Cathode corner presents the Scope Clock.

Sorry, I'm fresh out of scope clocks. I'll update the page when I get the new design done.

Here is the scope clock in a Plexiglas cabinet.

The scope clock displays the time on a small oscilloscope tube.
The numerals are formed from circles, arcs and lines. No pixels are used.

The scope clock displays the time on a 3" diameter oscilloscope tube (CRT). The numbers
are formed from circles, lines and arcs, just like the numbers on a Nixie clock.
The difference is that they are clear and crisp and much easier to read. And
they're green. This is NOT a raster, line-segment or dot display! The circles are drawn by
the beam following a precisely circular path on the screen.

Screen burn-in is dramatically reduced by a screensaver feature which moves the
entire image slightly once an hour. When the time comes for CRT replacement,
not to worry because it is a commercially available 3RP1A flat-face tube.

The red pushbutton controls the time setting feature, while the black button turns
the seconds display on and off and advances the digits in time-setting mode.

The holes in the left side of the cabinet provide access to brightness, focus and
positioning adjustments. Other adjustments for image size and circle proportions are
accessible with the cover removed.

The timebase is the microprocessor clock, but an optional rear panel connector ($25)
allows the clock to accept a 1PPS (pulse per second) time reference signal from an
atomic clock or GPS receiver. Voltage level is 5 volt CMOS, falling edge triggered.
The clock will use its internal timebase until it detects the 1PPS input.

How It Works

Here is a view of the circuit board that runs the scope clock.

The PC board holds a switching power supply, a crystal-controlled microcontroller
for generating the timing and scanning the digits, and an analog circle generator
system to draw the digits. It makes circles directly from sine and cosine waves.
That's why the curves look so clean.

The drawing of the digits is done in segments, each segment being composed of an arc,
circle or line. Angled lines are made by putting the same cosine wave onto both
the X and Y deflection plates.

The display repetition rate is synchronized to the power line frequency by the
microprocessor to prevent image 'swimming' in the presence of strong AC fields.
This allows the CRT to be free of magnetic shielding, which would add to the cost
and detract from the beauty of the clock.

This clock has a professionally made PC board to hold the electronics. The cabinet
is made by a local plastics fabrication company. All the parts are currently produced.

European Use

This clock will work ONLY on 120VAC. It can be provided to work on 50 Hertz.
I will assume that European orders require 50 Hertz.
It will run on 240VAC with a 240V to 120V step-down transformer.


Size: 5" W x 5.5" H x 10" D (excluding 1/2" tall feet)
Case: Clear acrylic plastic, 1/4" thick
Weight: 4 lbs
Power: 100-130VAC, 60 Hz (50 Hz version available on request)
Wattage: 10 Watts

CRT type: 3RP1-A
CRT life expectancy: 5-10 years

Timekeeping accuracy: 5 sec/month initial, adjustable


SC100 revision E clock kit assembly/user manual
The SC100 revision C, D, E schematic is here: Page 1 Page 2 Page 3.

Sorry, I'm fresh out of scope clocks. I'll update the page when I get the new design done.

Back to main page.

Last updated 4/3/2005