"Perpetual" Wristwatch

The simple and "Perpetual" WristWatch(project code name "LumiTime") with 12 red LEDs, it have LIR2430 Li-Ion battery and 12 solar cells, based on a simple Microchip microcontroller ATtiny13. It full open source(firmware and hardware).

Video demonstration:

https://youtu.be/T3b3lKKN2u0

How it's work?

Every 0.5 sec CPU wake up(cycle iteration time 100 nS) and increase milliseconds value and go to the sleep mode(3-5 uA). Wristwatch have one button "NOW" and 12 LED, if you push the button - show times on LEDs in the next algorithm - first, show hours(1, 2, 3, 4, 5, 6 etc....) and second is show minutes with 5 min. accuracy(5, 10, 15, 20, 25, 30 etc....), show 0.5 sec to the hours and 0.5 for minutes -> sleep mode again.

PCB have size 35 mm in the diameter. The thickness of the board is recommended to take 0.8mm otherwise it may not fit into the case.

https://github.com/techn0man1ac/PerpetualLEDWristwatch/tree/main/LumiTime/PCB

It's have simple schematic, for save pins I used Charlieplexing(35 components in total):

https://en.wikipedia.org/wiki/Charlieplexing

In this project i use for charging 12 light sensor BPW34S, on clear sun one cell make 0.5-0.6 V and ~2 mA, connect its in serial and make simply charging schematic - use 2 components, ZD1 to drop voltage 6 -> 4.7 V and make protection to leakage of current in solar panels in to diode D1 name LL4148(because it have little reverse current).

The diode add 0.7 volts drop(4.7-0.7=4.0V) and battery don't overcharge up to 4 V.

Here is pinout for AVR ISP programmer - unsolder battery and power up 3V pins to programmer 5V, MI->MISO programer(Arduino digital Pin 11), MO->MOSI(digital Pin 12), CK->SCK(digital Pin 13) RS->Reset(digital Pin 10) and GD-> programmer GND.

How to flash ATtiny13 with Arduino:

https://www.hackster.io/taunoerik/programming-attiny13-with-arduino-uno-07beba

ATtiny13 core selections:

• Board: ATtiny 13
• BOD: BOD Disabled
• Clock: 1.2 MHz internal osc.
• Compiler LTO: Enable
• Port: (Your Arduino port)
• Programmer: Arduino as ISP

Source code(for Arduino IDE - "12LEDWachATtiny13.ino") here:

https://github.com/techn0man1ac/PerpetualLEDWristwatch/tree/main/LumiTime/Code/12LEDWachATtiny13

This project full open source(PCB and code):

https://github.com/techn0man1ac/PerpetualLEDWristwatch/

Mission:

"To develop a straightforward and eco-friendly watch that integrates innovative technologies with minimal components, ensuring energy efficiency is within reach for all.".

Vision:

"We aim to achieve a world where energy-saving technology is accessible to everyone, where our watch serves as a symbol of environmental stewardship and innovative solutions in energy efficiency."