Detecting proximity

Discussion in 'Electronics Resources' started by RGT_UK, Nov 11, 2015.

  1. RGT_UK

    Thread Starter New Member

    Nov 10, 2015
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    As part of a project I'm working on. We need to detect objects coming within range, but also be able to establish whether the object is getting closer, static or moving away. Now i've found http://www.topqualitytools.co.uk/sensor-proximity-apds-9700-020/?gclid=CNmU2ZufickCFQ2NGwodovwPgw this from Avago Technology, which I think would work. It covers a maximum of 200mm range, which is ample for what we are doing (our minimum was 160mm range), and Im assuming the maths surrounding getting closer/moving away would be easily handled with programming.

    But my question is, do detectors like these work in a binary state (i.e. yes, something detected or no, nothing detected) or do they provide some data through the digital connection as to how near/far the object is? Does anyone have any experience with these types or sensors, or can anyone suggest another/better alternative?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    According to the sheet there is digital and analogue output.
    I have no experience with that particular IC however.
    Max.
     
  3. RGT_UK

    Thread Starter New Member

    Nov 10, 2015
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    Thanks Max. Having never used a proximity sensor, I'm just unsure as to what output is passed digitally. The data sheet doesn't actually say what the output consists of - but maybe that is me being thick!

    Do you have experience of other proximity sensors at all? Do they actually work out how far away an object is thats triggered the sensor, or just say whether its in range or not?

    Richard
     
  4. OBW0549

    Well-Known Member

    Mar 2, 2015
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    The data sheet gives the information you're looking for, and has a sample application circuit. The chip is intended to be used with their HDSL-9100 proximity sensor and provides both analog and digital outputs.
     
  5. RGT_UK

    Thread Starter New Member

    Nov 10, 2015
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    Hi OBW0549
    Thanks for taking the time to reply. Yes, I saw the sample application circuit in the data sheet, but i cannot see anywhere in that PDF where it answer the question about whether the output is on/off, or whether its actually giving the distance (or some data that allows changes in proximity to be calculated)? Im assuming that the analog output is simply on/off depending on whether the sensor has detected an object, but I'm hoping that the digital output may be more detailed?

    Could you point me in the right direction? I openly admit, I'm reasonably new to electronic hardware, so it may just be a lack of knowledge that is not letting me see something thats obvious to others.

    Thanks
    Richard
     
  6. OBW0549

    Well-Known Member

    Mar 2, 2015
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    They show the digital output going into a single GPIO (general-purpose I/O) pin, which indicates that the digital output is a simple yes/no, ON/OFF signal rather than some kind of serial data interface like SPI or I2C. They show the analog output at the PFILT pin going to a host microcontroller's ADC (analog-to-digital converter) input, suggesting that the PFILT output voltage probably varies linearly (or nearly linearly) with the reflected light intensity.

    This chip isn't going to give you an indication of the actual distance to a nearby object (unlike, for example, an ultrasonic rangefinder module), only an indication that something is or is not nearby.
     
  7. RGT_UK

    Thread Starter New Member

    Nov 10, 2015
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    Thanks for that - and for taking the time to explain. I now understand that principal. Are there any chips that would provide an indication of the distance that your aware of?
     
  8. OBW0549

    Well-Known Member

    Mar 2, 2015
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    You could try here, maybe something there will be suitable.
     
  9. RGT_UK

    Thread Starter New Member

    Nov 10, 2015
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    Many thanks for that - I think one of those may well be perfect for what we're doing.

    Cheers
     
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