Subject:
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Re: IR Sensitivity - Was: 1.5/2.0 infrared problem
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Sun, 26 Oct 2003 20:13:27 GMT
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Viewed:
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5403 times
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In lugnet.robotics.rcx, Philippe Hurbain wrote:
> Thanks for your answer, this will keep me from dismantling once again my RCXs !
Mine have been apart more often than I'd like, too! :-)
> So it seems that LEGO modified RCX2.0 to get better compatibility with
> Spybots/Manas. Now a question remains, why did they increased carrier frequency
> on new products? Better remote sensitivity? (I find that the remote control of
> these devices do work remarquably well). Or increased communication speed?
My guess would be mostly for increased communication speed. With the higher
baud rate, the duration of the 2-byte Spybot/Manas packets is halved. This
allows for fewer collisions from remotes on different channels and hence a
higher update rate for the motor commands being sent (i.e. the motors will
appear more responsive).
> IMHO, the choice of 76KHz carrier enables some sensitivity to older 38KHz
> frequency, there is probably enough second harmonic to get through receiver
> bandpass filter. Interestingly enough, 76 KHz is not an IR standard frequency,
> and Vishay who manufactures TSOP1138 makes receiver only in 30 to 56 KHz range.
> See documentation / tutorial here: http://www.vishay.com/docs/80069/80069.pdf
It's interesting, the responsivity chart in the above document only covers 0.7
to 1.3 the designed carrier frequency... I wonder what the relative response is
for half the carrier frequency - at least this would give us a ballpark figure
at what reduction in sensitivity we're experiencing at 38 KHz.
Might the TSOP-1176 parts have started appearing in RCXs prior to RCX 2.0?
Could there be any RCX "1.5" units with this new receiver?
Mark
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Message is in Reply To:
 | | Re: IR Sensitivity - Was: 1.5/2.0 infrared problem
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| (...) Hello Mark, Thanks for your answer, this will keep me from dismantling once again my RCXs ! So it seems that LEGO modified RCX2.0 to get better compatibility with Spybots/Manas. Now a question remains, why did they increased carrier frequency (...) (21 years ago, 23-Oct-03, to lugnet.robotics.rcx)
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