Ring Counter Clock Keeps on TickingBy Jerry Lowe
Tri-L Electronics, Inc.
40 Years and Still Going Strong
I designed and built this Ring Counter Clock in 1970. The base is a 12" diameter/2" thick block of walnut from a hollowed-out gun stock blank. The back side of the base has been hollowed out to hold the circuit board. I chucked it up in a large lath and turned it inside and out. Then I drilled 120 holes for the lights and five holes in the center for controls and a time base trimmer. The copper clad board was made by making a drawing board layout on Mylar with tape dots and strips, twice the size of the board. Then a board size photo negative of the art work was used to photo print the board.
This clock can maintain time of ±1 sec for months and has been operating for 41 years, except when it was necessary to replace a bulb and when it was moved from one state to another. I keep thinking I will replace the bulbs with LEDs some day, maybe when I run out of bulbs.
Many of you may be too young to know, but in 1970 we did not have microprocessor chips to perform every electronic function known to man. We actually made circuits to perform the functions we needed, without programming.
Clock's CircuitThe electronics of the clock consist of a clock circuit made up of a 1MHz crystal oscillator and a TTL divider chain down to a 1Hz pulse. I did not show the clock circuit because there are several more simple ways to arrive at a 1Hz pulse now then how I designed this in 1970.
Click here to enlarge
The ring counter circuit shown above is a modified circuit of one shown in the first edition GE semiconductor data handbook. There are three of these ring counters used in the clock: one 60 section ring for the seconds, one 60 section ring for the minutes and one 12 section ring for the hours. Each of the ring section is designed around a 2N4990 SUS (silicon unilateral switch), I believe this device is still available, if not, it should be. It has many uses.
The output of the last section of each ring returns to the first section to start the ring on "1" again. The output of the last section of the seconds ring also clocks the minutes ring. The output of the last section of the minutes ring also clocks the hours ring. When the seconds ring turns on the 60 second light, it indexes the minute ring. When the minute ring turns on the 60 minute light, it indexes the hour ring, and around and around it goes.
Also notice the start up capacitor on the gate of the first section of each ring. It holds the gate down when power is switched on, causing the first section of the rings to turn on for 12:00:00.
The light bulbs could be replaced with LEDs and a series resistor. I have changed light bulbs several times since 1970.
My last two children learned to tell time from this clock. At this clock's rate, my grandchildren will too!
If you have questions, email Jerry Lowe at [email protected].
If you have an electronics story you'd like to share, please send it to [email protected].