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M
mgagnon585
Visitor II
March 22, 2016
Question

Dual VL6180X interference & cover glass

  • March 22, 2016
  • 2 replies
  • 846 views
Posted on March 22, 2016 at 04:59

I was hoping someone could help me better understand how close two (or more) VL6180X sensors can be positioned if they are on the same plane and pointing in the same direction.

I would like to place two of these sensors side by side and use their ranging function. My main worry is that the beam from one of these sensors will get read by the second sensor, therefore inducing error. I've been digging through the documentation, but I haven't found any information with regards to interference that could be caused by placing two of these sensors in close proximity. Assuming both sensors are on the same plane, how close could I place them together? Can their beam cones overlap past a certain depth? (perhaps at a 255mm depth?)

My second question pertains to the cover glass thickness. I have found documentation on how to implement crosstalk compensation, which includes details on the air gap between the sensor and cover glass, but not the glass thickness. I also read that with crosstalk compensation, I shouldn't expect to read any values under 20mm. Could this mean that I could theoretically use cover glass up to 20mm thick?

Lastly, I also haven't been able to find any information on the lifespan of the laser. Do we have an idea as to how many hours this sensor should be able to function?

Thanks,

Mat

    This topic has been closed for replies.

    2 replies

    J
    Julien NGUYEN
    ST Employee
    March 24, 2016
    Posted on March 24, 2016 at 19:10

    Hi Mathieu,

    Since I already answered to your questions by email. Could you please share the answers with the community please.

    Thanks,

    Julien

    J
    John E KVAM
    ST Employee
    April 30, 2019

    The sensors do not appear to interfere with each other. Just prior to ranging each sensor samples the ambient light and takes a measurement. Each sensor considers the other sensors as ambient light. So go ahead and place them close. It works.

    The best cover glass is thin, transparent, completely smooth and very close to the sensor. Everything else is a compromise. Use the EVK to mock up your design and test it. Smaller crosstalk number is better. But as a practical note, a couple of mm thick is OK, but any thinker than that is asking for trouble.

    For more information view the video at:

    VL6180X Dirty Cover Glass: https://youtu.be/7INefyjvvdI

    It will explain the issue and give you some ideas on how to solve it

    Lastly, I also haven't been able to find any information on the lifespan of the laser. Do we have an idea as to how many hours this sensor should be able to function?

    The laser can be expected to last as long as an LED. Practically forever.

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