S.Ferguson@ucl-cs.UUCP (09/12/90)
From: Stewart Ferguson <S.Ferguson@uk.ac.ucl.cs> Yes, I too have seen the purple streak phenomenon you speak of, while listening to a radio with an LED tuning indicator in the dark. I believe that there was a good article in Scientific American a few years back (sorry can't be more precise) in the Amateur Scientist Section. Have fun, Stewart.
tgg@otter.hpl.hp.com (Tom Gardner) (09/12/90)
|Its because the display is Multiplexed. The digits are displayed one at a |time to save on chip count (presumably). All of the digits use the same |7 segment decoder chip as opposed to using a seperate chip for every digit. No. To save on pin count.
scjones@thor.UUCP (Larry Jones) (09/12/90)
In article <1990Sep6.002506.3313@wsrcc>, wolfgang@wsrcc (Wolfgang S. Rupprecht) writes: > I don't know anything about that, but a really neat effect occurs when > eating something extremely crunchy such as taco chips in front of a > CRT. Seems that the brain can compensate for a shaky optical > platform, but is really a loss when the viewed object changes rapidly > as a function of time. Try it. The picture really distorts. Another interesting effect can be seen by humming the lowest tone you can (the closer to the vertical refresh rate the better) while looking at a CRT. The whole screen will "swim" at the beat frequency. ---- Larry Jones UUCP: uunet!sdrc!thor!scjones SDRC scjones@thor.UUCP 2000 Eastman Dr. BIX: ltl Milford, OH 45150-2789 AT&T: (513) 576-2070 We seem to be out of gun powder. -- Calvin
antonyc@coil.caltech.edu (Bill T. Cat) (09/13/90)
tgg@otter.hpl.hp.com (Tom Gardner) writes: >|Its because the display is Multiplexed. The digits are displayed one at a >|time to save on chip count (presumably). All of the digits use the same >|7 segment decoder chip as opposed to using a seperate chip for every digit. >No. To save on pin count. i thought it was to save power
gordon@prls.UUCP (Gordon Vickers) (09/14/90)
In some article by someone whose name is now lost, they wrote: >|Its because the display is Multiplexed. The digits are displayed one at a >|time to save on chip count (presumably). All of the digits use the same >|7 segment decoder chip as opposed to using a seperate chip for every digit. > In article <1770017@otter.hpl.hp.com> tgg@otter.hpl.hp.com (Tom Gardner) replied: >No. To save on pin count. In some designs, it isn't just to reduce pin count, but power consumption also.
tgg@otter.hpl.hp.com (Tom Gardner) (09/14/90)
|>|Its because the display is Multiplexed. The digits are displayed one at a |>|time to save on chip count (presumably). All of the digits use the same |>|7 segment decoder chip as opposed to using a seperate chip for every digit. |> |>No. To save on pin count. | | In some designs, it isn't just to reduce pin count, but power consumption | also. There are some cases where this would be true (high clock frequency designs, technolofies with high static power dissipation (ECL)). But with display multiplexers and most SSI/MSI ics the pin count has a strong influence on the co$t.
mmm@cup.portal.com (Mark Robert Thorson) (09/20/90)
Here's a recent letter I received reinforcing my contention this is an
electronic -- not perceptual -- phenomenon. You armchair skeptics must
be imagining I'm opening the can by biting it with my teeth, or something.
Recent experiments seem to indicate the repeatability of the phenomenon is
not as high as I said it was in my first posting. I've blown a whole
six pack without getting a hit.
------------------------------------------------------
[Reproduced with permission.]
From: collins_t@apollo.com
Date: Fri, 14 Sep 90 15:02:06 EDT
Subject: Beer can physics
To: mmm@cup.portal.com
Hi Mark,
Everybody who has ever used a radio-control airplane knows that
you can get radio interference ANY TIME you have metal rubbing
against metal. In the RC field this is common knowledge: whenever
you rig a new plane you have to check to see that the servoes and linkages
don't cause "glitches." They show up when you move the control stick on
the transmitter a bit and the control surfaces keep twitching even after
you stopped moving the stick. Usually the cure is to eliminate the rubbing
or relocate the antenna. At extremely close range it is easy to
interfere with the signal.
Why? There must be small currents being produced in the surface of the
metal when it is stressed. The circuitry seems to be plenty sensitive
to pick it up. I bet you could get strange behavior from an RC plane
if you opened a can of beer next to it (when it is on the ground!)
Best wishes,
Tim