CMOS sensor noise issue

Discussion in 'General Electronics Chat' started by tallman, Sep 9, 2013.

  1. tallman

    Thread Starter New Member

    Sep 9, 2013
    5
    0
    Hello,

    My first electronics PCB project has an Omnivision CMOS (7740) and some Infrared 850 LED's nearby (1 cm from cmos chip).
    I'm getting noise in image when I turn on lights which you can clearly see in the image posted (with PWM or solid on), and I can't figure out if it's the light bleeding through the PCB and getting to the sensor, or if it's electrical noise somehow. I don't have LED traces near the sensor traces, but they do share the negative.
    I've tried to block the light with plastic parts surounding the LED's, but the IR light seems to end up everywhere.
    If it's physical what do I need to do to block it in PCB design, and if it's electronic, same question.
    Appreciate anyones review of this.
    Brent
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    What "plastic parts" are you using to block the IR?

    Try blocking the CMOS sensor optical input with black electrical tape and see if that affects the noise.

    What is powering the LEDs? Is it steady DC current?
     
  3. tallman

    Thread Starter New Member

    Sep 9, 2013
    5
    0
    I'm using abs plastic (from 3d printer) to surround LED's. I put black electrical tape and the tape I had doesn't block the IR spectrum range. I tried tape with aluminum foil inside of it, and it really has very little affect. The IR light seems to reflect and carry all over the place.

    I'm using constant DC power, same power used to power the cmos.

    Thanks for your review.
    Brent
     
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