Let's Make Robots!


This spring I’m trying to build a ROV for me and the kids to play with in the summer. I’m trying to make it as small as possible so it’s easy to carry and bring along.
Instead of feeding power down the tether I use a 12V 1.2Ah lead acid battery as the power source and ballast. There will be a webcam onboard and the only signals going down the tether is serial signals to control the motors and video signals up to my laptop.

The control box contains an Arduino and two thumb joystick. The Arduino translates the joystick input and sends serial information down to the serial motor controller http://www.pololu.com/catalog/product/1110 . Sins I have 3 motors I had to daisy chain two boards.

The hardest part to get built is the stuffing box. Luckily my brother has contacts that could machine them for me and they came out great.
Still waiting for the USB webcam to arrive and can’t do much testing before it has been mounted. When everything is assembled and found working (and balaced) I will coat the ROW with Plasti Dip to seal everything. http://www.plastidip.com/home_solutions/Plasti_Dip


Project update: 23/5-2010

Problem 1
With all installed the ROV has a negative buoyancy.
Remedy: Buy more 40mm PP tube and extend the connection joints. Some wiring also has to be lengthened.

Problem 2
My 35mm propellers at 1000RPM is not giving me enough thrust.  So I will be ordering some new 3-blade 52mm ones and hope that they will give me some more thrust.

Problem 3
With my 15m of cable the USB webcam is not giving me an image. The pc recognizes the device but the cable (a CAT5) is probably too long and I’m running into some sync issues.
I found some USB to CAT5 extenders that might help.
I need to hack them in order to make them fit into my tube and control box.
Has any of you any experience with USB to CAT5 extenders?

-- end of update --

Project update: 10/8/2011

This project has been on the backburner for over a year. I was about to scrap the whole project but my brother convinced me to have another go at it. So now I’ve pretty much ripped the whole thing apart. Thrown away my control box and started over.

So this is my new approach;

Using a USB based webcam didn’t work. So I have ordered a cheap CCD camera of eBay, together with a 7” LCD monitor. This is probably a good think as I can mount the joystick and monitor in a bigger box and there will be no need for a PC.

I have got the new propellers and rebuilt the shafts. It looks better but has yet to be tested.

One of my main problems was how to get a waterproof connection from the tether cable through my PP plastic plumbing parts. And mounting it on a round pipe made it even worse (PP plastic is almost un-gluable). So my solution became to add a 45deg t-fitting on the motors. That gave me a flat fitting with a regular garden hose adapter. These adapters come in and variety of different materials and will be much easier to work with.

I’m still not certain that this ROV will ever work, but I have a better gut feeling about this design than the last one.
The image shows most of the parts assembled and nearly all the of the wires.

My plan is to have the video signal and power in on the left side and the serial, error, and reset on the right hand side. They will be joined into a CAT-5 cable going to the surface.


-- end of update --


Mounting the thumb joysticks   

Inside the control box

The frame


Battery in place

 The main structure is mad from 40mm PP- pipefittings

The serial motor controllers and voltage regulator

Not much room

The stuffing box

Fill up with grease

Stuffing box assembled (updated: 19-05-2010)

And finaly mounted

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Nice! And really smart with "The stuffing box", I never thought of that way of doing it.

So, it will be made to just float, and a the propeller in the middle can take it down, is that it?

A thought; make a seperate chamber for the motors and whats behind them (propeller and the stuffing box). Isolate this completely, wather proof, and air tight. This way the grease will be less likely to push back into the rest, if you dive deep - because there will be no (less) air to press backwards. And shold something happen, it can still just float up to the sea.

Promise me to screen capture / video capture some diving, that would be awesome to see!!

Oh yes, and one addition / sugestion; A tiny and thin stick in the middle, pointing forwards. To hold bait for the fish :)

My aim it to have a small positive buoyancy so it floats to the surface when the system fails (not saying if, but when :-) ) and you are correct with regard to the center propeller, it will be used to pull it under or push it up.

What’s nice whit this design is that if I need more ballast it can be added down with the battery but  if I need more buoyancy the tubes holding camera an light can be pulled out giving it more volume. I’ll know more when the camera is installed.

When it comes to the stuffing box, it is mounted on the flange at the motor and bolted in place. So the grease can’t be pushed beyond the flange. The only place it can leek is between the stuffing box and the 40mm PP pipe, and there is where the Plasti Dip comes in making a waterproof membrane over the whole setup.

There will be video if the design isn’t a complete failure, -in which case this page will probably disappear :-)

Some bait for the fish is a great idea !!! Thanks.

"I need more buoyancy the tubes holding camera an light can be pulled out giving it more volume."

Oh, that is very smart!!

Did you consider the option of infra red light / switch to that mode in the light tube? The webcam will pick it up.

And I cannot stop being inspired by this, another idea, "The condition of the sleeping hunter":

Install an IR distance sensor (should be fairly easy, with the Leds out in the open) next to the fish-food. Let system sleep, apart from this circuit, simply detecting if there are changes in distance; When activity, system powers up, you get a Beep on the surface, and filming begins :)

Arh, I also want to play with this :D

That plastidip looks really cool, so you just spray it over the boat and it has a watertight coating? Seems to really beat the path of sanding/painting/clear coating. Can you dip circuits in there to?

As the plasti dip is rubber based I would think it would be a good insulator and you could probably dip a complete pcb into it and have it completely sealed. It’s worth a try.

Guess you would have to make the led lamp pan/tilt-able also?

The LED lights are more a cosmetic thing than a practical one. The ROV probably can’t go so deep that it has any practical use. I had an empty tube and thought it would be cool. :-)

I doubt if the extender you linked to will solve your signalling troubles. They look like passive connectors to me. Or at least the description on the e-bay page fails to convince me otherwise.

A passive cable is what you've got already. Unless these products actively process the signals (repeating or boosting), they will not make a differene.

Well for that price it’s worth a try.
Hopefully they are not just passive connectors and utilize the 5V from the USB port to boost the signal between the units. One would probably not get the full bandwidth of a USB 2.0 but if I get enough for a video feed I’ll be happy.
I will give you a report when I have tested it out.