Smartwatch 10 Years Ultra-Long Battery Life

Good news, the R3 of the PCB is in SMT.

I was approached by PCBWay for sponsorship. I would like to extend my thanks for their sponsoring a fairly expensive piece of hardware to go into the watch. Once the PCB arrives I will post my experience with them. So far the manufacturing has been progressing smoothly.

Thanks PCBWay!

Cheers.

The nano-amp-meter will arrive very soon, this will really help create a standalone toolset to measure the power consumption of the smartwatch. Will post more today as the project progresses.

Stay tuned!

Lunch time, and I redesigned the PCB, as well as added some extra stuff.

Skipping R4 for manufacturing, will go straight to R5.

Fun fact: The original iPhone PCB went through about 10,000 revisions, imagine that… Picture attached at the end.

I am estimating my hardware to go about ten revisions, until we get to Beta R1. Does that mean I'm three orders of magnitude better than them? Stay tuned!

Check out the first iPhone alpha mockup board, very educational.

Cheers!

Captain's log. Smartwatch date 2023.92.

Oh, wait. That's from another project, he he.

This project is entering an inflection point where the complexity increases exponentially and the tasks polyfurcate which necessitates strict planning and task management to avoid total feature collapse and morale sublimation.

In simple words, this is the moment where most self-driven DIY projects die.

Unless the projector is aware of the projected phænomeni, able to jump over the forks, keep track and overcome the myriad of small decisions and inter-connected project events which in a normal project are handled by a large team of project manager, focus group, feature designer, hardware expert, radio engineer, software designer and industrial design and manufacturing liaison, as well as supply chain coordinator, sometimes more than one... well.

Unless managed, this will turn into a quagmire of endless mistakes and re-iterations, and we must be cognizant of the lattice decision making and ladder-iterative waterfall design process; or else.

In plain words, we are a one-man orchestra carefully playing all instruments at once. Better not trip!

Cheers!

Project log.

The LCD will not display unless the voltage is around 2.69, let's say 2.70, therefore, we need a high efficiency separate booster for the display to keep it on. As a side benefit, having a regulated booster is really beneficial for the other auxiliary devices that require 3+ volts to operate.

TPS610985 or TPS610981 seem like good candidates.

Therefore, we feed the NRF52 directly with the power thus bypassing the booster, and use the booster only for aux devices. That would improve the efficiency. Note to self, need to add perhaps an extra circuit for the harvester, tbd.

Also, some decent low power level shifters to go with this

NTS0104GU12,115 / C2677363

NLSX4378ABFCT1G / C604195 (0.5uA best choice)

LSF0204DYZPR / C2677496

Some quick notes on harvesters:

BQ25504RG
LTC3105
AEM10941
ADP5091 / ADP5092

https://www.digikey.com/reference-designs/en/energy-harvesting

TPS61098x (not really a harvester but an ultra-low quiescent / high efficiency booster for the display, could double-duty as a solar cell booster)

More to come later.

The fully assembled watch you see is actually using a rechargeable Panasonic ML2020 battery, which is about 40mAh.

As of today, the voltage is at exactly 2.70V, which corresponds to 10% of the capacity based on the published material spec from Panasonic.

Based on the experimentally estimated 1mAh/day draw of the un-optimized hardware and code, we are currently looking at about 1000 days on a 1Ah battery, or about a little less than 3 years, give or take. The watch is not optimized for the rechargeable ML2020 battery, which performs best under a different use case, therefore I estimate a little over 1000 hours even on an un-optimized design.

Regardless, we are currently at 3 years on a charge, so that's a massive win for my original postulate that a 10-year battery watch life is wholesale possible.

On a side note I also proved that the watch would run on ML2020 which is extremely important use case one we add a solar cell, where we will need to use a rechargeable battery.

To put this in perspective, the longest life on a single battery charge smartwatch is about a month, so we are way ahead. Of course we are also talking a pretty thin functionality so that comparison is probably (most definitely) unfair, however, it points out that with some effort we can hit the 10 year mark on a certain set of smartwatch functionality that strikes a good balance between battery life and creature features.

Cheers!

It was really cold and windy, and at 4000 meters things look a little strange. Hope my pics were good.

Took the assembled watch with me on a week-long excursion. Mountain hiking, biking, driving, and some urban exploration, elevation 4km. Will post pics later. So far the smartwatch is performing... well, like a smartwatch. Which I guess is a good thing.

Good news, the ribbon programmer connector I designed works fine, not sure where the problem was with the first one, all connections looked OK, I traced all, soldering OK, no heat shrink breaks. My educated guess would be, the actual connector on that is defective, where the female pressure leads do not make correct contact with the male leads. That's a new one, I guess at such scale and my manual work with the small parts introduces a mechanical error. That's actually very good to know as the design is sound, but I might have to choose a less-error prone method for programing, pogo pins comes to mind. To do list later.