Diver buddy pinger

[scubalifer]

I agree with doc on this one. In low vis, I can turn around and my buddy stopped to look at something and I can hardly see them. The more entanglements, the more I stop turn around and "look" at them. I would think, although with the best intentions, this device would cause many divers with already poor buddy skills to get worse. The "I dont have to worry unless this squawk box goes off" mentality will sure to develop. When you are in a dark cold environment and you turn and dont see your buddy it is not a good feeling so you go and back track or do other "find your buddy" things (skipping details). But after a while I would be afraid you would look back and think well I haven't been paged so he'll be along soon Ill just wait. Meanwhile buddy is trapped, narc'd, tox'd, ad infinitum. i.e. cant reach his pager cant respond and now its too late.

Look what the t.v. remote has done. I dont ever get off the couch.

 

[miketsp]

Ok, a case in point, buddy and I in 5-10 feet vis descending to the thermocline where viz opens up to 20 feet. I look at my computer to gage descent rate, I look back to my buddy aqnd guess what...no buddy visible...continued to thermocline, looked for about 30 seconds and found him, however, on other occasions had to surface and sync back up. With the dive pinger could have got direction and we wouldn't need to surface to sync back up.

Out of air is only one of a dozen possible scenarios that can occur, entrapment, medical issues, injuries any of it can result in a need for your buddy. Believe me it can only take a few seconds for you to lose your buddy, even when you do everything correctly in low viz. Shot, something as simple as mask flood/fogging can get you out of sync just long enough.

Mike

Direction finding based on reception of an ultrasonic sound ping across a thermocline may get pretty messed up.
I also suspect that to get any sort of directional precision would require a certain sensor spacing - certainly more than a couple of inches. Returning to a comment from the OP you'd also need at least a third sensor to resolve which of the two alternate bearing lines generated by only 2 sensors is the correct one.

 

[wcl]

Ummm ... user error, not device problem ...

Lord knows if we used this logic on dry land, 30% at least of drivers would have their traction control and antilock brakes and airbags removed from them.

I'd still want it. When properly used, it ehances saftey.

Cheers,
Walter

I agree with doc on this one. In low vis, I can turn around and my buddy stopped to look at something and I can hardly see them. The more entanglements, the more I stop turn around and "look" at them. I would think, although with the best intentions, this device would cause many divers with already poor buddy skills to get worse. The "I dont have to worry unless this squawk box goes off" mentality will sure to develop. When you are in a dark cold environment and you turn and dont see your buddy it is not a good feeling so you go and back track or do other "find your buddy" things (skipping details). But after a while I would be afraid you would look back and think well I haven't been paged so he'll be along soon Ill just wait. Meanwhile buddy is trapped, narc'd, tox'd, ad infinitum. i.e. cant reach his pager cant respond and now its too late.

Look what the t.v. remote has done. I dont ever get off the couch.

 

[wilkie]

Not a bad idea, especially for low viz. I proabably wouldn't buy a set - cause I'm a warm water wuss, + I dive with a buddy that I trust - But it's not a bad idea at all.

 

[RiverRat]

If this technology were to take off, I would think maybe someday it would get incorporated into dive computers. Easier to sell it that way as most divers don't have a problem dumping bucks on a DC. Develop it and sell it for big $$$.

 

[Don Burke]

How about a dive computer that picks up the signal from the other diver's wireless air pressure sender and gripes if it loses the signal for more than about 20 seconds?

If the manufacturers could get together on the signal protocol, that just might work.

The capability to send a distress signal and to receive a recall signal from the boat would be pretty easy to add.

Pingers (I would actually use a responder) for those who do not use wireless pressure senders could be produced fairly cheaply.

 

[RayJayJr]

Hi, I've been toying around with this idea myself - and based on only a nightfull of research I've concluded that it is highly unlikely that it would be possible to acomplish this.

There are a host of challenges with small-package underwater communication:

The main difficulties lie in the fact that signal attenuation (attenuation being the loss of ability to transmit) in salt water is massive and the power output requirements for such a device would have to be very high. Additionally, depending on the frequency used, you may require a very large antenna. Anything longer that a foot is impractical, and in the most extreme cases, the antenna may need to be in excess of several kilometers long to work correctly.

A device operating under VLF (very low frequency) or ELF (extremely low frequency) is also subject to all sorts of laws - If you made a device that within VLF or ELF range, you could very well be violating local, state, or federal law.

You also need to account for Guassian Noise (re: shannon-Hartley Theorm) which relates to the bit-rate at which the device would be able to operate with little to no likelyhood for erronous data. The device's bit-rate would be extremely limited and you wouldn't be able to perform CRC checks on the data (i think??) so you be pretty limited in functionality.

The whole concept is rather complicated, and I haven't even begun to scratch the surface, in part because I dont know enough to conclusively post anything else without more research. Even for a very skilled person, reliable underwater comm devices that would not interfere with safe diving practicum is by and large impossible at this point.

If you find information that suggests otherwise, post it here or PM me and we can discuss it!

Cheers.

 

[miketsp]

Hi, I've been toying around with this idea myself - and based on only a nightfull of research I've concluded that it is highly unlikely that it would be possible to acomplish this.

There are a host of challenges with small-package underwater communication:

The main difficulties lie in the fact that signal attenuation (attenuation being the loss of ability to transmit) in salt water is massive and the power output requirements for such a device would have to be very high. Additionally, depending on the frequency used, you may require a very large antenna. Anything longer that a foot is impractical, and in the most extreme cases, the antenna may need to be in excess of several kilometers long to work correctly.

A device operating under VLF (very low frequency) or ELF (extremely low frequency) is also subject to all sorts of laws - If you made a device that within VLF or ELF range, you could very well be violating local, state, or federal law.

You also need to account for Guassian Noise (re: shannon-Hartley Theorm) which relates to the bit-rate at which the device would be able to operate with little to no likelyhood for erronous data. The device's bit-rate would be extremely limited and you wouldn't be able to perform CRC checks on the data (i think??) so you be pretty limited in functionality.

The whole concept is rather complicated, and I haven't even begun to scratch the surface, in part because I dont know enough to conclusively post anything else without more research. Even for a very skilled person, reliable underwater comm devices that would not interfere with safe diving practicum is by and large impossible at this point.

If you find information that suggests otherwise, post it here or PM me and we can discuss it!

Cheers.

I think you're committing a fundamental error in assuming that the only solution would be elctromagnetic propagation. Sure in this case you run into the problem that lower frequencies propagate with less attenuation but require large antennae whereas high frequencies using smaller antennae are subject to high attenuation and short distance operation.

As most posters on this thread were discussing, a divers system would probably be more conveniently designed around ultrasonic transducers. Just look at the number of relatively cheap depth sounders on the market, many of which are portable with low battery consumption eg
http://www.sailgb.com/c/forward_looking_sonar_echo_sounders/
The first one shown operates at 200kHz and gives 30hrs battery life.
The range is 60m and remember this depends on a weak echo.
If such a unit were modified to allow modulation and the return signal was coming from another active unit I would imagine a range of 200m+ could easily be achieved.
A buddy more than 200m away would not be much of a buddy so I would consider this adequate.
A 200kHz carrier frequency could easily carry low quality voice and a slow data stream with CRC.

 

[RayJayJr]

I think you're committing a fundamental error in assuming that the only solution would be elctromagnetic propagation. Sure in this case you run into the problem that lower frequencies propagate with less attenuation but require large antennae whereas high frequencies using smaller antennae are subject to high attenuation and short distance operation.

As most posters on this thread were discussing, a divers system would probably be more conveniently designed around ultrasonic transducers. Just look at the number of relatively cheap depth sounders on the market, many of which are portable with low battery consumption eg
http://www.sailgb.com/c/forward_looking_sonar_echo_sounders/
The first one shown operates at 200kHz and gives 30hrs battery life.
The range is 60m and remember this depends on a weak echo.
If such a unit were modified to allow modulation and the return signal was coming from another active unit I would imagine a range of 200m+ could easily be achieved.
A buddy more than 200m away would not be much of a buddy so I would consider this adequate.
A 200kHz carrier frequency could easily carry low quality voice and a slow data stream with CRC.

This is definitely true - but I decided not to even discuss this because I think the cost would be too high per unit.

A microcontroller could easily put you out 75-350 dollars depending I guess on how sophisticated the pinger is going to be. This, plus the cost of the sounder, plus the cost of redesigning or fabricating a new package for the unit, plus production costs per unit would probably make it a fairly hard sell for most divers wouldn't it?

I'm cheaper than some divers though...

EDIT:

But...for a personal item that you built at home as a project I guess it would work. Maybe you could find the sonar sounder's in pieces and just purchase what is needed to make the cost less prohibitive?

 

[miketsp]

This is definitely true - but I decided not to even discuss this because I think the cost would be too high per unit.

A microcontroller could easily put you out 75-350 dollars depending I guess on how sophisticated the pinger is going to be. This, plus the cost of the sounder, plus the cost of redesigning or fabricating a new package for the unit, plus production costs per unit would probably make it a fairly hard sell for most divers wouldn't it?

I'm cheaper than some divers though...

EDIT:

But...for a personal item that you built at home as a project I guess it would work. Maybe you could find the sonar sounder's in pieces and just purchase what is needed to make the cost less prohibitive?

I only gave the example of the echosounder to show what can be achieved. If they can sell it for that price the real cost is much lower.
I wouldn't use it as a basis for such a project.
A quick search on the internet for piezo ultrasonic transducers turned up a variety of products from very cheap to very expensive according to the type of encapsulation, precision and frequency range.

I would certainly not expect to spend much over 100USD on electronics. The real trick with such a project is to get the right balance between analog and digital processing.