Thank you for the release this very interesting work. I am currently designing my own smartwatch and many parts are in common.
Several questions appeared to me.
- casing : most of the casing seems to be in aluminium. Isn’t it a waste of energy in terms of radio transmission (for GPS, bluetooth and NFC)?
- display : it seems to be fixed only with glue. Have you test the shock resistance (IK 6) and IP67 (liquid ingress protection).
I am aware that this design isn’t made to be used as is; but I am very interested in understanding good practices, what works and what doesn’t work.
Moreover, if you have some for sale, I would be a buyer!
That’s great to hear! I hope the reference design is useful in your smartwatch development. Let us know how it goes
You are right: the aluminium casing is problematic for the radio transmission performance. The choice of material for the case was a trade-off. We chose aluminium for a few reasons: We wanted a premium aesthetic for our design. The use of metal over plastic allows for a more rigid structure (parts that are glued on could come lose more easily if the case were more flexible) Our capacitive touch panels require a metal backing, this is easily achieved if the case is already metal.
To help the radio components we created a cavity in the strap and put all the antennae into positions where the cross section of the metal casing is outside of the suggested keep-out areas for the antennae. It’s not perfect, there are still problems we had to overcome, but it works.
As for the display, you are correct again, it is fixed on with glue alone. This is common for devices of this size and with the correct selection of glue can be robust. It helps that the display is in a recess, meaning that all four outer sides as well as the edge of the underside act as adhesion surfaces. We have not undertaken any official ingress or impact testing, sadly.
Hope that helps,
Thank you for this clear answer.
I am trying now to integrate your specific display connector (Hirose FH19C-10S-0.5SH), but I find out that for the FH19C series the recommended thickness of FPC/FFC is 0.2mm (± 0.03).
The display FPC connector has a thickness of 0.3 mm.
Did you encounter some issues for assembling it? Or is it acceptable in an industrial assembling line?