Cathode Ray Tube Clock

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David Forbes has built a very interesting CRT (cathode ray tube) clock. It uses a 3 inch oscilloscope tube. The clock draws images by bending the CRT beam; this produces a smooth well formed numbers. This is a much different procedure than a TV uses to produce images on a CRT. At the time of writing David does not have any clocks to sell but he does intend to have some available in the future.
“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.”

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5 Comments


  1. I tried contacting David Forbes regarding the release of his latest version of the Scope Clock (I was interested in purchasing one), but have not received a reply to date.

    Do you have any suggestions or information?

    Thanks in advance.


  2. build those and sell them!! i would buy them!


  3. Though not completely self contained like David Forbes’ clock, the AVR Oscilloscope from Dutchtronix (www.dutchtronix.com/ScopeClock.htm) gives you a very nice looking clock on a CRT, just add an old analog scope with X/Y mode. Because it can run from both the on board Real Time Clock, or from an external 1 Pulse Per Second signal (think GPS module), it can run very accurately.
    Control is through a serial port and the clock can be quite fun to play with; it even has a DEMO mode!


  4. I just perchased this clock off ebay. Have never seen anything like it. Beautiful


  5. 顶起,我喜欢阴极射线管.

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