Could someone please explain to me how the sonar modules sold by Lynxmotion and Parallax are read by the microcontroller? I have an RC Submarine with some extra space in the watertight compartment and I figured real submarines use it so why can’t I. The only obstacle I would predict would be keeping the sonar unit dry. Can this be done?
It won’t work installed inside a water tight sub because the PING sensor would keep receiving the sub’s outer wall. It works different from sonar.
If you have it inside the sub, it will send a sound wave out untill it hits a solid object, (the subs outer shell) and then it would bounce back to the sensor.
What if you mounted the transducer “wet,” outside the water tight compartment? I know of a surplus house that sells them for about a dollar each so if they don’t last long I have not wasted a significant amout of money.
I second Mike’s concerns about the hull. As for mounting it wet, I’m not sure, but I think you need MUCH lower frequencies for working in water.
I don’t think this would work in water.
It is designed to work in the air and the lead contacts would need to be water tight to prevent a short. The construction of the sensor might not be water tight, so even if you protected the contacts the water may leak in elsewhere. Also, if you were to make it all water proof, there is the problem with the sound traveling though the water in a usable manor.
I’m not saying it can’t be done because I have never tried it, but I can see where there would be several problems.
there are some ROV groups that have had discussions like this. the general solution if im remembering correctly has been hacked fishfinders or your own circuit with a wet transducer. id start there but i question the usefullness of the device, RC subs never get really deep (signal loss in water), and are usually visible.
nick
I built a sub in an afterschool program, a few years back.
The only thing that I can vouch for is…
IT’S DAMN HARD TO KEEP WATER OUT OF IT!
I’m not trying to discourage you, just letting you know what you’re in for.
Thanks for the opinion guys. I think I’m going to do a little experimenting in the future.
A ‘sonar’ made for use in air will not work in water for several reasons like those already mentioned, but more importantly because the water will tend to conduct the sound from the emitter directly to the detector. You would not (realistically) be able to filter out this signal, and still hear the echo from another object that is nearby.
In real subs, they are detecting objects whose distance is measured in yards or miles. It works because the echo takes a relatively long time to return (and because it’s mega-sophisticated gear!).
What I described above is “active sonar”. It involves the familiar ‘ping’ sound seen in movies and such. Subs that are trying to stay hidden (which is most of the time) will use things like “passive sonar”, which is mostly a sophisticated microphone system. Using your active sonar gives away your position - it’s like sending up a flare. The purpose of passive sonar is to listen to noises generated by other boats, by fish, etc., and use that audio information to determine what’s around you. There’s some very complex signal processing involved. Meanwhile, the sonarman on the sub can listen to sounds such as those from an adversary boat, and tell you what type of boat it is, such as “Soviet Kilo-class”. The computers can study the sound in enough detail to tell you which Kilo-class boat it is (by name).
Pete
Pete,
I know the difference between active and passive sonar, I was aiming for the passive route because I would have liked the sub to have a sound seeking behavior. Well I guess that project went out the window. I think I’ll read up more on hacking fish finders…
One way I have found to waterproof things is by using regular hot glue. Easy to apply and mold to your needs, and waterproof as long as the surfaces are clean (a little texture seems to help also) and do not flex much (or at all).
As far as the issue of that sonar working in a wet environment, I have NO experience in that area, but as several other people have mentioned, I imagine the frequencies are quite a bit different.
I imagine you could rig up some sort of passive listening system fairly easily though. Do a search for “personal hydrophone” and you’ll find what you’re looking for, I think. I found several small personal type ones in the $100-$200 range, but I’m sure you can find them cheaper.
If you decide you want to do active, you’re probably looking at a much more expensive (and complex) system. You not only need a sending unit, but a receiving unit that is precisely timed to the sender as well. As someone above mentioned, your best bet on that is probably hacking a commercially available system such as this personal sonar unit.
You might be able to get some better help from a local dive shop. Its been over a decade since I’ve SCUBA dived, so I have absolutely no idea what the latest and greatest toys are nowadays.
Mike
Thanks Gemini, I wish they had developed personal underwater sonar units for divers that are cheap, but we aren’t there yet. I used to work at a diveshop before school started and I’m sure that we didn’t sell anything like that for less than 1500$. They are primarily used for archaeological dives and exploring caves and such.
According to this url: 64.233.161.104/search?q=cache:X0YNd4f2ckAJ:www.jawsclub.org/newsletters/JawsScubaNews1997_02(Feb).html+%22dive-scan%22&hl=en (you may have to click cancel on the password box), it cost $300 retail in 1997. This board does not seem to like the complex URL, so you’ll have to paste that into your browser, sorry.
I could not find them anywhere else on the net, including e-bay, but I did find this.
One of the guys I jump with is also a cave diver, and would probably know what sort of hardware is out there and what it costs. Unfortunately, he just left for a few weeks diving in some system near Florida, so I won’t be able to ask him for a while. I’ll ask around locally and see what I can find out though.
Mike
as far as waterproofing goes there are urethanes and epoxies that are acoustically transparent which Im sure would work well(because they are used for the commercial transducers)
Im not quit sure what your after but if your trying to have your sub autonamously navigate through a pool or something using just simple range type sonar I think its entirely possible and a cool idea. Personaly I would just pick up a few of these amazon.com/exec/obidos/tg/detail/-/B0009AHKOK/sr=1-9/qid=1137376318/ref=sr_1_9/102-6459198-1732902?%5Fencoding=UTF8&n=3409021&s=sporting-goods&v=glance
or the transducers in them atleast(the most expensive part). I would think as long as you had a microcontroller with a fast enough clock you could do it. Just make sure that each of the transducers operates on a different frequancy so they dont see eachothers pings. Fish finder transducers are going to be a lot more expensive since they have to be sensitive enough to see and calculate the sound waves going through the fishes swim bladder.