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Thread: Short when chaining multiple projectors

  1. #1
    Join Date
    May 2015
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    belgium
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    Default Short when chaining multiple projectors

    i have a projector that works perfectly when on auto mode or ILDA directly from the DAC
    but when i connect a second projector trough the ILDA out on this projector the problems starts.

    sometimes it makes a short or it has a low noticeable voltage on the outside case.
    what can be causing this problem ? i suspect it is a ground problem but in the power connector all the grounds are wired correctly
    with the multimeter it gives a beep from Ground pin to case and from ground pin to outside of the ilda connector but not from ground pin to ILDA pin 25 should this also be connected to the ground ?

  2. #2
    Join Date
    Feb 2008
    Location
    East Sussex, England
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    5,244

    Default

    Check how the interlock loop on pins 4/17 is wired on the second projector. A lot of safety boards will put 5 or 12v on this and it's wired incorrectly in the first projector, you may be connecting this to something it shouldn't be
    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

  3. #3
    Join Date
    May 2015
    Location
    belgium
    Posts
    21

    Default

    i just measured on the first projector (the one with short problems) there is a positive voltage of 5 volts over pin 4 and 17.
    on the second projector there is a voltage of 15 volts.

    if i connect pin 4 and 17 internal in the first projector the auto and sound active mode will be unavailable as the projector will think it is connected to ILDA?
    do you have any idea how to fix this?

  4. #4
    Join Date
    Feb 2008
    Location
    East Sussex, England
    Posts
    5,244

    Default

    Ok, a projector with interlock voltage should only present it on the input ILDA connector. Most DACs should just have 4/17 tied so that the projector can tell whether the loop is complete or not.

    The passthru 4/17 pins should just be tied (as if it were a DAC) or connected to a relay so that it can be lifted (this way if you use estop over ILDA, hitting the estop on projector 1 causes it to also open the relay going to projector 2, which in turn turns off projector 2).

    It sounds as if your projector manufacturer has simply paralleled all of the ILDA pin connectors between input and output connectors, which is why you're also seeing 5V on the output.

    Projector 2 is clearly passing voltage down its input connector (as it should) and its shorting with the signal from projector 1. If that is tied to ILDA ground and that to the projector chassis, you'll see what you're experiencing.

    Simplest solution is to tie 4/17 on the passthru connector on projector 1, so its not paralleled with the input.
    Frikkin Lasers
    http://www.frikkinlasers.co.uk

    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

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