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
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.
Then explain the purpose of your device. And don't tell us you are going to have some remote way of knowing the fish was detected, because then your box is NOT waterproof.
Let's focus first on one fish size, if the detection succeed so i can mechanically improve it. (that's more a second step) i would like to focus first to detect one size of the fish and check if those sensors can do it or not. thanks.
[Paul_KD7HB]
Is that really important? i think you are not answering the question, i am asking regarding the sensors, not about waterproof or not waterproof or detecting remotely. please stick to the question. thanks.
The I guess the question back to you is "what have you tried?". Have you tried IR sensors? Have you tried detecting the change in resistivity of the water as your fish passes by? Have you tried UV sensors?
That's why i am asking. I am asking so that i can get an idea from what the people think and what the people tried so that i can buy a suitable sensor. not buying 100 sensor and then nothing work. You understand? not all people can have the same budget as you to buy all kind of sensors and do all the testing. one approach is to ask people. no need to invent the wheel again. YOU SEE?
Thanks, so you think the best scenario is to use a UV transmitter on one side and a photodetector on the other side and check when it will be interrupted?
I suspect you are the ONLY one that have ever logged into the Arduino forum that wanted to detect a fish in a tube. So why do you even want to get an Arduino involved without even have a signal to monitor? Use your oscilloscope with a sensor and see if you get a consistent signal from the fish, THEN begin to monitor that signal with an Arduino program.
I can see three possible sensors. First is UV to detect reflection from a scaled fish. Second is an IR break-beam to detect a fish of any type passing. Third is the water resistivity change as the fish passes by. All fish have an insulating slime coating which will cause an increase in water resistivity.
So there are three sensors to buy/build and test. Each will show a signal on your scope.
Nobody asked you to get 100 sensors and try them out.
However you are expected to do your homework: look at how other people approached this problem, and what commercial solutions are out there already and how they work - there are lots of fish finders on the market already, so you can find lots of information about them. That gives you an idea about possible sensors used in this realm, both on commercial devices and hobby projects.
One big question I have about your project: how are you even going to get the fish to swim through your device, rather than around?
A thin, light rectangle of transparent plastic mounted on a spindle at the entrance, would be pushed downwards as the fish brushed against it on leaving the exit. Triggering a tiny reed switch close to the spindle. A small piece of sponge or similar would provide the return spring. Smaller fish would not get detected.
Will the tube be resting on the bottom of still water? If so, a fish of that size would probably create a sufficient disturbance to move a light, flexible vane or flap of some sort. Detecting that instead of the fish could bring the range down to a cm or less. (Although at a few cm I doubt that would be an issue anyway.)
P.S. Are you confident fish will be curious enough to make the journey? As a one time keen angler it was hard enough getting them to investigate my baited hook.
Terrypin
Thank you for your answer, i liked your ideas
Do you think the light rectangle of transparent plastic will not be affected by wave for example or any movement to the enclosure?
i think the water will not be that still.
I am going to make the tube move left and right so that the only space left is the entrance of the tube so the water can pass through it.
