What’s cooler than a clock that draws the time with a marker? One that does it with a laser of course! That was Mechanical Engineering and Computer Science student Tucker Shannon’s thinking when he made his glow-in-the-dark laser clock.
The clock is a variation of the “Plotclock” that is seen in the video below. Plans for building it are available on Thingiverse. Shannon simply substituted in a laser and glowing surface for the pen and whiteboard!
Both styles of clock use an interesting linkage system, where two servos combine to properly position the writing device. Each servo actuates a length of acrylic, which is then fastened to a secondary length of acrylic by a flexible joint. These are then fastened together by another joint, allowing the pen or laser to be positioned precisely enough to draw the numerals that indicate time. The whole thing is controlled by an Arduino Uno clone that Shannon had lying around, with the assistance of a real-time clock (RTC) module to keep it accurate. It lasers a new time with the press of a button, and will stay readable for about 10 minutes at night.
The amazing thing about this build is how well the design translates from a pen to a laser. Shannon covered what would normally be the whiteboard surface with a glow-in-the-dark sticker, and substituted a 405nm violet laser for the pen to create the bright glowing effect. The necessary modifications were made in the open source QCAD drafting package, which works similarly to AutoCAD.
Since the time written by a laser eventually stops glowing, there’s no reason to accommodate an eraser (ironically simplifying the build). In fact, the laser never has to be physically picked up, as with the marker assembly. Instead of a third servo, it simply supplies or cuts off power to the laser depending on when text needs to be marked. It seems so simple at first glance, but it requires quite the intuitive mind to pull off!
Shannon notes that the most difficult part of the build was getting the laser to work with Arduino pins. “The pins only output 40mA, so I had to use an NPN transistor and pull from non-digital pins that were able to supply the 70mA that the laser needed.” He estimates that this build would only take someone 2-3 hours to pull off if they has all the materials and tools handy.
The modified assembly is laser cut out of clear acrylic. While Shannon loves the look that the laser process produces here, he notes that the pieces could just as easily be replicated with a CNC router or 3D printer. Perhaps the design could be scaled up to draw on a real whiteboard or even be used as some sort of large city clock or art installation.
Shannon reports that he’s thrilled with how the build turned out, and thinks that the clock is both interesting to watch and has a practical use. It’s a great build. Hopefully it will inspire others to try making their own laser clock, or even adapt this design for another project with an entirely different purpose!