I love engineering, and although it’s fun to design my own stuff, it’s also fun to see how other people tackled the same challenge.  The watch I’m designing is pretty unique, but there are a few others that also use an OLED display.  To that end, I bought an Andalong MP4 Watch (similar to ones available from ThinkGeek) & took it apart. 

This watch features a 1.5” color OLED display and plays music & videos. The screen looks awesome (the above picture is real & unretouched) and the sound quality is great.  Overall, it’s nicely down, except there are two big flaws.

The first flaw is how you reset it.  See these two big buttons for forward and back navigation? Don’t ever press them at the same time, or else it instantly resets and turns off!

The second flaw is important to me.  This device works great as a media player, but isn’t so good at being a watch.  It’s got a pretty face:

... but it’s bashful.  When you’re playing music, the watch will use this as a screensaver.  But, if you’re not playing music, you need to hold the play button down for 2 seconds, and then either select the time display from the menu system, or wait 15 more seconds for it to go in to the screensaver mode - it’s far easier to get my cell phone than that.  If it’s not playing, it will eventually turn itself off. This timeout is adjustable, but the battery lasts only 11 hours in the time display mode.

The face of the watch is about the same size as my first watch, but it’s much thicker: 12.85 mm (vs. my watch’s thickness of 10 mm)

The case is held on with 4 small screws, which are self-tapping so they’re not too durable. The watch is also insanely *not* waterproof - I’d be afraid to sweat near it.  Besides the big holes in the case, the circuit board is bare; I plan on conformally coating mine to give it a fighting chance against corrosion.

The inside is dominated by a 250 mAHr battery (my watch used a 100 mAHr battery, but it has a low-power processor and a smaller screen to drive)

Underneath that is a circuit board:

The watch is powered by a Sigmatel STMP3506 processor -- similar to the one used in the iPod Shuffle, except it adds an MP3 encoder (used for voice recording).

You can see the six buttons arranged around the edges.  At the top left is the micro-usb connector used for charging and uploading music.  The smaller chip at the top is the TEA5767 FM radio. To the right of that is a small microphone, and the connector for the headphones (sadly, the normal 1/8” connector didn’t fit; they use a smaller plug).

The memory is on the back of this circuit board:

The OLED display is attached at the bottom, in a method similar to what I’ll use for the second version.  I’ll make my watch thinner by mounting components to only one side of the board (I’ll have a cutout for the driver chip that’s part of the OLED), and by using a thinner battery.

(I swear these are not my toes! It’s just that closeups of my

fingers look funny when squeezing something really hard!)

The design of my second PC Board is coming along... I’ve got the processor (E$1) and accelerometer (E$2) placed, but not routed yet.  I copied the power supply from my first design just to make sure it fits ... I might still tweak it.  I added 4 little buttons (but I’ll probably use just two because buttons are ugly).  At the bottom (in blue) is the where the OLED mounts.  It looks like there’ll plenty of room, but I’ve got a few extra components to add and a lot of routing to do.

The new OLED came in today - it’s tiny! I’m anxious to try it out.