Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Electrical Engineering


While the areas of time keeping and computers have been somewhat independent, there have been exceptions. The commercial time recording clocks have for many years been used of ring bells in schools and factories. An example of this type of system is the simplex control clock designed by International Business Machines in 1949. This type of clock relies on electromechanical logic. With the introduction of low cost digital logic and microprocessors, the designer has been given the opportunity to develop real time control systems and sophisticated digital clocks. The first attempt at this project definition was to develop a digital clock and some type of electronic storage and decision making system that would perform the functions of the Simplex system. Many approaches were considered and rejected before the complete system was defined. It was finally decided to have a digital clock connected to a microcomputer system that would compare the time to a table of times and commands in a read only memory. The computer would send commands to a series of circuits that would finally perform a variety of tasks. Features included which perform additional tasks to the simplex system include a calendar, intrusion alarm, Westminster chime system and a programmable cycle indicator. An important aspect of this project was the area of modularity and system layout. Several years ago the author was fortunate to have worked on the construction of a bowling score calculator to assist blind bowlers. This was a master’s project designed by Gary Wilhelm. Problems were encountered in construction that were not unlike those of Charles Babbage and the “Analytical Engine.” The genius of design was too technically intensive for the materials at the time. Significant improvements have been made since that time in the area of prototype components. Now it would be much easier to implement the bowling computer illustrated that successful completion of a complex clock would require breaking up functions into modules. By disturbing the system on a number of small boards each having an independent task, errors in design and construction can be located easily ad corrected. Except for the power supply individual boards can be checked without other boards placed in the system. Sequential circuitry is avoided wherever possible to speed system diagnostics and improve noise immunity. Another advantage of modular systems is the flexibility of the finished product. With a minimal set of modules a system can be configured in many ways by using different combinations of modules. Another aspect of flexibility is the opportunity of system expansion if the need arises. To demonstrate this modular concept, a number of responding output boards were created. These boards incorporate a variety of functions, design concepts, and device technologies to demonstrate the versatility of the system. Another factor that affected the overall design of the clock was the fact that it was to be primarily a demonstration prototype. This had the effect of making the design somewhat conservative at the expense of cost of optimization. These factors also added a number of controls and indicators that would not by needed in production models. The designs were achieved using over 150 integrated circuits, 500 miscellaneous components, 4100 interconnections, and two year’s work. The detailed discussion covering the clock system and the individual modules that follows will assume a knowledge of electronics and digital logic on the part of the reader. If tutorial information is needed, the works of Lancaster and Wicks listed in the references should be consulted. Conventions maintained to improve schematic legibility will be the omission of power and ground lines, decoupling capacitors, and data code tables from the schematics. The data code tables are listed in the appendix for reference. Because of the vast nature of this project, it would be impossible to be both complete and concise enough to satisfy all readers. Much of the background information, component specifications, and software documentation is referenced in the footnotes.

Library of Congress Subject Headings

Clocks and watches




Number of Pages



South Dakota State University