A “deep dive” into a few proximity sensors.
A research to find the correct sensor for the project void.
This one doesnt require a receiver on the other side like regular beam brake sensors since it is using the reflection from the object that is breaking the beam. Due to that it might have problems with different materials (such as certain fabrics) that would absorb the light and wont reflect it back to the receiver. Opposite problem may occur with a project that produces light that might be received as the broken beam (like in our project).
Sensing Distance: Up to 1m (depending on light levels, contrasting material)
Sensing Angle: <10 degrees
Composed of an integrated combination of PSD (position sensitive detector) , IRED (infrared emitting diode) and signal processing circuit. Basically 1 LED transmit infra red light and a detector that receives it. The calculation of the triangle formed between them and probably also the time it takes the beam to return is how the sensor gives reading. The classic IR sensor typically ranges from 20cm to 150cm (5feet). There are bigger ones (bigger also physically) that goes from 100cm to 500cm (3-16.5 feet!).
This ultrasonic (also called Sonar) sensor is similar in technology to the one we used for the midterm – might be better and less glitchy because of quality. This one has narrower beam angles which can improve the “glitchyness” of the other one we tried (less arvitrary readings from different objects in the arena). Detects objects from 0-inches to 254-inches (650cm).
Between the IR and the ultrasonic the IR is faster to give reading and typically used for close ranges (about a meter or more) while the ultrasonic is more accurate and used for longer ranges (up to 10 meters).
After some experimentations with it we found it worked pretty smoothly. Ranges are wide: up to 11.5 feet (350cm) but also says (see below) could get to 19.7feet.. “The Kinect sensor has a practical ranging limit of 1.2–3.5 m (3.9–11.5 ft) distance when used with the Xbox software. The area required to play Kinect is roughly , 6 m2 although the sensor can maintain tracking through an extended range of approximately 0.7–6 m (2.3–19.7 ft).”
PIR sensor (we avoided the use of this sensor in the midterm).
This sensor is actually 2 sensors that detects IR light combined in one. It is sensing wormer then the environment objects (such as human/animal) by changing the electrical charge in between them. A positive charge means a wormer object went in the area detected, or negative charge, when a worm objects left the area detected. Using a Fresnel lens (a shape of the lens that breaks the light in a way that can concentrate or in our case spread the light) to increase the area detected.
The gif below shows it use (similar to break beam) could be used as a switch (detects only if a person is there or not).
and now, to make sure I have 400 words, I would like to give a little poem I wrote:
Sensor sensor,
what do you detect?
what can you sense,
does it make sense?
chorus:
can you see me?
can you hear me?
can you feel me?
Sensor sensor,
you have to make sense!
chorus:
can you see me?
can you hear me?
can you feel me?
now it all makes sense.