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Thread: Strange behavior of LMJ-5T-DV-B

  1. #1
    Junior Member
    Join Date
    Aug 2021

    Strange behavior of LMJ-5T-DV-B

    I've got about 40 of these wireless dimming modules deployed, driving 0-10V dimming of a mix of high-end recessed light engines, and LED strip drivers. All works fine on INITIAL setup and 1-10V dimming control of the lights on RA2 Select. The problem occurs when module TRIM levels are changed in the RA2 App.

    At this point I suspect a bug in either:
    1. a bug in the Lutron app, where a wrong high-end trim value is stored into LMJ or gets screwed up
    2. Some other parameter is force-saved by the app but isn't present in the defaults (MAYBE for instance a current Sink/Source option setting?)

    The problem symptom: If I change *any* TRIM value (high-end or low-end trim), then the LMJ module is forced to a mode where that module is capped at 65-70% of peak dimming control output. Meaning the light fixtures can only hit 65% of their peak brightness. Even if I make high end trim = 100, or adjust only the low end trim, or don't change any trim value just hit SAVE n the device editing menu, this symptom is repeatable.

    I've confirmed the LMJ-5T-DV-B initially outputs correct 10V at the high end upon setup. But making any TRIM adjustment limits the max dimming control output to 6.34V (instead of 10V). This happens on every LMJ I tested in and out of the installation. Resetting the LMJ reverts the operation back to the correct 10V output max, and the fixtures operate properly (just with the wrong default trim, which I do need to adjust). There are no shorts in the installed control wires (tested the impedance), and I also confirmed with a module directly wired only 12" away to its driver.

    Debugging, initially I thought this behavior might be due to LMJ-5T-DV-B getting confused at auto-detect for current SINK or SOURCE on the 0-10V control [Some but not all of the installed light engines also have "auto-detect" sink/source, and the LMJ/RMJ 0-10V app note mentions these could cause complications). But I tested this with & without a load, and also with a "dumb" (source-only) LED driver, all ended up with same problem behavior.


  2. #2
    Super Moderator
    Join Date
    Sep 2020
    Hello! Thank you for your inquiry. To best troubleshoot this issue, we advise emailing a support file from your system to with a description of this issue. With that file, Technical Support and engineering can more thoroughly investigate the programming and uncover any bugs or issues that might be causing this.

  3. #3
    Junior Member
    Join Date
    Aug 2021
    Great suggestion! I overlooked the support logs submission in the App.

  4. #4
    Junior Member
    Join Date
    Aug 2021
    Lutron verified and informed there was a bug in the trim-setting software.
    An update to Hub firmware pushed out around October 15, 2021 that resolved my symptoms. Problem solved!

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