Build Log

Buttons & the Third PC Board

Wed, 18 Feb 2009 17:38:19 -0700

Progress continues... I made some experimental buttons (above) to test how they’d work and feel. I made a prototype with these buttons (shown here with a back piece), and it felt surprisingly well. But, they had to go... I changed some basic assumptions about how I used the space inside the case, and they didn’t fit anymore.

The new PC Boards came in yesterday, courtesy of Advanced Circuits / 4PCB (which is close to me, in Denver, CO). Here are the basic changes:

The new board had to be about 20% smaller to make the case symmetrical. This was the Spread Sheet disaster I made earlier.
The buttons where actually designed to fit with the case and the board - I made some changes that should make them work better. The buttons should feel better, be more rugged, and last longer... well, that’s the plan.
I added a battery level detect circuit because I want to know when the battery is going to die. Originally I thought that the microcontroller could do this without any additional components -- it’ll work fine when the battery is running (3 - 3.7 volts), but it exceeds the limits of the chip if you charge the battery (4.25 volts). This seems like a mistake on SiLab’s part ... it would be nice if the easily accommodated rechargeable lithium batteries.
I improved the ground plane for better noise - this isolates the 12v power supply from the sensitive accelerometer.
I also switched to a digital accelerometer. It costs slightly more, and there will be a slight power reduction, but I’m hoping that I’ll get less noise in the system. The accelerometer also some some nice features like a tap-to-wake detector.
I also fixed some capacitors that didn’t fit - I hadn’t left enough room for them. Tantalum are usually used for these bigger capacitors (4.7-10uF), but, to my surprise, some new ceramic capacitors have come on the market that are actually smaller (and also substantially thinner).
I used a thinner board - 0.031 inches instead of the usual 0.062. This means a thinner watch and/or thicker batteries. My previous board vendor, while they do an excellent job, would have charged 3x the price 4PCB did for this simple change!

But the big change was how I placed the parts. In the previous design, I put all the chips to one side and used the remaining space for the battery. Because I had to shrink the board and add more functionality, this wouldn’t work for the new design. So, besides the thinner PC Board, I made sure every component was thinner. The only components I couldn’t get thin - the switches and one power supply - remained on the edge.

Relative sizes are correct; Battery shown in red overlay.

I made a wax prototype (which is quicker to machine than plastic) to make sure everything fits with the new circuit board. Here it is:

While this looks very similar to my previous cases, I’ve totally redrawn it with a real CAD package. I can recommend Alibre Design - it has a lot of powerful features, and a limited-use version is available for free (windows only, though). They have good video tutorials, too. This opens the door to more complex designs (but I think I’ll keep it pretty close to this shape), and the ability to have other people produce the design from drawings.

At the lower right, you can see the new button switch. This should have a better feel and be more durable. At the top right is the new key cap -- this replaces the squarish ones I made shown at the top of this post. It’s in backwards, but that’s good enough to verify the clearance. It’s an off-the-shelf part with a nice textured finish, and here’s what it will look like:

(call me weird... I think that’s a good looking button!)

Next up: designing the back, making a plastic case, making a jig to accurately locate the holes for the buttons (my milling machine can only do top and bottom; it can’t do sides), and then testing/building up the circuit board. I’ve got software to take advantage of the buttons somewhat, but that’ll have to improve, too. Wow, still lots of work to do!

Other Watches

Wed, 14 Jan 2009 17:49:11 -0700

I love watches, so here are a few that have piqued my interest:

The Uni Watch by Quixen-p

This is probably the most similar one to mine - the design aesthetic is the same, but the guts are a little different. It uses a 96x96 pixel color OLED display in a 32mm x 32mm x 9 mm rubberized plastic case. It’s close in size to my upcoming third design (36 x 38 x ~10mm). Besides the look, it also has an accelerometer and is customizable by the user.

It’s unclear how far developed this watch is (or even if it physically exists - the pictures look awfully clean); they are looking for investors and hope to produce it at the end of 2009.

The Void v.01 Watch

I love the case on this watch; it’s just like what I’m designing! It’s a brushed metal with a black finish, with rounded corners. Even the back plate is much how I’ll be doing mine.

The insides, though, are totally different. It’s just a plain LCD watch wrapped in a pretty case.

Currently available to buy for 129 Euros (about USD$170), in a variety of colors and finishes.

Aeolab DELO Prototype

A very cool prototype with an OLED display and a variety of time themes available.

Milled with the a milling machine similar to mine!

uWatch DIY Scientific Calculator

This doesn’t look anything like mine in form or function, but there aren’t a lot of other DIY watches. I like how a PCB is used to make the faceplate.

This one is available as an easy-to-build kit (just solder the battery and epoxy the strap lugs), for USD$99 without a band.

Space invaders watch

I love the look of the invaders on the face, but, unfortunately, a lot of it is fake. Most of the design elements - the player, the ufo, the defense bases, the score - are all static. The invaders are actually just an 18x5 pixel display that is used to draw much bigger animations.

Still cool, but doesn’t quite live up to its potential.

Available for sale - 18,690 yen (about USD$210)

Liquivision X1 Dive Computer

Now, this is a serious instrument! It has a 128x64 oled display in a sturdy pressure-rated case.

Has a rebreather interface.

Available now, USD$1750

Spread Sheet Disaster!

Sun, 13 Jul 2008 15:48:10 -0600

See that image? That’s the result of a tiny miscalculation back in march :-( It’s still smaller than my first try, but it was supposed to be much smaller. See the “chin” on the bottom? It’s supposed to be the same size as the smaller “forehead” above.

This mistake goes back to when I picked a new OLED display. The idea was to make the smallest possible watch with the display centered. Because the display isn’t symetrical vertically (there has to be room on one side for the chip and the electrical connector), this isn’t as simple as it would seem... in fact, it’s so hard, that Albert Einstein might have had trouble with this at age 3. So, when I messed up the calculation in Excel, I didn’t notice until it was too late.

I designed and made the PC Board in a bit of a rush to take it to the Maker’s Faire. I didn’t want to damage the screen, so I avoided handling it -- it wasn’t until I got the PC board and the screen together that I realized the problem. But, even though it’s not as aesthetically pleasing, there was still stuff to learn by continuing on (not to mention that those PC boards were expensive!).

So, I’m making a case for the second version so that I can wear it as a watch. This one will hopefully have buttons (I need to machine this), and it’ll serve as a testbed for using the accelerometer as a user interface. A lot of the components are all new (but similar to ones that I’ve used before), so I’ll be testing those. And, finally, I’ve got a much better charging system connector to try (I’ll write about this later when I get some good pictures).

This second version as an attempt at thinness & a bigger battery - it would have worked, if I hadn’t made the case so big!! I didn’t have components under the battery, so I saved 1mm of thickness. But, one drawback this left was that I had a lot of wasted space above the circuitry - hopefully I can optimize it with the new design to eliminate that waste.

Next week it’s off for a whirlwind one week/three city vacation - I’ll be attending the Hope conference in NYC (not speaking this year - I spoke at Hope 6). I’ll catch a taping of The Daily Show, then visit my parents, and then attend the wedding of a good friend.

If you’re at Hope or in NYC July 18th-21st 2008 , drop me a line! john at maushammer and then dot com. Or, look for me at the show - I’m hard to miss with my shiny red backpack.

Second PC Board & New Parts

Sat, 26 Apr 2008 22:18:34 -0600

I’ve been speeding up development so that I’ll have some more stuff to show at the Maker’s Faire next weekend (I’ll be presenting Sunday at 1:00). Since the new design is a lot more complicated, I had the PC board professionally made rather than make it myself.

I finished up the board design monday night & got the boards yesterday (it’s great how much more automated PC board manufacturing has gotten). I eagerly soldered it up this morning. I tested the power supplies before adding the rest of the circuit so that, if they had been incorrectly set, they wouldn’t have fried anything. With everything in place (except the battery), it looked like this:

It looks dirty because I used a lot of flux to make sure the solder flowed where I wanted to; this will clean off easily with alcohol. I used yellow kapton tape to hold the OLED in the correct place while I soldered it, but it doesn’t have to be there; I’m leaving it on just as extra protection against bumping while it’s out of the case. Lastly, the OLED looks really dirty because it still has a soft protective film on it.

A quick tour of the PC board: First, it’s just a little bigger than a square inch. See the vertical line slightly to the right of center? All the parts are mounted to the right of that line so that the battery can occupy the left side. By doing this, I can make the watch a millimeter thinner. Lastly, the large rectangle at the bottom is a cutout for the IC that’s part of the display. The quick-turn PC Board manufacturing I used wouldn’t allow for cutouts, so I dremeled it out -- that explains the rough edge.

Although I’ve reused a lot from previous prototypes, this board is mostly new components. Both the OLED and the processor are parts I’ve never tested before, but they’re based on older versions that I’m familiar with. Other new parts include an updated accelerometer, a better battery charger, and a new +12v power supply (although this one is basically interchangeable with the old one). New features include two buttons, static protection on the charging port, a new way of connecting the charging port (still not wireless - if I had more time, I’d investigate that), and the possibility for loading new software in to the watch without ever opening it up.

That’s a lot of updates, so I’ll cover them in a new post. But, right now my main focus* is the Maker Faire - if you’ll be there, give me an email - john at maushammer, then dot com. I’ll be there both days (& probably thursday and friday too). I’ll also be helping some friends teach soldering classes.

(* besides my family that’s visiting, and, at my full-time job, the release of some amazing software in 2 weeks)

- - - - - - - - - - - - - - - - - - - - - - - -

5/12/2008 - Maker Faire Update: I had an awesome time!!! Of course this was kindof expected because Make Magazine puts on a great show, but it always surprises me in new ways. I didn’t have a booth this year because I wanted more time to walk around and take in the other exhibitors. I was lucky to team up with the awesome folks at Evil Mad Scientist Laboratories (don’t let their name fool you - they’re fairly well tempered) and got treated to the world premier of their cool Peggy 2.0 kit. Last year I missed seeing their awesome candyfab, and this year I got to sit right next to it!. Here’s a picture of our booth.

The IEEE interviewed me about my watch - they did an excellent job of editing together my rambling descriptions - thanks! See the video here.

So, besides showing off the watch (and I’ve got a case prototype that I’ll post about), I got to meet tons of cool people from all over the world. It’s an amazing community of makers - such creativity! I also taught some soldering classes, and had an excellent student - Jake - whose first attempts were better than most professional engineers I know - he’s a natural!

Lastly, I was honored with an Editor’s Choice award from someone I really respect (that makes it all the better!), Mark Frauenfelder. We’re both members of the order of people with ridiculous last names - thanks, Mark!

If you missed the San Francisco Faire this year, there will be another one in Austin.

MP4 Watch Teardown

Fri, 4 Apr 2008 21:40:41 -0600

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.