I love my Pebble smart watch. The fact that it is always readable is the absolute highlight for me. So I designed this watch to be always readable as well. It comes with an 150x150 pixel 1.5" e-ink display, Nordic nRF52 MCU, buzzer, display light and 4 buttons. It is driven by an CR2032 Battery and the best thing is, the wrist band is part of the PCB!
Components
1×
Flex PCB
1×
ISP1507-AX-RS
BLE enabled MCU
1×
GDEW0154Z17
e-ink display
1×
M41T62LC6F
Clock and Timer ICs / Real-Time Clocks
I just finished ordering the parts and PCBs for 10 watches. Price breakdown is:
* 25 PCBs for 180$ (+ additional taxes) provided by PCBgogo
* Parts for 10 watches + surplus because of MOQ 350€ provided by Mouser
* additional 5 Displays 36$ provided by Good Display
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Material price per watch ~ 60€
Now I wait for delivery. And will build up one sample. If that works well I will build up all ten of them.
After building up all of the ten watches I will be able to supply some of them to people interested. Price point will discussed when it is time to talk about selling. As you can see from the costs a price around 100€ is very reasonable and will mostly cover the cost of this production and previous experiments.
Next to the KiCad project I also added PDF files of schematic and layout.
Please have a look at it and tell me your opinion before I put 1000$ into ordering a couple.
Here are a few infroations about the design.
The Board outline is designed to be fabricated as a flex PCB. There are a few stiffner areas where there should be a plastic plate supporting the flex board.
The watch is powered by a 3V coin cell that sits in the holder in the middle of the board.
From the cell the 3V are going to the RTC and the writst band brace. If the watch is closed around the wrist it closes the circuit and powers up the DCDC boost converter U2. This generates 3.3V for the whole system.
I started on a project similar to this in 2013 (wow, how time files). I put up a presentation for a meetup group I did at the time on Slideshare: https://www.slideshare.net/ErlandLewin/yet-another-smartwatch I used a Sharp Memory LCD instead of proper E-ink display (but they are quite similar in almost not drawing any current with a static image). I also planned for a small LiPo battery with a USB connector in the watch to charge it. And I had a vibration motor for buzzing (but not audible alarm).
I wanted a touchscreen for interacting with the watch, or three touch sensitive pads below the display, but had issues with the IC I used for capacitive touch detection.
Is it difficult to do the impedance calculations for the nRF BLE antenna circuit with a flex PCB? Are you using a chip antenna or a PCB trace? Is the eInk display flexible? That would be really sweet, but I'm guessing it's not.
Amazing work! Keep on working!!! :-)