Digital Sundial

Digital Sundial


U.S. Pat. 4,782,472

“The first true digital sundial”,  North American Sundial Society.

      The Digital Sundial was developed by Steve Hines as an optical analog-to-digital converter and uses no electrical power.  It makes use of the changing angle of the sun, shining through slits, to illuminate optical fibers, that illuminate segments of a readable display, that can be placed inside a house, office or museum.



      Individual optical fibers are shown epoxied in holes in the clear Plexiglas encoding cylinder (analogous to the gnomon of other sundials).  The opposite ends of the fibers are attached to individual segments, of a 7-segment numerical display, with clear epoxy.  Depending on the angle of the sun, various optical fibers are illuminated to form the readable numbers.  

      An end view of the encoder shows the sunlight shining through slits, illuminating the ends of optical fibers as the sun moves across the sky.  When sunlight shines on an optical fiber, the opposite end illuminates a segment of the display to form a readable number.


Military application:  The electromagnetic pulse (EMP) associated with atomic explosions can disrupt the function of computer circuits and electronic communication.  This optical A-D converter technology is insusceptible to such an event.  This approach can be reconfigured to create digital optical signals to locate hot targets or incoming missiles, information that is critical for the defense of targeted sites.


The four categories of time-keeping devices:


How it works:

      During the day, bands of sunlight sweep over the ends of optical fibers in the encoding cylinder.  Light travels through the fibers to illuminate the segments of the display to form readable numbers.  The following digits are animated individually, without any timing, scale, or phase relationship.

Tens-of-hours display, (Xx:xx): A single wide opening in the cylindrical encoder exposes two fibers to sunlight from 10:00 AM to 12:59 PM, to form the “1” which is the tens-of-hours  display.





Hours display, (xX:xx):   In an interval of one hour, a single one-hour-wide band of sunlight illuminates a set of fibers to form the units-hours display between 9 AM and 4 PM.  During the day, this single band of light sweeps successively to each line of unit-hours fibers in the encoder.


Tens-of-minutes  display, (xx:Xx): Each hour during the day, a different slit in the encoder allows sunlight to sweep over this cluster of optical fibers to repeat the 0-1-2-3-4-5 sequence necessary for the tens-of-minutes display of the sundial.


Minutes display, (xx:xX):  Because of the soft shadow of the sun, due to its 1/2° subtended angle, the theoretical limit of accuracy of any sundial is ±2, or 4 minutes of time. The Digital Sundial is designed to read in the smallest available digital increment of time, 10 minutes, with the units minutes display fixed at “0”.


Construction Drawings:

      Construction drawings, sent by email, are available for $100 with a license to manufacture one digital sundial with an encoding cylinder of 5-inch-maximum diameter, for private non-commercial, non-institutional use.  Please contact HinesLab for a commercial or institutional license for a larger digital sundial, and for bank transfer instructions.  

YouTube video

Hines’ original lab notebook entries for this invention.

p. 38 p. 39

      HinesLab is actively seeking licensees to commercialize this technology.  To discuss licensing, please contact Steve Hines at:

HinesLab, Inc.

Glendale, California, USA