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Discussion Starter · #1 ·
Hey all,

I'm new here, but wanted to share a little about a project I've been working on for a while. I'm in the process of creating an open-source digital watch using a Sharp memory display (the same unit as in the Pebble) and a SAMD21 microcontroller. Full working (and potential) component list for those interested below.

As it stands, I have a busy looking breadboard, some admittedly amateurish code, and a pretty basic UI that currently tells the time in 12/24h modes and has a countdown timer.

My ambitions for the project are growing as I discover all the cool things other digitals on the market can do. I don't have much interest in turning my design into a "smart" watch, but some nifty features here and there that don't impact battery life too heavily couldn't hurt, right?

I've entertained the idea of having a 60 kHz receiver for atomic time calibration, a tiny solar panel, or an auto-quartz style kinetic energy harvester. Viability on these ideas vary from "pretty doable" to "the universe has conspired against my success", but each has been its own entertaining little research project.

If you could design a digital watch in 2021 with no smart functionality and an emphasis on usability and long battery life, what would you throw in? I'm interested in finding something really novel to incorporate in my design. One notable caveat: I'm seeking to use off-the-shelf components as often as possible. As part of the open nature of the project, I don't want to fill my project with proprietary parts unavailable to general consumers.

I hope I'm not barking up the wrong tree on this forum, I figured you all think a lot about watches. Thanks for your thoughts!

Parts list:
  • SAMD21G18 MCU (Arduino friendly)
  • DS3231 RTC
  • SHARP LS013B7DH05 display
  • Rotary encoder
  • Tactile button(s)
Potential part inclusions:
  • Rv-3032-C7 RTC (smaller, better than DS3231, harder to get ahold of)
  • PIC24F MCU (More advanced programming environment, less community support)
  • Capacitive touch strip (as potential replacement for encoder/buttons)
  • Multidirectional switch (as potential replacement for encoder/buttons)
  • Solar/kinetic energy harvesting power regulating IC
  • Low frequency radio receiver IC/embedded antenna
 

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Mod. Russian, China Mech.
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The rotary encoder would definitely be the piece of hardware worth pursuing. Goes all the way back to some of the earliest LCD digital watches, but these days has been (mostly) relegated to smart devices.

As for display/function, I think the option to display the time in many formats would be cool (analogue, digital, wandering hour, text, Roman numerals, etc.) Here's something that might inspire some ideas:

15851857
 

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I am working on similar project, but for now I limited myself to basic functions:
Hour, minutes, seconds, day of the week, day, month, year, stopwatch.

I have considered also other "advanced" features which depends on your power limitations.
The ones that were not mentioned yet:
Accelerometers and gyroscopes (wrist flip, tap/double tap sensing to replace buttons...)
magnetometers (e-compass)
Other MEMS sensors - pressure, humidity... you can make whole weather station if you want.
All of above are covered by STMicroelectronics as consumer grade ic and easy to get.
 

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Discussion Starter · #5 ·
The rotary encoder would definitely be the piece of hardware worth pursuing. Goes all the way back to some of the earliest LCD digital watches, but these days has been (mostly) relegated to smart devices.

As for display/function, I think the option to display the time in many formats would be cool (analogue, digital, wandering hour, text, Roman numerals, etc.) Here's something that might inspire some ideas:
That is a beautiful watch! I am likely to stick with one initial design, but I intend to make the main display functionality modular in the software, allowing for easy modification. Watchy, a project I've been following, has had great success with their community creating all sorts of beautiful watchfaces. Check it out!

Prefer BT time setting over WWVB.
What about an audible alarm? Rechargable battery might be easier than kinetic or solar.
Bluetooth or even GPS-based time calibration is definitely the superior technology over the >100 yr old radio station, I'll be the first to concede. My biggest mental roadblock around including either of those is that they are potentially harder on battery life and just less 'cool' in my opinion. I'm in the process of determining some sort of alarm feedback, be it a piezo buzzer or a LRA module. I'd be interested in learning more, thanks for the suggestion!

I am working on similar project, but for now I limited myself to basic functions:
Hour, minutes, seconds, day of the week, day, month, year, stopwatch.

I have considered also other "advanced" features which depends on your power limitations.
The ones that were not mentioned yet:
Accelerometers and gyroscopes (wrist flip, tap/double tap sensing to replace buttons...)
magnetometers (e-compass)
Other MEMS sensors - pressure, humidity... you can make whole weather station if you want.
All of above are covered by STMicroelectronics as consumer grade ic and easy to get.
I actually really like the idea of an e-compass. I'm curious to learn more about your design, have you put up any build logs I could read?
 

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I'm curious to learn more about your design, have you put up any build logs I could read?
No, sorry, the design is meant for commercial product therefore cannot go into details. Basically it is a LED solar powered watch.

I checked your page. Maybe it is better to do simultaneously design of software, electronics and casing, than you can eliminate functions that are not feasible or bring too big compromise in final design. Examples:
The size of components can quickly become a problem. Standard IC packages - not all are available in small SMT. Rotary encoders are quite big...
Battery becomes a problem since you cannot use custom IC as large manufacturers usually do. Standard parts are not as optimized for consumption as custom ones.
You can have problems with wireless data transmission for clock sync, if the case material is conductive.
Magnetometers will have problems with ferromagnetic metals - button cells are often ferromagnetic.
 

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Mod. Russian, China Mech.
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That is a beautiful watch! I am likely to stick with one initial design, but I intend to make the main display functionality modular in the software, allowing for easy modification. Watchy, a project I've been following, has had great success with their community creating all sorts of beautiful watchfaces. Check it out!
Ah, I understand better now. It's primarily about the hardware, but with an open approach to software. I like that you're watching Watchy and choosing an original path for your own project.
 

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Mod. Russian, China Mech.
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Here's a hardware idea dredged up from horological history. It's perfect if you like big knobs, otherwise you're welcome to just laugh. How about hand winding rather than rotor driven power supply?

15853569
 

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Here's a hardware idea dredged up from horological history. It's perfect if you like big knobs, otherwise you're welcome to just laugh. How about hand winding rather than rotor driven power supply?

View attachment 15853569
Amazing! Love the super-sized crown. I have big hands so I'd probably buy something like this. Awesome.

Sent from my SM-G955U1 using Tapatalk
 
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