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ISEB Mark III – Electronics Done!

Posted 2012.10.27 11.30 in Computers/Internet/Technology by Stephanie

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 by Stephanie

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 by Stephanie

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 by Stephanie

Another batch of boards from OSHPark has arrived.

More precision soldering in my near future.

Looking forward to it.

Moment of Weakness

Posted 2012.10.03 14.38 in Computers/Internet/Technology by Stephanie

My handy little 4GB SD card that I use for occasional backups and to ferry files here and there accidentally let its guard down. But just for a moment!

In that brief moment I saw its weakness, and instinct took over. I pounced, and just like that, the SD card had been skinned, its inside-y bits laid out for all to see.

Interesting stuff. I assumed there’d be just a single chip in there, or more likely, one of those blobs-on-a-board. Except – damn it, now I need to get a new SD card.

Actually a few weeks ago I had dropped the card in my office then run it over with my chair – quite by accident – and was surprised to find it still functional. The chair had cracked the outer shell though, and I’ve been trying to pretend not to notice ever since… today I couldn’t resist any longer. Had to see what was inside.

My Eagle Library

Posted 2012.08.19 9.06 in Computers/Internet/Technology by Stephanie

In my recent electronics adventures, I’ve had to learn to use Eagle, and in using Eagle, I’ve had to create some parts layouts.

I’ve a handful of parts (packages and symbols) set up. A few are mostly for reference, eg. items I created in order to make the schematics of my Thermostat V3, or the current prototype of my ISEB-6. The symbols are ok, but the packages (board footprints) are not tested and probably not accurate.

Other parts, that I have set up while working on the ISEB-6 Mark-II are more certain, eg. the TQFP-44 footprint for the ATMega1284P, surface mount TMP-36, et cetera. These parts’ footprints are tested and known good.

I’ve left comments in the library to indicate which ones are known to be good and which ones aren’t.

You can download the library by clicking right here: Stephanie’s Eagle Library.

More Purple PCB Goodness

Posted 2012.08.17 20.41 in Computers/Internet/Technology by Stephanie

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.