The Story of the Scope Clock
The Scope Clock started a long time ago, in the year 2000. I had recently connected with a local vacuum tube fan and weirdo named Tom Jennings. He had made all sorts of interesting art projects using obsolete technology. There were Nixie tube clocks and Teletype story tellers and Trinity blast site dioramas with Geiger Counters.
Tom introduced me to the idea of drawing Postscript graphics on an oscilloscope tube or a pen plotter. This seemed a bit ambitious, so I considered the possibility of generating a display of numbers, i.e. the time, on a scope tube using vacuum tube electronics. Even that seemed daunting, so I switched to using a computer and some analog circuits to generate basic shapes via Lissajous patterns. This required a circuit to make sine waves and cosine waves, and a couple cheesy digital-to-analog converters to place the circle somewhere on the screen and divide it into arc segments.
I developed a Lissajous circle drawing circuit using a little Motorola CPU called the 68HC705, which I had already been using to initialize the PLL in my pirate radio transmitter.I made this circuit do its thing on a big breadboard with my Tektronix 465 oscilloscope as the display. It worked rather well.
I began collecting interesting CRTs from eBay. They need a big beefy power supply, in addition to the fancy electronics to generate the image via X, Y and Z inputs. I gave myself the task of designing a power supply that would be small and efficient, since I didn't want to have a box full of big transformers. Fortunately, I had recently acquired a Morris coil winding machine and a box of ferrite cores and bobbins from an estate. I set to work learning about switching power supply design.
I ended up making a special type of power supply that uses voltage doubler on all of its outputs, so that the voltage regulation would be good for all outputs from 5V to 1500V as the input voltage changes. This allowed me to use only one transformer to run the CRT and the logic circuits from 120VAC. The transformer had six windings to generate all the voltages necessary.
I made a batch of PC boards called the SC100, and prepared to sell them to electronics nerds in May of 2001. I also designed a case for the clock out of acrylic. Then as I was getting ready to ship, my younger son was diagnosed with leukemia. Bummer. We worked our way through chemo infusions and spinal taps, and I made a redesigned clock in October. This one ended up selling a couple hundred copies, along with some Nixie clocks that used the same custom transformer.
I lost interest in the scope clock as I was developing the Nixie tube wristwatch in 2004. That went on to sell a bunch after the Woz saw it on the wrist of an early customer at the Computer History Museum's PDP-1 restoration shop and had to get one.
I redesigned the scope clock to use a fancier display with alphanumerics in 2007. This one also ran from 12V not wall power, to allow a UL-listed wall transformer to be used. I chose a 68HC908 processor. A few boards were sold, but I was unhappy with the redesign and didn't pursue it.
I also designed the round SCRA clock, with a lovely thick acrylic tube as the case, and the electronics on three round boards at the rear. This clock was beautiful but utterly unusable, as I had foolishly designed the controls into the rear panel so that it was nearly impossible to adjust them while viewing the clock face. Oh, well.
I then got into other projects for a few years. Many robots were made with the Typewriter Repairmen and the Bit Buckets. Video coats and bike sound systems distracted me.
The clock was resurrected in 2016 when I developed an Arduino-based version called ScopeDuino. It had a laser-cut plastic case with many knobs in front, and the main PC board behind the front panel. It worked, but the case design was rather clunky, and it had little aesthetic appeal. Back to the drawing board.
Life had some changes. I got together with the wonderful lady Sally Hunter who would eventually marry me. time was carved out of life to enjoy things and have fresh ideas.
In the summer of 2017, I found a Tektronix 321 oscilloscope at the surplus store. I noticed that its clean lines were formed out of a flat front with a sheet-metal cover having curved edges. I remembered that one could laser-cut smooth, radiused corners into plastic using a method called a living hinge, which is made of long alternating slots to allow the material to flex. A sketch of this idea resulted in the SCTV case. Eureka! I even added a little caboose in the rear for the tube base to live, in homage to old TV sets.
I made a few sample cases of wood and plastic with my son (he recovered nicely) at the local hackerspace Xerocraft. They worked, but it took a long time to cut the living hinges and their laser cutter was already oversubscribed. Oh, well. Sally and I settled down, and finally it seemed that the time was ripe to make scope clocks.
I started working on building my own 50W CO2 laser cutter in late 2019. I chose to save money by building one from scratch using a gantry kit from OpenBuilds as a starting point. It was mostly done when the pandemic hit in April 2020, and I had to move my day job home. Finally the day job moved out in June 2021, and I was able to finish the laser cutter and make my own scope clock cases.
I had also redesigned the clock circuits in 2019 to use the modern ARM processor on the Teensy 3.6 computer board. This little $30 wonder, which is part of the Arduino ecosystem, has two matched digital to analog converters that can emit a million X,Y points per second. I rewrote the clock display code to use the DACs and emulate the old Lissajous circle-drawing hardware in Arduino code.
Then I realized that I could use the position controls as game paddles, and Pong was born. Haikus followed soon after.
Then I realized that no retro gizmo is complete without Tetris, so I ported it from some Arduino libraries. I had to create a method of displaying the blocks as vectors instead of pixels, and I had to modify the controls to use knobs instead of buttons. That was challenging but very fun to work on.