Simple underwater communication

Projects General Guidance
1

hello guys

im working on project that requires underwater communication, i want to send a signal from point A to B underwater to turn on lights ,
i did research and found acoustic modem but they way over priced and way over for simple signal ,

thanks
Watson- ]:smiley:

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2

What kind of signal? What distance? Does it have to be wireless? Clear water or murky? Feel free to offer more details.

3

hello

any type of signal i want a way to trigger the lights on location B , yes it should be wireless the water is murky salt water the distance 400 m the more is better as for the depth max will be 20 m

thanks

4

the distance 400 m the more is better as for the depth max will be 20 m

400 meters is a non-trivial distance in air. Underwater, it's a huge distance. You are unlikely to find anything cheap that can send any kind of data 400 meters underwater.

5

400m is a long way. If all you want to do is turn a light on or off you could maybe setup a system where 'A' generates a regular "thumping" signal at a set frequency. If 'B' "hears" the signal it turns on the lights, if it does not hear the signal for a while it turns off the lights. You could research what frequencies travel best in water but you might need quite a lot of power. Also if 'A' and 'B' are at different depths haloclines or thermoclines might block your signal as would water currents.

6

thats what im thinking of , i dont have problem with power , could you give me link or circuit that i can start with ? it would be great !

thanks

7

This topic (underwater comms) has come up several times before so I suggest you search for previous threads. I usually suggest underwater ultrasonic transducers and fsk, however the transducers are not cheap.

8

true they are not cheap and im looking for simple comm dont need to send data just 1 signal coded or so

thanks

9

You really should look at the other threads on underwater transmission.
I will try being a bit more blunt. As I understand it, you'll need to go the complicated and expensive route because wireless transmission through water, especially salt water, is difficult. Things that might work in air do not work in water, since water works as a great attenuator for electric fields. If you want to go simple, I would go wired. There is no immediately easy solution.

10

There is no immediately easy solution.

At least not one that is also cheap.

11

They call him Flipper, Flipper, faster than lightning..

12

Sound travels well in water, so you might experiment with a microphone and something to make loud sharp pings in the water. Scuba diving, we often tap a knife or metal tool on the scuba tank to get the attention of another diver.

13

correct thinking of sound but need to find a way to send coded ping or so , most use special modems for that trying to build simple one Low Freq sound waves

14

Watson-:
correct thinking of sound but need to find a way to send coded ping or so , most use special modems for that trying to build simple one Low Freq sound waves

If you want simple ping transmission, maybe you should look into a Morse code variant.

https://www.google.com/search?as_q=arduino+morse+code&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=images&tbs=&as_filetype=&as_rights=

15

A technique that some submarines used to use was to float a tethered antenna up to the surface and transmit/receive via this.

simple and cheap, but probably not what you were looking for.

16

Sound will work. Sonar operates with a round trip of over 400m so it can be done, cost is a different question.

You need to research what sound frequencies travel well in water. Looking at sonar and depthsounder transducers would be a good starting point.

Experiment with Zoomkat's tapping a tool on a scuba-tank. I think that would work to over 20m, hitting a metal plate with a hammer might give you an idea of what that could be extended to.

A DIY setup might be;

At 'A' an oscillator, amplifier and loudspeaker assembly attached to a metal surface.

At 'B' a microphone/hydrophone.

'A' needs to generate at least 1 and prefereably 2 tones that travel well in water and can be distinguised from each other and background noise.

'B' needs to be sensitive enough to detect and distinguish the tone/s (which might be quite weak at 400m).

17

thank you so much i already got fish finder from garmin trying to mess with it

time to work :smiley:

18

got fish finder from garmin trying to mess with it

Personally I take things step by step, but good luck.

19

I might be able to help, I'm doing some work on an ultrasonic modem for underwater use. Buying or building low-cost underwater ultrasonic transducers is the main problem - they are not cheap.