It’s finally time to take the plunge and make Lightlog smaller and more robust. Moving away from the hand soldered, through-hole prototype boards, and to a custom multi-layer board using smaller surface mounted technology (SMT). Using specialist PCB layout tools such as Eagle CAD, and the Open Source KiCad, the prototype circuit needs to be re-created ready for a commercial board manufacturer to fabricate.
Commercial facilities requite a special set of custom files called Gerber files to produce boards with multiple circuit layers, vias (connections through the board), masking of areas from solder, front and back silk screen printing, drill holes, and the final board cutout shape. The image to the right shows the new board design, a full set of Gerber files can be found over on the Lightlog git repository.
The earlier electronics fitted within a box of 29mm x 29mm x 17mm, after these changes the size is down to 28mm x 26mm x 7.5mm. This might not seem like a huge saving, but by more than halving the thickness Lightlog is more discrete to wear and allows a wider variety of potential enclosure designs.
There are a number of part changes with the new board moving to the smaller SMT parts, but one more significant change is the new digital light sensor chip that I’ll try to cover in a future post.
Time to order a batch of these boards of testing!
As part of the Edinburgh International Science Festival, LateLab hosted a red, green, blue colour themed cocktail party at the University of Edinburgh’s School of Informatics. I was invited to present the opening talk on the effects of light on mood and wellbeing and introduce Lightlog project while the audience were being served a carefully curated range of colour themed cocktails and nibbles to match the talks. If you attended I hope you had a great evening and perhaps even enjoyed a little science!
Thanks to Emilie Baltz, Amanda McDonald, and Mark Daniels for all the event planning and organisation. As usual, Chris Scott took some lovely shots of the evening.
My slides are available here: Light Log RGB Cocktail event
It’s been a busy few days building and testing a fresh batch of six, new Light Log prototypes. They are almost all ready to ship out to their new homes, needing only some changes to the 3D printed enclosure (these are a little smaller than the last version), an update to their firmware (improved UI and timing accuracy), and calibration against known light lux sources.
Five will be off to Nigel A. Beacham, whom I met and chatted with at last year’s Northern Lights Conference. He’s a Research Fellow at Aberdeen University setting up a pilot study investigating the effect of light during informal learning periods. The sixth prototype will be winging its way to Talia Radford, a social product designer based in Vienna. She heard my Light Log presentation at the Wearable Futures conference back in December and is looking to include the electronics in her latest wearable project for the Milan Design Week in April.
The electronics are now down to 28mm x 28mm x 14.5mm in size (with a couple of millimetres added once you include the thickness of the 3D printed enclosure), and weigh 11g (14g with the battery). Each device uses two circuit boards stacked one above the other. One holds the micro-controller, memory, sensors for red, green, blue and clear (for low light conditions), with a white LED and tactile button providing a simple user interface for the front face. The second board holds the battery and serial communication components for downloading logged light data to your computer.
If you’d like to see the circuit schematics, component part-list, or perfboard layout (a type of circuit board designed for prototyping circuits), you can find them on the Light Log GitHub repository, along with other documentation. With the small size of these devices it does now need a little patience to build, perhaps an afternoon’s work, with the trickiest part soldering in the link wires.
I’m looking forward to seeing these prototypes fly from the nest later this week!
One of the goals of Lightlog is to help people engage with and reflect on light data they collect over time. Due to its size and power constraints, the physical Lightlog device has a minimal user interface (UI), just enough to display the daily light goal reached, and show if the current illumination is bright enough to be effective towards the daily goal (2,500 lux or above). Lightlog collects much more data than it can display alone, by synchronising to a device with a screen and more computing power, allows a rich, engaging, detailed views of your daily light profile, and the opportunity for additional analysis over the set of collected data.
The primary visualisation is designed around the full colour spectrum composing visible light. It’s an approximation of a full light spectrum as Lightlog records single sample points in the red (~614nm), green (~525nm), and blue (~468nm) frequencies; with a fourth sample unfiltered, capturing as much of the full spectrum energy as possible for lux calculation (an interesting future project could be to use many more sensors across the spectrum frequency to generate a high resolution spectrum with chemical absorption lines). For use with Winter Blues and Seasonal Affective Disorder, the three red, green, blue sensors provide useful information about the frequency of light exposure as some studies have shown shorter wavelength, blue light, is more effective, vs. longer wavelength red light.
Below shows an example image taken from real data displaying several days from November. Notice the relatively long nights and short Scottish days at this time of year.
Below is a close-up view of November 30th; note the strong direct sunlight between 12:30 and 13:30, this would have been more than enough for the recommended daily amount of bright light.