One of our requirements when designing WatchDuino was for it to be cheap as chips. Why bother having separate Arduino and BLE modules when there are integrated boards out there? Why not use a nicer screen? The answers is, of course, to optimize on price. More standard components are cheaper than those that are more specific, and this is why we've chosen them for WatchDuino.
Today we want to demonstrate just exactly how cheap it is to build a WatchDuino, by putting together a shopping list to buy the components in Aliexpress. And also, to make it as straightforward as possible for you to go buy them and build yourself a WatchDuino!
|Arduino Pro Mini 3.3V 8Mhz||$1.74||link|
|LiPo battery 240mah||$1.67||link|
|0.96" I2C 128X64 OLED||$4.27||link|
|(4uds) 3x6x2.5mm push button 2 Pin||$0.2||link|
|5x10mm flat micro vibrator motor 0.06A||$0.55||link|
|TP4056 Micro USB LiPo charger (5V, 1A)||$0.22||link|
|HM-10 Bluetooth 4.0 uart transceiver||$3.35||link|
|12mm piezo buzzer speaker||$0.18||link|
* = For development you are probably interested in a boarded one instead.
It renders a total price of roughly $12 per watch! All of these components ship internationally for free from China. You can find equivalent components shipping locally from your country in stores such as Amazon, Ebay, Sparkfun or Adafruit. They will likely be slightly more expensive, although more convenient to buy for some people.