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Flexible Smartwatch

A 2.5mm thick flexible smart watch with e-ink display, BT 4.0, and health sensors.

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This project aims to build a thin, flexible smartwatch. It's wrap-around display and touchscreen will allow it to display more data at a glance than current devices. Besides telling time and displaying notifications, the watch will feature pulse rate, blood oxygen, and step sensors for health monitoring.

Planned Features

  • 180mm x 32mm x 2.5mm flexible silicone bracelet
  • 4.9", 720x120 EPD (e-ink) screen (always on)
  • Capacitive touchscreen
  • Bluetooth 4.0
  • Pulse and blood oximetry sensor
  • Accelerometer/magetometer (pedometer and compass)
  • Notification vibration motor

Impact

The watch's sensors will allow its users to monitor their health and set fitness goals. Its thin, flexible design should make it less obtrusive and more comfortable than existing devices, increasing the amount of data gathered. Furthermore, its open-source nature increases the user's privacy, since there won't be a manufacturer that can benefit from selling user data.

Additionally, I hope the development process will advance the hobbyist state of the art, especially with the custom touchscreen.

Development Strategy and Status

To ease development, sub-components will be developed individually, then integrated together into the final design.

I've already acquired the flexible display (and its development kit), as well as a flexible battery. The power supply circuitry has been developed and tested. Currently, other sub-components are being developed.

Subcomponents

  • Power supplies (complete)
  • Microcontroller & BT
  • Touchscreen
  • Enclosure
  • Sensors
  • Firmware

Open Source Licensing

All design files and source code will be released. The electrical design will included Eagle, Gerber, and schematic PDF files, as well as a complete bill of materials.

Software will be licensed under the GNU GPL version 3, with a linking exception for manufacturer-provided microcontroller support libraries. (The libraries provided by manufacturers are usually incompatible with the GPL.) All other files will be licensed under Creative Commons Attribution-Sharealike version 4.

Power Supplies Test Data.xls

Results of power supply circuits test.

ms-excel - 12.50 kB - 05/02/2017 at 06:01

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Power Test Board r1 Design Files.zip

Power supplies development PCB.

Zip Archive - 1.04 MB - 04/29/2017 at 16:57

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  • Power Supplies & Test PCB

    Nick Ames04/29/2017 at 16:14 2 comments

    An electrophoretic (e-ink) display requires a bunch of different power supply voltages. There are a few off-the-shelf chips (such as the TI TPS65185) which can provide all of them, but they're physically too large. (To maintain flexibility, I'd like for each component to be less than 3mm wide.) As a result, the supplies must be generated by separate regulators. Selecting these regulators is a challenge, since they must be physically small while consuming very little power.

    Overall, the system requires seven voltage rails:

    VoltageICPurpose
    1.8V
    TI TPS62746Microcontroller/Bluetooth/Misc
    3.3VAD ADP160ACBZDisplay/Pulse Sensor
    15VLT LT8410Display
    25VLT LT8410Display
    -15VLT LT3483Display
    -32VLT LT3483Display
    VCOM
    (adjustable)
    LT LT6003
    Display

    System power is provided by a 0.5mm thick 40mAhr li-ion battery (single cell; 3.5-4.2V). (The TI BQ29700DSER is used for battery under-voltage protection.) The 1.8V regulator runs continuously. All the other supplies are controlled by the microcontroller, to be enabled only when needed.

    I made a PCB to characterize and test each regulator:

    Read more »

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Discussions

Patrik wrote 10/11/2017 at 18:46 point

Love the project. Really dont understand why people dont just use e-ink displays more often. Curios about GNU licensing for that one, technically wouldnt you be able to do a open-source prototype and then take it further in another version, patent and try to make money of it?

  Are you sure? yes | no

Nick Ames wrote 10/12/2017 at 01:48 point

I suppose? The GPLv3 contains patent grant language, but that probably just applies to existing patents. However, I know there's already prior art of a flexible smartwatch.

  Are you sure? yes | no

Nick Ames wrote 10/12/2017 at 01:48 point

Actually, publishing a prototype would constitute prior art in and of itself, making it impossible to obtain a patent on it.

  Are you sure? yes | no

Vasilis Georgitzikis wrote 10/10/2017 at 16:29 point

This is really interesting. Could you share some info on the battery you're using? You mention a flexible battery but nothing other than that

  Are you sure? yes | no

Nick Ames wrote 10/10/2017 at 20:46 point

I'm using the PGEB0052081 from Powerstream.

  Are you sure? yes | no

Vasilis Georgitzikis wrote 10/10/2017 at 21:25 point

great find! this is really interesting, can't wait to see more updates

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Bartosz wrote 09/26/2017 at 12:35 point

I need wifi or bt.

I need loot of memory (1 Mb or more)

and 2 months working on one charge.

Is possible programming it in assembler?

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EngineerAllen wrote 08/13/2017 at 18:43 point

This is better than my idea until i saw it's 10 times more expensive

Too expensive

  Are you sure? yes | no

Joshua Elsdon wrote 08/16/2017 at 11:19 point

I think the price is fair. Obviously there is cost of the development kit to the developer. I don't see why the final version would have to cost more than $300. This is in the range of most smart (and nice non-smart) watches. If it is designed in a 'timeless' way then I can see that it is worth that.

  Are you sure? yes | no

EngineerAllen wrote 08/16/2017 at 16:19 point

EPD is the future for wearable computers

If the function is just time and what $10 watches can do then it's not worth it 

even a speaker / mic combo with ai voice assistant would win over EPD for that

  Are you sure? yes | no

Johnny Karamello wrote 08/17/2017 at 09:12 point

What? You want an AI in your watch? Besides the connectivity/ computing issue, have fun talking to your watch in the public!

  Are you sure? yes | no

Trevor Johansen Aase wrote 07/16/2017 at 01:33 point

What cost did the display and dev kit run you? I have a few ideas for a 720x120 Display.

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Nick Ames wrote 07/16/2017 at 05:07 point

Total was about $1k, mostly in the dev kit. The display itself is $150 each in sample quantities. There's a price list at the bottom on this page: http://www.plasticlogic.com/products/displays-with-epson/

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oshpark wrote 06/22/2017 at 18:17 point

Wow, very exciting!

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GekkePrutser wrote 06/19/2017 at 17:08 point

Great project.. This would be so cool! Especially if you can manage to put the electronics on a flex PCB.

I wonder how fragile the display is. Will it easily cut or tear? I suppose it'll need some kind of plastic or silicone covering to stand up to daily use.

  Are you sure? yes | no

Johnny Karamello wrote 06/20/2017 at 06:17 point

Another display of the same manufacturer is used for this bracelet: http://www.liber8tech.com/news/

The backplane is a plastic substrate and won't break that easy. Of course there's always the possibility of scratches on the surface so a protective layer isn't a bad idea.

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Henry Wait wrote 05/19/2017 at 05:56 point

Hey, the Atmel SAM L21 would be perfect for something like this because of its ultra low power consumption, it could even be powered by a peltier thermo electric generator with plenty of power to spare for sensors and the display.

  Are you sure? yes | no

Joshua Elsdon wrote 08/03/2017 at 15:53 point

I would also consider the STM32L432, the nucleo dev board is nice, and has similar power characteristics as the above, and has FPU and M4 processor. With RTC 200nA, without 8nA. The choice probably depends on which eco-system you prefer. Thermo electric is a neat idea as well! 

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