connecting 2 Mega's over long distance

I am making an ROV with 2 arduino mega's. One on the surface connected to the computer and joysticks the other underwater connected to motor shields and sensors. The distance between the 2 Mega's is 100 meter. does anyone knows what's the best way to let them communicate. sorry for the bad english :P .

Grtz DS

One on the surface connected to the computer and joysticks the other underwater connected to motor shields and sensors. The distance between the 2 Mega's is 100 meter.

That is going to be a problem, and not as much the distance as the medium change from air to water. Can you get the antenna on the underwater unit above the surface?

edit: I have tested the Mega2560 with an ethernet shield with a high-power radio/router combination, and gotten a connection at 5 miles.

No then the antenna need to be at least 60m.

Dubsepp: No then the antenna need to be at least 60m.

Then you can forget about using any of the radios made for an Arduino shield. They will not have nearly enough power to overcome the medium change, much less the distance. I was using a 500mw radio with a 23db antenna to get 5 miles line-of-sight in air only.

Dubsepp: I am making an ROV with 2 arduino mega's. One on the surface connected to the computer and joysticks the other underwater connected to motor shields and sensors. The distance between the 2 Mega's is 100 meter. does anyone knows what's the best way to let them communicate. sorry for the bad english :P . Grtz DS

Most DIY ROV projects use wire as the method of communication. Google has a lot of information.

Yeah I knew radio control wasn't gonna work. Can I use wires to connect the 2 arduino's or is the distance also a problem then?

If you use ethernet shields, CAT5 cable between ethernet ports is limited to about 100 meters. And it is fast!

Ok thanks this helped a lot. I heard about I2C is this possible ?

Dubsepp: Ok thanks this helped a lot. I heard about I2C is this possible ?

Not for that distance.

Lefty