IR frequency ...

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  • chris_j_hunter
    Automated Home Legend
    • Dec 2007
    • 1713

    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 ?
    Our self-build - going further with HA...
  • Geps
    Automated Home Guru
    • Nov 2010
    • 136

    #2
    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?

    Comment

    • chris_j_hunter
      Automated Home Legend
      • Dec 2007
      • 1713

      #3
      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 ...
      Our self-build - going further with HA...

      Comment

      • Karam
        Automated Home Legend
        • Mar 2005
        • 863

        #4
        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; 8 October 2011, 09:01 PM. Reason: addendum

        Comment

        • chris_j_hunter
          Automated Home Legend
          • Dec 2007
          • 1713

          #5
          detail point, but maybe I should have said 455KHz ...

          as per this :



          "... 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; 8 October 2011, 11:44 PM.
          Our self-build - going further with HA...

          Comment

          • Geps
            Automated Home Guru
            • Nov 2010
            • 136

            #6
            Originally posted by chris_j_hunter View Post
            detail point, but maybe I should have said 455MHz ...
            Still not quite there

            Comment

            • Karam
              Automated Home Legend
              • Mar 2005
              • 863

              #7
              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?

              Comment

              • chris_j_hunter
                Automated Home Legend
                • Dec 2007
                • 1713

                #8
                OK, then 455KHz - is that within the capability of Idratek IR modules ? !
                Our self-build - going further with HA...

                Comment

                • chris_j_hunter
                  Automated Home Legend
                  • Dec 2007
                  • 1713

                  #9
                  PS: might be useful, in this context :



                  Last edited by chris_j_hunter; 9 October 2011, 12:15 AM.
                  Our self-build - going further with HA...

                  Comment

                  • Karam
                    Automated Home Legend
                    • Mar 2005
                    • 863

                    #10
                    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.

                    Comment

                    • Geps
                      Automated Home Guru
                      • Nov 2010
                      • 136

                      #11
                      Alternatively Chris, if you can wait a couple of months I'm going to be writing a small app that communicates with a virtual Idratek device and the serial port and transfers data between the two. I'm using it for some RGB controllers but it wouldn't be too difficult to change the strings within it to have the functionality you need.

                      Am very busy atm though with both my house and work unfortunately.

                      Comment

                      • chris_j_hunter
                        Automated Home Legend
                        • Dec 2007
                        • 1713

                        #12
                        Geps - that would be brilliant, ace ...

                        we need to send ASCII strings to & fro at 1200 baud (full duplex, GND TX RX, one start & one stop bit, eight data bits, no parity) - in case of interest, details are here :

                        ftp://ftp.studer.ch/Public/Products/..._B203_Info.pdf
                        Our self-build - going further with HA...

                        Comment

                        • Geps
                          Automated Home Guru
                          • Nov 2010
                          • 136

                          #13
                          Hmm, doesn't look too horrendous.

                          I'll contact you nearer the time. Prod me if you don't hear anything in case I've forgotten.

                          Cheers,

                          Comment

                          • katman
                            Moderator
                            • Jan 2004
                            • 247

                            #14
                            Originally posted by chris_j_hunter View Post
                            we need to send ASCII strings to & fro at 1200 baud (full duplex, GND TX RX, one start & one stop bit, eight data bits, no parity)
                            Why not convert to RS422 and sent it over CAT5. ?

                            You may find that the serial ports on your PC already have that option built in so you would only need the RS422 line drivers at the distant end.
                            KAT5.tv - affordable high quality AV Distribution
                            http://www.kat5.tv

                            Comment

                            • chris_j_hunter
                              Automated Home Legend
                              • Dec 2007
                              • 1713

                              #15
                              RS422 - yep, might well have to do that, to increase the range, co-location being tricky to achieve in our case ...

                              'have a feeling Geps' prospective code will be the start of something big, because RS232 comm's are quite widely used, in AV devices & a host of others, and if it can be readily adapted from his application to mine, then ... magic !

                              being able to send & receive would be key ... plus maybe extensibility in the virtual Idratek device ...
                              Our self-build - going further with HA...

                              Comment

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