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I’ve always been fascinated by both interesting ways of telling the time and binary code. It’s amazing the amount of information can be stored in simple ON/OFF signals. I knew I wanted a new wrist watch so why not combine binary code with a wrist watch, and do it as an awesome DIY project?
This is the kind of idea that lodged itself in the back of my mind. Always present and constantly evolving until it reached a saturation point where the project had to be done!
There were several challenged that had to solved to make it the watch of my dreams. Most of these challenges can be traced back to the small area of a wrist watch. It would have been easy to make a big or ugly watch, but that’s simply not what I wanted from this project.
I will take you through the process from idea to making your own binary wrist watch you can wear with pride.
Let’s get started!

The watch has 4x4 minus three LEDs arranged in a multiplexed matrix. Where one column corresponds to one digit in digital time. The time is shown in binary coded decimal and one of digit is represented as with a maximum of four bits.

It both looks exceptionally stylish and works great with a simple user interface and battery life up to two years. Arriving at the final design was an iterative process where a lot of different problems had to be solved. In my opinion the end product turned out great and is something I love to wear on a daily basis.

One of the first things people would notice with the watch was of course how it looked. I wanted a watch that looked good and reminiscent of an actual product. In short, it had to be something I could wear to meetings at work.

The design, when the watch is off, is a simple two-tone combination of black and silver. This si present in the leather watch strap and clasp, along with both the case and the PCB.

I hid most of the components on the backside of the PCB and had it produced with a black solder mask. I thought it was cool to keep the black silicone chips on the front side with the silver soldered leads. That way even the electronics and PCB match the two-tone design of the rest of the watch.

The watch body needed to be solid when put together, yet easy to open up for changing the battery or making modifications to the code. That would mean no glue where I could use something less permanent. In fact, the only glue used in this build was for the crystal glass.

The opening and closing was solved with the main body being made of two parts: the watch case back, and the front watch ring. The watch case holds all the components like the PCB, watch band, and watch crown. The watch ring holds the glass, and slides down into the case back where it’s secured with two tiny screws.

As discussed in the step about selecting components, this had to be really low power. It would be no good watch if you constantly had to change the battery every few days or even weeks. It would have to last for at least half a year to not be a real bother. Luckily this was solved! The watch spends most of it’s time in deep sleep before waking up when the watch crown is pushed. In deep sleep it consumes as little as 10µA. This gives a battery life of more than two years!

Intuitive. The watch had to be intuitive and easy to use and understand. Well, at how understandable a binary watch could be at least. The time is represented in binary coded decimal (BCD) instead of just regular binary numbers. In BCD you take one regular decimal number and converts it to binary. This means a longer decimal number is is split up in each of its digits, and each individual digit is converted to binary. The system is beneficial for coding the time, because this means the biggest individual number in BCD is 9 (1001), instead of 2359 (100100110111) as with regular binary. More on how to use BCD to read the time in step 5.

As far as user interface goes, you simply press the watch crown to wake the watch where it immediately gives the time. Press the crown once more and you get the date. Because the watch has a battery life of two years you can easily toggle between daylight savings time without connecting to a computer. Simply press the button 15 times in rapid succession to toggle adding or removing an hour.”

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