Today I took the watch for a spin. 1 hour to work, and then 6 hours after work, bringing me up to the present moment.
Everything generally went without a hitch. Connection stayed strong throughout until about 4 hours in when I noticed that the connection dropped twice in quick succession. I thought it could be due to weak signal so kept the phone close to the watch and lo and behold, problem fixed…
…Until I got in the car on the way home and the watch stopped working altogether.
When I got home I took it apart to find a broken solder connection in the wire of the strap. Well that explains everything.
A bit of solder and some hot glue to reinforce the joint and everything is back to perfect.
Still waiting to see how long the batteries last.
After last night’s disaster, I’m pleased to report some good news. The straps are largely done and the watch can be worn. Even if it looks a little crude for now.
On my wrist!
As you may be able to see, the wires are slightly exposed. I plan to fix this by attaching a cover over the top of the watch (with a hole for the LEDs and buttons) which will attach by velcro to the strap.
After that, all that is left to do is figure out how I will make the buttons accessible through the case.
Laid out flat. I apologise for the poor image quality.
Today was pretty productive; I now have more or less functioning straps – there will be a detailed post on this soon – but the aim of the post is to describe a disaster that (I hope) I managed to avert.
I was working on installing buttons in the case so that the electronic switches could be pressed from the outside. First thing’s first, I need to drill some holes… The lid comes unglued, the drill slips, the lid is ruined. Not a big deal – I have plenty of plastic and it only takes a minute to cut.
This time I drilled the holes before gluing the lid on – success.
Now lets put the circuitry back in – it doesn’t fit.
Confusion. Scrape away the glue from the edges. Okay, it fits.
Right, so lets take the circuitry out and put the buttons in the holes. Damn fiddly, but fine.
Now to replace the circuitry… A switch catches on the button and comes clean off the circuit board.
Hair torn out.
Test other buttons with new program. First button – fine. Second button – fine. Third button – fallen off. Fourth button – doesn’t work.
More hair torn out.
By repeatedly reheating the joints of the non-functioning button and adding a little more solder the button seems to work 85% of the time. Okay, that’ll do for now.
Soldering on the fallen-off-button – turns out to be a piece of cake. Can I have my hair back?
Having been let down by my original battery supplier (they never arrived from the Philippines) I ordered new ones from Cool Components on the weekend, this time 2x110mAh 3.7v LiPo cells. Impressively, they arrived today and they are much smaller than I thought!
Definitely going to fit two of these on my wrist 🙂
Now I just need to order some JST connectors to wire them up in series and get some leather to make a strap!
I like to think today has been pretty productive. Major advances on the case have been made to the extent that it can now be strapped to my wrist. Clearly there is no power the the watch, because the strap is only temporary and doesn’t contain a battery. Furthermore, the buttons are covered by a layer of plastic and cannot be pressed (more on this in another post). However, I am happy with the shape of it and am confident it can be progressed. The case consists of only two parts which will (probably) be held together with a rubber band.
Structure of the case
The next step will be to drill holes for the power wires and also attach velcro for the strap.
This issue has been playing on my mind for the last 3 weeks, all of which (bar 2 days) have been spent abroad, with miles of ocean between me and trying out my ideas. Finally today I got a chance to mess around with case ideas. Prior to travelling, I ordered some free samples of different cases from OKW Enclosures. Both of the models I ordered were incorrectly sized in one dimension. A lot of modifications will be needed. I will be posting progress slowly over the coming days.
The enclosures I ordered from OKW Enclosures
The enclosure I will be modifying to fit the board.
After a bit of a break, I finally continued with the project. The first thing to do was to solder on pins to which the power is connected – pretty simple.
Then came the harder bit of attaching the bluetooth module. This was scary as it was so close to the dodgy jumpers I had soldered before and I didn’t want to melt the solder holding the jumpers in place. To minimise damage should this occur, I covered the jumpers in super glue so that, even if the solder melted, the jumpers would be held in place. With a quick dab of solder the joints were made and everything worked. A small anti-climax but a large relief.
I later realised that the bluetooth module isn’t quite parallel to the other two board, but there’s no way I’m desoldering it.
I modified my original code to fit the new board and tried it out. Here are the results:
It might be a little fragile, but it works and hopefully when it is in it’s case, it will be protected and comfortable.
Taking on board what I learnt yesterday, I repeated the procedure of making the PCB. This time the PCB came out better than before, with no bad connections 🙂
Soldering went well at first; all LEDs, resistors and switches went on with little problem and all work as expected. The trouble came when I was soldering the jumpers. I wish I had thought this through a little bit more before-hand and used through-the-hole, but nonetheless it is now working. I used Sellotape and printer paper to insulate the underlying tracks and then soldered the jumpers. After a number of worrying failures and a little bit of lost copper track (fixed with solder), it was done.
The jumpers are messy, but I couldn’t be happier with the other passive components.
The only concern I have now is that when I solder the bluetooth module to the pads on the right-hand end, the jumper will unsolder and/or break. Fingers crossed.
Yay, the LEDs work.
Today was the day I etched the (first) PCB. I began by printing the design onto paper and ironing the trace onto a copper clad board (remembering to mirror the image because it is SMD).
I then etched the board in Ferric Chloride, washed it, cut it to shape and drilled the necessary holes.
After multiple rounds of checking connections and scraping off incorrect connections it was time to ATTEMPT to solder the SMD components.
I began with the resistors. What I had done before was to pre-solder the pads before placing the components down. Massive mistake. This deposited loads of solder on each pad meaning I had to reheat and “solder-suck” repeatedly resulting in traces melting off the board and ruining it 😦
Accepting that this was a lost cause I chose to practice different methods of soldering.
I finally came upon the perfect method: Flux on the component, a tiny bit of solder on the component, flux on the pads, hold the component down with a sewing needle and heat each pad. This resulted in really neat joints which somewhat made up for the disaster.
Sorry for the poor image quality
Perhaps you can just make out some very neat resistors to the left and right and a complete massacre in the centre. I think this speaks for itself.
I will repeat this process again tomorrow, hopefully with happier results.
Perhaps a bit prematurely, I wanted to start designing the case for the watch.
The main principles of this case will be:
Attachable/Removable to/from a watch strap
Two contacts to allow for power input.
Ideally I would like to 3D-print the case, but since I don’t have a 3D-printer I need to make sure I get it right first time because it’s pretty costly to buy individual items online. (Or perhaps I could get access to one at uni?)
Therefore I have decided to first make a prototype of the case by layering up 1mm thick cross-sections of plastic.
I used PTC Creo Parametric 2.0 to design a first draft of the case and this is what I came up with:
PTC Creo design. Left to right: Hidden line, shaded, 3rd angle drawing
So, this design includes:
Floor/short-edge panels at each end for a large metal contact set into the body. A small screw will pass through the body to connect GND and VCC to the outside of the strap.
Outer edge panels (each with a small screw) to connect the transparent top cover. Having not actually designed the cover yet, this part may well change.
I’m pretty pleased with the design. Possible modifications include thinner walls, thinner pannels… and everything.