Underwater Transmission

Hello,

I am new to the Arduino platform and am very enthusiastic about my first build. So far I have been able to design the project with little trouble. However, there are a few areas I have noted that could be potentially problematic.

This will be an underwater "probe". It is designed to record and store sensor data about the water and environment surrounding the probe.

I need to transmit and receive data from the probe in order to guide and maneuver it. However, water is not exactly a hospitable environment for RF signals. Additionally, I am designing a remote for this project that will give me greater control over the probe than a standard RC controller.

I'm sure I'll need another small Arduino module to build the controller.

I have anticipated two problem areas; A.) Is it possible to use one Arduino module to manipulate another? B.) Does anyone know of a low frequency transmitter/receiver combo kit?

hiremenow:
A.) Is it possible to use one Arduino module to manipulate another?

Yes, as long as they can communicate.

2 thoughts come to mind both require a pair of underwater ultrasonic microphones transducers of the type used by depth detectors and some simple electronics. The first uses standard IR control codes to be amplified and transmitted by the microphone and the second might be required.. There is a device used to talk between submarines that uses a frequency modulated ultrasonic signal as a medium for transmitting voice between submerged vessels using data instead of voice is a trivial exercise.I do apologise for the omission/error. I meant a piezo type transducer or speaker / microphone. It is trivial to make a pair of two way transducers work in this manner. It's the way the 'Ping Pair' works except the transmitter and receiver are the same piezo element in one case. Depth finders do it by emitting a pulse of ultrasonic energy and displaying the returns or echoes on either an LCD or chart recorder spaced apart by the temporal differences

Doc

Would an XBee work?

An Xbee is a radio whose operating frequency happens to be heavily affected by water, Worse it isn't waterproof.

Depending on the depth, you could possibly tether a floating antenna.

Electromagnetic Wave Propagation into Fresh Water

Electromagnetic Propagation in seawater and its value in military systems

http://www.docstoc.com/docs/2867858/RF-Communications-under-water

The usual solution underwater is ultrasonic transmission, and you need to use transducers that are designed to be used in water, not air. There are a couple of suppliers of these in the UK e.g. http://www.rapidonline.com/electronic-components/underwater-ultrasonic-transceiver-200khz-519174/, I don't know who sells them in USA. Search for "underwater ultrasonic transducer 200khz".

To send data over them, I would hack the SoftwareSerial transmitter code to send 1s and 0s as two frequencies, one slightly above 200kHz and one slightly below. You can generate these frequencies from one of the timer/counters, by dividing the 16MHz clock by (for example) 78 and 82. At the receiving end, you could use a CD4046 PLL to recover the signal and feed it into the RxD pin.

Using Laser Communication Above Water and Underwater

I guess if the distance is short and the water is clear enough, you could use blue LEDs and photodiodes. The graph towards the end of http://www.lsbu.ac.uk/water/vibrat.html suggests that IR won't work, but blue or near-UV light has low attenuation in water. Interference from sunlight might be a problem though.