Open ROV electronics


#1

I just took a quick look through the Open ROV offering and the entire thing looks pretty simple. The only item I see missing is details on electronics. Am I overseeing something? Can anyone provide a link to electronic details? I have a hard time believing this all runs directly off the Arduino board.


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#2

Joshua,

We're glad to see your interest, and sorry for the lack of detail on electronics- we hope to post more info on that soon. Because many of the parts of the ROV structure require very high tolerance, it may be tricky to make everything fit together well unless the pieces are laser cut ....but don't let that stop you! It would be very interesting to see how well you can do with hand made parts.

In lieu of electronics details, I can suggest starting out with the motors and ESCs listed in the Bill Of Materials and just wiring a thin tether to the antenna port of an RC receiver so you can use an RC transmitter to test drive the ROV. Here's a video of me doing that with the OpenROV 2.2 prototype.

Anyway, good luck- we'll try to have more build details for you soon!


#3

Eric,

I'm sure I'll be fine with parts, I've got a mill, lathe and CNC router. Electronics are not my forte however.

I'll play with a RX coupled with a small monitor and make mods as I go. I know from diving that I am going to want to have lights, a sensor pod and a tether with more power and possibly an air hose to inflate/deflate a small air tank in ROV, we'll see. Also Gimballed drives and possibly a little arm or retrieval device.

You might consider getting into wireless a bit now, I know a lot of people who would like to see waterproof communication come out of the proprietary realm. Just a thought.

JOSH


#4

Josh,

You can also check out http://www.homebuiltrovs.com/ or Harry Bohm & Vickie Jensen
Build Your Own Underwater Robot and Other Wet Projects.

I look at this project as making it look more professional, and looks to be a great resource.

Rob


#5

Eric,

I built the OpenROV 2.0 kit with you and have not yet ordered the motors, ESCs or impellers (been waiting to see how things progress on the designs). In the interim I have mostly been exploring onboard electronics and software possibilities and have started with a BeagleBone board that I will want to interface with the ESCs. I generally will want more computational power on-board the ROV (toward a direction of AOV one day) and thus the interest in the BeagleBone (http://beagleboard.org/bone).

Some questions: 1) Can I upgrade my OpenROV 2.0 to the 2.2 design?

2) Should I still order from the 2.0 BOM - motors, ESCs, connectors (Gold and nylon) and 3" Impellers?

3) I see you have a ducted fan approach with the 2.2 prototype - is that the same impeller as above?

4) If I go with the RC receiver and transmitter to test things out (while developing the BeagleBone) do you have some recommendations on inexpensive RC gear?

5) with the RC approach did you use onboard batteries and a teather just for the radio signal or did you supply power via the tether?

Thanks,

Jim


#6

Jim,

The BeagleBone is a great platform for the ROV, and in fact, Bran Sorem has been doing a bunch of development work with that very system to get it to stream video from a webcam and control the motors, servo, and lights. He's also working on a GUI that can be hosted from the BeagleBone (or whatever Lynux system it is). You guys should get in touch!

To answer your questions-

1) YES! I can get you some updated parts for your kit once I get back from my travels (I'm off to MIT right now to talk to some people about Android+IOIO board+OpenROV). If not right when I get back, we'll hopefully have another build day coming up and we could get you a new kit then.

2) The motors are the same, the ESCs will work fine but I've found slightly less expensive ones, and the other items have changed slightly- I'll update the BOM for 2.2 soon.

3) Good observation. I would now recommend an impeller made by E-flight called the DeltaV-15. They are stronger and better built, and are also more reliably available. I'll also add these to the BOM.

4) I don't have any particular recommendations for RC equipment, but if you're going to try the ROV out in the water, try to get an older 72 or 75 MHz system rather then one of the new 2.4GHz radios since higher frequencies don't travel very well through water.

5) I used onboard batteries for power, but sort of "ducted" the RF through the water using a tether attached to the receiver on the sub that just came out of the water and didn't attach to anything.

I hope this helps!

Eric


#7

Eric,

Thanks for the reply and have fun in Cambridge.

I will wait for the BOM update before I place an order. It is good to hear Bran is working with the BeagleBone - I will follow up with him and also order at least one ESC to experiment with.

Regards,

Jim


#8

I may have an ESC laying around you could play with as well. I’ll try to dig it up when I get back.

All the best!

Eric


#9

Im from boston is there any way i could sit in on your talk?

side note: In the future i plan you rent one of MITs pools for rov testing

How do i get my hands on a kit?

On the RC side of things you could always use DSC .


#10

Hay Shane!

It's awesome to see that there are people following OpenROV in every part of the country I go to! I'm by no means giving a talk in Boston, in fact, I'm coming to listen to someone else, Ytai Ben-tsvi, go over his awesome brainchild, the IOIO Board, and participate in a IOIO Hackathon to try to develop a way for it to be used in OpenROV. My hope is that with the help of some guys here at MIT, we might be able to do some great things with it! (Plus I just really love learning about this sort of stuff and what people use it for)

I arrived in Boston this evening and am visiting family before the event this weekend, but I'll be in Cambridge on both Saturday and Sunday. I'll have a better idea of my particular schedule once the weekend starts, but let me know if you'll be in town this weekend- I'd love to meet up!


#11

Thanks - that would be great. I read up a bit about the input signals required for the ESC (PWM 1-3ms wide, depending on the value 0-100%). It would be nice to generate this from the BeagleBone and drive an ESC and control a brushless motor. I don't know if Bran has done this already. I will check when I hear from him.

Let me know when you are back and we can talk.

Jim

jtrezzo@trezco.com


#12

Jim,

The ESC should respond to a standard servo input which is a pulse lasting between 1.25 and 1.75ms at a 20ms period. While scouring the internet for people doing this with the BeagleBone (or Beagle Board) I found this awesome YouTube video which shows it's possible. The guy who created the demo pointed me here for more information. The bottom line- it can be done, and it looks like the 3.3v bus of the beaglebone is enough to support the signal input without amplification. I look forward to diving into this with you further when I get back home!

Eric


#13

Eric

Hackathon thats part of techfair?

Id love to meet up. I work at Boston Conservatory and will be getting out for work every day at 6ish. i could always give a back stage tour.


#14

Thks

Jim


#15

look in to DSC its plug and play for RC transmitters/receivers and it take care of not being able to send radio waves in water


#16

Hi,

I would also very much appreciate more information about the electronics. We purchased all the parts on the list, but there is no arduino or any other board on that list. Also, we are not sure how to make all the parts talk together and wire them up. Any hints as to how to get started on the electronics part would be great! We are located in NYC at Columbia University.

Best,

Petr


#17

Hay Petr, et al,

Sorry for the incompleteness regarding electronics. We're actually trying to get that bit figured out right now (this is the majority of our development work currently) so please stand by for more info. Generally, we plan for the OpenROV hardware to be a platform for various electronics packages which may vary depending on use case.

For instance, one approach may be basic (1) with an RC receiver and analog camera controlling and sending video from the ROV respectively. An intermediate electronics approach (2) may use an Arduino with Ethernet or RS485 to control the ROV in place of an RC receiver (this way it could also send sensor data such as compass and depth) but would still have an analog camera for sending up video. Finally, and advanced package may use an full on-board computer such as a Raspberry Pi, BeagleBone, or Android phone to host sensors, control the ROV, and send video from a digital (webcam) camera or similar via Ethernet.

We'd really like to know what people would like to do with their ROVs (which feeds into what the electronics should be like - cost vs capability), and we'd also love to hear about the approaches people are taking on their own to get the hardware working.

As for now, recall that all you need to control the ROV is servo output to drive the ESCs. If you just want to get the ROV moving, I suggest getting an old (non-2.4GHz) RC receiver and "snorkeling" it's antenna up the the surface.

Let me know if you have any other questions or technical needs!

Eric


#18

Hey Eric,

Thanks for the response! I am working on this OpenRov project with a mid-school kid (quite talented one). It's a fun and learning project for us and a sort of an outreach program, too. Okay, we will most likely start with the RC receiver and get the basic version running. Once that works, we will start experimenting with Arduino and build in more advanced features. For now, the basic version schema would be very helpful. We will do some research on our own while awaiting some basic electronic schema to be put up on this site. This is a great project, guys! Keep up the originality! :)

Best,

Petr


#19

Hay Petr,

I'll try to put a more comprehensive diagram up in a bit but things are a little busy right now so I've just quickly drawn this scheme in paint. It just shows the basics of how things are attached but I thought it might be helpful. Let me know if you have any particular questions.

Good luck!

Eric



#20

Thanks a lot, Eric! This doesn't look that bad at all! Do you have any recommendation regarding what RC receiver/transmitter to use? If you already answered this question somewhere here in the forums, don't worry about answering. I will look around.

Thanks, Eric!

Petr