I want to create a device that I can receive data from onto my tablet. basically the device will be submerged underwater and will send info to my tablet which will be located out of the water. I am planing on having several of these devices sending info simultaneously to the tablet which will gather info.
My 2 cents
As far as I can remember from my science classes you can easily send signals in water.
The problem is that you want to go from water to air.
My thinking is you only need 1 device that converts a water signal to a air signal.
Best regards
Jantje
Floating antenna?
Your requirement is too vague.
How much data and at what speed?
VLF communication with submarines is fairly well understood and robust, but data rates are measured in bits or fractions of bits per second, and requires antennae tens of kilometres long.
@TurboTronix:
You'll probably need much lower-frequency waves (kHz range) than standard wireless transmission (which might be 2.4 Ghz or several hundred Mhz), if you want to transmit data underwater without significant attenuation/absorption.
Maybe try ultrasound?
Or if it's just a short distance and you don't need 100% reliability of data transmission, you can maaaybe get by with Xbee 868 Mhz, or even better 434 or 315 Mhz transmitters, like these:
Or how about somehow integrating an IR-LED-based transmission?
More information, regarding your exact application, would be helpful to give better answers.
I need it in order to receive 2 data parts:
- location inside a rectangle water tank
- pressure sensor data
I want the part in the water to be as small as possible and also be able to retrieve info from several of these at once.
Basically the tablet will have the data stored in some kind of a DB.
You're still missing the fundamental questions of how much data, over what range and how fast.
Lets say olympic size pool and instant data transfer (lease delay possible).
This is really like trying to get blood from a stone.
How much data and how fast?
Define "several".
Define "least latency".
instant data transfer
Don't be silly. We are asking for the data speed, that is how many bits per second, not the propagation time.
At a rough guess I would say you have no chance of doing this.
AWOL:
This is really like trying to get blood from a stone.
How much data and how fast?
Define "several".
Define "least latency".
Might also be worth defining "tablet" too. It's a bit of a vague term these days. Android? iOS? OS X? Linux? Windows?