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Thread: IR frequency ...

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    Automated Home Legend chris_j_hunter's Avatar
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    Default IR frequency ...

    anyone know at what frequency the IR modules work - looking at the manuals just now, it isn't said - could they handle 433MHz, for example ?

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    Automated Home Guru Geps's Avatar
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    Are you trying to make something RF controlled into something IR controlled?

    You need to establish the data rate as well as the frequency of the carrier and the encoding method as well. IR remotes use manchester encoding I think?

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    Automated Home Legend chris_j_hunter's Avatar
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    we're looking to communicate between two distinct AV systems & the BM system (Idratek) ...

    to set scenes & limit interruptions - when watching TV & movies, and listening to music & radio ...

    the obvious & most convenient way is via RS232, which both & many other AV systems use ...

    but Idratek can't handle that ...

    so the options are via volt-free relay contacts working into digital inputs ...

    or via IR (which both our AV systems also have) ...

    IR systems have various protocols & work at various frequencies ...

    one of our two works with modern protocols but at 433MHz, which is rather higher than the norm (and hence the question) ...

    and the other works with rather old-fashioned protocols at more usual frequencies ...

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    Automated Home Legend Karam's Avatar
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    433MHz is one of the license free radio transmission frequencies. Most remote control type IR is carried over 36-40KHz (though there are some odd bods at 56KHz and elsewhere). So if something has a label with 433MHz on it I'm pretty sure it'll be radio not IR. The problem generally is not so much intercepting the signal whether it be RS232, IR or RF - for which the electronics is relatively straightforward - but more a case of understanding how to decode the protocol carried on this.

    Possibly the most reliable to intercept would be RS232 since it is hard wired. If its a known protocol then it may be technically possible via existing IDRATEK hardware such as the X10 gateway or older PCA modules with firmware bespoking. But it might be easier all round to connect to a spare RS232 port on the PC and write a small bit of software to receive and then interact with Cortex via the API.
    Last edited by Karam; 8th October 2011 at 09:01 PM. Reason: addendum

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    Automated Home Legend chris_j_hunter's Avatar
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    detail point, but maybe I should have said 455KHz ...

    as per this :

    http://www.remotecentral.com/features/premotes.htm

    "... the overwhelming majority of IR remotes operate in the 30-56KHz range, normally 38-40KHz, several brands such as a Bang & Olufsen, particular Kenwood equipment, and some lighting control systems, use a 455KHz frequency ... "

    BTW - the daughter-board on our Mini-ITX provides 4x RS232 ports ...
    Last edited by chris_j_hunter; 8th October 2011 at 11:44 PM.

  6. #6
    Automated Home Guru Geps's Avatar
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    Quote Originally Posted by chris_j_hunter View Post
    detail point, but maybe I should have said 455MHz ...
    Still not quite there

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    Automated Home Legend Karam's Avatar
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    Yes KHz not MHZ . 455KHz rings a bell as being the IF used in MW radio receivers. Wonder if there's a connection - maybe since its getting into RF domain unlicensed?

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    Automated Home Legend chris_j_hunter's Avatar
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    OK, then 455KHz - is that within the capability of Idratek IR modules ? !

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    Automated Home Legend chris_j_hunter's Avatar
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    Last edited by chris_j_hunter; 9th October 2011 at 12:15 AM.

  10. #10
    Automated Home Legend Karam's Avatar
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    Quote Originally Posted by chris_j_hunter View Post
    OK, then 455KHz - is that within the capability of Idratek IR modules ? !
    No, the native IR receiver component is centred around 38kHz. On an ITR module it would be possible to connect an external sensor centred at 455kHz such as the TSOP7000, but I don't know whether the modulating data would be decodable - the pulses may be too short and I don't know anything about the protocol. If you have details of the protocol (and signal format) I could investigate whether this is a practical possibility.

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