underwater electrical connections - wireless 1

[hjain73]

Hello,

First off - I should say that I am not an engineer - just a researcher trying to solve a problem. We are in the water fountain industry and are interested in finding out how we can minimize the number of underwater electrical connections for powering systems, and for controlling the movement of nozzles. Typically, when something goes wrong with the wiring, it is very difficult to address the problem if it is underwater.

Are there any wireless technologies suitable for addressing this problem? How would I search for such information? (i.e. what keywords should I use when searching the literature).

Any information that you can provide would be greatly appreciated.

Thanks for your help,
Hitesh

 

[peebee]

Wireless is generally a bad method for transmitting power regardless of the environment.

Wireless can be an economical solution for controls, depending on the application. Unfortunately, RF generally does not transmit too well through water, so you'd need to investigate something other than typical RF.

Sound transmits very well, that's the basis of SONAR. Light also transmits well, maybe you can do something with visibile or near visible light (possibly IR -- I'm pretty sure water blocks UV). Very-low frequency RF might work, I think the Navy does something with low-freq RF; those antennas are like hundreds (if not thousands) of feet long, though, due to the very long wavelength of low frequencies. So, for wireless, you're probably looking at sound, light, or low-frequency RF.

Sound might be the easiest to play with -- waterproof mics, speakers & transducers are readily available. There's also lots of sonar-based fishing equipment out there. Another attractive feature of sound for you might be that it's relatively non-directional, and transmits well through water: if you put a mic & speaker in reasonable proximity to each other, you're almost guaranteed a clear channel. A possible downside might be the effect on marine life, you could have a negative effect on fish, etc.

Light, in concept, wouldn't be too bad either. But the available parts might be somewhat more limited. And you'd need to concern yourself with aligning a transmitter & receiver. Take a good look at the transmission of light in water for whatever frequencies you have in mind; water is very clear to some wavelengths but rather opaque at others.

Low-freq RF probably does not make too much sense for you to explore.

For more info on using sound or RF in water, I'd try Google searching for articles on the Navy, they do the most of that kind of stuff by far.

Just curious, have you considered fiber optics? This might be the easiest solution to implement, the parts are readily available, you'd need to do minimal engineering/hacking, it would be relatively cheap, and you'd overcome most of the issues of mixing water with electricity.

Hope this helps, good luck.

 

[peebee]

Here's another thought:

"Wireless" typically refers to transmission over a distance.

But it occurred to me that perhaps you are primarily attempting to avoid problems at the metal-to-metal contact points at your wiring terminations, and that otherwise you have no issue with running the wires underwater. You just want to get rid of the underwater plugs & receptacles. If this is the case, there may be another solution for you that would take care of both your power & controls termination issues -- induction.

I've got a rechargeable electric toothbrush at home that uses induction -- there's no metal contacts on either the toothbrush or the base. Instead, on the base, theres a small plastic plug that fits into a small plastic hole in the toothbrush. Hidden behind the plastic on both pieces is a coil of wire. When the two coils are brought into proximity with each other, they form a transformer, with the base housing the primary coil and the toothbrush housing the secondary. A similar concept has recently been introduced for lighting within the last few years; there are new induction light bulbs that have no metal connection to their sockets.

It would be easy for you to build such a connection, or to hack a toothbrush, and to waterproof these "plugs" and "receptacles" onto the end of each power and/or control wire.

If you provide some more details about the problems you're trying to solve you might get some more specific answers and from more different members here.

 

[nbucska]

You need power : Use the pover line for info xfer, too.

<nbucska@pcperipherals.com>

 

[tonymac]

Regarding the first answer by peebee, he's absolutely right. RF is a bad idea for in-water transmission, and water does block UV completely after a few inches (the denser particles and the short wavelength cause that). IR is used by the Navy in some situations, but the transmissions are extremely slow and are transmitted on a rediculously low frequency. I wouldn't recommend light, because it doesn't go very far, either. For data, fiber optics with sealed connectors would prbably be the best bet. Power connections could use the induction method, but be careful of magnetic fields around sensitive electronics.

Good luck

 

[peebee]

Here's another idea: pneumatics. Air pressure could be used for power, there's plenty of air-driven motors & pumps around. And air pressure can also be used for control -- I believe that air switches are the standard method of control for nearly 100% of the hot-tubs (Jacuzzi's) out there, for about the same reason you're looking at, to keep electricity away from water. Does that fit your definition of &quot;wireless&quot;?

By the way, when you say water fountain, do you mean drinking fountain or a 50-foot jet of water shooting out of a pool in a park somewhere? Sounds like the latter. Not that it matters much, I just want a better idea of what you're talking about.

 

[hjain73]

Thanks all - for the great suggestions. Peebee, I am referring to the type of water fountain that you would see in a city centre, or in Las Vegas --- where the water shooting out is co-ordinated with music, where the nozzle movement makes interesting shapes etc.

So to clarify the application --- instead of wiring the nozzles that control the water shooting out and the movement of water, directly to an electrical source ---would it be possible to do this wirelessly?

I think some of the ideas you provided are definately worth looking into. Thank you!