I am an ME student currently working a project which requires the remote activation of an object underwater. The idea essential is to deploy a buoy attached to a lobster pot resting on the seabed via ultrasonic signal. In theory the distance would be 20 meters however for the purpose of demonstration 1 - 2 meters would suffice.
The area in which I need assistance is the sending/receiving of the signal. At the beginning I was hoping to use a pair of JSN SR-04T Water Proof Ultrasonic Sensors, sending from the trigger pin of 1 sensor and receiving on the echo pin of the other. I have come to understand that not only do these sensors not work submerged, the nature of the module itself does not allow for this function?
Luckily enough I have managed to come across this video on one-way ultrasonic transmission:
It appears now that my issue is now sourcing underwater modules. Looking through the forums I found lots of useful information by user DaveEvans here:
My question now is, Am I able to combine the recommended methods above (either MaxBotix or hacking a cheap Fish Finder) without disassembly?
if you do a web seach for underwater ultrasonic sensor you will get links to commercial sensors
what exacty do you want to do?
why not run a cable from the buoy to the lobster pot?
The aim of this project is to help recreational fishermen against anti-competitive practices of industry. Commercial fishing companies are somewhat protective over "their" waters and the theft/damage of equipment is not unheard of around these parts. Therefore a cable to the surface is unsuitable for this application.
What I would like exactly is to be able to place a sensor in the water, and have a servo motor actuate rough 1 - 2 meters away (Ideally the receiving sensor would be powered by the Arduino alone, but it's not a deal breaker).
The budget for commercial sensors may be available, however I would like a little confirmation that I am going in the right direction before ordering expensive parts at the universities expense.
possibly the thing to do is to communicate with the manufacturers of commercial sensors - explain your requirements and see what they suggest
often companies will gives samples or loans of products for university research
For ultrasonic communication or echo ranging to work under water, you need transducers designed to couple the acoustic signal to water, rather than air.
They tend to be quite expensive and require several hundred volts AC at typically 150 kHz to drive.
The transducers in the cheap "Lucky Fish Finder" work well and give up to 100 m range, but the circuit used to drive them is not easy to modify or build. Lucky Fish Finder New | eBay
There have been some attempts to make an inexpensive underwater acoustic modem, but none seem to have made it to the hobby market.
Why not just do a timer? Would be simpler and could be mechanical. When you drop a trot of pots you need to come back to lift them within a set time so you just set your timer and the pot buoy could stay submerged until close to the time you need it.
I think developing underwater communication is unlikely to work since sub marines struggle with massive military budgets
In the country I am currently studying, those without a license are permitted to set 5 traps at 1 time and keep 1 lobster a day (given the catch meets criteria).
I'm just giving the jargon I wrote in my report, the other forums where I've asked for help think I'm trying to stash something underwater. Lol
Yes, this was discussed in our group and is our plan B. We ultimately decided against as this somewhat limited the user with a time constraint.
You're most likely correct, I pitched this to another lecturer on my Microcontrollers and he gave me a weak "maybe".
I became aware of the difficulties of underwater data transmission during the research segment of this project last semester (I found VLF Radio waves particularly interesting).
Fortunately though, I am not trying to transmit data. Just trying to actuate a servo when a wave detected.
Not to be too discouraging, but underwater communication sometimes comes up as a project here, I think I've never seen anyone show proof of completion at any time during the last more than 5 years. So if you do, it might become a reference thread.
You are indeed sending data: "wave detected". To be received reliably, the data must be sent in some way that can be detected over the background noise.
Yup, after looking at few threads this seems to be the consensus. Do you think the receiving module can still operate on solely the 5v supplied by the arduino?
Thanks! In my original post I produced a link from hackaday where the transducers stripped off of a HC-SR04 Ultrasonic Sensor. I am kind of hopping to replicate this with something along the lines of your suggestion. I think I'll have to come to terms with taking the fish finder apart and figure out a way to water proof later so a cheap fish finder is a big help.
I was advised at one point to look into DTMF but was later told overkill as I am not trying to transmit data. It appears I have miscommunicated, I just want to actuate a servo motor so a simple HIGH/LOW would suffice.
DTMF is actually useful in similar situations because it has a high tolerance to line noise. I wonder, are you following up on the things you are told? Because a lot of things people tell you might be false, questionable, or out of context.
The suggestion for DTMF came from a user on reddit. I then followed up with the lecturer of my Microcontrollers applications module and was advised against.
Perhaps I am not getting across what I am trying to do correctly.
Why not approach this as an engineering project... first gather requirements and make initial experiments and tests... scope out a design... put together and test... tweak and improve...
You should begin with some existing research and facts about underwater communication.
Places like Reddit are not where you should be looking for this level of knowledge. It's a waste of your time.
You need to break down the project, for example first just build the comm device and test it.
