Subject:
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(no subject)
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sat, 12 Feb 2000 00:03:13 GMT
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Original-From:
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FRED MARTIN <fm2852@chi.ANTISPAMdevry.edu>
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Viewed:
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777 times
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Maybe somebody could help.
I am try to use the IR output. the problem is that the HB is modulating the
signal at 41kHz and I need to get it down to 38kHz.
I have checked the resistor and capacitor used in generating the frequency.
R = 3.81 K
C = 0.0068uF
f = 1/(3.81k)(.0068uF) = 38.5981kHz
at least in theory.
When I run the command poke(0x1000, 0x40); as Fred suggests in the test
procedures I get about 43kHz at the output of U9-Pin 2(hex inverter)
Which is high compared to the suggested output. (39k - 40k)Hz
I am really trying to avoid replacing the res. and cap.
I was wondering if anybody else had a problem with their IR output.
If so could you let me know your experience. I am baffled as to why there
is such a difference from theory to actual.
I have been through the HB archives and cannot find a thing. So any help at
all is welcomed and appreciated.
Best regards,
Fred Martin
(NOT the Fred you might be thinking about!)
We are prone to judge success by the index of our salaries or
the size of our automobile rather than by the quality of our
service and relationship to mankind.
- Martin Luther King Jr.
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Message has 2 Replies:
 | | Re: 41Khz not 38KHz
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| The 3.81K resistor is probably more accurate than its rated 1%, but the capacitor may be much less precise, unless you got a tight tolerance metal film one, (as I think the part list specifies). Precision also relies on the thresholds of the Schmitt (...) (25 years ago, 12-Feb-00, to lugnet.robotics.handyboard)
| | | Re: (no subject)
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| (...) The obvious question is how you are measuring your capacitor and resistor values?. Resistors (presumably metal film), are typically +/-1%, but capacitors are unlikely to be 'better' than +/-5%, and may be significantly worse than this (many (...) (25 years ago, 12-Feb-00, to lugnet.robotics.handyboard)
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