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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

oshpark wrote 11 hours ago point

Wow, very exciting!

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GekkePrutser wrote 4 days ago 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.

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Johnny Karamello wrote 3 days ago 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.

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