only supplier, but one that is available in reasonable sizes and a variety of sources is Norland optical adhesives. These are UV cure, which I like better than two part, since you don't need to degas to remove bubbles. Leaving the parts in bright sunlight might be enough to cure the UV adhesive.
Think about this for a moment.
Take 2 chromed wrenches with same size and paint 1 white and do nothing with the other one. Hang both wrenches on a string in full sun for lets say 30 minutes and touch both wrenches after that.
You will find out that the unpainted chrome wrench is much hotter than the painted white one, because the chromed wrench absorbed more light. I don't know what is worse, a chrome wrench or black painted wrench left in the sun.
What I would do, sand the edges with very fine sand paper and polish the edges, then paint them with a shiny white paint.
Also, I would use clear epoxy to hold the LED's to the plexi glass and fill all the gaps.
With all due respect to the author, who said-
"Using reflective material will reflect more light back at the same shallow angle it needs to stay inside the plastic. Silver and aluminum are very nearly purely reflective (At least in visible light)"
All of my college classes that touched on reflectance of light did mention that white is a better reflector than "silver" which is gray, which is partly black. The flatness of a surface enhances reflection, and mirrors show an image better because of the absorption (blackness so-to-speak) of some of the light.
Taking into account the amount of light reflected versus the quality of a specular reflection from a standard mirror... the photometer reads more light coming off a pure white surface. Paint is often too rough, thus diffuse reflections result. So the choice of materials will affect the angle of reflection, or diffraction, or refraction, etc. depending upon the optical design.
When containing the light within the clear sheet, polished and flat edges are preferred. And a smooth reflective backing such as foil tape is an easy way to get a much flatter surface.
In a theoretical perfect world, one might want to use a nano particle sized coating of Titianium dioxide applied to a perfectly square and flat polished edge... HA! (Not going to happen for most of us unless we have access to optical fabbing equipment!)