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Thread: Circuits For Signals

  1. #1
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    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Default Circuits For Signals

    SINGLE AND DIFFERNTIAL CABLE DRIVERS AND RECEIVERS

    THIS IS OUT DATED FROM A ILDA STANDARD NOW OBSOLETE
    THAT USED A 40 PIN CPC CONNECTOR INSTEAD OF A DB25

    HOWEVER THE CIRCUITS WORK AND WERE THE RECOMENDED
    PRACTICE AT THE TIME. THEY ARE NOT STATE OF THE ART, BUT ARE STILL DECENT.
    USE OF OTHER THEN A BiFET or SIMILAR FET INPUT LOW OFFSET OPAMP IS NOT RECOMENDED. THEY MEAN IT WHEN THEY SAY USE A TL082 or TL084 FAMILIY PART.


    THE VOLTAGES MATCH THE CURRENT STANDARD, I'm not gonna post the whole tech specs, for cable capacitance, short circuit current, common mode voltage etc, if you want that, by all means join ILDA and get a current copy of their standards. This is posted as a start of a discussion and to answer questions of many people who have problems interfacing hardware. We need some images of sample circuits, here they are:

    Attached is a file called diffsingle.pdf

    Steve Roberts
    Attached Thumbnails Attached Thumbnails DIFFSINGLE.PDF  


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    Thanks for the post, this seves to further solidify the proper differential/single-ended voltage levels for a compatible DAC design. Also, for long runs it appears that they are suggesting a 150 Ohm source impedance, but a 10-20k ohm termination impedance. Is 150 Ohm cabling typically used for long run control signals for the ilda connector?

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    Hi Drlava

    Im currently using 400ft cable run from the desk to the projector

    the cable im using is Cat5e stranded ( for flexibility, do not use solid core ) twisted pair network cable, each pair has a foil shield with drain wire and an overall copper braided shield

    The cables typical impedance is 100R and the differential amps at the projector have an impedence of 10K

    this provides a great "noise free" solution over a long run at a lot lower cost than audio multicore, i have a secondary cable taped to this for the safety interlocks etc... the cable usually is routed with mains cables for the lighting rig with no visible noise pickup

    best of all should the cable ever be damaged ( 2 year old now and still good as new ) it wont cost an arm and a leg to replace

    Steve thanks for the circuits ..... they certainly make it easier to explain to people

    all the best .... Karl

  4. #4
    mixedgas's Avatar
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    ILDA spec for those circuits spec 150 ohms and minimum drive of .1 uF capacitance, termination is 20K I dont know what the DB25 spec is, I imagine similar, but I'm not rejoing ilda to find out.

    NOT bad math you guys.

    Steve Roberts

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