MAKER:mblaz／Translated by: Interesting Endless

This watch, which is only 10mm thick, can be used for several years, powered by a CR2032 battery, and features a built-in DS3231 clock (RTC) chip that provides accurate time and temperature compensation.

Material List

Arduino Uno × 1, ATMega328 × 1, 3V 20mm CR2032 Button Battery × 1, 603 RED LED Diode × 12, DS3231 RTC Chip × 1

PCB Schematic and Layout

Create PCB using Autodesk Eagle. First, import the component library from the schematic, check the datasheet, and determine the correct logical connections. Then, I designed the layout of the PCB and generated Gerber and Drill files.

The specific specifications of the PCB are:Layers: 2, Size: 35mm × 35mm, Thickness: 0.8mm, Impedance: No, PCB Color: Black, Surface Treatment: Hot Air Leveling (Lead Free), Copper Weight: 1 ounce, Gold Finger: No, Material Detail Information: FR4 – Standard Tg 130-140C, JLCPCB Group: No, Flying Probe Testing: Fully Tested, Honeycomb Board Holes: No

Design files can be downloaded from the project file library. https://make.quwj.com/project/213

Burning Bootloader

If your ATmega328 (or ATmega168/88) is brand new, you need to burn the BootLoader for it first.

If there is no initial code, the microcontroller will not be able to interpret Arduino’s instructions. It needs a bootloader, which functions similarly to a BIOS driver on a computer.

The bootloader must be burned before soldering. Please click this link to see the steps: https://github.com/MCUdude/MiniCore#how-to-install

The details of the options for burning the microcontroller are as follows:Mainboard: ATmega328, Bootloader: Yes, Clock: Internal 1 Mhz, Compiler LTO: Disabled, Variant: 328P/328PA, BOD: 1.8V

After successfully burning the Arduino bootloader to the ATmega328p, you can use the USB to serial converter (FTDI chip) on the Arduino board to upload programs.

Soldering and Assembly

The assembly process is very simple. Prepare all materials and start from one side of the watch. More details can be found on my website. https://mblazevic.com/iowatch-soldering-top

If you are still a beginner at soldering, I recommend checking out some tutorials on soldering 0603 components. https://www.sparkfun.com/tutorials/category/2

Programming

Using the FTDI test (connection) pads provided on the back of the PCB, you can upload code using an inexpensive FTDI converter.

I created a custom FTDI converter that utilizes the micro USB B interface on the watch PCB. Therefore, modifying and uploading code is very simple and convenient; just remove the battery and connect the custom converter to the watch PCB for programming.

For more detailed instructions on how to get the time, set the time, and read the temperature, please click this link. https://www.sparkfun.com/tutorials/category/2

3D Modeling and Printing

Designed in Fusion 360, what you see is the final draft. Everything except the watch band and glass is 3D printed.

Specifically includes:Watch body, watch fixing ring, base, button

The settings in Cura are as follows:3D Printer: Prusa I3 MK3S, Material: PLA, Layer Height: 0.1mm, Shell Thickness: 0.8mm (Nozzle: 0.4-2), Top/Bottom Thickness: 0.8mm, Fill Density: 100%, Filament: 1.75mm, Support Type: Any Type, Platform Adhesion Type: Skirt

The watch glass is press-fitted, and the fixing ring on the body is also press-fitted. Use M1.4 screws to secure the PCB to the bottom case, and then secure it inside the main body case. Don’t forget to place the 3D printed button.

Please download the STL files and .f3d files here: https://make.quwj.com/project/213

Completion

If you want to know more about assembly and soldering, you can visit the author’s website. https://mblazevic.com/project/iowatch

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