Two 7490 integrated circuits. The date code tells us that they were manufactured in September of 1972.
Although I was unaware of the new integrated voltage regulator circuits when I built this clock, I was familiar with an early series of integrated logic circuits, the 74xx TTL chips (TTL stands for “transistor-transistor-logic”). Again, the ability to replace multiple circuit boards of discrete components that implemented a specific logic function with a single integrated circuit chip, was revolutionizing electronics.
An example is the 7490, a small 14-pin device that implemented logic that could count to ten. I used two of them, configured to count to 60 and then start over. I fed it a clock input that was derived from the household AC line, 60 cycles per second, and it delivered a logic pulse once a second to the first relay in the clock.
I wanted to keep this relic of a circuit in the renovated clock, and so I adapted its input to the AC signal from the new power supply. But I had forgotten the rules for using the ancient TTL logic, which required much higher current than is used today. Modern CMOS logic uses almost zero electrons to do their magic, which is why your phone doesn’t discharge within a few minutes, blistering your hand with the heat.
My first attempt to trigger the old timekeeping logic resulted in paralysis. No ticks.
It may not look like it, but this is a clock, one of the world’s first digital clocks, circa 1973.
When I was twenty or so, I built a clock. It was a clock that used electromechanical relays to count the seconds, minutes and hours. I was early in my electrical engineering studies and barely understood Ohm’s law, but I was aware of electromagnets, and how they could be used to make mechanical movements. Some of us call them solenoids, coils of wire that magnetically push or pull an iron piston to make and break switch contacts.
My dad, in his ham radio hobby quest for cheap electronic components for whatever future project he might undertake, had acquired various relay mechanisms. He showed them to me and explained how they used electrical pulses to move a metallic wiper to a series of successive contacts. These were telephone relays, used when you “dialed” the phone. One relay, responding to a single rotary dial action could connect you to ten possible neighbors. Cascading it with another set of relays would allow calling up 100 neighbors. More phone digits would extend it even further, you get the idea. I barely understood how to deliver current to energize a relay coil, but I could figure out how to connect the contacts to make a sequence that counted.
Another item from my dad’s ham shack inventory of salvaged components was a numeric display, something you might see in an elevator (60 years ago) indicating the current floor. It used incandescent light bulbs to project a numeric figure on the screen. Ten separate bulbs, each behind a number glyph mask; one of which was selected for the current digit value. I figured out how to connect the telephone relays to the elevator displays to make a clock.
I was quite pleased with the result and when I got it working, I showed it off to my friends. But it had several drawbacks. First, it was noisy. Relays are mechanical devices that magnetically pull metal contacts against each other, resulting in a click-clack noise as they activate and release. The relays counted seconds, so there was a click-clack noise every second. And at ten seconds there was an additional click-clack, as the next relay responded to the carry pulse. And at 59 seconds, there was a carry to the minute-counting relay. As the carries propagated to the hours, a peak acoustic disruption occurred as the clock transitioned from 12:59:59 to 01:00:00.
The other drawback was that the clock got hot. As I said, I did not yet understand the relationships of voltage, current, power and heat. I just hooked up the components to make the displayed result I wanted. The numeric display, comprising light bulbs, used quite a bit of power. And the relays required power too, and my power supply was terribly inefficient. As a result the clock, in the glass case I made for it, built up an enormous amount of heat. I tried to ameliorate it by installing an internal fan, but this seemed only to make things worse (the fan used power too).
I kept the clock as a curiosity piece, displayed on a fireplace mantel in our home. It was intolerable to run continuously, so I would switch it on to show visitors that it actually worked, and then shut it down to stop the noise. Eventually, the clock got packed up during one of our moves and stayed so.
The boxed-up relay clock was in storage for at least 30 years, but I would occasionally encounter it hiding among my workshop parts and supplies. I recently ran across it. It had endured the desecration by (and excrement of) rodents, the decay of electrical components, and the binding of mechanical joints. I wondered why I had saved it all these years.
Well, the idea of resurrecting a contraption that I built half a century ago carried a certain appeal to me. Having since learned the principles of electricity, maybe I could bring it back to life and its former geek glory!
In the next series of posts, I will describe the process of restoring this pioneering clock.
Some “before” pictures showing the deterioration of my relay clock
State-of-the-art power supply in 1973 next to a modern (for over 40 years now) voltage regulator.
As I mentioned, I was not skilled in power supply design in 1974. I am still no expert, but I have acquired some familiarity with them over my career. Back then, one needed to understand transformers and bridge rectifiers and capacitors. They were simple, but limited.
Think of your basic plug-in wall charger. A few years ago, they were made of a dense and bulky transformer, diodes, and a capacitor, the smallest components that the designer could find to meet the power requirement. They were not terribly efficient and could only provide a few watts.
Today your cell phone and computer chargers can deliver hundreds of watts but are smaller and lighter weight than those old “wall warts”. They are the beneficiaries of new power supply technology that uses high frequency internal circuits to replace the old iron cores of the 50-60-cycle transformers.
I could now replace my old 24V center-tapped transformer-based power supply with a modern “AC to DC converter” that could provide more power at higher efficiency than was possible back then.
I needed some more voltages: 12V and 5V. The old supply took the “center tap” of the (24V) transformer to provide 12 volts for those relays that needed it. The 5V for the logic circuit that generated the one-second pulse was obtained by a crude arrangement of diodes and resistors powered from the 12V line. I’m amazed it worked.
But that was what was available back then: diodes and resistors. Today it is trivial to generate stable power supplies by using the ubiquitous 78xx series of voltage regulators, a component that has three pins: voltage-in, ground, and voltage-out. These breakthrough parts were first manufactured in the early 1970s, a time when “integrated circuits” had recently been invented and were being applied to an ever-increasing number of applications. In this case, elaborate voltage regulation circuitry that had previously required dozens of discrete components were now implemented by microscopic semiconductor junctions contained on a single “chip”. At the time I built this clock, regulator chips were becoming available, but I did not yet know about them.
Today (and for the last 40+ years), I use the 7805 to provide a +5 volt supply, and a 7812 to generate +12 volts. This will be part of my power supply renovation.
AC to DC converters (black modules) for the renovated clock. One provides 24V, the other supplies the 6.3V for the display lamps. The object plugged on top of the power cord is an isolation transformer that provides the primary timing signal.
A closeup of the ten-step relay. It moved sluggishly and got held up on the tenth step when the carry contact (upper right) could not close, stopped by the bump on the circular cam.
I re-wired the relay coils for the improved control circuit and hooked up the new power supplies. A set of micro-switches were used for setting the time—they momentarily applied power to the relays with each button push. I could now see if the relays still worked. They did!
Well, they mostly worked. The contacts had tarnished and needed cleaning, and some of the mechanisms got stuck in one or more positions. I applied the usual treatment for things that stick—WD40, but it was not enough. The lubricant that finally allowed the decade stepper relays to move freely was something called “Nano-Oil”, a substance using “Magnetically induced Molecules of 0.09 microns”, that my son had gifted me a few years back. At the time I wondered what I would use it for, but he evidently saw my future need for it.
“Nano-oil” helped to re-lubricate the moving parts on the relays.
A short video showing the (restored) relay activation and contact movement.
I had no schematic and my memories were vague, but I recalled that there had been three types of relays, all operating at different voltages, which made for a complicated arrangement of relay contacts and coil terminals. There was yet another voltage involved in lighting up the display. I wanted to figure out how I had managed all this complexity back when I barely understood power supplies, and then figure out how to renovate it, with the least amount of re-wiring.
As I went about tracing wires, confirming contacts with an ohm-meter, I gradually built up a re-understanding of how the relays were interconnected. Some of the wires had broken and so I could only guess their destinations. I eventually figured out how the three different relay types managed to propagate the time signal from one level to the next. As I worked on this, there were more than a few times when I wondered “how could this have ever worked?”
A photograph taken by my grandfather in the 1930s. Where is this unusual entryway?
In recent weeks I have been reviewing old family photos in preparation for a covid-delayed memorial. Among the too many pictures of unidentified people and places are some intriguing treasures. The relatives who could tell me more about them are now gone. I can’t ask them, which is one of the more frequent and sad experiences I have these days.
But sometimes it is possible to follow clues in the photos to find the answers. In this case it is a photo that my grandfather took, possibly back in the 1930s. It shows a beautiful composition of light and shadow of a building entrance/lobby. I liked the lighting, but I really enjoyed discovering the detail on the door panels that were casting the shadows: insects and plants. What building would host such artwork?
Google search is an amazing technology. A response to “door panels insects plants” did not yield anything useful, but by adding “Harvard” to the terms (knowing my grandfather had studied biology there) and looking for image results, I found a unique building: the Harvard Biology Laboratory.
The building was built in 1931 and obviously impressed my grandfather, where he likely spent considerable time in it pursuing his doctorate. It continues to impress, as recent posts attest. As I look at the pictures of the outside of the building, who wouldn’t find it intriguing?
It turns out that there are three doors to the entry; my grandfather’s shot depicted two. But there is a hint of another– a bicycle is parked there, and sure enough the current pictures show a third door, adorned by sea creatures. All of them, and the sculptures outside, created by Katherine Lane Weems.
All of this makes me want to visit. I now have a memento from the past that would be fun to re-create!
When Management Graphics adapted their film recording technology to support motion picture film formats, it was quickly adopted by movie studios to bring special effects from their computer memory images on to film. There were some problems however, and one of the most serious was the difficulty in obtaining the full brightness range found in typical scenes, especially when they included lights—candle light, desk lamps, car headlights, streetlights. Any light source, even a glimpse through a window to the bright outdoors, would cause a large flare in the final film frames, washing out detail in the scene. Our customers complained, and we started down a path to research and solve the problem.
We understood what the fundamental issue was: halation, an effect caused by the glass faceplate of the cathode ray tube used for creating the image. The bright spot on the phosphor screen was internally reflected at the glass surface which then illuminated the phosphor coating. If phosphor were black, this would not be a problem, but phosphor coatings are white, as are most materials made of fine powder, and it resulted in this internal reflected light overexposing the film. In the absence of a black phosphor, there were few other ways to mitigate the halation effect.
An example of halation on a photographic film plate. The circular haloes and flare are apparent around the street lights in this 1910 image.
One of our customers was incorporating our film recorder into a full workstation system. Quantel, a company in Newberry, England, had become successful in the early years of digital video and was looking for a way to expand its editing tool offerings into the motion picture market. Quantel’s engineers understood the halation problem as well, but they didn’t want to rely on our figuring out a solution: they had an aggressive development schedule.
I’m occasionally asked about the Academy Award that my colleagues at Management Graphics received. It was during the early days of computer-generated special effects in motion pictures. A product I contributed to, the Solitaire Image Recorder, was selected as a technology advance worthy of the Academy’s Technical Achievement Award. These awards are delivered in a parallel ceremony to the one we are all familiar with. It features celebrities of a different kind: nerds.
This is the story of how my friend Rick Keeney ended up on that award stage. It has been adapted from his personal account and is a bit technical, but don’t let those details detract from the overall story line.
Rick Keeney, with the Academy Award for Technical Achievement, 1992.
Invention and Innovation
In the formative days of digital photographic imaging, output back to film was produced using specialized, often hand-built, image recorders that were difficult to align, calibrate, and keep running consistently. As one of the early companies in the business of building and selling graphics workstations, Management Graphics (MGI) recognized that the drawbacks of the available film recorders were limiting its workstation sales. MGI kicked off a development effort to build a film recorder that would be a robust and easy-to-use product.
Career “trophies”, coffee mugs, one of which was created by dye printing technology (depicting our development team), the other a memento commemorating the issue of an arcane patent.
There is a more general problem related to the “what to do with old lab notebooks” that some of us face. It is what to do with our shoeboxes of photos (virtual digital shoeboxes and real ones). And written correspondence. Love letters. Birthday cards and holiday cards that caught our attention enough that we saved them. The trophies, actual physical trophies, or the certificates of commendation for a job well done. Birth and death announcements. Souvenirs of our travels, the mementos of the high points of our lives.
All of them carry great meaning to us, invoking a romantic haze of fond memories from those times and places, for those people and events. Yet those memories are internal to us; they are not shared, even with the persons we may have shared the moment with—at least not exactly. Each of them has his or her own version of those scenes. And they are not shared in the same way with our children, and certainly not their children. Our lives are an abstraction to them. They weren’t even around when the main story was unfolding.
I have come to realize this in the last few years as I have processed the items left behind by my parents after their deaths. I have a high regard for my father’s technical acumen and his many projects. Some of them were to gather and archive family history, others documented his personal interests. He was always an early adopter of technology and embraced digital photography well before I did. He acquired a large collection of both film and digital pictures, organized in shoeboxes and digital folders. He worked to digitally scan historic family photos that dated back to the 19th century.
There is a treasure trove of history here, some even recent enough to overlap with my own, yet I do not find myself compelled to explore it. And therein lies the problem. If I am not inspired to carry forward the artifacts of prior generations, why would I expect subsequent generations to propagate mine?
The title page of my grandfather’s PhD thesis, a thick volume of scientific discovery, each page typewritten in carbon-paper triplicate by my grandmother during their time at Harvard. Interestingly, it was submitted on his (54th) birthday.
“Long before the term ecology became a part of the vocabulary of the scientist, primitive man, looking out over the expanse of blue-green water which characterized his favorite fishing haunt, was probably aware of the fact that notable alterations in the color and clarity of this body of water would occur as the seasons changed.”
The introductory sentence of Theodore Olson’s PhD thesis on algae blooms.
I was witness to my grandparents’ transition to an assisted living apartment from the home they had kept for more than half a century. Though modest, it was the center of a busy family’s activities, and had accumulated the corresponding mementos through the decades. It had also collected the technical artifacts of my grandfather’s scientific career, specimens of insects and fish and algae from his ecological and entomologist specialties. He kept copies of his and his peers’ published works, along with those of his doctoral students, who carried on these disciplines, with the scientific rigor and methods that he taught them over their years in his tutelage.
I was there on the day when he had to empty the ‘wall of books‘ in his home library, which included the dissertations of his students. There was no space for everything at the new apartment. A few important reference volumes could be retained, but the others? What to do with them? Here were the compiled and distilled understandings of pioneers in biology, acquired through years of painstaking research, building upon the pyramid of human knowledge. These breakthroughs of their time have now been incorporated into our general understanding of modern biology.
What should happen to the first-ever photomicrographs of blue-green algae blooming to produce cyanobacterial toxins? What should become of the tabulated counts of seasonal species of mosquitos that were the vectors of mosquito-borne diseases? What should be the fate of that first chart correlating taconite processing and asbestos-like fibers in Lake Superior? All of these new discoveries had been first reported in his research and in the dissertations of his PhD students.
