Hi all, this is my first post here, so go easy on me
I was wondering if anyone has any ideas how a simplistic form of underwater communication could work using an arduino to receive simple messages.
Something like the way an IR remote control works, but using (i guess) high frequency audio instead of light/radio.
My goal would be to send a signal at the surface of the water ( few inches under) using some kind of tone pulses, then have the receiver/hydrophone/detector or whatever analyze the signal, and react to it.
Any ideas or information that could steer me in the right direction would be appreciated.
Thx, I like the idea of using a light, however; to expand on the application, this would need to work in open water where you could not see the receiver, but you knew the general location of the receiver.
It would be used to remotely activate a device that is under up to 200 50 feet of water, and not visible. It would just require that the receiver is in range, and that whatever signal that was sent could be read.
Kinda looking for ideas to play around with, I don't have the budget to acquire expensive equipment.
Just to continue this discussion, let just say the depth is 50ft and I could keep the arduino dry.
You have to use somthing like piezo to hear, arduino can not take real mic as the audio signal is ranging from negtive to positive voltage, but rectified it could work.
Find a "broken" mic/hedphone, make rectifier amplifier circuit that outputs 0-5V.
Use something like this http://www.ladyada.net/make/waveshield/
to generate audio to the recever.
Play different small mp3 for each command
lol, that would be slick- but mp3 music under water??? How does it tell one mp3 from the other? Wouldn't the sound need to be higher frequency to be clearly interpreted by the receiver?
I got the idea one day at the pool- i could use my timex watch beeps to make a signal.
My brother (at the other end of the pool) could hear the beeps... so I tested him, had him tell me how many beeps I sent.
Worked great, now I just want to expand on that idea, but have the arduino interpret the beeps, and make the beeps stronger so they travel further through the water.
Thx for tip about piezo- seems like the way to to listen to sound underwater - a cheap hydrophone
How to do the 0-5v rectified amp circuit?
the fish might not like the music and attack my receiver!
You can communicate under water using radio. The nuclear submarines do it. The trick is to remember that the dielectric constant of water makes the wavelengths of the RF much longer so you need bigger antenna to compensate.
An other method is to use a magnetic field, having inductive loops under the water, the range is limited by the magnetic field's inverse cube law but it works for ground communications like underground telephones for cave rescue.
Then there is a straight forward electrical signal, two electrodes as far as possible will set up an electric field that can communicate to two remote electrodes. I have used this method myself to communicate through the ground, picking up the signal on a pair of headphones and a couple of kitchen forks.
Finally there is sound, both ultra sonic and sonic. Sound can travel a long way in the sea, and a pinging submarines can be heard over a thousand miles away. The salinity layers in the sea act a bit like tropospheric ducts propagating the sound over great distances.
the piezo does not need rectifiing i think, look for knock detector in the arduino examples or playground.
mp3 is just sound file format right
you wanted to send commands by sound ? right ? (sound=sonar).
Are you getting the drift
make a sound files (morse code or similar sounds) with your commands that are few tens of ms long. That is the mp3 played.
each file plays different command.
It's not that heavy metal sound for 300 ms turns the ROV left, and NewAge for 300 ms is for dive to hell ;D
I beg to differ, you get a positive and negative spike out of a piezo. Just because some projects choose to damage your arduino doesn't mean they all have to.
@ArduinoM - I get what you are saying about the mp3's, nice flexible solution. The idea of using different music genre for command is intriguing in a funky way.
From what everyone has said, it looks like a possible solution would be:
For the receiver end:
Make a hydrophone using a piezo
Couple that piezo mic to the arduino via a rectified amp circuit
Program the arduino to analyze the voltage from the piezo, and do something with it.
Put all that in a waterproof enclosure (with the hydrophone in direct contact with the water to ensure direct sound wave pressure transfer)
For the transmitter end:
Build or hack a transducer to send an audio signal through the water
Feed a signal/pulse (from another arduino or some other circuit) or whatever to the transducer as a message for the receiver to respond to.
Or I suppose to refactor the whole concept, just build an audio based transmitter/receiver that sends simple signals (using pulse spacing- thx @Grumpy_Mike) similar to what an IR remote does. Like some sort of automatic arduino morse code machine- but not as complicated as an audio ethernet system.
It would be nice to store the signal code(s) on flash memory or something so both the transmitter and receiver could be paired up uniquely.
And would need to make this work for pretty cheap as a proof of concept.
Does this sound like something that could work? reliably?
Thanks again for any and all feedback. I am a programmer- trying to make progress with a hardware project.
I don't really have an idea of where to begin with this atm.
I think for even just 15 metres, you're going to
a) have to make a lot of noise at the sender end
b) have a pretty sensitive mic at the receiver end - I'm not sure a piezo will do the job reliably.
Just because your fairly discriminatory human ears can hear watch beep doesn't mean to say a piezo will fare as well.
You can communicate under water using radio. The nuclear submarines do it. The trick is to remember that the dielectric constant of water makes the wavelengths of the RF much longer so you need bigger antenna to compensate
The US Navy uses 76Hz (yes, I said Hz!), with a wavelength of over 3600km. That quarter wavelength dipole is going to be impressive! ;D
Maybe get hold of some scrap fish-finder / small boat sonar components would seem to me to be the best way to go because that's what they're designed for.
As someone said, even keeping the water out of the electronics is no trivial matter.
Don't know about the FCC, but the CIA might have some say in it. :