Digital Sundial


Digital Sundial



U.S. Pat. 4,782,472


Recognized by the North American Sundial Society as

“The first true digital sundial”


      The Digital Sundial was developed as an optical analog-to-digital converter and uses no electrical power.  The sun shines through slits, onto the ends of optical fibers, that illuminate segments of 7-segment numerals at the opposite end of the optical fibers.







      Optical fibers are shown epoxied in holes in the clear Plexiglas encoding cylinder (combining the functions of a rotary encoder and the gnomon of other sundials).  The opposite ends of the fibers are attached to segments, of a 7-segment numerical display, with clear epoxy Depending on the position of the sun, various optical fibers illuminate segments to form the numbers.  


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



The four categories of time-keeping devices:



Sundial Information:


How it works:

      As the sun moves across the sky, sunlight shines through slits in the top of the encoding cylinder and sweeps over the ends of optical fibers in the bottom of the cylinder to illuminate the segments of the numerals.  The following animations are without any phase relationship.









A single opening in the top of the cylindrical encoder allows light to illuminate two fibers in the bottom of the cylinder, from 10:00 AM to 12:59 PM, to form the “1” which is the tens-of-hours numeral.


In an interval of one hour, a single one-hour-wide band of sunlight sweeps across the ends of fibers to form the units-hours numeral between 9 AM and 4 PM. 





Each hour during the day, light shining through a different slit sweep over this cluster of optical fibers to repeat the 0-1-2-3-4-5 sequence necessary for the tens-of-minutes numeral.


The limit of accuracy of any sundial is ±2 minutes.  The Digital Sundial reads in the smallest available digital increment above 2 minutes: 10 minutes, with the units-minutes fixed at “0”.












      PDF-format construction drawings and license to build one 4″-diameter cylinder digital sundial are available for $200 from Steve Hines, at HinesLab LLC, P.O. Box 2271, Virginia Beach, VA, USA  23450.  


YouTube video



  • plans ordered by Rick Steenblik, September 18, 1985
  • U.S. Patent 4,782,472, issued to S. Hines, November 1, 1988
  • Solar Today Magazine, August 20, 1994 issue, p. 39
  • plans ordered bt Phillip Rogen, September 6, 1994
  • plans ordered by Robert McGrath, September 10, 1994
  • plans ordered by William Georgian, September 27, 1994
  • plans ordered by Robert Siebert, Nov. 1, 1994
  • plans ordered by William Georgian, September 23, 1994
  • plans ordered by James Luttrell, January 21, 1995
  • plans ordered by Hans Sassenburg, May 1, 1999
  • information requested by Sundials magazine, November 29, 2001
  • plans ordered by Till Liepmann, April 1, 2002
  • incorporated in paper presented by Bob Kellogg, at the North American Sundial Society conference in Banff, Alberta, Canada, August 21-24, 2003
  • plans ordered by Charles Ashcroft, Sept. 7, 2007
  • plans ordered by Punjab Engineering College, India, February 6, 2008
  • plans ordered by Bret Niemeyer, June 28, 2011
  • plans ordered by Pat O’Grady, Sept. 4, 2014
  • North American Sundial Society (NASS) declares it “The First True Digital Sundial”, October 2, 2014
  • plans ordered by Edgar Kogler, April 24, 2018
  • Great design“, Jean-Baptiste Rouquier, Dec. 27, 2022



Hines’ original lab notebook entries for this invention.  

p. 38 p. 39



      PDF sundial plans are available by email for US$200.  





P.O. Box 2271

Virginia Beach, VA, USA  23450





ph. 818-507-5812