Sleep mask prototype assembly and initial testing (or, now that the hardware's built, it's only 90% of the project left to do)

The next step in the development of the Sleep Mask was fabricating the 'final' prototype, and doing some initial testing to make certain that there were no shorts.

The front and back of the assembled board (with battery and display attached) are shown below.  The smallest surface-mount parts (including the charger and headphone amplifier ICs) were placed on syringe-applied solder paste and 'baked' into place using a cheap electric skillet; the remainder of the parts were applied manually, using a conventional iron (the reason for this roundabout assembly method is detailed in a previous post; long story short, I bought the wrong paste).

Being extra-cautious, I checked each of the solder joints on the tight-pitch ICs before adding the rest of the components.  Being extra-paranoid, I introduced cuts into the power traces, so that I could monitor current usage as I re-connected different subsystems (this is evident in the backside image).

Front of assembled board; display not yet mechanically fixed

Back of assembled board; display not fixed; connector to mask lights/sensor at bottom

With everything reconnected and no programming loaded into the controller, the device drew 4.6mA; with phones plugged in (and, again, no programming and thus no signal being output), the device drew 44.5mA.  Even with the tiny battery I have connected now (450mAh), this is low enough to allow for a full night's use on a charge; of course, this doesn't take into account the power used by the IR REM sensor illuminator, the display or the extra power which may be expended to generate actual sounds with the headphones.  However, power use appears to be dominated by the audio system, so I am not too concerned right now.

I connected the assembled board to the mask (shown twice below); additionally, the display is scotch-taped to the board to secure it mechanically (but reversibly so).

The only things left for the hardware are to fix the board and battery to the mask and to install the red LEDs in the eyecups (these will be used to flash at the user during alarm conditions).  I'll also need to install a header to allow for repeated programming.  All that's left for the software... is everything.

Or course, this is the roughest sort of prototype, meant to prove the concept and develop the basic REM detection algorithms and the framework of the eventual overall program architecture.  In addition to about a million changes to the overall mechanics of the mask (formed neoprene base? injection-molded face for the buttons/display), the main board itself would undergo a lot of beneficial changes, mostly to decrease its size.  As I've commented before, the components I've used are ones I have a stock of locally; as such, they are rated for far more current/voltage/power/dissipation than needed for the current application.  Additionally, the controller is the easy-to-hand-solder TQFP, rather than the absolute smallest package available.  As a result, I suspect that a future version of the device, with all the same functionality but reduced part size, could be as small as one quarter of the area of this version.