Hello all…Long-time lurker, just started posting. I posted this in the “Build” section of the forum, but was thinking this might be a more appropriate location so I deleted that first thread, and will re-post it here…
I am in the process of researching a BR2 to get started. I live in the Great Lakes region and would like to perhaps do some fisheries-related research activity(s) with the unit, so I am trying to decide which unit might be best to get started.
I’ve spent a week or two now on the BR website, and going through all the forum pages. There are some incredible builds listed here! I’ve also spent hours and hours watching all the YouTube videos I could find about the BR/BR2 stuff. Wow! Here’s a little background information about me (and my use case), so that you might better understand where I’m coming from with the questions I want to ask.
I have degrees in both aquatic biology as well as Computer Science, and have been working as an embedded systems developer (I use Qt a lot) as well as a mechanical designer (Solidworks) for the past 8 years or so. I also have years of experience in aviation and aircraft maintenance, and have all the usual fabrication tools (welders, lathe, mill, etc). So eventually I would love to be able to tweak the ArduSub software for my needs–and possibly even design/build some custom vehicle components. I will primarily be working depths of less than about 125 feet or so, although it does get somewhat windy in the areas I’ll be spending time. So that being said, I was considering either 150m or 200m of tether–as I would maybe rather have a little too much tether rather than too little.
That all said, I would greatly appreciate input on some questions I have:
Base kit vs “heavy configuration”? If I plan to go to the heavy configuration in the future, is it advisable to just do right away?
Does the heavy configuration essentially force you into the Outland Tech power supply, in order to be able to run the extra motors?
Is it advisable to just buy a longer tether (and a spool) up front, instead of getting the 100 meter stock tether, but then having to upgrade in a year or so? Seems like a guy wouldn’t go wrong with the 150 meter tether, are there any latency issues with longer tethers? I haven’t looked at the software source code much yet so I’m not sure about things like baud rate, etc. But since all conductors have a resistance value, and since line noise is always a potential issue, is a shorter tether “better” in that sense, or is it irrelevant?
Add-ons. I can see myself adding the sonar, gripper and other add-ons fairly quickly. So this is another reason I’m considering just moving to the heavy configuration straight-away. But again–I’m not sure about the extra power requirements of the extra motors in this configuration, and really don’t want to have to get into ground power unit right from the start.
Anyway, those are just a few of the things I’ve been trying to sort out. I have found some details in various forum threads, but I just thought it would be nice to have all the questions asked in one thread so it would be easier to keep track of the information.
Thank you in advance to anyone who shares their experience(s) and opinions with me. I greatly appreciate the information.
I guess your decisions depend on your budget. It’s not a big deal to start with a basic vehicle then add on, but I would advise starting with the 18 hole end cap which you’ll need if you upgrade to heavy and other accessories.
The Outland power supply is great if you’re doing a survey or something that requires you to be on target for extended periods. The downside is you require mains power or a generator. You don’t necessarily need the Outland power supply for the heavy configuration. If the vehicle is trimmed well, the two extra vertical thrusters won’t use up much extra power unless you are pitching and rolling the vehicle a lot.
(Blatant plug alert) -You could add an extra battery with this battery multiplier that we sell.
Here’s one of my BR2’s with two batteries and a 4k camera:
150m is a good length of tether as the max depth rating is 100m. If you’re diving to 100m you’d probably want to attach a clump weight to the tether about 20m from the vehicle and some extra for a deck cable. There aren’t any latency issues with longer tethers.
Excellent information, thank you very much! I actually thought about just getting the heavy configuration to start with, and an extra 18 Ah battery. Certainly much cheaper than the shore power option, and since most of my missions would be well under 90-120 minutes in duration, I think that should suffice to get started.
Your battery multiplier looks great. I will study the information on that page in hopes that I can learn something! I might even give you a call if you’re available during the week?
Thanks for all your help @gcelec. I worked with Brian there and got an order placed for the items we discussed. I definitely appreciate your time on the phone this morning, and can’t wait to start assembling the parts when they arrive!
IMHO, i’d get the biggest, heaviest ROV you can afford. Because in reality, these hobby ROV’s are really just expensive toys. Any real current or tether drag will pull and shove them all over, making getting good video or grabbing an object nearly impossible. There isn’t even an option for panning the camera so you can look at something that just swam by before it’s gone, without having to slew the whole ROV around to look.
I’m working on a 9-dof manipulator, like a small Shilling Robotics type, that will feature leds/microcam on the wrist, Festo-style flexible fingers, a grip that changes from linear to circular, and haptic feedback so you can feel when you are touching something. Magnetic angle sensors for positional feedback.
I concur…that’s why I ordered the heavy configuration kit right out of the gate. I will likely be adding a bit of weight to the thing anyway, so I figured that I might as well spend the extra money and assemble the heavy configuration kit with the initial build.
Your project sounds incredible–good luck with it! I plan to learn the ArduSub software myself, and then maybe start experimenting with it a bit. Since I’m very familiar with the Qt framework anyway, it would seem like the logical place to start.
It looks like between the help of @gcelec here and @kklemens on our support email you’re all set!
I’d like to point out a couple additional things just to clarify, mainly for future readers than come across this thread:
The biggest advantage of the heavy configuration is the additional of pitch stabilization and full 6 degree of freedom motion. Anytime I fly a heavy, I feel spoiled by the additional stability, which in many cases can make it feel like flying a quadcopter/multirotor underwater. If you are not limited by funds or size/weight constrictions, I would go for a heavy right away, though the additional thrusters are easy to add whenever. In most cases, any increase in power draw is not a significant factor, and the additional stability/maneuverability is absolutely worth it.
The main advantage of the Outland Topside Power supply is infinite energy for long term operations, there is no needs to swap out a battery. However, note that the power output of the battery is higher than the topside supply, which tops out at 1000 W. The battery can do 1000 W constant to full discharge no problem, but it can also handle short term discharge over 2000 W as well. In those cases, the topside power supply will reduce output voltage to keep power at the 1000 W max. Therefore for absolute duration the Outland topside power supply can’t be beat (infinite), but for max power output/performance the battery does have an advantage. Either will handle an 8 thruster heavy configuration just fine.
There is no latency increase with a longer tether, the speed of light is pretty fast. However, as tether length increases, bandwidth does go down. A 300 m Fathom or 200 m Fathom Slim tether are the longest lengths we sell, due to these bandwidth limitations. Those lengths will perform great and still have plenty of bandwidth left over for additional devices over the same data link, but anything longer could start being a limitation.
A gripper and sonar do increase power draw, but to such a low degree that the specifics of your dive and the environmental conditions you’re flying in have a much greater impact. Similarity, charging your phone while driving will reduce your mileage slightly, but going up a hill will have a far greater influence.
By the way @Oddmar, if you would like to add camera pan to your vehicle, I thought I would point out that AduSub does in fact support a camera pan servo under the advanced settings on the camera setup page. We don’t outfit the BlueROV2 with one by default, since we find vehicle yaw is plenty zippy and accurate enough to track an object, that the additional expense and complexity isn’t justified for most of our customers use cases.
Wow–great information Adam, thanks! I am pleased that I went with the heavy configuration, and Geoff basically told me everything that you just stated in regards to just doing it up-front. So that’s the way I went.
Regarding the speed of light, yes…it’s very fast. However electrical conductors have resistance, and it is proportional to the length and (inversely) to cross-section. So assuming you don’t change the wire size, making a longer cable/conduction means increased voltage loss. Maybe latency wasn’t the correct way to ask the question on my part, but voltage loss (and capacitance) would have been a better way to ask it. That said they use tethers that are VERY long on larger ROVs, but I don’t know how high the voltage is on those units. But I understand the bandwidth concept, so your explanation was helpful.
Thanks again for the information. Hopefully the equipment will arrive here sometime next week, so the construction/assembly can begin.
A solution to getting infinite energy without sacrificing max power output/performance could be a hybrid combination using our MBM-150 battery multiplier to switch between the Outland power supply and a battery configured like this:
The MBM-150 switches between the power source with the higher voltage so it would draw down a fully charged battery until it reached the 15v output of the Outland supply at which time it would become the power source. When the power draw is more than 1000 watts and the voltage of the Outland drops below 15 volts, the MBM-150 would switch to battery power to take up the surge.
You wouldn’t have infinite full power as you draw the battery down, but it could be good compromise.
Thinking more about your comments regarding the decreasing bandwidth with longer tethers, do you find that’s mainly due to increasing noise on the longer line…or is there some other reason? Just trying to understand the concepts in play here.
I can tell you a little bit, but unfortunately some of the specific details and how they interact are beyond us! The Homplug communication standard (2 wire Ethernet) uses a series of 84 sub carriers in the frequency range from 4.5-21 Mhz. When dealing with multiple high frequency electrical signals, the sum behavior and how it varies with cable construction can be difficult to predict.
See here for some additional details I previously posted:
During past testing, we actually found that some specific cable constructions actually exhibit increased bandwidth past a certain point at longer lengths before decreasing again. We believe in those cases that we hit upon some multiple of the frequencies involved in some way.
That’s good information Adam, thanks. I’ll research this Homeplug Communication standard more. I read the wikipedia page on it, and it sounds interesting. I also read the other forum thread you linked to as well.
