Metric Clock

Project Completed: June 2000


Introduction

This project came about when my dad wanted a clock that ran on metric time. I thought it was a good idea too. I wanted to look at a clock
where I could say, "Wow, look at the time! It's 78 past 4." or "Oh my goodness, it's almost E!"
  • Metric Time:  10 Hours/day, 100 minutes/hour, 100 seconds/minute. You can also see what percent of the day is gone by looking at the first 2 digits. For example 8:65:71 means 86.571% of the day is past.
  • Hex Time:  16 Hours/day, 16 minutes/hour, 256 seconds/minute displayed in hex (base 16). So actually it reads F hours per day, F minutes per hour, FF seconds per minute
  • Circle Time: 2pi radians makes up 1 day (6.2832).
  • Documentation

    mertricclock_schematic.pdf -- Schematic Diagrams
    metricclock_doc.html -- Quick description and instructions
    metricclock8b.txt -- Source Code (written in Hi-Tech C for the PIC)

    Design Notes

    The clock keeps time quite accurately by using the 60Hz from the transformer (alarm clocks do this too, that's why the transformer can't be external). There are six 7-segment displays which are multiplexed at about 55Hz. The colons run separately and can flash at the rate of a normal second or at the rate of the time being displayed (or both).

    The brain of the clock is a PIC microcontroller (PIC16F873) running at 4MHz. I was lucky enough to be able to complete this project using a C compiler for the firmware (otherwise the oddball conversions would have taken forever to write!). I have decided not to post the schematic or the source code, but email me if you're interested.

    Two boards were built: One to hold the display and one to hold the microcontroller. They were etched in my basement on 1-ounce single-sided copper clad board. I layed out, etched, drilled holes, and stuffed the boards myself. Most of the components are on the bottom side because I used mainly surface mount.

    The concept of redefining time is a bit tricky. There are 86,400 regular seconds in a day but there are 100,000 metric seconds  in a day. So a metric second is a bit shorter than a regular second. The clock has gets a pulse ever 1/60th of a regular second so it has to turn 5184000 pulses into 100,000 seconds in each day. That means the metric clock is incremented 1 second every 51.84 pulses. Hex time has 65536 seconds in a day so the conversion is similarly complicated.

    Pictures

    Here is the inside:

    Last Updated: Dec 16, 2001