The Pendulum Clock

If you've ever rode the Link Light Rail in Seattle to the airport, you may have glanced out of the window while traveling through a tunnel and seen playing cards illuminated on the walls. These images are not made from two dimensional screens. Each display is just a row of lights that changes rapidly as the train drives by, giving the illusion of a two-dimensional picture.

The University Street station also has rows of lights blinking on the walls on the mezzanine floor. I always point out the artwork whenever I walk through the station with someone. At first glance the displays just appear to be red lines, but if you move your eyes rapidly from side to side, there are images hidden in how the lights blink.

That was the inspiration for the Pendulum Clock.You might not see it at first, but it is showing an analog clock face that reads 2:40. Usually it takes a couple swings to see the picture. Once you see it, it becomes very easy to read the time.

The Pendulum Clock has a row of 64 white LEDs that change based on the position of the pendulum. I've used it to display an analog clock face, but it can be used to display any 2D image. The motion of the clock is not powered; you have to manually push the pendulum to one side to start it moving.

It's powered by a simple Arduino Uno, a DS1307 RTC for keeping time, a MAX7219 LED controller, and a bad ass rotary encoder. The case is a Hammond box, which fit all of the components with just the right amount of room. The face is a 4″x24″ piece of basswood.

For more detail: The Pendulum Clock