The Pre-CRT Oscilloscope

Oscilloscopes are especially magical because they translate the abstract world of electronics into something you can visualize. These days, a scope is likely to use an LCD or another kind of flat electronic display, but the gold standard for many years was the ubiquitous CRT (cathode ray tube). Historically, though, CRTs were not very common in the early days of electronics and radio. What we think of as a CRT didn’t really show up until 1931, although if you could draw a high vacuum and provide 30 kV, there were tubes as early as 1919. But there was a lot of electronics work done well before that, so how did early scientists visualize electric current? You might think the answer is “they didn’t,” but that’s not true. We are spoiled today with high-resolution electronic displays, but our grandfathers were clever and used what they had to visualize electronics.

Keep in mind, you couldn’t even get an electronic amplifier until the early 1900s (something we’ve talked about before). The earliest way to get a visual idea of what was happening in a circuit was purely a manual process. You would make measurements and draw your readings on a piece of graph paper.

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[Dino]’s One-year Extravaganza Is A Laser Oscillograph

Readers of Hackaday may have noticed the weekly posts featuring whatever [Dino Segovis] of Hack A Week has cooked up in the last seven days. For [Dino]’s one-year anniversary, he’s pulled out all the stops and put together one of his coolest hacks to date. It’s a laser oscillograph that projects waveforms on a screen just like an oscilloscope. What’s more, the entire contraption is built out of a dead hard drive and a few motors and mirrors [Dino] had lying around.

The build uses an old hard drive to draw the vertical component of the waveform. Because hard drives usually use a voice coil to move the heads around the platter, it’s very easy to connect a hard drive directly to the headphone output of [Dino]’s laptop. Playing a sine wave on his computer makes the drive heads move up and down, but [Dino] still another dimension. For that, he used a rotating mirror that reflects the wave onto a paper screen.

[Dino]’s finished build isn’t that much different from an oscilloscope or projection TV. It’s possible for [Dino] to improve upon his build and make a genuine vector display with the addition of additional electronics and optics, but we’re not expecting that until at least the two-year anniversary.

Check out [Dino]’s build video after the break.

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