Homebuilt ROVs Forum

Hi, I'm new to the forum but have been working on building an ROV for a couple of years now.....ever since my son lost his waterproof camera off a dock and I vowed to retrieve it!!
I've done lot's and lots of thinking about solutions to problems, read what others have done and formulated some of my own ideas. Here's what I've come up with:

2 Veleman 2 wire 10 channel boards for 20 total control channels- built and working
3 thrusters with 1/4" oil seals - built and working
camera, Panasonic color security camera and enclosure - built and working

tether:
I've decided to use a tube with just the stranded cat6 wires run inside (2 pair-control, 1 pair-video using baluns, 1 pair-120v power). I've bought 100' of 1/4" ID (3/8" OD) polyurethane air hose for the tubing, if it all works well I'll eventualy add more length. I've experimented with the tubing and have found that 4 pair of 24ga wire is positively bouyant and 3 pair of 24 ga and 1 pair of 20 ga is very slightly negative....what's better, slightly + or _? I'm going to pressurize the tubing with a small 12v air compressor at the surface and let the air bleed through a check valve at the ROV. This will serve three purposes....

1-pressure compensate the components of the ROV to minimize water leakage (I'll connect everything with very small diameter tubing...even the thrusters)
2-Use a pressure gauge on the surface and use it for the depth reading
3-I think the bubbles which are vented from the ROV will help locate the ROV's position from the surface.

I found 100' Dewalt 1/4" poly air hose online for $29 plus shipping from Home Depot online store. It's yellow too!!

control:
2 joysticks and various switches...all bought but not assembled

monitor:
7" lcd tv with inputs...bought ($24 from Newegg.com last week)

camera tilt:
motors and gears bought but not assembled yet

about all I need to buy at this point is a small air compressor and a tether hose reel ($29 from Harbor Freight). I have a 1000w voltage inverter to supply 120V to the ROV along with a GFCI for safety and the battery. I'm thinking of using an old laptop charger (4a?) to keep an onboard battery (12v 7a) charged)

I'm going to get focused on the project within the next week or so as I have a self imposed deadline of August.
This system is a simple no frills project so I've kept the computer out of it on purpose...I'm using the KISS theory! (keep it simple stupid)

Once I get this all up and running I'm going to add an arm with a grabber.....that's what all the other control channels are for.

So, what do you all think? Let me know.

Bill

Sounds like you have everything under control and well planned out. How about posting some pictures as you get nearer to completion so some of us just in the planning stages can get some other ideas?

remember NEVER to charge the internal battery without having the pressure hull opened, and ventilated, to atmosphere! Hydrogen loves to blow.

I read this article today about pressure comped batteries:

http://www.deepsea.com/pdf/articles/Sea ... UI2010.pdf

"...G. Battery charging should be possible with the battery installed in the underwater system as long as
the operator is able to inspect for outgassing and open the vent if needed. The charger must be
designed to limit charge rate and total charge to minimize gas generation."

The above being an excerpt from the PDF pointed at by SeaDragon (Thanks!). The writers assume an ROV operation can afford to have personel doing only one thing at the time, i.e., watching the battery while it charges. That maybe so, but trust me, it is not something you CANNOT afford to do. If your battery is not being vented to atmosphere while you charge, you better have a very good understanding of your charger, your battery, and your clues as to when switch the charging modes. Be safe, vent.

now, if I could only find one of those compensated battery at my local recycling depot...

Thanks for the input

The battery I have is a gel cell and, it will be vented:

add purpose #4 to the following:

I'm going to pressurize the tubing with a small 12v air compressor at the surface and let the air bleed through a check valve at the ROV. This will serve three purposes....

1-pressure compensate the components of the ROV to minimize water leakage (I'll connect everything with very small diameter tubing...even the thrusters)
2-Use a pressure gauge on the surface and use it for the depth reading
3-I think the bubbles which are vented from the ROV will help locate the ROV's position from the surface.
4-vent possible hydogen gas from the battery enclosure

The batteries on the turtle were charged off the vehicle and had vent on the cover. the battery cases were filled with drakeol 32 to evacuate air out of the batteries and the battery case. there was a vent at the top to eliminate the hydrogen. There are several battery vent options but one thing is sure hydrogen is flammable at 4% concentration and explosive at 8% concentration.

So safe venting is possible but I agree charging the batteries off the vehicle is a best safety practice

will work on best option for comped battery venting

willlgord wrote:Thanks for the input

The battery I have is a gel cell and, it will be vented:

add purpose #4 to the following:

I'm going to pressurize the tubing with a small 12v air compressor at the surface and let the air bleed through a check valve at the ROV. This will serve three purposes....

1-pressure compensate the components of the ROV to minimize water leakage (I'll connect everything with very small diameter tubing...even the thrusters)
2-Use a pressure gauge on the surface and use it for the depth reading
3-I think the bubbles which are vented from the ROV will help locate the ROV's position from the surface.
4-vent possible hydogen gas from the battery enclosure

The air concept is intriguing I think that it changes the displacement of the vehicle. It should be ok for shallow water. The real problem I think would be having pressurized air/hydrogen/and potential sparks from relays and electronics. also worried about active compensation pressure, It doesn't take alot of pressure to blow out an o-ring or to crack a case.

Here is a drawing of the ROV I'm working on. Eventually I'm planning to work at a depth of around 200' (around 100psi) but will start with a 100' tether. As far as concerns for a hydrogen explosion go, the batteries will be in a vented, seperate enclosure. If it were still a concern I could use a compressed gas to equalize the pressure or switch to some other sort of battery such as nimh or nicad.

I don't understand what you mean by the displacement of the ROV changing, could you explain this?

Thanks for the input, Bill

with oil as pressure compensator the displacement is less than air. The air volume makes the floats and control box displace more water.

cool drawing wish I could draw like that.