Slow Week / OLED disassembly
 
I had planned to prototype the power supply this weekend, but my 2-day shipment of parts has taken its sweet time. So, I’ve been learning Blender 3D in hopes that I can use it with the milling machine I should be getting next week. I’ve just barely drawn a box ... it’ll be a while before I can show some renderings of the case. I also ported over the code from my Microchip processor used in my prototype to a smaller TI MSP430 chip I’ll use for real. The first try used 2020 of the 2048 bytes available!
 
 
I also took apart my OLED display. OSRAM sells it with a bunch of options, but the only way DigiKey sells it is with the steel frame. I plan on ditching this, so I wanted to make sure I could remove it without damaging the screen -- turns out that this was pretty easy.
 
I took some close-up pictures to show how the OLED display is constructed.
 
Here is how it looks stock:
The green flex circuit is standard; the yellow flex circuit is an option.  It would be easier for me to connect to the green flex and move the components on the yellow flex to my board... that way, I can place them where I want them instead of in the middle of the watch.
 
There is one major problem with that, though. The green flex is designed to be attached with an Anisotropic Adhesive (also known as ACF). That’s a fancy term for a glue that conducts vertically but not horizontally. It’s great for manufacturers because it connects 20-200 wires easily and permanently. But, being glue, it’s hard to take apart. And it’s a technique that is out of the reach of hobbyist because it requires a heat press, special fixturing to hold the parts exactly in position, and many tries to get the process right.
 
So, I’ll stay with the yellow flex. I’ve ordered a connector that it should fit easily.
 
Curious what’s underneath the yellow flex, I peeled it back from the glass:
A close-up shows the patterns of metal on the glass:
Half of the rows connect on the left side (not shown), the other half connect on the right (seen above). All columns connect on the bottom.
 
The green flex connects to the rows and columns on the glass to a driver IC. The control signals for this IC then connect to the yellow flex:
 
 
You can see the glass is made up of three layers. On the top is some sort of filter (not sure what it would be [updated: see next paragraph]). The larger glass has a metal pattern and connects to the green flex (again through the same type of ACF process, but much finer than I could solder to!). Below that is another piece of glass, presumably with the horizontal wires (there is probably an electrical connection between the two pieces of glass). In between the pieces of glass is the OLED material.
 
Update 1/3/07: I did a little research and found out that the top layer is a polarizer. LCDs require a polarizer to form an image, but OLEDs don’t. So, why is it in? It’s to create a dark black for the off-state. Crossed polarizers are a great way to eliminate ambient light, greatly increasing contrast. But, they cut the OLED’s brightness in half and also cost money to add.
 
 
Sunday, October 1, 2006