turtle dude:
Wow, I’ve opened a real can of worns here haha.
The start of a project is the time to examine all the options, get all the info on the "table" so the best solution to actual problem is most likely to be the result.
turtle dude:
Most people are either happy to reel off or are much better at visual navigating than I am, i assumed (the mother of all f**k ups) that this would be a simply job of fitting a couple senders to a waterproof housing (housing battery and board for ping approx 1-2 pings per sec) and a receiver to diver mounted unit with screen showing distance and direction to senders (accurate to about 2-3 metres).
I don't know that it's really all that more difficult than you describe. One thing is that you won't get distance w/a simple pinger on the line and a receiver on the diver. Then again I would ask if this is really needed ? If it is then you need a 2 way communication channel btw the pinger and diver, similar in concept to how air traffic control gets distance from an aircraft's transponder (when in flight). I figure if the device tells you right/left bearing to the line and your Dc already tells you your depth then that's enough to get back "home" safely.
As for the device … a lot depends on how bling you want it to be. A heads-up display in your mask is uber bling and thus also uber hard and $$s. A box attached to belt (or ??) is much easier. The simpler the readout on the box, the simpler the design can be (and less $$). In it’s simplest form you could have an LED that says “I hear the pinger” and (perhaps) 2 other LEDs that tell you to “go right” or “go left” or (both on) “go dead ahead”. I might maybe even be able to do that kind of device w/o any microcontroller in the box (though I’m not sure that would be the smartest way to do it).
One thing I envision is that if you are completely lost as to which direction to go in, you’ll need to do a slow 360, aiming the box outward as you rotate until it’s pointed in the general direction of the pinger. Said another way, a simple design means the box can only hear the pinger and do it’s direction finding function when it’s pointed within +/-“X” degrees of the pinger, X to be figured out. If you want X really large, even omnidirectional so you don’t have to point the box, then yes you guessed it … it’ll be more complex (more hydrophones) and thus more $$s. And physically larger too … which is a good time to ask just how big a box would you like this to be ? It’s min size will be dictated by the hydrophones, those you’ll have to buy because I don’t think anyone here is versed in making such things.
One big design driver will be over what range must this work. What’s the maximum distance btw you and the pinger ? This will dictate how loud the pinger must be and how sensitive the box must be. It may also influence the ping frequency as high frequency sounds don’t travel as far a lower frequency sounds (I ran across an equation for that).
In the end I think your basic box would be something like 2 hydrophones, 2 pre-amplifiers for those hydrophones, either some analog circuitry or a microcontroller, a battery and it’s associated circuitry and whatever type of display you want. See, not all that complicated. I could see the addition of a 3’rd hydrophone to guard against certain potential problems and I could see all this eventually integrated into 1 dive computer.
The basic principle involved …
http://en.wikipedia.org/wiki/Acoustic_s … of_arrival
http://www.eng.uwaterloo.ca/~dcbickfo/i … zation.png
