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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.

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.

Yay! Party On!

Posted 2012.05.08 22.00 in Computers/Internet/Technology, Pointless Blather

Yay! More solder!

Solder Party’s Over

Posted 2012.05.08 17.10 in Computers/Internet/Technology, Pointless Blather

Awww. Solder party’s over.