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Posted: Feb 10th, 2008 01:27 PM |
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Jeff
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EVP_Babs wrote: Don't think I dropped off the face of the earth here. I am reading and trying to assimilate the knowledge.Hey Babs. I agree with your thoughts on a photo-sensitive arrangement. Most phototransistors work on tight, filtered, infrared spectrum. So any light energy outside of that spectrum would be ignored just because of the nature of the photo sensitive base of the transistor. On those types of sensors, there is actually an infrared transmitter, and infrared receiver. The transmitter is producing the infrared energy via a a lense that focuses the energy away from the receivers lense. When something solid enough to reflect that energy comes withing that focused area, the beam is reflected back into the receiver. This changes the receiver's gain into the amplifier it is feeding. The closer the object, the more, or less gain is produced by the receiver. In the case of the Theremin, the gain is decreased to lower the audio volume of the instrument. The RF Theremin, which was the instrument I originally posted on, can sense proximity within its RF field. This is why the thought occured to me in the first place. Hope this helps! Jeff
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