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Mad Scientess Jane Expat

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Whiz Kids: The Next Generation [20110605|18:21]
Mad Scientess Jane Expat
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I brought my tripod and camera down to the first-year Physics lab last week to take some shots of my students' projects.

The theremin is a fairly simple instrument conceptually, although by no means easy to construct. It consists of two oscillators (or wave-makers) that produce waves at frequencies that are well beyond the reach of human hearing. The human hearing range is between about 20 Hertz (20 Hz) and 20,000 Hertz (20 kHz), although the top end of that tends to drop out rather quickly with age. Anyway, the two oscillators produce waves in the megaHertz (MHz = 1,000,000 Hz) region. The mixer takes the two waves and puts them together. The resulting sound is the "beat frequency", and is in the range of human hearing.

One of the oscillators can be varied by moving a hand over an antenna. This changes the frequency of the outgoing wave, and therefore changes the beat frequency, or the sound that you hear coming out of the theremin.

These are the theremin chaps. The yellow trace on the oscilloscope is the output from their theremin.



One of the oscillators and the mixer.



Theremin chaps diagnosing what turned out to be a wonky transformer on their circuit. (Well, actually, the one in the pink shirt is talking to a girl who was trying to sidle into the picture.)



The Very Low Frequency (VLF) receiver picks up low-frequency radio signals that occur naturally. These signals are related to electrical activity, such as lightning strikes, in the upper atmosphere/ionosphere. These can be heard as crackles and crunches. It consists of an antenna, a filter that passes only a specific set of frequencies and an amplifier. My students tried out their circuit on a prototyping board, and they've just completed the portable version of it. They'll be trying to take some measurements outside this week.

A 2 kHz signal being passed through the receiver circuit.



Closeup of the circuit.



VLF receiver chaps admiring their handiwork. Students building a radiation detector out of a coffee tin futilely attempting to hide from the camera.

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Comments:
[User Picture]From: cosmiccircus
2011-06-05 18:16 (UTC)
Interesting! Being a visual person, I appreciate the photos!
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[User Picture]From: nanila
2011-06-08 08:38 (UTC)
Hm, maybe I should put up the slides from my talks about how the theremin works. Do you think people would be interested?
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[User Picture]From: cosmiccircus
2011-06-08 13:41 (UTC)
Sure, you never know!
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[User Picture]From: senusert
2011-06-05 19:35 (UTC)
Off topic, but your boys are cute!
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[User Picture]From: nanila
2011-06-08 08:40 (UTC)
^.^ Photogenic physicists!
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From: anokapolis
2011-06-05 21:19 (UTC)
Hands on work is always fun, and they seem to be enjoying it:)
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[User Picture]From: nanila
2011-06-08 08:41 (UTC)
They are. They got frustrated easily at first, but it's been a pleasure to see them become more patient and determined over the course of the last few weeks. They've grown fast. :)
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[User Picture]From: bowtomecha
2011-06-06 07:07 (UTC)
I was about to watch porn but this works quite nicely.
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[User Picture]From: nanila
2011-06-08 08:42 (UTC)
I wonder if there's a word for someone who fancies prototyping boards. Electrosexual?
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[User Picture]From: danaid_luv
2011-06-15 04:25 (UTC)
Interesting! I really enjoy the second shot down, btw. The colours & crazy lines zigging in & out of the shot are...pretty.
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[User Picture]From: nanila
2011-06-15 08:54 (UTC)
I'm hoping they like it enough to use it in their reports. :D
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