Long term ROV project

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leeinmt
Posts: 27
Joined: Jun 9th, 2013, 4:41 pm

Long term ROV project

Post by leeinmt »

My ROV project is about half done and sure is fun:

1. Basic external frame is 8” (20 cm) square, 2 foot (60 cm) long, made from 1/2” (13 mm) pvc pipe. Cheap, easy to work with, and doesn’t corrode. Frame has many holes and is thus ‘wet’ when diving. Not glued, but secured with stainless cotter pins for later disassembly.

2. This frame contains two 2 inch (50 mm) side by side pressure chambers (pvc pipe) that holds two Mobius HD cameras and all the electronics at atmosphere. The cameras look through 1/2” (13 mm) thick Lexan end caps that have grooves machined into them to accommodate the pvc pipe. Concentric O rings in these grooves make the seal against water pressure. Why 2 cameras? 3D for depth of field. The Mobius has live video out.

3. A third 3 inch pvc pipe mounted under the two pressure chambers serves as a buoyancy tank. It is divided into three internal compartments and operates from a scuba diver ‘pony bottle’, whose valve is controlled by a very fine adjustable gear motor. This allows buoyancy control not dependent on thrusters. Small pumps move water front to rear to control center of gravity, and in & out for buoyancy.

4. Only two actual thrusters mounted outside the frame halfway between front and rear, driven by brushless motors secured to the rear of the frame. The motors are inside pvc motor pods encapsulated in mineral oil so no worry about sealing against water pressure. The motors can run forward, reverse, or opposite, thus providing the maneuverability of turning left, right, forward, and reverse - sort of like a Skidsteer.

5. Front and rear elevators (as in RC aircraft) mounted on upper frame to control vertical movement when moving through water.

6. Robot arm mounted on top at front of frame for picking stuff up. Six axis of movement.

7. Lot of online research on underwater photography lighting. Best approach seems to be two filtered LED mounted to illuminate from left and right angles to minimize back scatter glare.

8. All of this controlled via tether connected to older JR RC 72 MGZ Transmitters that have the DSC jack connector (direct servo control). This allowed RC hobbyists to check their servos without transmitting a radio signal causing their friend’s airplanes to crash. This was before RC went to the 4 Gig that is used now.
This DSC signal goes through 2 thin wires directly to the receiver - I have tested it through phone cable as long as 400 feet (110 meters). Controls 10 functions with only 2 wires.

Many problems still. Struggling with Arduino. Can't seem to get my head around it and I will be needing it for sensors.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: Long term ROV project

Post by bigbadbob »

Hi Lee.
The forum seems very quiet these days.
The old threads are still good for reference though.
Good luck with the arduino, code can drive you sensless after a while. :lol:
leeinmt
Posts: 27
Joined: Jun 9th, 2013, 4:41 pm

Re: Long term ROV project

Post by leeinmt »

Thanks
I bought the arduino novice kit that came with various components and am experimenting. It's like learning another language. I used to program in Fortran, Machine, BASIC, but this is another creature.
Right now, I am making the motor pods water proof with O rings and silicone rubber glands for the brass shaft to exit. The pods will be filled with very light mineral oil so as not to worry about water pressure at 150M depth. How to fill them without air pockets is a challenge, but I think I have it figured out. I will try to send photos.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: Long term ROV project

Post by bigbadbob »

So many languages... so little time. haha, know the feeling.
I like the oil pod idea. :-)
you could try a hyperdermic syringe for filling, if you can get the needle down the side of the shaft, the air can come out around it as you inject oil in.
pics would be good, I use flikr to host them these days since photobucket started charging for linking to pictures.
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