Help with choosing a control system for my ROV

[trogdor]

Hi everyone,

I have recently decided I want to work on a electronics/engineering project of my own. Since I have an Oceanography Degree which i completed a few years ago (my current job has nothing to do with it tho ) a ROV as a project really appeals to me.

Anyway I am planning to make a fairly simple ROV to start with but I want decent thrust and control as a main priority.

I have changed my plans a lot during my research but I think I have got the propulsion sorted.

I want to use brushless motors to provide propulsion, this requires ESC's for each motor which is fine, I have found an american site that can sell me three brushless motors and three ESC's and a suitable camera for approx £60.00 which is a very good price, (Why are all the good sources of things like this from america?)

I the future I plan to run microcontroller control to operate these motors but for now, can I use a aircraft transmitter to control them? I realise that the radio waves wont penetrate thro the water but is it as simple as connecting a wire to both aerials? Ie one of the wires within an ethernet cable? If so then getting proportional control using one wire would be great!

My next question is can I run the ESC and brushless motors from above using a car battery? I plan in the future to run them off on board batteries (possibly Lipos as they are getting cheaper!) but for now I plan to use suitable cable as part of the tether.

If anyone can help I would really appreciate it.

[manhattan]

Hi Trog,

I build something similar. I am still in testing phase though (in water). Go through some of the earlier posts, they will explain some of your questions. I got 90% of info needed through this site and forum. I don’t understand your control question. You want to run one wire down directly to the esc? Don’t think it’s possible (not sure)

Running esc with top side power is possible but with some limitations. Voltage drop being one of them. If you want decent trust you should probably go with batteries on-board so your rov don’t need to pull all cables around.

Check out the topics in the forum. You will find a wealth of info.

Best

[thegadgetguy]

I'm not sure about the whole "antenna through the tether" idea. Seadragon was going to do a test with a wireless router, but I don't think he's posted the results yet. I personally don't see why it wouldn't work, but I'm not an expert, so my opinion shouldn't count for much. For the ESCs with the car battery, as long as everything is 12 volts and they can handle the amperage per motor, than it should work. I think the only problem would be what manhattan mentioned with the voltage drop. If you have a 40 foot tether, it's not a big problem, but if you have in the 100+ foot range, you should look into another option than sending straight 12 volt DC down the tether.

Welcome to the forum and I wish you sucess on your project.

[biglakeexile]

Hi Trogdor,
Yes, RF from an RC controller will travel through the water with a "helper" wire. My ROV is proof and it made it to 70ft. I have a small gauge wire tied to the receiver antenna on the ROV which run up the tether with an end to connect with an alligator clip to the controller. However, I haven't had to clip the wire to the transmitter antenna yet (or aerial, depending on which side of the pond), the fact that the extra tether coiled up topside is nearby is picking up plenty of signal to send through the water.
Also, the ESC's should have no problem with the 12VDC from the car batteries. Especially the newer "3S" or 3 cell Li-Po compatible ones since a 3 cell Li-Po is 11.1V. I'm running three brushed RC boat ESC's because they offer reverse, and they were on sale. But I think they were designed for 6cell or 7.2v Ni-Cad packs for an RC boat and they're running just fine off the 12.8V I'm supplying to them.
And BTW, although the many of the cool gadgets are available in the states, they're still made in china like everything else us americans seem to buy.

[Seadragon]

I'm not sure about the whole "antenna through the tether" idea. Seadragon was going to do a test with a wireless router, but I don't think he's posted the results yet. I personally don't see why it wouldn't work, but I'm not an expert, so my opinion shouldn't count for much. For the ESCs with the car battery, as long as everything is 12 volts and they can handle the amperage per motor, than it should work. I think the only problem would be what manhattan mentioned with the voltage drop. If you have a 40 foot tether, it's not a big problem, but if you have in the 100+ foot range, you should look into another option than sending straight 12 volt DC down the tether.

Welcome to the forum and I wish you sucess on your project.

I tried the wireless router on 1000' of thhn 18 ga. wire tied to the antenna leads on a linksys B router on one end and the other end on linksys B usb dongle with wire soldered to the antenna point. I set the antenna gain down to 6db to start. Had my friend with my thinkpad and usb at one end of the property and connected my compaq at the wireless router via ethernet cable.

transferred a short video to the thinkpad and it did it in the normal time. My boss came out and said whatcha doing and I told him he used his network detector and saw the networkfrom 40' lateral to the cable all the way down. This made him very happy as we have old wires throughout the plant so when he had the IT guys come out they used their lappy to connect all the way done the line.

So in conclusion It seems as if it works. The only bad thing was respooling 1000' of wire . So if you are going to do that with your jobs wire make sure you share any good news with your boss. Oh and the IT guys hate me now . I will try again when I make a control program. I am thinking of writing one in Java anyone have something like that already?

[Rover]

Look at the VEX Robotics Transmitter and Receiver. It has a jack on the back that allows you to communicate with the receiver via 2 wires. You could use a single twisted pair of wires to control motors.

Jim

[Sea-ker]

Trogdor, do you mind sharing the American website that you obtained your motors and ESC from?

[derelicte]

actually, most 4+ channel rc transmitters have trainer ports on the back that output the ppm data stream. you can send this signal down to the receiver over two wires. you will need to inject this signal after the rf portion of the receiver so it can route the correct signals to the escs.

another feature to look for with rc systems would be one with dsc (direct servo connect). this does the same thing, but provides you with jacks on the tx and rx to make it easier to do.

if you want to do mixing between the left and right thrusters, look for a computerized transmitter. it will allow you to do this type of thing.



http://www.hobbyking.com/hobbyking/stor ... ware_.html

[rvanscotter]

Am I to understand that I can use my trainer plug on my Futaba 10C and send that signal down the CAT5 Cable and wire it directly into my RF Receiver, somewhere. That's very interesting concept, the only problem I see is that many of these advanced controllers use some fancy hi-tech code to link the TX with the RX, the data coming out the back is just the commands, where to splice in the raw command only signal will be challenge to find. I think the 2.4GHz pairing will inhibit things and be an issue, although I have absolutly no what the F im talking about so maybe it will work???

[derelicte]

That won't work. Most 2.4ghz radios don't have dsc ports (direct servo connect) because the 2.4ghz link eliminates interference and isn't needed. I don't recall seeing any futaba 2.4 ghz rxs with dsc inputs. none of mine have them.

however, if you replace the rx in the rov with a microcontroller (like an arduino) then it could decode the ppm pulse stream from the trainer port and do what you are asking.