The Light Emitting Vegetable Diode


Years ago, a few of the folks in Digital's Semiconductor Engineering Group plugged a pickle into the wall. It glowed. Soon after this discovery, colleagues at Digital's Western Research Laboratories published a technical report Characterization of Organic Illumination Systems detailing their own experiences with a variety of pickles. The work was illuminating to say the least.

So, a few of us were sitting around the lab after finishing the design database for Digital's 21066A, a low cost implementation of Digital's Alpha processor architecture and wondered what to do. We had a box sitting around that we'd used to light a pickle (so as to reproduce and further investigate the phenomena described by other researchers) and In Sung Kim had a hunk of horse radish kimchi sitting under a waste basket in his office. He had procured it for the sole purpose of answering the obvious question: Does kimchi light up when you pass current through it? So we hooked up the kimchi sample, the electric pickle box, a Varian autotransformer, a Black and Decker Dustbuster, and a Tektronix 7xx oscilloscope. Tears began to well up in our eyes. (The kimchi was very ripe.) No one remembers who threw the switch.

The kimchi, as you might guess, glowed a pleasant yellow as it gave off a rather unpleasant vapor. (The Dustbuster and carbon filter system was not sufficient to keep up with the smell.) Then Dan Jackson noticed the oscilloscope trace. The lower trace showed the voltage across the kimchi. It was running at about 140 V RMS. Then he saw the upper trace. The upper trace showed current pulses of about 4 amperes in amplitude. Dan called out "Hey! The kimchi is acting as a rectifier!" The kimchi only conducted when the voltage across its terminals was greater than 90V. Further, it only conducted in one direction. (Pickles did not produce such an effect.) Knowing that we were likely witnessing the first light emitting vegetable diode, we grabbed a 'scope camera and shot a pack or two of film. This is what we saw: (We were so giddy with excitement that we didn't bother to adjust the 'scope settings.)

The rectification was witnessed by Insung Kim, David Kravitz (who also manufactured the pickle samples we had used earlier), Larry Biro, Dan Jackson, and Matt Reilly. The apparatus was constructed at the laboratories of New England Radio Design for use by Digital Equipment Corporation's Semiconductor Engineering Group.

We immediately notified our colleagues at the Western Research Labs. The text of the memo can be found here Priorities being what they are, we were forced to move on to other projects, since it was not clear at the time that this new technology could be of use in the construction of high performance information processing devices.

Here's a picture of the apparatus:

The box on the right is a variable autotransformer that produces at its output a variable AC voltage of between 0 and 140 V RMS. It is connected to the box on the left which contains instrumentation to measure current through, and voltage across a vegetable sample. The sample itself is enclosed in the pickle jar mounted on top of the box on the left. If you squint, you might see a bit of a glow and some steam inside the jar. The steam is exhausted via a pump connected to the vacuum hose in the center of the picture. The holes in the front of the box are to provide a fresh air intake to the jar.


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