Ultrasonic Depth Finder - RC Boat

[sn4il]

Hi there!
I'm building a RC Boat equipped with on board video system and gps waypoint navigation (just in case something goes wrong with radio signal).
I was also planning of adding a sonar.
All I need is to read current depth of water (up to 60-80') and send it via OSD (on screen display). OSD is not a problem, sonar is.
Do You guys have any ideas or know source of schematics that would help me achieving this point?
Regards,
sn4il

 

[dknguyen]

Here is the only waterproof transducer I know of:
The only "hobby" retailer I know that sells it:
http://www.hobbyengineering.com/SectionS.html
The manufacturer (specs):
http://www.prowave.com.tw/english/products/ut/uwtx/uwtx.htm

Now, if the depth is 80 feet, do you really need to measure it? It's an RC boat so it's small so you're limited. The transducer is 200kHz and in air this barely travels past 1.5m (but that's with a 300-500mW transducer). This is a 50W transducer however which is way more powerful than anything I've worked with, so it might just work at those ranges. There's also all that thermal water layer stuff bouncing sound waves back and forth and messing up readings, though I don't know what depth they kick in at.

That aside, it's pretty easy to generate an echo, especially if all you want is some sound and not a clean precise waveform. Use a piezo transducer for this. Cheaper and easier to drive (lower voltages). Of course, you don't have much choice since the transducer has to be waterproof too. It's also easier to drive high power inputs to transducers if you use simple methods that are just for ranging and not much more. All you have to do is drive a square wave through it (with a simple transistor connected to a 20V supply)with the same fundamental frequency as the resonant frequency of the transducer. The transducer filters out the adequately harmonics generates a modest waveform. You can also use an H-bridge type circuit for more drive. If you don't have 20V, you can also use some inductive flyback methods and stuff. It's in this article:
**broken link removed**

Receiving is also in the article.

 

[winterhunter]

Actually, yo do not need a waterproof transducer if the hull of the boat is fiberglass. Just make sure that both transducer and receiver are well coupled (acoustically) to the hull (you can use vaseline for this, if you make sure that no air bubles are traped inside it).

Regards,
Gonzalo

 

[ericgibbs]

hi sn4il,

You can buy yacht acoustic 150KHz/200KHz transducers, about 25-50 watts to go down to 50mtrs, 30cm dia, 10mtrs cable,
try your local marine chandlers shop.

If you can source a LM1812 semiconductor ic, youre half way to making a ultrasonic transceiver.
A circuit is on the datasheet at,,, www.datasheetarchive.com

As winterhunter points out, mount it inside your fibre glass hull, use vaseline,as advised, no air gaps.

Whats the size of the boat?

Eric