Build a Awesome DIY Smartphone Projector Using a Shoebox

by craftmin | December 12, 2017

Did you know you can build a DIY Smartphone Projector using just a shoebox? Unbelievable but definitely doable with this detailed step-by-step practical hack for the technological-inclined. Do you want to show off your vacation pics to family and friends, or just show them funny memes you downloaded from the internet? Then this diy projector is the one for you! Just give it enough time to let the glue dry.

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The science and tech behind the DIY Smartphone Projector

How does a projector work?

First off, a little overview of how these gizmos work, then we can go onto the nuts and bolts of our smartphone diy projector.

In 1894, Charles Francis Jenkins blasted light through a celluloid film and the first diy projector was born. Now, 120 years later, projectors have come a long way. With their first-tier technology, home theaters can basically meet the quality of commercial theaters head on.

Currently, there are three different projector technologies available on the market.

Liquid Crystal Display (LCD)

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LCD (liquid crystal display) technology projectors use polarized light (from a lamp or light source) beamed through three liquid crystal display panels (one for each primary color – red, blue and yellow). This light recombines in a prism and, with a filter, it then “projects” the image through the lens.

Digital Light Processing (DLP)

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On the other hand, DLP (digital light processing) projectors use a DMD chip. This “digital micromirror devices” chip contains millions of minute mirrors, but each of these chisp measure less than 1/15 of the diameter of a human hair. DMD chips work together to create a mosaic effect which displays a color in each mirror.  Each of these mirrors is a pixel – so for a 1920 x 1080 sized projector, that will be more than 2 million mirrors.

Viewed from far away, it’s a beautifully defined high-definition picture but up close, it’s nothing much.  That’s technology for us nowadays.

Liquid Crystal on Silicon (LCoS)

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The latest in projection technology is sort of a hybrid of the first two, LCoS or Liquid Crystal on Silicon. Think of it as an LCD panel on a mirror. Since it’s still in the development stages, LCoS is much more complex and a much more expensive projector.

What can we say about it? The clarity and color of LCoS projectors are superior to any of the other projectors on the market. However, LCoS manufacturers haven’t corrected the motion blur problems that DLP projectors have resolved. Nevertheless, so far, it seems LCoS is the way of the future.

The last word – what works best is what you need. If you’re into color and all its richness and subtleties, go for DLP. Now, if you are a gamer and you’re going for response time, than LCoS is the way for you.

Sources: HowstuffworksGadgetreviewIndepthinfo, LCos Projector

The Magnifying Lens

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First, for anything that has to do with magnifying things we use a lens, a word actually derived from the Latin for a lentil, the shape of which most lenses are very similar to

Most magnifying lenses we buy for the house use convex lenses (also known as converging lenses). What does that mean and how does it work for our diy projector?

When we say convex lens, that means the sides bend outwards which helps in catching, bending, and focusing all the light inside a box (why it’s better to go all-black inside the box).  All that light is then projected onto the wall.

Source: Image formation by lenses used in diy projector

Step-by-step DIY Smartphone Projector

(1) Get what you need:

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  • Shoebox
  • Magnifying lens
  • Smartphone
  • Foam board
  • Double-sided mounting tape aka foam tape
  • White glue
  • Glue gun and glue sticks
  • Crafter’s knife – use an X-ACTO if you have one
  • Hacksaw
  • Heavy-duty cutter
  • Ruler
  • Pencil
  • Cutting mat – optional
  • Compass – optional

(2) Getting the optimum focal length of your diy projector

diy projector focal length

First, find out how far the smartphone should be from the magnifying glass by going to a darkened room beforehand and then opening your phone’s display to its brightest.  Place it about 5 -6 inches behind the magnifying glass, then check the distance that gives you the sharpest focus.  Remember this distance because you will be placing your phone that far behind the lens later.

(3) Prepare the shoebox

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Check your shoebox.  If it’s a typical one, then you will need to reinforce the flaps at the short ends of the box. Using white glue, stick the loose flaps to the short end to strengthen that area.

Leave to dry.

Tip: I suggest that you paint the inside of the box with black acrylic paint. The less surface there is to reflect the light, the better and more efficient the diy projector will be.

(4) Prepare the magnifying glass

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While waiting for the glue to dry, work on the magnifying lens. Get your hacksaw and use it carefully to remove the handle of the magnifying lens. Then, set aside and check on your box.

(5) Measure and cut

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Stand your shoebox on one end then, using your ruler, make two diagonal lines to form a big X on the short end facing you. Place the magnifying lens so its center sits perfectly on the middle of the X, then trace the outline of the lens. Set aside your magnifying lens where you won’t accidentally break it or drop it to the floor.

Cut out the shape with an X-ACTO knife and set aside the circular cutout; you will be using this later.

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Tip: For a perfect circular cutout, attach the X-ACTO knife to a compass, press the blade firmly to cut out the shape then push out the cutout.

Check that the magnifying lens fits the circular hole snugly.

(6) Position your lens and then glue it

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Okay, this time put your lens in the hole you just cut out then, using the hot glue gun, glue the lens in place. You can glue it from the inside. If you are not too particular about how your diy projector will look, you can also reinforce it and apply glue from the outside. Leave to dry.

(7) Putting the lid on it

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First, make sure that the shoebox lid is not covering the lens. Put it back on and then mark the part that is covering the lens.

The best way to tdo this is to use the cut out circle we popped earlier to trace the part you will have to remove.

(8) Cut off the excess

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After tracing the excess part of the lid, cut it off by using the X-ACTO knife. Remember to slice the cardboard carefully.

Tip: You can tape the edges together using rubberized black electrical tape or you could glue them.

(9) Making a stand

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Now, you will be building a stand for your phone. Remember that distance you checked earlier? That comes in play at this part. Get your foam board and make two rectangular pieces then glue them perpendicular to each other, checking the angle to make sure it’s a sweet 90 degrees.

Check that your stand will fit inside the shoebox with the lid on, making sure that nothing is protruding and there is no sliver of space where light can enter.

Leave the stand to dry and try not to hurry this part. You can drink a mug of coffee or put up your feet on your diy coffee table while you wait.

(10) You are more than halfway done

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You are almost done now. Tape your smartphone to the stand you just made, using the double-sided mounting tape. Make sure that your smartphone is in the middle of the stand and that it perfectly aligns with the magnifying lens.

Great tip: You can also make an alternative stand using two paper clip.  Instead of using mounting tape to secure your phone to the foam board, bend the paper clips and then attach them to the board. This way, you can simply put your phone without taping it.

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If you are confident about the distance between the magnifying lens and your phone, you can do it this way without using a foam board at all. Use rubberized duct tape to secure the paperclips to the floor of the shoebox.

(11) Smartphone setup

First, set your phone’s brightness to its highest setting.

Second, lock the screen so it doesn’t rotate and get things mixed up. Just disable auto rotate settings.  Remember too that the light source is your smartphone. When it passes through the magnifying glass, the image will be inverted.

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Tip: A great option is to get an app that can flip the image on your phone.

(12) Make some adjustments

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Place the stand and your smartphone inside the box, remembering to turn it on and set it to the slideshow you plan to show off. Adjust the distance from the magnifying lens to sharpen the focus or to make it softer.

Tip:  In case you didn’t have the time to check the focal distance needed, put the stand and mounted phone at the farthest end of the shoe box, then slowly adjust by pushing the stand nearer the magnifying lens until you get the focus you want.

(13) Clean up

Almost there, just do the clean up which is really necessary with all those blades and hot glue lying around.

(14) Wait, what about the wall?

Wait up! Hang a white sheet or use a white wall as your projector screen.  This is also the best time to check and adjust the distance of the diy projector from the wall.  Just move the shoebox-slash-smartphone diy projector closer to or farther from the wall for greater clarity and focus. It would be best to turn off the lights for the test.

(15) Enjoy your DIY Smartphone Projector

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Finally, get your popcorn bucket ready, or your nachos and beer, if that is what you prefer. Remember to put the lid on the shoebox after you have set the phone for your show. Turn off the lights and enjoy your diy projector.  You can also enjoy hot cocoa, tea, and coffee with these cool diy mugs if it’s a cozy family vacation viewing evening.

General DIY Smartphone Projector tips, aka hacks scoured from all over the internet:

  1. For better focus, put another magnifying glass behind the first one. Before affixing this second magnifying lens permanently, check out the results first.
  2. If you have an old camera you  don’t know what to do with or maybe just an aperture camera lens, useit  instead of the magnifying glass.
  3. You could also personalize your smartphone diy projector by decorating the shoebox.
  4. Instead of a shoebox, use a wooden box for more stability and, well, it definitely looks better. It also gives quite a vintage appeal, especially if you decorate the outside.  However, remember to make sure no light can get inside the box. Darkness is our friend when it comes to the diy projector.
  5. It would be best to use only black-colored things for the inside of the diy projector – foam board, tape, paper clips, etc.  The less chance there is to reflect light, the better it would be.

Extra: DIY Smartphone Projector for the kids

This is the same project but adapted for kids.  Yes, kids!  A  diy projector that a five year-old can do, with just a little supervision and help from Mom or Dad (or older sister or bro) especially when handling the knife.

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Materials your kid would need:

  • Small cardboard box – we suggest something  bigger than a shoebox because kids need more elbow room than adults
  • Smartphone
  • Magnifying glass – kid-size would do
  • Tape
  • Sharp knife or a pair of scissors

(1) Working on the box

First, your child can tape the sides of the box for more stability.

(2) Tracing the magnifying glass

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Next, have your child trace the magnifying glass on the outside of the short end of the box. We won’t be hacking off the handle.

(3) Cutting the hole

It’s better to let the adult do this. Or, if your 5 year-old is like my niece, you could end up holding and guiding her hand like I did. A serrated steak knife will also do for this part.

(4) Tape the magnifying glass

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You know the drill.  Your child can now get the magnifying glass and then tape it inside the box.  Guide them to make sure that there is no gap between the hole and the glass.

(5) Making the stand

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Next, using an extra piece of cardboard, maybe one of the cardboard short end flaps, your child can make the stand.  Bend the cardboard to form a triangular stand.

(6) Putting the stand in its place

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Now, your child can slide the stand on the floor of the diy projector.  You can assist with helping her or him figure the best distance.

(7) Why questions

This is also a great time to introduce the kids into some more STEM info regarding lenses.  Put on the smartphone and you can see that the images are inverted. See if your child also notices that the image is inverted.  

Why does it do that?

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First, most magnifying glasses use convex lenses, as we have already mentioned.  In simpler terms for your child, the convex lens gets all the light.  It makes  images look bigger because it then scatters all that light.

When things are enlarged, they get focused all inside the focal length of the magnifying glass.  The focal length is the distance between the center of the lens and its focus, the point where an object can be viewed clearly through a lens. When we use a magnifying glass, the focus is just a few inches from the lenses.  That’s why you can have a diy projector inside a shoebox.

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However, if you use two magnifying lenses, the image won’t be inverted.

Our eyes have similar lenses to those of the magnifying glass, but our brains have learned to flip the images that we see. It’s so automatic that you don’t even have to think about it.  Just think of your brain on autocorrect when it comes to refracting light.

(8) Enjoy!

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The science has been done and I’m sure you and your child will enjoy some caramel popcorn as you both lay back and enjoy the slideshow.

Source: The Stem Laboratory: Smartphone DIY projector