Electronics > Projects, Designs, and Technical Stuff
Radar to detect mosquitoes?
Marco:
The idea is to identify it in a narrow corridor between an emitter and a retroreflector, plenty of contrast.
_joost_:
Bats detect insects with sound waves they emit bouncing back. Frequencies with a wavelength larger than the insect do not bounce back but rather curve around the insect. Rather then emitting a single frequency bats send out a chirp which allows them to estimate the size of the insect by the frequencies and strength of each bouncing back. Different bat species have different chirp frequency ranges.
To compute the frequency needed to detect a 5mm insect, this is computed with: f = v/lambda with lambda being the wavelength and v the propagation speed which is the velocity of sound in this case. So for lambda being 5mm this comes down to: f = 330m/s / 5.10^-4 = 660kHz. This is the lowest frequency needed to detect a 5mm insect, higher is fine also.
To be able to place an insect at a specific location, you need at least 2 detectors (ears) so that a phase correlation can be made between the sounds received. For practical application, the spacial distance between the receivers, the transmitter and where the insect is all need consideration and optimization. E.g., an insect on a line/cone somewhat in the middle between the two receivers will be easier to detect than way off to one of the sides. Additionally detectors/emitters may be needed or some sort of apparatus that lets the emit/detect contraction scan the room (like a radar).
The problem you will encounter with this type of detection is that your ultra sounding receivers and emitter need to be extremely (phase) accurate. The cheapo distance type thingies you often see in Arduino like kits aren't going to work for you. Small phase offsets quickly lead to large distance/angle estimations. So your ultra sonics are going to cost you a pretty penny.
So why not a camera as some folks suggested? Simple compute the phase angle you'd need for a 5mm insect at distance x and determine the pixel resolution you need (I'd leave it to you to compute).
In case you wonder; I developed an ultrasonic detection method for pipe vibrations for industrial applications. Not quite the same as your insect problem but has similar aspects to it. I was able to detect (very) small vibration levels (orders of magnitude smaller than 5mm) at considerable distance from the pipe.
PartialDischarge:
--- Quote from: _joost_ on July 31, 2020, 04:04:16 pm ---To compute the frequency needed to detect a 5mm insect, this is computed with: f = v/lambda with lambda being the wavelength and v the propagation speed which is the velocity of sound in this case. So for lambda being 5mm this comes down to: f = 330m/s / 5.10^-4 = 660kHz. This is the lowest frequency needed to detect a 5mm insect, higher is fine also.
--- End quote ---
So in part you're implying that bats probably use higher frequencies that those usually reported in studies I've seen(100-300k). Some birds are just incredible in how specialized they are:
-Bats (although bats are mammals) in detecting flies and mosquitoes
-Eagles can spot small animals kilometers away
-Owls are totally silent when flying
-Woodpeckers can carve through wood by banging their heads against it, no trauma suffered.
max_torque:
I suspect that detecting mosquitoes is much like detecting submarines, in that it is far easier to just let them come to you, than try and find out where they actually are!
The "convoy" system used to protect merchant shipping in WW2 worked because it attracted the subs to it, meaning they were easy to attack!
So what you need is something mosquitoes are attracted too?
Berni:
--- Quote from: max_torque on July 31, 2020, 04:27:58 pm ---I suspect that detecting mosquitoes is much like detecting submarines, in that it is far easier to just let them come to you, than try and find out where they actually are!
The "convoy" system used to protect merchant shipping in WW2 worked because it attracted the subs to it, meaning they were easy to attack!
So what you need is something mosquitoes are attracted too?
--- End quote ---
This is actually how i deal with them.
If im awake and hear that dreaded high pitched buzz i just stay still while keeping my hand near by and listening closely to try and track its location. Once i feel it land i wait for a fraction of a second for a bit of a false sense of safety before quickly swiping by with my hand. Tho its still not perfectly reliable, so it often takes more than one try to catch it.
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