Control Options??

[Sterno]

I've been working on a low-cost Search and Recovery ROV and have been working towards a PC based control via USB (optic) or RS-485. Reading through the forum it seems that this isn't a popular option which makes me think I may be making the system more complicated than it needs to be.

I need a tether length of at least 900 feet as many lakes around here are over 500' and up to 850' deep. I will be controlling 5 ESC's, and a 3 axis manipulator with claw as well as lights and a tilt/pan camera.
My main concern is that the connection be reliable which is why I've shied away from Hobby RC remote controls. Video Integration (heading, depth, speed, etc.) is also desired which I had planned to do with software but most of you are doing with an on-board microprocessor and video overlay.

Power, propulsion, flotation and pressure housings have all been solved, all that's left is control and video and all input from the community would be greatly appreciated

Thanks

[thegadgetguy]

Welcome to the forum.
RS-485 would be a good serial protocol to use. What do you have going on ROV-side for control of your ESCs? Are you using a microprocesser?
When you say USB (optic) do you mean USB over fiber optic cable? As I recall that can be somewhat pricey.
If I understand your control scheme correctly, you want a computer topside for inputing control information and for displaying live data about the ROV, and you want to connect the computer to the ROV via a RS-485 or USB connection. Do I have this right?

I personally like this type of control scheme, but the main reason people shy away from it is because you, of course, need a computer, which just makes things a little more complex when it comes to setting up and such. It does, however, give you more flexiblity as to what you can do, since software code is easy to change around.

Since you'd like to use serial or fiber optic in your tether, you'll probably want to find a microprocesser that will work with either of those requirments (finding serial compliant devices is easier) and then make sure it can interface with your 5 ESCs and your Manipulator and any other accesories.

Also, what kind of camera scheme are you thinking about?

Well, that's my $.02

[Sterno]

I had planned to use a Pololu Mini Maestro 24 USB servo controller at the ROV end to control the ESC's and Manipulator servos, it also can be used as a data interface for compass, pressure etc. All processing would be handled topside, the ROV's internal electronics would be very basic. The Optic link for USB is the only option I've been able to find that will let me use usb 2.0 over a 1000' range (industrial USB range extender and yep, it's pricey). I would prefer USB over RS-485 simply due to the plug 'n play factor as new laptops no longer come with a proper serial port and rely on a USB dongle to convert to RS 232, or 485 for that matter. It's just another layer of potential problems imo.
USB 1.0 is too slow for video as the camera was to also be USB based, This way there's no need to muck about with video capture hardware on the PC, software can handle it all. I had considered using ethernet based controllers but I can't see how i'd reset the connection without a physical switch (having to haul the ROV up), or cycling power to the unit, usb seems so much neater.

If anyone knows of a supplier that can do USB over 1000' via CAT5 or some other cable I'd gladly switch to it to save some money.

p.s. by "low-cost" i mean under $5k as most ROV's of this class that I've seen start at 10k+

[thegadgetguy]

Would this type extender here work? It's in the (barely)sub $1k range. I'm not sure how much the Optic link unit is, in comparision.
http://www.startech.com/Server-Manageme ... V565UTPDUA

The specs say it'll do 1,640 ft at full USB 2.0 speed. Do you mean $5k for your whole ROV, or just for the tether interface system?

-thegadgetguy

[Sterno]

Nice find, that unit is very similar to the one I'd considered (http://www.icron.com/products/usb_new/u ... tender.php), even the price. The cost savings would be in the cable as the 1000' multimode fiber optic would cost around $600 versus around $150 for stranded CAT5. Something to think about.

$5k total cost, not just the Control system. I know this is a tight squeeze budget-wise but I figure $2000 for electronics, $1000 for flotation (syntactic foam isn't cheap!) and the remaining $2k for mechanicals like chassis, servos and motors.