Digital watches are a pretty neat idea, and are a great way to experiment with designing and building low-power circuits. That’s what [Eric Min] did with this neat smart watch build. It’s based around an nRF52832 SoC that does all of the heavy lifting, including connecting to a smartphone to get the time when the battery is replaced. It also has a decent quantity of blinky LEDs, which is important on any project of this type.
[Eric] freely admits that there are still some issues to overcome in his prototype. For one, the display tends to dim in use, probably because the 3V Lithium coin cell actually ends up delivering a bit less than that as it discharges, and the display is designed to work on a minimum of 3V. For the next version, he is thinking about using a 3.7V Lithium Polymer cell and a 3.3V regulator, which should be able to drive the display a little easier and keep it nice and bright. Or perhaps switch over to a nice OLED or eInk display.
Perhaps our favorite feature of the design from this 17-year old is the call-out on the back of the PCB: “I love you Mom and Dad”. Aww. I’ll bet your Apple Watch doesn’t have that, does it? 
Definitely would like this more with an OLED or something along those lines, but if he’s happy with it that’s all that matters.
Yeah, an OLED would’ve allowed for fancier graphics and a smoother UI, but I think the segmented LEDs really add to the aesthetics. I focused on looks as much as functionality, maybe a bit more.
Neat indeed. I wonder if the backside fully touches skin or if some protection is used.
The watch strap goes under the PCB from the top slot and back out from the bottom slot so it covers the electronics on the bottom side. It is actually pretty comfy to wear and my wrists don’t sweat like they do with resin or silicone straps.
If he used a one-piece strap threaded through the slits, the PCB would sit on the strap, so only the strap would touch the skin.
Ah yes, of course.