Detecting proximity

Thread Starter

RGT_UK

Joined Nov 10, 2015
11
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?
 

Thread Starter

RGT_UK

Joined Nov 10, 2015
11
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
 

OBW0549

Joined Mar 2, 2015
3,436
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.
 

Thread Starter

RGT_UK

Joined Nov 10, 2015
11
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
 

OBW0549

Joined Mar 2, 2015
3,436
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.
 

Thread Starter

RGT_UK

Joined Nov 10, 2015
11
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?
 
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