You are currently browsing the diy tag archives.

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.

Thermostat V3 Schematic

Posted 2012.06.19 9.45 in Computers/Internet/Technology, Hobbies

Here is a schematic for my Thermostat V3. It’s something of a ‘block diagram’ as I did for the ISEB6 layout, as it is another project that was mostly assembled from off the shelf modules.

You can download the PDF version here.

I have omitted the lux / luminosity sensor in the above schematic, because it’s not working very well and I find it’s fairly pointless. I’ll likley remove it from my thermostat next time I’m doing work on it.

For something of a BOM and assembly instructions, please download the zip file that was linked in the original Thermostat post.


Pow! Schematics!

Posted 2012.06.14 17.32 in Computers/Internet/Technology, Hobbies

Ok so Eagle is tough and the learning curve starts off very, very steep. But it seems like if you can get past the first 2 hours, it suddenly tapers off after that.

(Or click here for PDF version)

To get the above schematic to come out, not only did I need to figure out how to make a schematic in Eagle, but I had to make my own parts library and create four devices – the Pro Micro itself (as a discrete device rather than its own board and schematic), the OLED board, the compass module, and the Lilypad LED boards.

The reason I did this rather than laying out all those individual components was that I’ve assembled the ISEB6 out of these boards. That’s what it is. So it didn’t make sense to chart out the separate bits that go into each board – just get the boards. Or if you want to look at their schematics, get them from the source (Adafruit, Sparkfun.)

Note that 3 modifications were made to the Pro Micro board directly: the diode D2 was removed, which cuts the connection between UVCC and RAW. This prevents the LiPo from being exposed to 5vdc when a USB cable is connected. The Amber and Green LEDs were removed and hookup wire soldered to them, to connect to the two Lilypad LED panels. Oh and I removed the red power LED since it wasn’t needed. 4 modifications, then.

So if you’re looking to reproduce the ISEB6 yourself, hopefully the schematic alongside the build notes and the code (available here) should be enough.

Finally – I am already working on a Mark 2 version of the ISEB6 which in fact will do away with the Pro Micro board, and will have its own PCB (hopefully) allowing me to make it all neat and tidy and eliminate the rats-nest of hookup wire that forms the backbone of the current ISEB6.

The Fun of It

Posted 2012.06.04 22.25 in Computers/Internet/Technology, Pointless Blather

So last week I did a write-up about my ISEB6, parts of which ended up making the rounds on various maker / tech blogs. I noticed a lot of people were wondering why someone would bother doing this? Why ‘waste’ so much time, money, energy, and effort making something like this?

The simplest answer is, for the fun of it.

Sure, there’s a level of enjoyment to be had from simply having the finished product, from using it. There’s the utility of it – it was designed to do a thing, and it does that thing. There’s the sense of novelty, that one might get from any new toy, be it a cellphone, computer, tv, or whatever. In this case all that is augmented or magnified by the fact that I built it myself.

When you build something yourself, you have the sense of achievement, in seeing something through from initial concept to final build. You have the knowledge and experience gained, from learning the hows and whys and whats. And you have the pride of knowing that you made something – you set a goal for yourself, and you accomplished it.

And there’s the sheer fun of solving problems and challenges. Physical computing projects like these give you the opportunity (or the challenge) to work with very limited resources. How many functions can you include, how many features can you code, when you are limited to 32kB in which to fit your entire program? And when you have only 2.5kB of RAM in which to execute that code?

Wearable projects add two more dimensions of limitations: Size and Power. How many features / peripherals can you add without making the whole thing too big / heavy / unwieldy? And how much power does everything draw? How long will it run before you need to recharge, or do you need bigger batteries?

I’ve seen a few comments that basically asked, why not just strap a smartphone to your wrist? The simplest answer there is, that’s not what I wanted. That might work for some people, of course. Find something that someone else has built that’s close enough, or good enough, buy it, settle for it.

Why settle though? I live in a world where if you want a specific product to do something the way you want it, if noone else has built exactly what you want, you build it yourself. Build it yourself and you have exactly what you want, the way you want it. And if it ever breaks, you have the know-how to fix it.

(A close runner-up is, buy something that’s mostly there, then hack it to make it perfect. Add those features, fix those functions, and get exactly what you want that way.)

Stuff does break of course. Especially when you’re building and experimenting and learning, all at the same time. Sometimes it’s part of the fun of the challenge, sometimes it’s less fun but you still roll with it. Last week the OLED screen died, I never figured out why but luckily I had a spare so I just replaced it.

Two days ago the Micro-USB port snapped off the LiPo charger. I consider that a component failure since it’s supposed to withstand plugging and unplugging. I didn’t have a spare charger board, so I’ve contacted the manufacturer to ask about a replacement, and in the meantime I did some delicate solder-surgery to enable me to keep using the broken one, for now. (That was less-fun.)

And since that write-up last week, I’ve made a dozen revisions and upgrades to the software, changed / improved some of the leather work, switched out the dull dark hardware for shiney brass, and added brass snap closures to keep it on my wrist instead of the elastic string I had started with. I still plan to redo the top leather layer to make it more attractive.

That’s part of the fun too – projects like these are never really finished. You can go on improving them, enhancing them, upgrading them, until the next big idea comes along.

Oh. My. Goodness.

Posted 2012.05.20 7.51 in Computers/Internet/Technology

I have to confess, when I soldered the final power connection and this came to life on my wrist, I kind of geekgasmed a little bit.

Yes, I mounted the parts and did the final soldering with it already on my wrist. It was the only way to be sure things would have the right fit and feel. And it was damn fun too, despite being awkward – soldering iron in my right hand, holding the solder in my teeth, keeping my left hand still…

In the photo above, it’s still ‘just’ the bare circuitry and power supply mounted to a leather bracer. There is still some debugging to do of the software. And I have to finish the exterior.

When completed most of the goodies will be hidden under a top layer of leather, with openings of course for the screen, light sensor, etc. but the idea is that the delicate parts will be protected.

The only thing it doesn’t have yet, is a proper name. It’s kind of a wrist computer, except it’s not really a computer. I’ve been jokingly refering to it as the Wrist-mo Comp-ulator. I’m not sure I want that name to stick.

Thermostat Three

Posted 2012.05.09 21.27 in Computers/Internet/Technology

This might just be the fastest project I’ve ever done. Saturday morning I started the hardware build, by Saturday evening I had also begun the software. By Sunday afternoon I was halfway through. Sunday evening saw it 90% completed. Monday was finishing touches and adding some extras just because. Tuesday I finished it. This afternoon I installed it.

Some of the things that aren’t obvious in a still photo: The the block above the screen has two RGB LEDs behind it. These aren’t programmable, but one cycles through the colours slowly and the other does so quickly. Together they provide a sort of swirly multi-colour effect that I think is reminiscent of ST:ToS effects.

The red circle ‘red alert light’ is wired to the XBee’s RSSI so when the XBee receives a wireless command, the red light comes on for a few seconds.

The white gridded rectangle is the DHT22 sensor (temperature and humidity). I felt it would ‘blend in’ enough that it should be mounted right up front for all to see. The little black hole to the right of the DHT22 is for the light sensor.

Why is there a light sensor? Why not? Also: because I had an extra one laying around.

The screen display is mostly self-evident. Time, day, date. Heat/Cool. Run/Hold/Override. Target temp (small) and actual temp (large). Fan status (on/auto) and humidity.

The last line is EV (exposure value) and free memory. That’s 657 bytes. Not kB or MB, just bytes. It probably won’t ever change but it’s there just because there was space for it.

The following images have some more build details / information:

The sketch code, and a text file with lots of my design and build notes, can be downloaded here: