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Q & A: Plasma balls inside computers

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Most recent answer: 10/22/2007
Q:
Hello. I’m wondering, if something that utilizes the ionization of a gas, such as a plasma ball were made inside of something that contains a circuit board, would it create any electromagnetic disturbance to the device? For example, if you had a clear computer case and you created a smaller air tight case to be placed in any extra space within the computer, evacuated it of air and inserted a fill gas such as argon and placed an electrode in the internal volume of the second, smaller box (making a square plasma ball within a computer case more or less) Would it disturb the functionality of the computer itself, or would it render it completely useless? Hopefully I have elaborated enough on my question, if not please ask any questions you need in order to be able to answer my own, I’d be happy to elaborate further if needed! Thank you!
- Evan (age 18)
Maryland
A:
Hi Evan,

It sounds as if there is a risk of making the computer stop working, but it's always worth a try if you want to make a cool-looking computer.

Lots of computers sold for the gaming market these days have clear sides and tubular neon lights inside. These already do what you say -- a neon tube really is just a plasma light. You might get more electromagnetic interference from whatever high-voltage power source is needed to drive current through the plasma than you actually get from the plasma itself. I'll bet such setups ground the case of the power supply for the neon lights very well to prevent interference with the computer.

Anecdotally, I can mention that I used to have an old chess computer (1980 vintage or so), that ran on TTL (5-volt signals) internally; it had a Z80A processor chip inside. Whenever I used it underneath a desktop fluorescent light, it would sporadically fail. It could be that the power supply in the thing was marginal and it barely ran to begin with, and adding only a little bit of ambient electrical noise pushed it over the edge into failure, who knows. These days, voltages are usually 2.5 or 3.3 volts (and even less inside the chips, but they have metal grounding planes to prevent noise pickup), so it could be that it takes less to corrupt the signals. Your sensitivity to EM interference inside the computer also depends on how the cables are laid out. Circuits that make big, open loops act as good EM interference antennas. It'll probably take some experimentaiton to see what works.

Tom

I suspect that a plasma ball will give even worse interference than a neon light, because the plasma pattern flickers all over the place. Failure will be sensitive to the worst paatterns, or the worst flickers, not to the average behavior.
Mike W.

(published on 10/22/2007)

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