"Perpetual" Wristwatch

The simple and "Perpetual" WristWatch("LumiTime") with 12 red LEDs, it have LIR2430 Li-Ion battery, 12 solar cells, based on Microchip CPU.

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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:

Our mission and vision

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


"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."


Device face

JPEG Image - 1.64 MB - 03/17/2024 at 10:57



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

ino - 4.25 kB - 03/17/2024 at 10:56


  • 1 × Microchip ATtiny13A SU SOIC 8
  • 2 × R0805 10K
  • 4 × R0805 470
  • 2 × C0805 100n X7R
  • 12 × 0805 RED LED

View all 9 components

  • Order a prototype for testing

    Serhii Trush04/07/2024 at 08:16 0 comments

    You can order a prototype for testing here(completely ready device without firmware):|

  • Power consumption

    Serhii Trush04/07/2024 at 08:10 0 comments

    In standby mode (when the button is not pressed), the wristwatch consumes approximately 5 μA, the battery have capacity - 50 mAh, in time show mode watch consumes 2.5 mA, if you look at the time every day 6 times(0.25 per hour), the operating time is 1.5 seconds, using these data we can calculate battery life time. For example - calculator from Oregon Embedded:

    We have ~year of work, of course, as the voltage drops, the consumption of the watch will also drop (for example - 2.7 V, the consumption is ~3 μA), therefore, the resulting lower value is the guaranteed uptime:

    However, if you give the device 5-10 minutes a day of street light (for example, take it out of your sleeve), and the working time will immediately increase several times. Here in the video I show how the watch charges even in cloudy weather:

    It is worth noting that LED bulbs, which are now very popular for indoor lighting, do not provide a sufficient level of light in the spectrum at which solar panels work, so charging is possible only very close LED lamp.

  • Add project name

    Serhii Trush03/17/2024 at 10:59 0 comments

    Now it's have name - "LumiTime" 

  • Schematic

    Serhii Trush03/09/2024 at 10:10 0 comments

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

    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.

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