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ISEB Mark III – Electronics Done!

Posted 2012.10.27 11.30 in Computers/Internet/Technology

I could be wrong, but I’m pretty sure that as of this morning, I’ve finished the electronics on the Integrated Sensors Electronic Bracer Mark III. (Wait haven’t I said that before?)

I’ve mounted the last electronic component. It seems to be working fine. All that remains to be done from this point, is finishing the software and the new leather bracer. And an enclosure.

The last part was the micro TV-B-Gone that I assembled a while back.

I’m pretty happy with how things have turned out, even if it has taken a few months to get to this point. It’s all self-contained and even though there are a couple wires, nothing is going to be flexing around – it’s one solid unit.

One minor challenge is the name – ISEB-6 is not entirely applicable as the Mark III has more than 6 sensors… and ISEB-8 just doesn’t roll off the tongue as well. #madscienceproblems

Mark III Rev D – It’s Alive!

Posted 2012.10.21 10.40 in Computers/Internet/Technology

The ISEB-6 Mark III revision D is alive! I put the finishing touches on the soldering this morning. All that’s left now is finalizing the software. And making the actual leather bracer. And mounting the electronics. And building a slick enclosure. And…

Ok there’s a lot more to go yet. But still – look!

Isn’t it kewl?

The only real bother I ran into was the display’s only got 3 bolts instead of 4. It’s still sturdy, the data connections are all soldered solid. The problem was when I routed all the traces, I forgot to leave room on both sides of the board for the hardware. So the top-left corner under the screen has two SMD resistors that would short against the nut, and the bottom of the board has two traces that would be cut if I counter-sunk the hole to accomodate the flat-head bolt. Bummer.

Apart from the problem with that one bolt, everything else went together fairly smoothly. Mostly.

The image below shows it almost ready for the screen – the BMP085 is in place for sensing temperature and air pressure; the ADXL345 is in place for measuring accelleration. I’ve also added a white LED to serve as a flashlight, and with some creative snipping and soldering, I fit the Lillypad Vibration motor in underneath the screen too!

When the whole thing’s done and finished, I’ll be posting everything (code, board layout, BOM, assembly) so anyone can make their own ISEB-6.

Also noteworthy: there are still two available analog inputs (A0 and A1) and three available digital IO ports – B2, C2, and C3. Expansion possibilities!

I positioned C3 near the ICSP port so one could add a SPI peripheral by using C3 as a slave select (the display is already using the default SS pin). C2 is on the sub-board with the buttons, to allow expansion there. The other three available I/O pins, along with the I2C bus and power are available at the top edge of the board for easy expansion.

Building & Testing

Posted 2012.10.20 9.59 in Computers/Internet/Technology

Last night I started the build of the latest version of the ISEB-6 circuit board. So far it’s all been surface-mount parts, but I was able to get it to this point using a standard handheld soldering iron with a fine tip.

The smallest-pitch part is the FT232R chip (USB to serial) which has 28 leads that are only 3/10ths of a millimeter across, and about 3/10ths of a millimeter between each pin. That’s basically soldering with your nose to the board, the soldering iron right next to your face, and while using a 5x jeweller’s loupe to see what you’re doing.

At least, that’s my technique.

Apart from the microcontroller and the USB chip, I’ve installed & tested the GPS module, temperature sensor, humidity sensor, light sensor, a voltage-divider for monitoring the battery charge, the voltage regulator and the LiPo charger. And of course all the sundry supporting passive components, and a smattering of LEDs.

There’s only about a half dozen surface-mount parts left to be mounted. The three remaining ICs though are tricky. They don’t have leads – they have pads on the bottom, so you can’t actually get to them with a soldering iron.

To get these soldered, I need to use a hot air tool and some luck. There’s the air-pressure sensor, an accellerometer, and the magnetometer. I’ll put them down in that order (from least-complex to most, and least-expensive to most.) and test between each one to ensure they’re working. All three use I2C so it’s pretty straightforward to test if they’re working or not.

Then the last bit of work on the circuit-board is to mount the display screen. This will require a little bit of hardware work to securely mount it with the mounting holes. It has to be last since it covers some of the other circuitry.

And after that, the leather-work begins – making a new wristband, and mounting / enclosing the circuitboard.

Yummy Purple PCB

Posted 2012.10.16 21.56 in Computers/Internet/Technology

Another batch of boards from OSHPark has arrived.

More precision soldering in my near future.

Looking forward to it.

More Purple PCB Goodness

Posted 2012.08.17 20.41 in Computers/Internet/Technology

Whilst working on the ISEB-6 Mark-II, I have also been preparing some peripherals to work with the latest greatest version of the Electronic Bracer. It seems obvious really, that ontop of everything else, the ISEB-6 should be capable of turning off annoying televisions.

This tiny circuit board (less than one square inch) houses the circuitry for a totally self-contained TV-B-Gone. Pictured below are two populated and one bare board.

Designed to be triggered by another microprocessor rather than a manual push-button, this miniature TV-B-Gone will be integrated into the new ISEB-6 – providing TV off-turning abilities, built right into a wrist-mounted platform!

As evidenced by the Purple PCBs, these boards were fabbed via OSHPark, for only $5 for the three of them. Have I mentioned how much of a fan I am of Laen’s OSHPark service? Yeah, Laen rocks.

Got Some Soldering Done

Posted 2012.08.14 8.20 in Computers/Internet/Technology

This past weekend I got the new version of the ISEB-6 mostly soldered out.

It all went together fairly easily, with two unfortunate exceptions. The BMP085 barometric pressure sensor, and the HMC6352 magnetometer/compass. Both components are surface mount ‘leadless chip carriers’ – and both proved harder to hand-solder than I expected.

The thing is, unlike the ATMega1284P which is a TQFP-44 or the few SOT23 parts — all of which have ‘pins’ sticking out (albeit tiny pins), the two aforementioned sensors are in LCC packages where the connections are all underneath the part. There’s nothing visible from ‘above’.

I had some tricks in mind to solder them, and the tricks failed. In the end, I unfortunately destroyed both parts. Boooooo. Fortunately I did have a spare BMP085 laying around, but the HMC6352 is kinda-expensive and I didn’t have a spare.

Also-fortunately, I had a backup plan for soldering these tricky parts – hot air. I have a Sparkfun Heaterizer XL-3000 which I hadn’t actually used before. It did the trick though, allowed me to remove the dead parts without destroying the rest of the ISEB6 board, and I was able to solder the new BMP085 with it.

When I get a replacement HMC6352, I’ll use the Heaterizer once again to get that in place.

After that, the next steps will be to assemble a new leather bracer, and then build it out, with all the peripherals.

Got Some Soldering To Do

Posted 2012.08.10 8.48 in Computers/Internet/Technology

Yesterday I received more purple PCB goodness from OSHPark / Laen. The ISEB6 Mark IIa circuit boards came in!

I must say, I am really looking forward to moving from the current “prototype” version (which yes I am wearing every single day) and the Mark II.

Partially I am eager to be able to take advantage of the new software — I’ve been working on the software upgrades for weeks, taking advantage of the 128kB flash and 16kB sram — but I’m also really looking forward to not having any more ongoing problems…

Yes problems. The current version is a ratsnest of hookup wire. Between two layers of leather. That flexes on my wrist.

Seems like every week one of them breaks. (Grumble grumble.)

Mostly it’s been the battery sensor wire – that one is vulnerable because it does wrap partway around my wrist, and is subject to flexing more than the others. Suddenly I’ll get battery alarms that VBat is at some crazy level like 1.27 volts or 5.82 or whatever. Impossible levels. (Grumble grumble.) Annoying but not fatal.

Sometimes though it’s another wire. This morning the D/C line to the OLED broke. When that happens the display goes crazy, then goes dark. (Grumble grumble.)

With the Mark II, these problems won’t occur any more. Ok there might be other, different problems, but broken wires won’t happen any more. No more %*)(^%& hookup wire!

Except…. quandry.

I designed the board around Adafruit’s original 128 x 64 OLED display. While waiting for the boards to be fabricated, Adafruit came out with an upgraded, larger 128 x 64 OLED display.

It’s a ‘drop in’ replacement in the sense that the driver chip is the same, everything is identical, no software changes are required, and you can use the same exact set of connection to make it go.

It’s not a ‘drop in’ replacement in the sense that a) it’s a different size, and b) the pins are totally completely utterly different.

And I really like it. It’s a perfect size.

So if I go with the display I now want, I’ll have to use hookup wire. If I go with the display I designed for, I’ll be sad because it’s ‘too small’.

Ok the third option is redesign my board but dangit! I don’t want to wait another month, I want to build now!