there are plenty to be found in art supply stores but they can be expensive and every one i've ever seen has required you to be plugged into an electrical outlet for power. sometimes having to deal with a cord while you're trying to turn the table to a different angle is just annoying so lets get on with this instructable so i can get back to the drawing board.
Step 1: Materials.
an acrylic sheet. you generally don't want a clear sheet because a translucent white sheet will help diffuse the light so it's a bit more even across the board. it should also be thick enough to write/draw on top of .177" thick should be good for most but if you're making a big light table you may want to get something a bit thicker.
walls and a floor. doesn't matter too much what these are made of so long as it's sturdy enough to hold up the acrylic sheet and take whatever pressure you put on it while drawing. needs to be opaque (doesn't let light through) and something white or that you can coat white on the inside somehow. just use your common sense and don't make it out of anything harmful to your health.
LEDs. personally i'd go with white but if you want a trippy hippy light table that's your call to make... you could probably hang that on your wall or something... yea.
Resistors. don't wanna burn up your LEDs.
Electrical Wire. spreading out your LEDs will help even out the light across the drawing surface.
Batteries. needs power
Battery holder(s). because holding them yourself gets tiresome.
Power switch. it's easier than taking the batteries out.
Step 2: Think About It a Bit
Having a lip can keep things from sliding off the side as well as give you a corner to easily line your pages against but it limits the size of page you can work with. Having a smooth top surface allows you to work with smaller portions of a larger page but leaves you without an easy way to keep pages lined up with each other.
If you want a lip then you'll need a router. For a flat surface you don't need a router but you'll need to a way to countersink your screw holes in the acrylic to keep the top surface flat.
you're going to want the last piece of the box to be removable so you can easily replace anything you may need to in the future.
Step 3: Sawing Your Parts.
To compensate for that I always cut a little outside of my marked line to give me a buffer area that i'll be able to sand down to the right size or angle later.
First, I measured the long sides of my acrylic and cut two walls to fit them.
Once I had the long sides cut I used my dad's old dremel and his routing attachment to cut the groves for the acrylic sheet.
Next I set them up holding the acrylic to measure how long the last two sides needed to be and proceeded to cut them.
Lastly, I measured and cut the bottom out of some scrap plywood.
Step 4: Glue
it takes longer but it can bond the pieces together stronger than if it were just one piece of wood and unlike screws it isn't focused at a few points.
i lined my parts up on the bottom and carefully glued one side down at a time. the glue i use requires 3 hours of clamped time and 24 hours before putting any stress on it.
in the time it takes between waiting for the glue to set enough to remove the clamp and glue another wall you can move on to another step.
Step 5: Time to Fiddle With Some Glowy Bits.
i plan to throw a jewel thief circuit in here once the parts i ordered actually get here but until then i'll stick with something simple.
you can easily figure out what you need, including the resistors, using this LED series/parallel array wizard.
remember, connecting batteries in series adds their voltage together while connecting batteries in parallel will let them last longer but won't add voltage.
create your circuit. you finally get to play with your LEDs.
I'm using two battery packs from some LED flashlights i had laying around.
My battery holder for them was made out of InstaMorph plastic. it doesn't look the best but it gets the job done.
Step 6: Make the Insides White.
a white surface will help diffuse light in order to create a more evenly lit drawing surface.
using a curved white surface inside the box greatly cuts down the total area that needs to be lit while also allowing you to hide your batteries inside the box.
to do this i'm cutting a larger piece of some of my heavier paper and folding down the two ends so it sits properly.
Step 7: One Last Then and You're Done!
i think i'm going to experiment with some different arrangements for the LEDs to see if i can even the light out but it certainly works well enough to get the job done as it is.