Time required: 20–40

Cost: $75–$125

My Open-Source SmartWatch combines readily available breakout boards, careful soldering, and a 3D-printed frame to make a one-of-a-kind timepiece that displays notifications from your smartphone and is easily customizable in function and appearance.

The watch design is straightforward, consisting of four major sections: a battery charging circuit, vibrating motor for silent alerts, programmable Arduino-compatible core with power regulation and Bluetooth LE, and an OLED display with pushbuttons.

Breadboarding the project is a snap. Wiring it into a small enclosure meant for the wrist is quite another matter. Break out your fine-point soldering iron and follow the complete instructions at oswatch.org.

Battery Charging

A 3.7V 500mAh LiPo battery is wired to a JST connector and a two-position switch. Switched to the right, the circuit is in battery mode. Switched left, it’s ready for LiPo charging via the JST connector.

Programmable Core

Within the 3D-printed frame an 8MHz Microduino microcontroller is connected to a programming port, a Bluetooth Low Energy board for communicating with your smartphone or other devices, and a voltage regulating circuit.

Vibrating Motor

The simple vibrator circuit consists of a diode, 1K and 33Ω resistors, capacitor, NPN transistor, and motor. The circuit is then connected to the Microduino to buzz your wrist when new calls or alerts come in.

Pushbuttons and OLED Display

Four momentary pushbutton switches are wired to three pull-up resistors internal to the Microduino and a single external 10K pull-down resistor.

An OLED screen and two small LEDs are wired directly to seven of the digital pins on the Microduino to display time, text, alerts, and more.