Infrared distance control and command receive

Discussion in 'The Projects Forum' started by Edmunds, Feb 14, 2015.

  1. Edmunds

    Thread Starter Active Member

    Sep 27, 2010
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    Dear all,

    I'm working on a project where a robot would have to stop movement in front of an obstacle and be able to receive infrared commands at the same time. I was very excited to find out about VL6180 Time-Of-Flight technology powered distance sensor. I would like to try to use it for my project.

    I'm confused about the fact VL6180 is using IR light to measure the distance. Technically, I would have to put VL6180 and a TSOP infrared receiver side by side. Would that work? What do I look for to see if there would be interference between the too. Wavelength? The actual IR "pattern" of the command and the distance control sensor?


    Thank you for your time,

    Edmunds
     
  2. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    I'd pay close attention to what the datasheet has to say about tolerance to exposure at other light frequencies. But yes, I'd choose a different wavelength for the remote control, so as to be able to operate the two simultaneously. IR remotes, however, also have a frequency window that you'd have to check and make sure doesn't overlap with the sensor's.
    What I'd do is get the sensor and make it work to 100% of what I need, and then buy several IR diodes working at different frequencies and test them. The experiment wouldn't be too expensive nor would it take too much time or work to perform.

    Here's your sensor's datasheet, by the way.
     
  3. WBahn

    Moderator

    Mar 31, 2012
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    IR sensors are bathed in IR from all sorts of sources and so most of them that are used for any form of communication work with signals that are modulated in some way. A typical remote control modulates the signal at 36 kHz. You might look at the RC-5 protocol to get an idea:

    http://en.wikipedia.org/wiki/RC-5

    Time of Flight sensors might use a variety of techniques and it would be possible that the coding might interfere with the comms channel. But the ranging feature probably uses a laser diode while the comms probably just uses and LED. This might result in the wavelengths being far enough apart that the receiver for one won't be very sensitive to the light from the other. You'd really just need to experiment with it because even if they are reasonably separated and orthogonally coded, just the energy from one might saturate the receiver for the other.
     
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  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    The ST6180 is uses a type of laser. Here is an application note for the device: https://cdn.sparkfun.com/datasheets/Sensors/Proximity/VL6180_ApplicationNote.pdf

    SparkFun offers a pre-made module for about $25USD. SF make a point about the absolute range being 25 cm. That datasheet is a little fuzzy on the range and states 50 cm, but has it footnoted.

    Assume the practical range in normal light and reflection is not more than 25 cm, will that be sufficient for your use?

    John

    Edit: Here's a description of the type of laser used:
    http://optekinc.com/pdf/App Bulletin 227.pdf
     
  5. Edmunds

    Thread Starter Active Member

    Sep 27, 2010
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    John,

    Even 100mm max will suffice.


    Thank you all for your input,

    Edmunds
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    If you are in a well-lit area and the object you are ranging to is not very reflective, you might get considerably less than 100mm of range detection.
     
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