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Topic: IR Receiver Underwater? (Read 2 times) previous topic - next topic

encryptor

I'd like to achieve 4.5 foot depth underwater.  I thought a BT module or WIFI board would work fine sealed in a submarine.  Radio communication reflects off water? Also, what if I heat shrink-wrap an ultrasonic ping sensor, mount it on top the hull and use it for obstacle avoidance?  Will the chirp and echo work underwater?

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peace*&^

PeterH

#6
Jan 18, 2013, 11:34 pm Last Edit: Jan 19, 2013, 02:54 am by PeterH Reason: 1

I'd like to achieve 4.5 foot depth underwater.


Are your sender and receiver going to be directly on top of each other, or do you also have a horizontal distance to consider?
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Grumpy_Mike

Quote
I thought a BT module or WIFI board would work fine sealed in a submarine.

No they would not.

Quote
Radio communication reflects off water?

No the water changes the wavelength of EM waves. It makes them longer, that means the antenna are no longer tuned up correctly. Plus the fact that water absorbs the radio waves. Submarines have to trail very lone wires, in the order of a few miles to compensate for the change when receiving signals with only a Km or so wavelength. With UHF you have no chance.
Try it and see. 

dc42

#8
Jan 19, 2013, 12:08 am Last Edit: Jan 19, 2013, 12:10 am by dc42 Reason: 1

I'd like to achieve 4.5 foot depth underwater.  I thought a BT module or WIFI board would work fine sealed in a submarine.  Radio communication reflects off water? Also, what if I heat shrink-wrap an ultrasonic ping sensor, mount it on top the hull and use it for obstacle avoidance?  Will the chirp and echo work underwater?


The problem with taking transducers designed for air and using them underwater is that you get a very bad acoustic impedance match. So very little of the ultrasonic energy that the transducer generates get transmitted into the water, and very little of the reflected energy in the water makes it back to the transducer. It's the same reason as why when you swim underwater, you can't hear the noise above the surface.
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encryptor



I'd like to achieve 4.5 foot depth underwater.


Are your sender and receiver going to be directly on top of each other, or do you also have a horizontal distance to consider?


Let's say it's going to be in a hotel indoor pool.  Also I'm not going to be on the edge of the water surface with the remote.  I'm going to be standing with the remote 4 feet above water.  I know the IR receiver works in any direction horizontal, vertical, diagonal at least indoors with a direct line of sight, so I don't understand why I'm asked how much horizontal I'm aiming for.  To give an answer though, I would like 10 feet out from pool edge.
peace*&^

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