Introduction: The Binary Clock - the City Clock

This is a special clock I made. It's called "The City Clock".

It is a binary clock hidden inside a typical Parisian building. My idea was to create an object that does not look like a clock until you know how to read it. It is also a metaphor of time passing by as people live their lives in their apartments :) Disclosure : I made a Kickstarter from this idea. The clock is available here :

This tutorial is for those who don't want to pay - want to build their own - want to learn the story of this clock :)

Step 1: Here Is the Video of the City Clock

Step 2: How to Calculate Time

Each row of the clock (floor of the building) is a power of 2 : 1, 2, 4, 8.

You simply add up the dots in each column to get the corresponding digit of time.

Step 3: Circuit

My circuit is based on an Arduino which is ideal as I have 13 leds to control and Arduinos generally have 14 Digital I/O Pins.

I basically made a "hat" in which I plug an Arduino nano.

Step 4: Circuit

The Kickstarter circuit is a printed board but I'm going to show you how to solder one manually.

Step 5: Circuit Layout

This is the circuit of the clock. You can add an optional RTC module which I'll explain later.

Step 6: Holes for LEDS

To make the soldering process easier, I drilled 5mm (as I used 5mm LEDS) holes in a thin sheet of plywood. The pattern of the holes should match the position of the 13 windows.

Step 7: LEDS

This helped me to hold the LEDS in place while I solder everything.

Step 8: Bend the Cathodes

Then I bent all the cathodes. The goal is to solder them together to make a GND grid and spare some cables.

Step 9: Solder All the Cathodes

To solder all the cathodes together I made some perpendicular "combs".

Step 10: Cathodes Are Joined Now

All the cathodes are joined now.

Next step : solder a 220 Ohm resistor to each anode.

Step 11: Arduino to Circuit

Take a random point of the GND grid and link it to the Arduino GND.

Step 12: Link Anodes to Corresponding I/O Port of the Arduino.

Then link all the anodes to the corresponding I/O port of the Arduino. Check the image above with the number to know which port each led should match. If you don't make exactly the same circuit, you'll have to modify the Arduino code to match your connections.

Step 13: Circuit Done

Tadam, the inside of the city clock !

Step 14: Code

Here is the code to use without the RTC module :

You just have to check that the LED matrix matches your layout and then upload it to the Arduino.

Step 15: Operational Circuit

Optional : to get a more accurate time (the Arduino is not very accurate and loses 1 minute each day) I decided to add a DS3231 to my circuit.

The DS3231 is a low-cost, highly accurate Real Time Clock (RTC) which can maintain hours, minutes and seconds. When associated with a coin cell battery it also keeps track of time even if the circuit is off. SCL should be linked to A4 and SDA to A5 of the Arduino Nano. Here is another program if you decide to use the module : Above is the typical operational circuit.

Step 16: Wood

The building is made out of thin wood (2mm).

I used a scroll saw and a band saw to cut out the windows and the details (also very time consuming but fun).

Step 17: Design

It is inspired on Parisian buildings but maybe you should make it match your city design ! (and send me a picture :) : )

Step 18: Making Some "mansardes"

Making some "mansardes"

Step 19: Size

Size is approximately 15x15x25 cm.

Step 20: Prototypes

Here is a quick overview of all my trials :)
I liked the plastic one but unfortunately we couldn't really see the engravings on it.

I've finally opted for a laser cut version with two layers glued on top of each other to give relief to the building.

Step 21: Stand

The stand is a block with notches to fit facades and a hole for the USB cable.

The clock needs a 5V power supply (USB) to run.

Step 22: End !

Et voilà !

If you have any suggestions I'll be happy to hear them. If you like the clock or the Youtube channel check out the Kickstarter. It's a real one, made by real people, intended to deliver on time to its beloved backers <3

Invention Challenge 2017

Participated in the
Invention Challenge 2017