I'm working on a project where we are trying to figure out how to use some Arduino sensor to detect an object moving directly toward a person. Right now we've been looking at the HC-SR04, but the problem is that there is constantly an object (the person), partially in front of the sensor at all times (within 6 inches), and we want to be able to detect something when it is 1 to 2 feet away moving towards the sensor, but of course the presence of the person is making it impossible to differentiate between the moving object and the person.
Is there any ultra sonic sensor that could even work for this application? What would you suggest we use as a strategy to detect the object moving towards the person? Any feedback is appreciated.
If may be possible to use the concept of the Theremin to detect moving objects but units I have seen have been constructed to not overly extend the sensing range beyond a foot or two.
The idea of using RF to generally detect moving objects when all other objects are stationary may work in your 2 foot range simply by detecting the shift in the RF frequency which would be a tone shift in the Theremin which could be detectable to an Arduino as a frequency shift of the audio.
