Wednesday, October 8, 2014

Smart-watch, first real steps

So I have this awesome idea: A watch-like device that would show me scheduled notifications. And probably time. And for sure log my temperature!
It's mainly to keep me focused and organized. More like an independent device than a smartphone dependent one. It will of course be paired to my smartphone but that's not the main function.
Yeah, lets get right to Hardware.

I haven't decided on the most important part: mcu, the brains.
But otherwise I will have a temperature and humidity sensor touching my skin, an accelerometer that senses up to 1,5g, to react to me bringing my arm up and tapping the device -- the wake-up gesture.
Also a 2.4" qvga resistive touchscreen lcd with dimmable led backlight :p
So far these are all serial devices. So I won't have to have a huge mcu on it. Just a relatively powerful one.

I want the thing to have Bluetooth, preferably 4.0 low-energy. And I wouldn't mind the mcu being together with the wireless in one chip. It'll keep the footprint smaller.

Right now I have an old 550mAh lipo that has nice dimensions, I'll try to find a new one that's the same and design around that.
I'll have to do a lot of power management to keep the power stable and the requirements really low.
I thought about including wireless charging but that would make the device too bulky.
I have plans to fabricate the pcb myself out of a thin strip of plastic and some copper foil. A two sided sandwich.

I want to have the temperature sensor touching my skin, so on the underside, opposite of the mcu. Then I want the 4-5 magnets in each corner and maybe in the center. So the bottom of the pcb would be routing and ground plane. Every other component will be on the topside.
I want to have the space under the screen divided in half, one side for the battery, other for the pcb..
Out of the same thin copper foil I use for the pcb, I want to make a case. It won't have to be sturdy, just nice looking. Maybe also a thin protective cover for the lcd, I'll see how well the resistive touch plate handles any obscuring objects.

Overall I am expecting it to be around 7mm or less, without the magnets(they'll be only 1mm anyway. With a diameter of 3mm.) We'll see :D

Bought so far:
The display
The temp sensor
The magnets

The accelerometer comes from an old Creative X-fi 2 (The same place as the battery xD)

What I have done so far:
Packages and devices in eagle for all of the mentioned devices. The touch controller, the humid/temp sensor and the accelerometer.
A lot of planning on paper, in my head and modeling out some of the components.

Next time:
Pictures, part names and datasheets.
An mcu announced.
Communications planned out.
A bit of the algorithm done.
Ideas for the user interface.