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The ultimate guide to reverse polarizing a clock

You're at a party and it's late. "Do you have the time?" asks a friend. This is the moment you've been waiting for. You whip out your awesome reverse polarized digital watch and everyone stops and stares. You then say "It's 12:34 and 46 seconds...KICK IT!" The DJ fires up some techno and you make your exit while moon walking on your hands out the door. All because of your super sexy, futuristic, easy to read, reverse polarized, digital watch that you made using this simple guide.

How does it work?

Well, to understand how a reversed-polarized LCD works, you need to understand how a regular LCD works. When light hits the front panel of an LCD, it becomes polarized. The first layer of an LCD is a layer of plastic with thousands of "lines" that all face the same direction and block any light undulating in another direction:

I'm a horrible artist and I did this freehand with a mouse. Gimme a break! Anyway, these are supposed to be light waves facing toward the viewer, the very front is kind of a cross section. Note: Light waves are not to scale

Because polarized light waves only wave in one direction and a polarized film blocks out all directions but one, when polarized light moves into a plate with perpendicular polarization, all of it is blocked (at angles like 45 degrees, only some of the photons go through, but that's quantum mechanics). Think of it like a jump rope going through a fence. If you make a vertical wave, the wave will carry on the other side of the fence, but if you do it horizontally, the fence will stop the wave.

After the light becomes polarized in one direction on the front of the clock's screen, it passes through the liquid crystal. When no charge is run through this crystal, the light is twisted so that it is now polarized at a different angle. After this it passes through another polarizing film that is polarized at the angle of the now twisted light. Here, this should sum everything up nicely:

Okay! I get it! I can't draw!

This will make the screen light-colored at the time because it is letting light pass through it. Now to make a dark area (like a number) show up, the watch/clock puts a charge through the liquid crystal making it become straight instead of twisted. When the light passes through the liquid crystal, it keeps its vertical polarization, and gets blocked by the second polarizing layer on the way out. Here's a picture:

This creates a black area on the screen.

So, to actually make this mod, all you have to do is switch one of the polarizing layers around. If both layers have the same polarization, then twisted light will not pass through while straight light will.

The victim:

Now would be a good time to let you know that I did this entire project before I had my new camera, so I took all of the pictures of this project after I was already done (I took it back apart). This would explain the ridiculously small picture of the un-modded alarm clock (it was the only one I could find online).

I think this is a new record. This caption is bigger than the picture!

This is a Sharper Image alarm clock that I got because my old alarm clock had an alarm so loud that I would wake up before it went off just so I wouldn't have to hear it. Although this thing looks pretty slick in this picture, it's actually very bulky. The base holds a staggering six AA batteries. I'm assuming that these are required to power the blue backlight when it's on the road. The coolest feature of this clock is that the clock face/clock circuit are powered by a small watch battery so it never loses time.

The reason I wanted to reverse polarize this clock was because with the massive backlight, the numbers were hard to read from far away; they often just got blurred out. I heard somewhere that it's easier to read light colors on dark backgrounds, so I decided to give it a try.

Voiding the warranty

Sorry for the horizontal lines, but my new camera does that sometimes when the fluorescent light on.

The whole clock came apart pretty easily. Everything was screwed together so I didn't even have to break or cut anything. When I took apart the top section, I was surprised to find that the clock's circuit was in the top. This means that the bottom of the clock contains nothing but buttons and THE MASSIVE AMOUNT OF BATTERIES.

I love the fact that the Sharper Image uses masking tape to hold their products together.

Inside I found the electroluminescent sheet which was surprisingly flimsy. It felt like a thick piece of plastic. It looks like a white piece of plastic that has two wires coming out of it:

The blemish in the bottom right corner is actually somehow built into the sheet. I was surprised to find something so blurry on a Sharper Image product.
Removing the screen

Alright, here's the part when you're gonna have to trust me because, like an idiot, I didn't take pictures. The face of the clock is just a thick piece of glass with the liquid crystal somewhere in the middle of it. To get the front filter of, I used a small flat head screwdriver. I actually chipped a lot of glass off the corner, but luckily, it's pretty durable and thick. Once I got the corner off, the rest of it peeled off, but it wasn't easy. This thing was not designed to be taken apart by anyone, so they used some pretty killer glue to hold it on. Once the film was completely off, I noticed that it was coated in the aforementioned glue. I tried to use a solvent like Goo-Gone, but I found out that this actually messes up the film and makes it very blurry. The best/only method for removing this glue is rubbing. I sat down in front of good movie with my thumb all warmed up and started rubbing. Very very slowly, the glue started to roll off, similar to the way that rubber cement does. This part isn't that hard if you're doing it to a smaller clock.

The rest of the steps

The front sheet on most clocks is polarized in a diagonal direction so all you have to do is flip it over. If it was polarized from top left to bottom right, now it's polarized from top right to bottom left.

Creepy! It's like a secret decoder! What's actually happening is that all the polarized light coming off the clock is visible, but when it hits the front polarizer, some of it is blocked (creating the numbers).

When the polarizer is flipped and fastened and the whole clock is re-assembled, it looks something like this:

Testing the clock

Now for the final test: how does it look in the dark?

Oh, yeah, I forgot, my new camera totally sucks in low light situations, but trust me, it worked.

Well, there you have it. Now you can make your own very sexy and easy to read reversed polarized clock!