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- Bob Parker
March 17, 2005, 2:40 pm

G'day,
I've been asked to help fix a Sharp CRMC-A310JBEO remote control
for an air conditioner. All that seems to be wrong is that it's been
dropped and the ceramic resonator's broken into tiny bits, making it
impossible to see what frequency was marked on it.
If someone can tell me what the resonator frequency is, I'll be
massively grateful! :)
Regards,
Bob

Re: Sharp remote control ceramic resonator frequency?

Not one frequency, necessarily; but usually only a very few resonators. The
last time I had one which was (physically) broken, I pulled another from the
first nondescript remote I found in the junk box, and it worked fine.
Remember, many frequencies can be synthesized from one crystal. Try one out
of a junk remote and see if it works...can't hurt.
jak


Re: Sharp remote control ceramic resonator frequency?
Yesterday I started trying a few different resonators/crystals of
assorted frequencies in the remote. With a 455kHz resonator, the
output frequency to the IR LED was something over 4kHz, and all
functions were incredibly slow.
Figuring that the IR frequency should be close to 40kHz, I put in a
4MHz crystal, a frequency I'm sure I've often seen in remotes, and the
IR frequency was about what I thought it should be= just under 40kHz.
We're going to give this a try and see if it works.
Thanks again to everyone for their suggestions!
Bob


Re: Sharp remote control ceramic resonator frequency?

Thanks Terry,
I've seen the same thing happen. Now I know it wasn't my
imagination that I've seen 4MHz resonators in many remotes. :)
The remote still hasn't been given back to its owner, but I think
it will probably work OK now.
Cheers,
Bob

Re: Sharp remote control ceramic resonator frequency?
Bob Parker wrote:

Was that because you had plenty on hand, or was it recommended for
the microprocessor you selected? :)
**** As 3.579545 MHz is the NTSC colour burst frequency,there are millions
of these crystals around the world.Because of availibility and low cost,they
get used in all sorts of circuits.
Brian Goldsmith.

Re: Sharp remote control ceramic resonator frequency?
"Brian Goldsmith" ( snipped-for-privacy@nospam.echo.com.au) writes:

But if it was recommended, chances are good that it was because they
are common. If there's no need for a specific frequency (because the
crystal isn't being used to supply something else that does need it)
one might as well go with a cheap crystal in the general range desired.
Michael

Re: Sharp remote control ceramic resonator frequency?

Gee, Brian, I've known this since the mid '60s. I have a few oddball
color burst crystals, including an early Zenith one in a glass envelope
like a miniature TV tube. I am disabled, but I have worked as a
broadcast engineer at three TV stations. I guess you didn't see the
winking smiley?
--
?
Michael A. Terrell
Central Florida
?
Michael A. Terrell
Central Florida

Re: Sharp remote control ceramic resonator frequency?
Hi Brian,
Everyone else answered your question for me! As they said, NTSC
colorburst crystals are very common and very cheap. The firmware in
the micro doesn't need a higher clock frequency than that, so that's
why I chose it.
The micro internally divides the 3.58MHz by 8950 (179 x 50) to
produce a 400Hz reference for all its timing. It worked out pretty
well. :)
Regards,
Bob

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