Author Topic: Underwater to Surface Wireless Comunication (Read 2598 times)

voyager2 · « **on:** August 30, 2010, 07:45:22 AM »

Hi All
First thing, this is for my fish (I bet you guessed that anyway)
I need a for my fish to communicate with my computer 2-4 meters away.
The fish end needs to be as small as possible, 2cm³ is probably max size.
The computer end doesn't really matter, so long as it is either USB or serial, and works with Hyper-Terminal.
And it can't be really expensive either...

Apparently water blocks radio waves, but how does a remote control sub work then

Voyager2

madsci1016 · « **Reply #1 on:** August 30, 2010, 08:02:18 AM »

Water slows down the propagation of EM waves. A toy sub at a low enough RF frequency will work for a meter or two before the effect kills the signal. 2.4Ghz will hardly go a few inches. You can try to find very low frequency radios, but it would be 100x easier to just use a tether.

The proper underwater robots i use at work (I work for the Navy) have acoustic modems to communicate underwater.

Razor Concepts · « **Reply #2 on:** August 30, 2010, 08:03:04 AM »

Rc subs use the low frequency range which can work in shallow depths, its the high freq stuff that gets blocked very easily.
I would recommend just using a tether system, it is just so much easier to do so. If youve seen some robot fish in research, they start out tethered which makes it easier to focus on more important problems, not annoying things like batteries and recovery

Hawaii00000 · « **Reply #3 on:** August 30, 2010, 02:28:19 PM »

How about ir leds? It would be limited to line of sight, but its cheap.

SmAsH · « **Reply #4 on:** August 30, 2010, 02:51:15 PM »

Im going to say tether it with ethernet cable or something similar.

Metal Slug 2 · « **Reply #5 on:** August 30, 2010, 05:33:23 PM »

Quote from: Hawaii00000 on August 30, 2010, 02:28:19 PM

How about ir leds? It would be limited to line of sight, but its cheap.

Careful with that one, because unless the IR leds are underwater, you will limited to a line of Refracted sight

madsci1016 · « **Reply #6 on:** August 30, 2010, 05:41:03 PM »

Quote from: Hawaii00000 on August 30, 2010, 02:28:19 PM

How about ir leds? It would be limited to line of sight, but its cheap.

Your not going to get much out of that either. Red light is rather weak, IR even weaker. It will absorbed by the water rather quickly.

voyager2 · « **Reply #7 on:** August 30, 2010, 07:59:14 PM »

If there's such a thing a Infra Blue, I might try it out, non of you ever read one of these optics books?
Well Blue and Greens travel well through water, that's way the oceans blue-green.
Red and yellow is quickly absorbed due to its short wavelength!

I don't mind tethered, but since part of the fish is likely to be above water it might be possible to have a link...

voyager2 · « **Reply #8 on:** August 30, 2010, 08:37:10 PM »

I was thinking though, is it possible to use long-wave?
Blue light has long waves...

Or should i make a 555 timer transmitter (I've heard its possible) that transmits at 64 Hz?

chelmi · « **Reply #9 on:** August 30, 2010, 08:50:13 PM »

Quote from: voyager2 on August 30, 2010, 07:59:14 PM

If there's such a thing a Infra Blue, I might try it out, non of you ever read one of these optics books?
Well Blue and Greens travel well through water, that's way the oceans blue-green.
Red and yellow is quickly absorbed due to its short wavelength!

http://en.wikipedia.org/wiki/Visible_spectrum

Red has a longer wavelength than say blue or violet.

Infra-blue would be ... cyan I guess ? I think that's not what you meant

Higher frequency is ultra-violet. UV LEDs do exist, but I doubt it will solve your problem.

Metal Slug 2 · « **Reply #10 on:** August 30, 2010, 08:59:11 PM »

Quote from: voyager2 on August 30, 2010, 07:59:14 PM

If there's such a thing a Infra Blue, I might try it out, non of you ever read one of these optics books?
Well Blue and Greens travel well through water, thats way the oceans blue-green.
Red and yellow is quickly absorbed due to its short wavelength!

Infra-blue, interesting. Based on the latin meaning for the term 'infra', which is "below", (because Infrared has a Lower frequency than red) wouldn't "infrablue" then just work out to be a green?

Perhaps some ultraviolet data communication system might work. That way you could wirelessly communicate with your fish, AND possibly disinfect your fishes aquatic environment at the same time!!!

blackbeard · « **Reply #11 on:** August 30, 2010, 10:00:42 PM »

what about something like a 100mw green laser? have one on each end and a system that aligns it and with sensors to receive the data as pulses?

voyager2 · « **Reply #12 on:** August 31, 2010, 06:32:12 AM »

Since part of the fish is likely to be above water in the early stages of development, IR might do...
I've got some IR leds and a photo resistors, but my guess is that a photo resistor doesn't react fast enough...
I think i have some photo transistors, from a computer mouse, they might be fast enough, i'll have to test them.
Also two way would be nice...

@Chelmi
http://en.wikipedia.org/wiki/Visible_spectrum#Spectral_colors
Top right, wavelength is measured in nm (nano-meter)

@Blackbeard a system like that could work for 100s of meters, however it would be large and cumbersome, however it would be useful for larger systems.
It would be limited by the horizon and refraction (and line of sight).

chelmi · « **Reply #13 on:** August 31, 2010, 10:35:43 AM »

Quote from: voyager2 on August 31, 2010, 06:32:12 AM

@Chelmi
http://en.wikipedia.org/wiki/Visible_spectrum#Spectral_colors
Top right, wavelength is measured in nm (nano-meter)

Yes, I know that. Your sentence "Red and yellow is quickly absorbed due to its short wavelength!" did not really make sense since blue has a shorter wavelength and is less absorbed.

waltr · « **Reply #14 on:** August 31, 2010, 11:29:36 AM »

I did a google search on "absorption of light in water" and found these articles that seem to be more on subject.

http://www.d-a-instruments.com/light_absorption.html
http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_10.htm

As to a link to the 'fish bot', low frequency radio does work. One can easily receive AM broadcast stations (550-1550kHz) several meters or more under water. Here is a link on this subject:
http://www.qsl.net/vk5br/UwaterComms.htm

This would restrict the data rate but for simple commands this should be a problem

voyager2 · « **Reply #15 on:** August 31, 2010, 09:02:03 PM »

Low frequency radio, seems like a good challenge to make one myself...
All the fish is sending is light levels, and in the future battery level info, it's not like it's sending live feed video.
Could I use a 27MHz toy car transmitter? I've got 2, and there pretty small.
I'll see what else i can do...

blackbeard · « **Reply #16 on:** September 01, 2010, 05:12:25 AM »

Quote from: voyager2 on August 31, 2010, 09:02:03 PM

Low frequency radio, seems like a good challenge to make one myself...
All the fish is sending is light levels, and in the future battery level info, it's not like it's sending live feed video.
Could I use a 27MHz toy car transmitter? I've got 2, and there pretty small.
I'll see what else i can do...

you can try but AM is much better since it operates at a much lower frequency. AM is an absolute pain in the ass so expect as much though.

voyager2 · « **Reply #17 on:** September 01, 2010, 05:26:55 AM »

I think I'll try the IR LED approach, it's not like I'll be using a bootloader to program...

Metal Slug 2 · « **Reply #18 on:** September 01, 2010, 06:24:50 AM »

Sounds good. I would first try using a tether for communications, and then go for IR. You could probably get away with quite small gauge wire for the tether also, as the water would probably dissipate any heat pretty quickly.

voyager2 · « **Reply #19 on:** September 01, 2010, 06:50:23 AM »

I have some ultra thin wire from a PS2 controller cable, I can tell that IR is not going to be good for bootloading

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Author Topic: Underwater to Surface Wireless Comunication (Read 2598 times)