Metropolis Time

In an earlier rambling, I introduced the Metropolis Oscilloclock, themed after the classic 1927 science fiction movie. The clock seems to have garnered some attention, and thanks to the kind folks over at Hackaday, I now have two additional facts to relate:

  1. The “Maria” robot in Metropolis inspired the design for C-3PO in Star Wars!
  2. Some folks have considered the Workers’ clock to be Decimal !

The first point stands without dispute, but let’s take a closer look at this “Decimal” aspect, as I’d never considered it before.

Decimal Time vs. Metropolis Time

Below is what got folks interested – the 10 hour clock face. The Masters used this to dupe the Workers into believing they were working short shifts, when in fact they were slaving away for a full 12 hours. Ingenious!

But this is not Decimal Time, where time is divided into units that are purely decimally related. Yes, there are 10 hours on the face, but there are 20 hours per day, and 60 minutes to the hour. And, if you bother to count the dots around the edge, you can see there are 72 seconds per minute. None of these are decimally related.

Speaking of decimal time, I fondly remember a Metric Clock article in the April 1987 edition of Electronics Australia. Being but a wee lad at the time, I was gullible enough to believe that true Decimal Time was going to be introduced in Australia imminently. I ‘convinced’ my father (he led me on) that it was really happening, and I was just about to purchase the kit to build my own Metric Clock… when in the following month’s edition, the magazine came clean that it was actually an April Fool’s joke!

But enough fooling around – let’s now take a closer look at the Oscilloclock implementation of Metropolis Time…

Metropolis Time vs. Regular Time

The two clocks in Metropolis differ only in one way: the length of an ‘hour’. This is easy to grasp, since there are 20 hours per day in one, versus 24 hours per day in the other.

But from here, Metropolis messes with your mind! Below are some revelations that [Andrew] and I battled over numerous e-mails to come to terms with:

  • The hour hands on the 10h face and the 12h face must always be exactly aligned (they must go around at the same speed).
  • Since an M-time hour is 20% longer, the minute hand must go around slower.
  • To make the M-time minute hand go around slower, the second hand must also go around slower.

Even if this makes sense so far, the crunch comes when you think about how to implement it. If it were a physical clock, the tick speed could be slowed and the gears could be modified to make the seconds and minutes go slower but the hour hand itself move at the same speed. Easy!

But it’s not a physical clock, and in the current Control Board design, the tick speed is NOT readily adjustable as it is derived from the MCU clock, which all the critical display routines are optimised around. So essentially, the length of a second cannot be changed.

Without changing the length of a second, how can we make the minute hand go around 20% slower? Well, there are only two options:

  1. Have 72 seconds per minute, with 60 minutes per hour
  2. Have 60 seconds per minute, with 72 minutes per hour

We decided on the first option, and you can see from the video below that the second hand indeed moves through 360 degrees in 72 steps (actually half that, since there is a half-tick).

An interesting tweak here is the shape of the hands. Note that they have triangular outlines, to more accurately mimic the hands in the film. But computing the angles and projecting these outlined hands using Circle Graphics was a true challenge – especially as the current Oscilloclock firmware is written 100% in PIC18F assembly code! Assembly is great for optimizing timing, but with no maths related processor instructions or functions to leverage, this feature was a huge effort…

Why assembly code? Just because I can!

Digital Metropolis Time

Everything was now all fine and dandy for the analogue 10h clock face, but what about all those nice digital faces that are stock standard in every Oscilloclock? Could I make Metropolis Time make sense in a digital format as well?

Of course! Except there was one hitch. Since we have 72 seconds per minute, the clock would show times like 09:16:65. This would look odd. Andrew wanted to keep the seconds in the range 0-59, like in a normal clock. Something would have to give… but what?

The answer was to simply ‘ignore’ one second in every six; i.e. the 5th second shows for 2 seconds before incrementing. This is easiest illustrated with another video (note what happens at the 10:57:55 mark):

But easiest of all is to see this in Excel. The duplicate second is highlighted:

Switching between Metropolis and Regular Time

Now, let’s face it: Metropolis time is really not very useful in day-to-day life; not for us Masters. Andrew wanted to be able to revert all faces at will to show Regular time instead of Metropolis time (except the 10h analogue clock face).

This was duly implemented during production of the 2nd Metropolis Oscilloclock – which will be presented in an upcoming post. Stay tuned!


If, like me, you are hopeless at simple time zone conversions but you’ve actually managed to fully get your head around the above, Congratulations! Stay tuned for more posts in the Metropolis series.

Metropolis Mania!

Oscilloclocks are special. Oscilloclocks are unique. We know this. But in November 2015, a request for something exceptionally special and unique arrived from [Andrew] – he wanted me to craft a Metropolis movie themed timepiece!

Metropolis Movie PosterMetropolis is a classic science-fiction silent movie created by Fritz Lang in 1927. It’s an amazingly beautiful film with a fascinating plot, passionate acting, and attractive futuristic props and architecture heavily influenced by the Art Deco and other artistic movements. (Haven’t seen this movie? Watch the newly reproduced full version here!)

Well, Andrew was building a very large space at his home dedicated to the Metropolis movie. It would be a full-on “man cave”, with a lounge/bar, music and video venue, mad scientist lab, and collection display space. The mad scientist part of the building would house various scientific demonstrations based on vintage physics or chemistry experiments, with a dose of mad science thrown in.

Andrew was collecting themed art and memorabilia for his man-cave, and had even commissioned a full size ‘Maria’ robot (#3 in the world) from the licensed manufacturer…

But there was one thing missing – a Metropolis 10-hour clock.

Metropolis Time

In the Metropolis movie, the Rulers enjoy their lives in normal time, but the Workers are forced to perform their heavy-labour duties in 2 shifts of 10 ‘worker hours’ each day. The Workers’ clocks are thus labelled with only 10 hours.

Metropolis clocks for Rulers and Workers

Metropolis clocks – Normal time for Rulers (top), but 10-hour time for Workers (bottom)

The 10-hour clock features in multiple scenes throughout the movie, as clear symbology that the controlling and oppressive Masters can even manipulate Time – if only on the surface!

In this scene, Freder struggles with the clock machine...

In this scene, Freder struggles with the clock machine…

[Andrew] wanted to commission an Oscilloclock that would display an authentic 10-hour Worker clock face with accurate hour, second and minute hand movement, as well as the normal 12 (24) hour Ruler clock faces. He also wanted all numerals and characters rendered in the Metropolis font. This could be THE talking piece of the man-cave!

Presenting… the Metropolis Oscilloclock!

After 8 months of discussion and development, the first Metropolis Clock was finally delivered. This unit is based on the same beautiful Toshiba ST-1248D vintage oscilloscope model used in a previous conversion. However, it incorporates some wonderful new features, including LED-backlit valves and an external input feature to support Lissajous figures generated by an iPhone or other device!

The Metropolis Clock - Toshiba ST-1248D - 01

Metropolis Clock - 06

Artwork on the splash screen evokes an image of the skyscrapers in the movie poster…

The clock keeps both 'normal' and Metropolis 10-hour time!

The clock keeps both ‘normal’ and Metropolis 10-hour time!

Realistic LED backlighting - enjoy the valves without actually heating them up!

Realistic LED backlighting – enjoy the valves without actually heating them up!

To be continued…

Each of the new features built out for this exotic creation deserves a post on its own. Stay tuned for many more pictures and information about Lissajous inputs, backlit valves, and Metropolis time switching!

Also, careful readers would notice my use of the phrase “first Metropolis Oscilloclock”. Andrew was so delighted with the Toshiba ST-1248D unit that he commissioned a second Metropolis clock with even more firmware enhancements, based on the Tektronix 520A. Another topic for another day!


See the Metropolis Archive for all other posts in this series!


Like what you see?

Metropolis is just fantastic as a theme for a custom Oscilloclock. But if you have a different passion that needs horological augmentation, let me know!