This prototype unit (predecessor to the current production model) was the result of nearly one year of painstaking design, software engineering, and hand construction.
Forget pixels and dotty graphics. Everything you see on this screen is made up of CIRCLES! Blank out part of a circle and you get an arc. Squish an arc and you get a line. This clock simply draws circles, lines, and arcs of different sizes at various points around the screen. It does it quickly. And it does it very, very well!
The lovely blue/white phosphor CRT is from a Telequipment S51B, circa 1978, hauled out of the university dump. This company was a British joint venture with Tektronix, and they didn’t scrimp on quality with this scope. I was sad to gut it. But what finer end could it have than reincarnation into an Oscilloclock?
I lashed out to get very high quality cast acrylic, but couldn’t justify the expense of having it pre-drilled and tapped. Doing this myself took many hours, but was a great break from etching the PCBs!
The double-sided PCBs are all hand-etched. Aligning the front and rear to 10 mil accuracy was a monumental task, not to mention drilling a thousand holes. If that doesn’t turn you off, try dealing with safe neutralization and disposal of these delightful chemicals.
At prototype stage, there was no way I could afford a made-to-order transformer! Instead, this baby is powered by an old modem isolation transformer, hand re-wired and tested iteratively until it seemed to work. The end result is extremely inefficient: the transformer gets very hot, and doesn’t supply enough current for a bright beam. Not to mention that it’s possibly quite unsafe – the auto-off feature is a bit of a safeguard here!
I wanted crisp, clear, and classy figures. But I found out too late that sending a fast 100V pulse down the length of the CRT cable generates a LOT of noise, and is pretty lossy. My beautiful strokes were fuzzy and warped. Some hackery resolved it – by moving the blanking transistor into the CRT unit, only the 5V low current pulse goes down the cable.
The chip is a PIC. I chose a PIC arbitrarily because I had a few hours’ experience with one once. This 18F has only 8-bit addressing – memory bank switching required!! I thought I’d never see that again after my 6502 programming days. Well, porting Cathode Corner’s Motorola code across to this device was tough, and 100 hours later I almost regretted not choosing a Motorola to start with! But once ported… I was free to embellish it with some value-added features…
… one of which is language switching! This is the ONLY scope clock in the known world with a Japanese-language display. And vector drawn to boot! I painstakingly defined every character, segment by segment. No, I did NOT define all 2000 standard characters; only what I needed. But it was still quite a chore.
Setting clocks can be fun, but this one doesn’t need it! It adjusts itself straight from a Garmin GPS unit, which supplies accurate time every nn seconds (configurable). An animated circle in the right corner of the screen shows the GPS status. Of course, the whole shebang can be turned off, for those who just like to adjust every once in a while.
As always I give immense credit to www.cathodecorner.com, for inspiring this project and for publishing a brilliant design and source code under the GPL license. This project would have taken a lifetime without these resources.