Underwater fish detector

Community Projects
1

I would like to create an underwater fish detector - completely operating underwater (personal project)

The enclosure will be a waterproof hollow cylinder (possible material to use are: acrylic, Polycarbonate or PVC), a PCB will be sealed inside that enclosure containing the sensor (the sensor of choice should not be waterproof because it will be inside a waterproof enclosure).

The fish can pass through that hollow and will be detected while passing. the inner diameter of the enclosure will be in the centimeter range to allow one fish to pass at a time.

Note:

I am not dealing with precise measurements or long range (no need for those expensive high precision sensor)

I cannot use big or expensive sensors due to budget related reasons and size constrain

max operating voltage of the PCB is 12V (preferably 5V or 3.3V)

Here’s a link to picture that illustrate the idea for better understanding

https://drive.google.com/file/d/13LIXOK … drive_link

I am using 2 sensors so i can make sure i detect that it passes through

optional receivers can be implemented if the sensor i use is just a transmitter and not transducer

Here comes the challenging part, the sensor choice, i will list some i thought about and i hope i can get some ideas from you that can help me.

  • Ultrasonic sensor (i saw some people successfully did it but nothing is documented with low cost sensors):

Challenges:

Blind distance of ultrasonic sensor for small measurements.

I don’t know if the acoustic wave can pass through acrylic hit the fish and be detected

  • Optical sensor (such as VL53L1 or any other choice)

Challenges:

Require clear water

water can scatter the light but i am using it for short distance so i don’t know if it will work or not

require transparent enclosure

  • ESP32 camera (image recognition algorithm)

Challenges:

Require complex algorithm

Require clear water

I would like to hear if you have any other idea or if i can improve one of the suggested ideas to successfully achieve the project.

Thank you very much.

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2

Optical, for sure.

It will be difficult to predict what kind of emitter/detector pairs might work for the expected water turbidity.

Fortunately, the distances seem pretty small (few inches/10s of cm) so, unless the water is verging on mud or there’s a lot of debris chunks, I think standard (though submersible) infrared beam break stuff will work fine.

You didn’t ask and, it all depends on why you’re watching fish, but I’d consider a third sensor between the entry and exit detectors.

This can determine that a fish is fully within the tube and is not one that, say, sniffed your murky danger cave and noped out before entering.

Perhaps this approach/decline behavior data can even be useful for making the tube more inviting to other fish.