Tag Archives: ChronosMEGA

Atmel-based ChronosMEGA measures time

A Maker by the name of N.fletch has debuted the ChronosMEGA, a beautifully designed wristwatch powered by Atmel’s versatile ATmega328P microcontroller (MCU).

“I’ve always loved watches; not only are they aesthetic and beautiful, but they are functional, precise and useful. An elegant fusion between engineering and art; two normally opposed perspectives, now joined in harmonic unison,” N.fletch explained in a recent Instructables post.

“However, all technologies like the dial-up internet, the CVT monitor and the abacus, inevitably will become relics of our past with the advent of advancing technology and have since become less pragmatic for the typical person to own. Unlike these archaic technologies, the wrist watch still thrives on the wrists of many, standing forever as a testament to one of mankind’s greatest inventions: the measurement of time.”

Aside from Atmel’s ATmega328P, key ChronosMEGA specs include binary time encoding (via 10 Blue 1206 LEDs), a slew of buttons to control time, sleep mode and display, a 32.768kHz external crystal and an 8MHz internal clock source.

Additional key features?

  • Micro-USB and charge management controller (for 400mAh Li-ion battery)
  • Draws 4uA in its Deep Sleep mode to last up to 11 years on a single charge
  • Battery indicator 0603 LED
  • Boost TI switching regulator for power regulation
  • Low loss PowerPath controller IC for power source selection
  • Total form factor of 10mm x 40mm x 53mm
  • Custom 3D designed case cast in pure polished silver
  • Genuine crocodile leather watch band

As you can see in the videos above, the layout of the watch configured in a circular array of 10 LEDs. Four of the LEDs account for hours, while six of the LEDs account for minutes.

“The LEDs count in binary to display the time on the watch face. By utilizing a combination of the 10 LEDs, the watch can display any possible time accurate to the minute,” N.fletch continued.

“This is a very clean and elegant way to display time. I also really like this technique because of its esoteric and mysterious nature.”

In terms of the MCU, the ATmega328P is wired in a straight-forward manner, connected to power and ground, with a pull up resistor on the RESET pin. Essentially, the AVR is tasked with driving all the LEDs from its GPIO, although one of the MCU’s AVR’s ADC pin is connected to the battery to detect the voltage level. As such, the watch is equipped with a small red status LED to indicate when battery power is low.

“The AVR has a 32.768 kHz crystal wired to its XTAL pins. It uses the 32.768 kHz crystal to drive its Timer2 module asynchronously for counting the seconds, [while] its internal 1MHz RC clock drives the SW,” N.fletch added.

“32.768 kHz is a very common frequency to drive Real Time Clock (RTC) systems because 32,768 in decimal is equal to 8000 in hex. Therefore, 32,768 can be evenly divided by multiple powers of 2 including 1024. Dividing 32,768 by 1024 yields 32, so configuring the timer to count to 32 with a 1024 pre-scaler will equal an exact second.”

Interested in learning more about the Atmel-based ChronosMEGA? You can check out the project’s official Instructables page here.