Hello Everyone,
I am designing a quad-copter version that works under water for scanning the ocean surface and I checked a lot of articles and websites for underwater communications [wire] + [wireless} types, the result I got is ambigous yet, but for my first prototype I am thinking to connect a cable to arduino [ NANO ] but, actually I don't know how can I connect a 500 meter cable without loosing data. If you prefred acoustic system for 80-150 KB / sec? may you tell me the solution?
check RS485 - ( do not know the detailed specifications )
RS-485 is up to 100 meters with a twisted-pair cable.
You can lower the baudrate (a lot), I think that 500 meters should be possible.
The 500 meters cable will be very heavy. But I think that wireless needs a lot of power for a range of 500 meters (long wave RF or sound or light).
Can you give more details ?
Is the data going in both directions (sending commands, retrieving data) ?
How much data at what rate (only 100 samples of 16 bit per second, or much more) ?
Do you want to scan the ocean floor or the water surface ?
I just read that 100 meters is what it used to be.
With a good cable and good RS-485 drivers, you can go up to 1000 meters.
So a cable will work for sure, everything else is a big question mark.
conceptuality, cable of any length is no problem to send signals down,
Atlantic cables are thousands of Km long,
BUT
as said above, pulling that would be very difficult.
if you have a 1mm diameter cable, and a 1 knot tide, thats going to be 10's of Kg force,
the cable might not brake, but can the drone fight even that slow rate !
The big boys do mother ship techniques,
They have a big craft that can drag a big line, and from that have a small craft that does the short distance.
If its on the surface, stick an aerial up
Why did nobody suggest fibre optic cable for this? Should be good to a few miles quite easily. Albeit a tad expensive.
I suggest you research what others have done as to cabling. Just for communications a single thin coax cable might could be used in several ways.
ELF or VLF is used for Navy data, unless you have a large ship for a spooled cable.
Is your cable for just data or do you want to also power your device from the surface?
You say you want to examine the ocean surface. Do you mean the surface of the ocean bed or the surface of the water?
I think that the communication is doable, but you need to describe exactly what sort of cable you have on hand to do this, rated of course for underwater use which clearly means not your standard cable from the electronics shop, and what sort of submarine vehicle you have to do this; it clearly would not look anything like your average "quadcopter".
Also of interest, we are talking of a vehicle of the order of 50 or 100 kg - from what ship do you propose to launch it? You of course need a crane and a drum assembly for the cable so you are looking at a small commercial fishing vessel for a start. It's a big project!
If you don't mind having to get your device back to the mothership (aka the ship released the device) from time to time and lose the ability to process the data in real time you can probably get away without a cable: stick a microSD card to it and when it is filled up, catch your device and pull data out of that card. A small speedboat will be enough to be your mothership since there is virtually no load to carry.
If you need that real time performance you can try some marine-grade Category 6 cables carrying RS-485 and power from your mothership to your device. Speedboat may be too light for this, a small fishing boat may be required for this.