LightWriter Clock: Resurrected?

The original idea for the LightWriter Clock was to play with the ephemeral nature of time – in that each specific measurement of its passing quickly fades into the past. In a very literal way, this clock writes out digits of the time onto a phosphorescent media which then slowly fade away.

Here’s the latest and long awaited update of the LightWriter Clock project, and yes, I did paint the body a lurid shade of lime! (Why, because I can! or at least had a can?)

The final design is covered with a sheet of clear acrylic, the bottom section of which is painted with several coats of a phosphorescent spray paint. Every 3 minutes, the LightWriter bursts into life articulating the two arms to write out, using a UV laser, the four digits of the time, in 24 hour format, onto the phosphorescent coating.

LightWriter Clock

LightWriter Clock

While it does work, I am quite disappointed with the brightness of the display panel and clearly need to do more experimenting with the phosphorescent coating and the 405nm laser.

Initial results seemed to indicate that the written characters would be a lot brighter but when hung on the wall (and please excuse the fact that it is currently mounted on my rather dirty garage door), the brightness is quite poor, even at night. The 50mW 5V UV laser appeared to work well with the phosphorescent spray paint that I bought at Rona so maybe this is something to do with its beam focus.  I have a higher power laser on order and will check that out as well.

LightWriter Clock

LightWriter Clock: showing part of the laser trace for the number 4

For those interested in the workings, due to the isosceles geometry of the system, the laser at the apex of the arms traverses a roughly triangular “usable” area, and the four time digits are crammed into this space.

LightWriter

LightWriter Clock: showing how the four digits of the time are written into the “usable” area traversed by the laser

The numbers on the plot above relate to the left and right stepper motor position. In the software, I have created an array for each number that can be written into each of the four digit positions. The array is a sequence of coordinates to describe points of each character form. Due to the “sweeping” nature of the arm movements, some digits are better resolved than others and more work is necessary to refine the shapes.

The work continues…

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