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Picture of Edge Lit Displays
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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"

 
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Step 1: Credits And Theory

Picture of 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.

Step 2: Materials And Tools

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Skills Needed:
  • You should be able to wire an LED to light up and not burn out.
  • You should be able to use a rotary tool with some precision without causing irreparable damage to yourself or others.

Materials and Tools:
  • Clear plastic. I recommend this polyester sheeting from McMaster-Carr. (Thanks EMSL!) CD cases will also work, but they tend to chip and crack.
  • LED(s) 3mm or 5mm, any color, though the brighter (more mcd) the better. The white one used in this tutorial is a 6000 mcd 3mm.
  • Power source for LED. If you don't know how to power an LED use this calculator to find out. You can also use a CR2032 button battery.
  • Rotary tool A Dremel or similar with a fine grinding bit to carve or etch your plastic. A needle or craft knife will work in a pinch. If you're using acrylic you can laser etch, but the polyester sheets will just melt. CNC mill would probably work great.
  • Craft Scissors (aka: Not the good scissors) To cut the clear plastic. A saw, hobby knife, or rotary cutoff disc can work too. (Don't use scissors on CD cases or other acrylic, or it will crack.)
  • Aluminum tape Usually sold in the hardware store in the HVAC department to seal ducting. You can also use plain black electrical tape, but your display will be dimmer.
  • Safety equipment. Yeah, I know, it's no fun, but eye protection is a must when using power tools. And I recommend a breathing mask too.

Time:
  • About 10-30 minutes, depending on your tools, materials, and the complexity of your design.

Step 3: Make And Etch Your Design

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First:
Figure out what you want your design to look like. If it's complex, like words, you might want to print it out rather than draw it freehand. However print them backwards (mirrored left to right). This is because we're going to etch the back of the plastic, not the front (it will be brighter this way) and we don’t want our words to come out backwards.

Second:
Cut your plastic to size. You can cut it to any size you want but allow at very least 8mm (3/8") on one of the sides--this is the side where we're going to put our light.   If you're using polyester sheets you can use scissors to cut. If you're using acrylic sheets it's best to use a power tool with a blade meant for acrylic to avoid chipping.

Third:
Put your design on the front of the clear plastic for reference. If you're doing it freehand, you can stick some clear tape on the front and draw it. (Or many plastics come with a protective layer that you can draw on with a marker.) Otherwise tape your printout in position so you can see it from the back and use it for reference.

Fourth:
Etch your design. We use a Dremel with a fine round carving tip at about 10-15,000 RPM and etch to a depth of about 1/2 the thickness of the material. You can also use a needle, knife, or file to mark your design, anything as long as you rough up the surface.  (I've even tried sand paper.  It worked but it came out very sloppy.)

Step 4: Shape And Apply Lighting

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First:
Slim down an LED. We want to get as much light as possible from our LED into the plastic, so we're going to grind down the plastic shell of the LED to fit better. You can find rectangular LEDs that will be the right thickness, but we find they're rarely bright bright enough and come in limited colors. We used a rotary tool with a sanding cylinder, but you can use whatever works (sanding table, sand paper, grinding wheel, etc). 3mm LED's don’t need much modification, just a tiny bit off the front and back. Be more careful when working with 5mm LEDs since you can accidentally go through the plastic case and remove some of the more important bits of the LED. Work slowly and carefully holding the LED in a pair of pliers to save your fingers. You can also shorten the height of the LED since we don't need the lensing effect of the case.

Second:
Wire up your LED. This depends the details of your project. If you're soldering it will be a lot easier and safer to do it now rather than when it's embedded in the plastic. It's also a good chance to make sure you didn't damage the LED when grinding it to size
.
Third:
Cut a place for the LED in the plastic. Use your rotary tool (or a file, etc) to carve a cutout along the edge the same size as our LED. It should fit snugly with only the wires sticking out. If you're using really thick plastic you can even drill holes in the edge to hold the light.

Fourth:
Hold the LED in place with aluminum tape. Apply a thin strip of aluminum tape along the edge that contains our LED. Make sure it runs on the front and back of the plastic. Cut out a notch around the LED wires so the metal on the tape doesn't short it out. The aluminum tape will not only hold the LED in place but will direct as much light as possible back into the display.

Apply some more reflective tape along the remaining edges. This is optional, but it will improve the brightness of the display and keep light from leaking out.

If you're not satisfied with the brightness of your display add more LEDs along the edge. Very long or large displays will be more evenly lit if you spread the LED's along the edge.

Step 5: Other Applications + Get A Patch!

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Taking it further:
Lets say we're making an electronic Tic-Tac-Toe game. Ideally we want either an X or an O in the same place. To do this we make and X and an O with a separate LED for each one. Since each piece is essentially transparent when off, we can put one behind the other to have a display that can show an X or O in the same space, depending on which LED we light. You can also use the same effect to add more than one color to the same display or animate parts of an image like some animated neon signs.

Show me what you've done and get a patch!
If you make this Instructable, post a photo of it in comments and I'll send you a Master of Edge Lighting achievement patch and you'll get your name on the Hall of Fame.
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Anubyss88 made it!2 months ago

I did this one because I'm a big space fanatic. Thanks for this instructable!!!

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Vick Jr3 years ago
We used the same method, but with a laser cutter for etching, to make a sign for our organization. Thank you!
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alienfive4 years ago
here some other images.....maybe you like them...
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Z0M8I34 years ago
I love this instructable! I was inspired to do it myself from the first time I seen it and have made a few small business card sized panels with my friends businesses on them and gave them as gifts. Yesterday I did one a little more elaborate for a good friend of mine and I think it's the best I've done. Normally I wouldn't even bother to put up a post to anything but your inspiration brought out a new skill for me to master and I thank you for that!

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!
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To jestrada9:

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!
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alienfive4 years ago
Hi! Nice idea! I have done it with the childs from our youth camp. I used 10mm Plexiglas and blue LEds! lg alienfive
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jestrada95 years ago
Once I saw this I knew exactly what I was going to do.  Build a night light for my daughter.  I built a frame around it with the power supply in the back.  The edge closest to the display is white and the outer edge is pink.  The background is light purple (some of the colors from her room, the designs are in her room also).  I was going to use black, but didn't have any and I thought the purple looked alright.

Again thanks for the great instructable!

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Grathio (author)  jestrada95 years ago
What an awseome use! Thanks for taking the time to share it, it looks fantastic!
SimonD82 months ago

How well this method works in a well eluminated enviroemnts?

jordanwade1 year ago

So is it the cut from the engraved areas that are distorting the light making it visible like that?

I have a question... will this method work on plastic slides nicked from my biology lab? TIA!!

ya...it will work on any transparent material...even glass, plastic also....make sure that the material surface is free from dust n scratches for clear vision.

pmk2221 year ago

is it possible to do something like this but making it so you cannot see the image (or have if very hard to see) without the light being on?

Grathio (author)  pmk2221 year ago

I don't know of any way to make it invisible, but there are a few tricks you can use.

One is to use much finer lines than I show in my examples. A very fine craft knife blade can make cuts that are hard to see but will still glow if you put enough light into the edge.

Another is to place it in front of an interesting background. A complex pattern will hide what's really there. A more complicated solution is to use two pieces of plastic. The first with your etching on it, and another behind it with its entire surface etched. When you put light into the edge of the back piece it will all light up and you won't see the foreground piece. Light up the front piece and turn off the light on the back and the "real" message will be clear.

A third idea is to polish your engraving (or make the whole thing from a single piece of cast acrylic) so that the roughness isn't as visible.

Best of luck!

pmk222 Grathio1 year ago

the second idea with the complex background, could you use a piece of frosted plastic/glass and a very thin etched piece in front and only light the top piece? i ask because this would be a cool idea for a business card to give to more important people and to light up the back all the time would not be practical

Grathio (author)  pmk2221 year ago

I think it might work. The only way to be sure is to try.

jonyman1231 year ago

This Instructable really helped a lot. Ive been looking for a way to easily edge light the holographic display on the Dead Space plasma cutter i've been working on.

Cool !
yaly2 years ago
I'll try with smd leds and glass microscope slides then try to make an avr controlled tic tac toe with this technique.
rocketfire42 years ago
what do u engrave it on and where can u get it
nerd17013 years ago
I could make one crazy cool desk nameplate with this idea
Nirzaree3 years ago
Wonderful i'ble!

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!
Grathio (author)  Nirzaree3 years ago
Engraving tools have diamond tips so they will very definitely scratch acrylic. It will work, but they don't go very deep so you won't get a very bright image.
ok.. so I guess I would bettr get a rotary tool..  as I would definitely want some deeper engraving.. 

CodeKid10014 years ago
quick question. Is it possible to make one that you can write on and erase with a marker or something that's not permanent?
Highlighter pens work brilliantly. Almost invisible when you write on the perspex, but glows brightly (with blue light) when lit!
nystrom5 years ago
Definitely should add some optical adhesive.

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.
also, how about optical adhesive + aluminum foil rather than aluminum tape round the edges?
Hmm... Isn't white more reflective than silver/chrome/mirrors/etc...? Perhaps painting the edges in pure white paint would reflect the most light back in? I think the only thing more reflective than flat white might by silver mylar. Am I off base?
speaking of pure white paint, how about 'backing' the etches with something like correction fluid? that way, you have less light escaping the wrong way and so more brightness, but it will be opaque so it wont work with the multi-layered panels on the next step............... another idea i had was to use UV LED's instead of visible colour LED's, then 'backing' the etches with UV paint... i wonder if it will work well? i suppose you will be 'soaking' the paint into the etches rather than painting them on
Grathio (author)  carmatic5 years ago
White diffuses the light (reflects it in a bunch of different directions) which means more light will escape through the front of our plastic/glass. 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) and very little light is lost when bouncing it off these substances. (It's the same stuff that's on the back of almost all mirrors.) The VU paint would be an interesting experiment. If you do it post some pics!
DIY-Guy Grathio4 years ago
A simple and inspiring instructable. Nicely done!

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!)
Grathio (author)  DIY-Guy4 years ago
Thanks for the information!

If you look at the aluminum tape it is actually white on the sticky side. But unlike using plain white tape it's also optically opaque, so the light it doesn't reflect it absorbs, which enhances the effect.

paqrat Grathio3 years ago
I have not tried it out yet but there is a paint called Looking Glass that supposedly puts a mirror finish on glass. It is made by Krylon and I have seen it here at WalMart (possibly cheaper online. Google Looking Glass paint) Might be worth a shot rather than attempting to glue aluminum tape to the edge.
but i thought the point was to reflect as much of the light as possible, hence no absorption at all?
Grathio (author)  carmatic4 years ago
Of course. However nothing is 100% reflective and any time light impacts a surface there will be some absorption.
shortw OniTora4 years ago
You are correct.
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.
nwlaurie5 years ago
I used to sell edge-lit noticeboards for pubs (I'm in England) and shops - they used a fluorescent tube along the bottom edge for lighting and - and this is the clever bit - if you wrote on them with wax crayons that would make the writing glow, with the added benefit that you could rub it away and change it whenever you wanted. No engraving needed.
paqrat nwlaurie3 years ago
That sounds very very cool. Would make a great hi-tech chalkboard for a kid's room.
hey...i know its 2011.
but can plain glass be used instead of plexi-glass to make these signs?
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