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Thread: Projector/LED light interference

  1. #1
    Join Date
    Apr 2008
    Posts
    8

    Projector/LED light interference

    Customer called today saying his ceiling mounted tv projector makes a buzzing noise when he turns on the recessed LED lights in the room. He has 2 zones of dimmable LED lights, contolled by 2 seperate LED compatible dimmers. He says the projector makes no noise with lights off, but when he turns on either zone it starts and as he increases the brightness of the lights the buzzing increases in the projector. Projector continues to operate properly while buzzing. I am assuming the ceiling receptacle for projector is on the same circuit as the lighting, which is causing some sort of interference. Any ideas what causes this or how to fix it?

  2. #2
    Join Date
    Apr 2008
    Location
    Ann Arbor, Michigan
    Posts
    6,335
    171103-1716 EDT

    Phase shift dimmers and/or LEDs can be substantial audio and RF noise generators. The same circuit is not even a criteria. However, he closer the noise source (dimmer, or LED, or dimmer plus LED) is to the affected devices the greater is the likelyhood of objectionable interference.

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  3. #3
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    18,366
    Are you using an analog audio input to the projector? Or is the projector feeding an audio output to an external amplifier and speaker system?

    Buzzing, rasping, etc. is much more likely to be interference on an unbalanced audio feed or poorly twisted and shielded audio cable than digital communications interference.

    Try to isolate (by disconnecting) the point along the audio chain where the interference is getting in.
    It is a longer shot, but still possible, that the problem is conducted noise along the AC branch wiring to the projector.

  4. #4
    Join Date
    Apr 2008
    Posts
    8
    I haven't gone to the job yet. Hopefully will get there today, but from what the customer told me there is an external speaker system that does not seem to be affected. I will check the audio wiring. If it turns out to be interference from the LED lighting, I am thinking of installing some ferrite noise suppressors around the projector cord to see if that eliminates the issue. Any better options?

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