Author Topic: Underwater ROV controller question (Read 31238 times)

chelmi · « **Reply #60 on:** June 29, 2010, 06:38:43 PM »

Quote from: CrazyCossack on June 29, 2010, 06:01:17 PM

We're currently trying to find CAT5/6 available in Ottawa

Yay! I didn't know there were other people from Ottawa on SoR!

Where do you plan to test you ROV? The Rideau canal?

CrazyCossack · « **Reply #61 on:** June 29, 2010, 06:56:15 PM »

Haha I always seem to find people from Ottawa on every forum, small world. Testing in the canal would be pretty epic, I could probably get away with it too!

madsci1016 · « **Reply #62 on:** June 29, 2010, 08:37:12 PM »

Your propeller problem reminds me of an idiosyncrasy at work.

One of my jobs at work is an operator for Unmanned Underwater Vehicles for the Navy. The vehicles we use were originally invented by an Oceanographic Institute for scientific purposes. The Navy saw how they could be used for anti-mine warfare, and placed an order for more. Sine the institute couldn't mass produce them, a private company was spun off (that's now foreign owned, for crying out loud) to start production. Now the Navy is chained to that company for it's UUV needs. The propeller on them is machined out of a single piece of metal, bends easily and costs the government $1000 for each new replacement.

The original Institute that invented the vehicles started with, and still use today $5 plastic airplane props. They keep several in their spares kit, when one breaks, they just replace it on the spot. There vehicles swim just as well as ours do.

It hurts my head to think about sometimes....

CrazyCossack · « **Reply #63 on:** June 30, 2010, 03:32:42 PM »

Woot found some cheap propellers on Ebay, way to go Hong Kong - they seem to have everything! That is a pretty crazy inefficiency, maybe a lesson in not privatizating? Does anyone know how Cat 5/6 cable fairs if it is just left in the water, like if we just attached it to a tether, but not actually inside anything. Would there be too much noise from the water and kill the signal?

dunk · « **Reply #64 on:** July 01, 2010, 05:02:38 AM »

Quote from: CrazyCossack on June 30, 2010, 03:32:42 PM

Does anyone know how Cat 5/6 cable fairs if it is just left in the water, like if we just attached it to a tether, but not actually inside anything. Would there be too much noise from the water and kill the signal?

my hunch is it will be fine as long as the plastic coating on the individual strands is in tact.
it might be worth being careful about kinking the cable to prevent wear on the plastic insulators.

the space between the outer plastic sheath and the inner 8 cores will fill up with water but that shouldn't matter.

out of interest: salt or fresh water?

dunk.

CrazyCossack · « **Reply #65 on:** July 02, 2010, 01:34:16 PM »

Yeah, I guess we'll look at how expensive each kind of rope is to procure and take it from there. It'll be running in fresh water basically exclusively (just due to us being far from salt water).

CrazyCossack · « **Reply #66 on:** July 25, 2010, 01:52:06 PM »

Hey all, haven't posted in a while so just a little update, and pictures as promised

We're still waiting on the batteries before we do anything else. As requested are some pictures of our design.

http://img839.imageshack.us/img839/3016/dsc4557.jpg

http://img842.imageshack.us/img842/8355/dsc4558.jpg

For reference the smaller PVC is 2in and the larger is 4in. The little motor looking things are thrusters, converted bilge pumps. The skids and ballast (2in at bottom and 4in at top) aren't yet attached to the rest of the frame, and they will be closer to the edges. The electronics area/camera place with the plexi-glass window is a little large, but we'll cut it down when we know exactly how large the electronics area will be. There will be one thruster on the grate pointed upwards, and the other two facing back on either side. We have an option for a 4th if we need one more but I doubt it. We also have two lights which I forgot to put in the picture.

We're still looking for a length of 300ft ethernet locally, rather than buy one from the States or China which costs like $70+ after shipping.

dunk · « **Reply #67 on:** July 26, 2010, 06:18:25 AM »

Quote from: CrazyCossack on July 25, 2010, 01:52:06 PM

We're still looking for a length of 300ft ethernet locally, rather than buy one from the States or China which costs like $70+ after shipping.

RS Supplies have branches worldwide and will have it although they are not always the cheapest.

they seem to go by the name of http://www.alliedelec.com/ in CA.
Offices in Ottawa.

try any local trade electrical suppliers as well.
an electrician will definitely know where to source this locally.

dunk.

madsci1016 · « **Reply #68 on:** July 28, 2010, 05:21:42 PM »

A suggestion:

http://www.societyofrobots.com/robotforum/index.php?topic=11724.0

CrazyCossack · « **Reply #69 on:** August 06, 2010, 06:59:36 PM »

That seems like a great deal, thanks for the link! We may just end up settling on 100ft for now, or try to string 3 lengths of 100ft together although might be trickier with the tether.

Madsci, we bought four of those batteries you recommended, would there be any sort of problem with having four on the ROV instead of the two? ie, is it more unstable? We are going to go with the 15amp fuse still I think.

madsci1016 · « **Reply #70 on:** August 06, 2010, 08:37:04 PM »

The trick to stability underwater is a large difference between CB / CG. (Center of balance, Center of gravity)

You want your dead weight to stay towards the bottom of your ROV, and keep the floats high. The larger the distance between CB/CG, the more stable the ROV will in the water.

So more batteries are OK, just keep them towards the bottom of the ROV as possible, and keep your floats as high as possible.

CrazyCossack · « **Reply #71 on:** August 07, 2010, 06:36:11 PM »

Ah sorry I should have been more specific, I'm not really concerned with the weight, but more of the stability of the circuit. If the batteries are less stable then conventional ones, will be putting four batteries in there instead of two make it twice as likely that the 15amp fuse breaks at any given point? Should we perhaps put two of them through a 15amp, then the other two through another 15amp...so if one fuse breaks we'll still have the power from the other two batteries? Or is this just overkill?

madsci1016 · « **Reply #72 on:** August 07, 2010, 07:42:42 PM »

O, oops.

No, there will be no difference in your electrical system other then if things go horribly wrong, it will make a bigger boom. Just keep your fuse inline as close to the batteries as possible, to keep the 'unprotected' part of the circuit as small as possible.

And remember, don't EVER throw water on a lithium fire, nor throw a burning battery into water.

CrazyCossack · « **Reply #73 on:** August 08, 2010, 01:48:09 PM »

Got it, I'll keep that in mind - thanks!

CrazyCossack · « **Reply #74 on:** September 05, 2010, 06:29:37 PM »

Hey guys, we've been very busy but we have made some pretty decent progress considering. The ROV is almost completely assembled minus some small issues with attaching the propellers properly, securing the tether and the electronics.

We have the electronics all ready to go, we'd just like to confirm that this circuit will work, and what we've done is not completely crazy or something (this is our weakest area).

Once you guys have OK'd it we'll throw it all together and have some pictures for you all.

Here is the diagram: http://img693.imageshack.us/img693/2893/rovschem.png

Cheers!

madsci1016 · « **Reply #75 on:** September 05, 2010, 07:12:13 PM »

How is the LED array wired? You show it as directly connecting to the Arduino. The pins of the Arduino do not handle enough current to drive those LEDs directly.

CrazyCossack · « **Reply #76 on:** September 05, 2010, 08:22:09 PM »

Thanks for the quick reply, how much current is the Arduino able to output in one pin? Because we've got two sets of 3 LEDs. If the Arduino can't power the LEDs we're really not sure how wire this so that the LEDs get the 5v power from the switch regulator while still being controlled by the Arduino.

madsci1016 · « **Reply #77 on:** September 05, 2010, 08:37:23 PM »

an Arduino pin can only handle about 20mA.

But never fear, that's why we have transistors.

Something like this would allow you to switch the LEDS on or off. just make sure whatever transistor you use can handle the current. A regular 2n2222 will do about 1Amp, so you could use two, one per LED chain and be ok. Just tie both base resistors to the same Arduino pin.

CrazyCossack · « **Reply #78 on:** September 05, 2010, 09:51:25 PM »

Excellent that makes sense, so we just put a transistor before each LED cluster on our diagram and that ought to do the trick?

madsci1016 · « **Reply #79 on:** September 05, 2010, 10:22:07 PM »

yup. I'd also have a resistor in line with the LEDS like the diagram, just to protect the LEDs, since 5v is higher then there 4.5V need. A 1W or greater 1 ohm resistor should do the trick.

Admin · « **Reply #80 on:** September 06, 2010, 08:34:20 AM »

Quote from: madsci1016 on September 05, 2010, 10:22:07 PM

yup. I'd also have a resistor in line with the LEDS like the diagram, just to protect the LEDs, since 5v is higher then there 4.5V need. A 1W or greater 1 ohm resistor should do the trick.

The resistors are required for limiting current, doesn't matter the voltage involved.

I'd use a MOSFET here instead of a transistor simply because they are more efficient, can operate at much higher currents, can switch on/off much faster, and don't require a resistor at the gait.

madsci1016 · « **Reply #81 on:** September 06, 2010, 08:45:15 AM »

Quote from: Admin on September 06, 2010, 08:34:20 AM

The resistors are required for limiting current, doesn't matter the voltage involved.

It matters when calculating the needed resistance.

Quote from: Admin on September 06, 2010, 08:34:20 AM

I'd use a MOSFET here instead of a transistor simply because they are more efficient, can operate at much higher currents, can switch on/off much faster, and don't require a resistor at the gait.

Works either way. MOSFETs tend to be more expensive then BJTs, no? Switching times don't matter for this application. And regular BJTs should handle his current just fine.

Also, you spell 'gate' funny.

Admin · « **Reply #82 on:** September 06, 2010, 09:05:11 AM »

Oops, I was thinking of 'robot walking gait' vs 'MOSFET gate' lol

MOSFET's do cost more, but for a one-off thing, only like 50 cents more. You'd only save if you were to make a few hundred/thousand of them.

CrazyCossack · « **Reply #83 on:** October 05, 2010, 04:26:48 PM »

Hey all, so a short update and a little question. We have the electronics mostly assembled but the damn camera crapped out on us, we could never get a connection. Either the camera was defective or we damaged it some way by opening it up/modifying it so many times. We really want a different model of camera as this one was a pain to deal with and really quite bulky. It is hard to fine a good ethernet bullet camera to fit our dimensions that won't run us $300.

I was looking at this webcam http://www.logitech.com/en-ca/webcam-communications/webcams/devices/6816. The camera has decent quality and autofocuses very well which is key. And using a usb-rj45 adapter. Question is, after using the rj45 adapter, then running that through a 10/100 switch to the laptop, will we be able to use the Logitech software to control it?

Thanks,

John

madsci1016 · « **Reply #84 on:** October 05, 2010, 05:00:07 PM »

Depends, what's this USB to ethernet adapter you talk about? Is it an accessory for that camera or some third party thing?

CrazyCossack · « **Reply #85 on:** October 05, 2010, 07:59:21 PM »

Third party adapter, was thinking of just buying a cheapy from ebay.

madsci1016 · « **Reply #86 on:** October 05, 2010, 08:21:47 PM »

You have to give us a link; datasheet, something. I've never heard of a USB to ethernet camera adapter, so I want to make sure it does what you think it does.

CrazyCossack · « **Reply #87 on:** October 07, 2010, 01:02:11 PM »

Something like: http://cgi.ebay.ca/USB-RJ45-Ethernet-Card-10-100-LAN-Network-Adapter-/390245465376?pt=LH_DefaultDomain_0&hash=item5adc713d20

I'm not sure it would work power wise either, presumably I'd have to get some POE going. I don' think the 10/100 switch does POE, but I'll have to confirm later.

chelmi · « **Reply #88 on:** October 07, 2010, 01:41:11 PM »

Quote from: CrazyCossack on October 07, 2010, 01:02:11 PM

Something like: http://cgi.ebay.ca/USB-RJ45-Ethernet-Card-10-100-LAN-Network-Adapter-/390245465376?pt=LH_DefaultDomain_0&hash=item5adc713d20

I'm not sure it would work power wise either, presumably I'd have to get some POE going. I don' think the 10/100 switch does POE, but I'll have to confirm later.

I'm pretty sure this is not what you think it is. This is a network card, and it needs a USB host (like a PC) to work. Your webcam is a USB device as well (not a host), to have the two work together you will need a PC.

Chelmi.

madsci1016 · « **Reply #89 on:** October 10, 2010, 04:24:00 PM »

I agree with Chelmi, this is not want you want. That's a device side USB to ethernet chip. You would need some sort of host-side USB to ethernet server that was specially coded to work with a logitech USB camera.

Your best bet is to buy a real IP video camera. The alternative would be to buy a Video over IP converter box and a analog camera, but that would cost more then a standalone IP video camera.

News:

Author Topic: Underwater ROV controller question (Read 31238 times)