Homebuilt ROVs Forum

I've been running around the bays for a couple of days using my new Lowrance StructureScan system (side scan sonar). One thing I've quickly learned is how hard it can be to get on top of a specific spot and then stay there. Once you drift off it takes some work to find the same location, even with GPS. One of the things I'd want to do with an ROV is send it down to investigate interesting structures found with my sonar. The visibility in the bays around here is good - for a bay! But not good for seeing much more than a few feet away.

This got me thinking about these new high resolution sonar systems and how nice it would be to have a forward facing sonar (they have them for big boats!). I almost collided with a sunken 40 foot sail boat Sunday. It was within two feet of the surface at the highest point. It was first spotted on the side sonar, but my downscan had showed it the highest part that I went over to be about 8 feet down. I did notice long shadows and should have heeded that better. Going back towards it to get a better scan, my wife suddenly yelled a warning and I stopped the boat immediately. It was HUGE and shallow!! All of this is on video around 3:20 at http://www.youtube.com/watch?v=e5ocaqkz ... ture=inbox

Anyway it would be useful to have at least a basic echo display on the ROV. I envision it being forward facing, but mounted on a swivel. The movement pace would be not unlike a typewriter. A 'slow' scan from left to right (typing) and then a quick return to the start position. Rinse. Repeat! Timed correctly, the information on the display would form a sort of forward picture ahead of the ROV. Yes it would be a scrolling picture, with the fast return making a distorted break between each slow scan pass. Most imporantly, distance measurement would be accurate. In theory this could be useful in navigating to a large enough target such as a sunken boat.

I know HumminBird specs allow a 50 foot extension on many of their units. Who knows what the ultimate limit would be. I know the low rez units only have a couple of wires and a shield. Downscan units have a lot more wires. The ultimate would be to use a Lowrance downscan unit, but that would set you back $300 at least. If the cable can't be extended, well there's always putting the display inside the ROV and pointing another camera at it. Best avoided though!

Sorry for my off the deep end thoughts, but they keep me going!

This is the image we got of the boat:

I should mention that this 'forward looking' sonar would still display like a bottom scan.. I guess you could say it would give you a forward looking profile view. It would look like there was no bottom but close objects should show up. I need to find a cheap transducer for the Humminbird 150 I've got and test the theory.

Have you searched the Humminbird forums for info? You're not the first to think of this and a couple folks have already tried this with some success. As for extending the leads on the Lowrance transducer here's a thread on the topic: http://www.geotech1.com/forums/showthread.php?t=18295 and here's the lowest cost forward scanning sonar I've found (bottom of the page) http://interphase-tech.com/shopsite_sc/ ... page7.html (although I never was able to find out if the transducer wire could be extended).

I would think you could use an imu to hold a position. They do the same thing with quadracopters and it works pretty well.

I made a video of my concept rov (design is based on the rov's I've seen on this forum). I forgot to add lighting but this video is mainly to show how the sonar would be configured. I'm going to start my rov project with buying a cheap sonar and testing this concept before I make any other part of the rov. Doesn't matter if it fails, just gotta satisfy a curiosity!

http://www.youtube.com/watch?v=JQzya9nQ60M&sns=em

NCUWI, I did run across that first forum you mentioned. Pretty interesting stuff they're doing with those fish and 'birds!

I've been having a look at sonar for a while and have come across a few options that might work

http://www.hackolog.com/2010/10/08/ardu ... ar-system/
http://www.mbtelectronics.com/side-scan-sonar.php

one if for a FFS and one is for a tow fish.

although i would prefer not having to lug a laptop around for sonar imaging it seems a decent option at the moments as sonar and fish finders are quite costly in ZA.

Regards

Turu

the first link you posted is for and ultrasonic range finder commonly used on robots. they don't work when you seal them up. I tried that here:

viewtopic.php?f=16&t=543

derelicte wrote:the first link you posted is for and ultrasonic range finder commonly used on robots. they don't work when you seal them up. I tried that here:

viewtopic.php?f=16&t=543

Has anyone considered placing the transducer flush against the base of a 35mm film container containing mineral oil?

A quick search also produced the following water resistant transducers.

http://www.mikesreelrepair.com/humminbi ... 99194.html which could be hacked to fit the requirements.
Alternatively there's this http://www.instructables.com/id/Hacking ... c-Sensors/

the difference in frequencies used by the air and water transducers is fairly substantial, so I'd guess that an air one won't work to well (if at all) when submerged.

Supposedly these http://www.robotshop.com/maxbotix-lv-ma ... der-1.html can be modified to work underwater, and all it takes is a little silicone. They're a little spendy, so I haven't tried that yet.

I'm getting one of these http://www.ebay.com/itm/Waterproof-Ultr ... 0721354139 in the mail soon. I'm hoping they can be made completely waterproof relatively easily. I'll post an update if it works.