The UQBAR Clock!
I built a clock for UQBAR, my favorite café in Berkeley, California. Full disclosure: My daughter and son-in-law, Jennie and Benji Smith, own and operate the café, and they asked me to build theclock for them.
The UQBAR clock is unusual in several ways. I’ll describe them here.
Telling time
The top row of the display on the clock is the current time — at the moment that this photo was taken, it was 5:07 in the afternoon.
Metric time
The second level of the display shows the current time in a different way. It’s the current metric time.
To calculate the metric time, I divide the day into 10,000 equal-sized parts. The day starts at 0000, which is midnight, and continues until 9999, the instant just before midnight on the next day. The clock ticks these off as they pass.
I’ve been interested in keeping time using a metric system for quite a while, and have built a bunch of metric clocks. That was one of the reasons that Jennie and Benji asked me to make one for the restaurant.
If you broke the day into one million equal-sized pieces, each one of them would be one microday. Using 10,000 instead, each of the ticks on my metric clock lasts one hundred microdays. That’s a lot to say, so I’ve named the unit of time a “mike” (which is, by coincidence, my name). A single mike lasts 8.64 seconds. 100 mikes is just about 14 and a half minutes long.
You can also look at the metric display and think of it as “percent of day passed.” In the picture above, it’s 5:07 pm, or 7131 metric. That corresponds to 71.31% of the day since midnight already having passed by.
Prime time!
Every now and then, you’ll notice that the metric time changes color. Whenever you see that happen, it means that the metric time is a prime number. Prime numbers are divisible by one and by themselves, but by no other integers. Every integer that exists is either a prime number itself, or can be produced by multiplying a unique set of prime numbers together.
I’ve been captivated by primes since I was a kid. They’re important in many ways in mathematics. They’re also the basis for a lot of the encryption and security software used for shopping and communicating on the internet. One of the most important encryption techniques we use relies on the fact that, while it’s easy to multiply two prime numbers together, it’s much harder to take a big number and figure out what its prime factors are.
So, out of respect for the important work that prime numbers do, whenever a metric time is prime, the clock lets you know!
Sound level
The third line on the display shows the current noise level in the café, in decibels. This was a particular request from Benji — he’d seen a live decibel display in another restaurant, and thought it was interesting and useful. I agree with him. I’ve got moderate hearing loss and wear hearing aids. Background noise makes it harder for me to hear what people around me are saying, and as the noise gets louder, the problem gets worse. It’s nice to be able to glance up and see how loud the kitchen, music and chatter in the café are.
Inside the clock
One of my favorite things about the UQBAR clock is that you can open the front panel and look inside it. If you reach up from underneath, you’ll find there’s a lip on the front panel. You can use your fingers to pull it outward. It’s hinged on the left hand side, like a cabinet door, and will open easily.
Feel free to do that! The reason you can open it is so that curious people can look inside it whenever they want. Please don’t, however, touch any of the internal parts — it’s a running piece of electronics, and we don’t want it to break or malfunction.
Here’s what it looks like when it’s open:
The three big rows of numbers are the hour and minutes, metric time and sound level displays. I used a computer-aided design program to create those and printed them on my 3D printer. Then I used several long strands of LEDs to string all of the segments in the seven-segment display digits, as well as the colon and decimal points in the display.
Up in the top right corner, there’s a power supply.
On the right, a cord from the café’s wall outlet connects to the supply. The silver box is full of electronics that converts that 120 volt alternating current to a 5 volt, 40 amp direct current supply, suitable for running all the electronics. The red wires coming out on the left go to the LED strands and are the primary power source for all the computing and other components in the clock.
Down in the lower right corner, there’s an Arduino Giga R1 wifi compute board.
Arduino boards are pretty popular for electronics projects like this one. I chose the Giga R1 because it can connect to a wifi network (I use wifi to get the current time), can connect to an app on your phone using Bluetooth (café staff have a special app for setting the display color, brightness and other things) and can control the long string of LEDs that make up the display.
In the center of the clock at the very top, there’s a sound level meter.
That has a microphone (the small black button-looking thing at the bottom of the circuit board, right in the middle) that continually monitors the noise level in the café. When the front panel door of the clock is closed, that microphone is lined up with a hole in the polycarbonate sheet that is the front face of the clock, so that sound can get in.
On the left-hand side of the clock near the top, there’s a breadboard — an electronics prototyping tool that I used to connect up a bunch of supporting components.
That makes sure that the wires feeding power and data to the LED are carrying good signals.
Underneath that, on the left hand side near the bottom, there are a set of controls and power components.
The button lets café staff connect to the clock via Bluetooth from their phones, to change display colors and brightness.
The knob lets them adjust the sound level meter, in case it needs to be calibrated.
Just below the knob, there’s a circuit that changes the voltage coming from the power supply, changing it to a higher voltage that the Arduino board needs to run correctly.
And at the very bottom, the switch lets me connect to the clock from my computer over a USB connection, for troubleshooting problems and uploading new software updates.
Over on the right-hand side, at the bottom of the clock, there’s a status bar.
If the clock encounters any problems — can’t connect to wifi, for example — it will turn on trouble lights on the status bar. Under normal circumstances, you shouldn’t see this turned on. But it provides an easy way to monitor the clock for issues, which can be fixed over Bluetooth or by using the USB connection from a computer.
Why?
The café needed a clock, and Jennie and Benji thought a metric clock with a sound level meter would be interesting. I agree!
But I also wanted to create one that, even though it’s a piece of electronics, is also a piece of art hanging on the wall. The case that holds the clock is a hand-built walnut box, nicely stained. The components inside the clock are all laid out and labeled in a way that lets curious people look at them, trace the connections among them, and understand how it works.
I hope you like it!
Please remember to close the door when you’re done looking ;-).
