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I'm planning to make ROUV that use raspicam to take under water video and stream it using Edimax wifi module to the web-server. RPI and raspicam will be underwater and Edimax can be settled above water level (by floting transmiter) to take raspicam data and transmit it to webserver. Raspicam should be able to switch on and tresmit video data through RPI to Edimax automatically, when I power up RPI ( cuz after I seal the ROUV, I no longer have access to RPI when its underwater) Any help that anyone can provide with my matter?

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Unless you're planning on:

  • keeping your ROUV within 5-10 metres of the Pi (the useful range limit of the Edimax adapter)
  • keeping your ROUV at a depth of no more than 5 metres (the maximum length of a USB cable)
  • dealing with rapidly varying video quality

... this is a non-starter. Most, if not all, effective ROVs use neutrally buoyant cabling for data transmission to shore, and use something like cat5 rather than USB. There are generally too many varying environmental factors on the surface to reliably handle with WiFi, unless you're using some kind of monster antenna. It's also kinda scary piloting an untethered ROV - if anything goes wrong, you're not getting it back unless you're in a paddling pool. With no shore power supply, if your battery dies (likely in low temperatures) your ROV's a goner.

If you're interested in building workable ROVs, I highly recommend starting with OpenROV.com. Their units are based off Beaglebone Black controllers, but I don't see why you couldn't substitute a Pi as long as you're prepared to put in the hours needed to figure the software out.

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    I'll make an uneducated guess and say that wifi probably has an underwater range measured in centimeters so a tether is probably the only real option. – goldilocks Aug 11 '16 at 11:03
  • The question did suggest that the antenna would be above sea level, and tethered over USB. There are subsea 'Bluetooth' (not actually Bluetooth/generally bad) systems that are used to allow ROVs to collect data from pipeline sensors, but they're pretty high powered and have a range of about 60mm on a really good day. Water is a really really really bad place to try and get things done. – goobering Aug 11 '16 at 11:09
  • Rather than fake bluetooth, surely blue LEDs would be better? I wonder how easy it would be to hack up an IRDA dongle to use blue LEDs. – Chris H Aug 11 '16 at 11:12
  • You could extend the USB beyond 5m using a USB-over-cat5 kit. But you would need a separate power cable if you're powering the Wifi dongle off the Pi -- USB over cat5 hardware behaves like an unpowered hub by default but some have a power input. – Chris H Aug 11 '16 at 11:15
  • For most purposes, light doesn't work very well either. Unless you're in gloriously crystal clear waters, sediment kills visibility down to a couple of metres. I'm sure I've read research papers discussing LED based comms, but they were unimpressive. Very low data rates with very high error rates. Low frequency acoustic transmission is better, but subject to bundles of interference, is still slow, and is limited in range. It may also bother whales. Extending the USB range over cat5 might be an option, but you're going to have to account for cable mass at some point. – goobering Aug 11 '16 at 11:17

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