New ROV - The Mimee

[Tal]

This post is for all the people out there who look at everyone's amazing projects and say, "I'll give that a go", contrary to the fact they have a small fraction of the ability, and have so very much to learn....but we will get there in the end

So this relates to my main body, as pictured above, with the clear acrylic window for my camera. What you can't see in the picture above is that there is only a very small amount of thread coming out the back. The bolts are too short if I want to make the most of the nylon threaded nuts I bought, so I took off back to the hardware in search of longer bolts. Well, seems they don't have any longer (with the hex bolt head) unless I go from 5mm up to 6mm in diameter. Oh well, up to 6mm I guess, along with new washers and nuts. It all adds up. Silly mistake that could have been avoided. So the old 5mm sets will go away in a drawer and hopefully be useful for something else along the way. Am I the only one who makes little mistakes like this?

SO.....I get home, head out to the workshop, and get the 6mm drill bit out. I have a drill press that my Mum got me from a garage sale (does everyone else have garage sales' in there countries?) that is really awesome but needs a new chuck, so all my drilling is being done with a power drill, or cordless. So I only need to enlarge the holes by 1mm, and, "CRACK". So out with the pencil and jigsaw, and I'm cutting a new window. I start drilling the holes again, and, "CRACK". This happened twice more, before I realised that I had to drill super slow, which is really hard to do with a cordless drill. Aargh.....but I took it super slow and finally got the holes drilled. Deep down, I know that someone is going to tell me that I'll need more bolts because the gaps between the bolts is too large.....lol. I'm hoping the water pressure will press the window up against the rubber gasket and provide a better seal as I go deeper?

I guess I didn't want to post all the progress without the ugly mistakes and mishaps that I'll be making too. It just wouldn't be honest for all those folks who are about to set out on their first ROV build, and decide to read my journey.

[scubersteve]

Oh it's not just you. If I could have avoided experimentation and failure on my projects I probably could have cut the costs by 25%.

It's all part of the journey...enjoy the ride.

[Tal]

While a picture speaks a thousand words, I thought I'd take a couple of moments to update you all without pics, this time. Since my last update I've completed the assembly of the main water-tight compartment housing. After peeling of the protective paper of the acrylic sheet, I discovered a small crack. While it won't effect operation initially, I'll have to cut another window for the camera.....I'm thinking I might wait for a new drill press. I spent precious ROV project time, stripping my old drill press to try and solve a wobble, only to discover that I cannot find a replacement spindle and I may be better off buying a new drill press....So I'll be stuck on some areas of the housings until I get this. I've also spent more time on the inner aluminium frames of my thrusters, cutting the ventilation holes in the mount to match the motor casing. I've also done a little more work on the arduino code, and have started looking at processing.org as a possible solution for a gui, but don't want to get too far ahead of myself

Equally as exciting was the arrival of some parts. I got my drive dog for the vertical prop assembly, and the prop nut. Just ordered a tap and die set, to put some thread on my 4mm shaft and that will be all complete. My new lead acid battery (12v7ah) arrived but I'm still waiting on the main thruster prop assemblies, and the Arduino Uno that I'll use on land. I'm excited to set up the tx/rx between the two arduino's and see how it all works. As I've started to realise, even small progress is exciting and I hope you are all enjoying your respective projects. I've got just enough time to scout the forum and check your projects

[Tal]

Well, more learning curves....

I was really excited to have received my prop assemblies, only to discover that, while the shaft diameter was correct for my drive shaft, and prop, the actual length of the bolt is way too short. This is about the third set I've ordered incorrectly. Last time I assumed the shaft diameter was the same as the prop diameter....so in light of the issues I've already spoken about with the coupler I couldn't find (and would have had to fabricate), I think I'll just dump these props altogether, and start again with new props, prop assemblies and shafts. I've already decided to run 4mm shaft's like the vertical thruster that I have nearly finished, and have the same setup all the way through. It makes perfect sense to have everything uniform but I was just reluctant to have to replace parts I had already purchased. Better planning would have avoided this but because I've been learning as I go, I guess I'll have to accept it.

On the subject of learning curves, I'm after some feedback. I've watched some of the tutorials you've all recommended, and also read a heap, but was hoping to save some time and money!

My initial plan was to use an Arduino in the ROV for control, and I am progressing well. However, it only recently occurred to me that I'm going to have a bundle of wires in my tether. A clever way of managing this would be to have an Arduino on the surface, and have them communicate. This would only require a CAT5 cable, both affordable, and more manageable.

My understanding now, is that I can't just run a couple of wires between two arduino's tx/rx, play with code, and expect it to work for 1000'. This is RS232? and would only be good for a short distance?

Could I just do away with the land Arduino, and plug directly into my laptop, assuming I could cut the usb programming cable and extend it?? Sounds dodgy but I just want someone to confirm it wouldn't work.

Same again, could I just buy a couple of ethernet shields for arduino, and run a terminated cat5 between the two arduino's? What protocol would it be using if I did this? I assume it would still be RS232 but do they change the comms on the shields to improve distance? or is it the same as above?

I've already ordered 4 MAX485's so I can set up RS485 communication but don't want to over-complicate the project, if there is a simpler method. My main concern here is that the code will become unmanageable or too difficult and result in limiting my options later in the project.

I'm looking forward to your feedback and opinions. Thanks in advance.

[KR2_Diving]

My understanding now, is that I can't just run a couple of wires between two arduino's tx/rx, play with code, and expect it to work for 1000'. This is RS232? and would only be good for a short distance?

Correct... I am not sure on the "official" terminology, but you are basically correct. Deakel gave a pretty good summary over on this post.

Could I just do away with the land Arduino, and plug directly into my laptop, assuming I could cut the usb programming cable and extend it?? Sounds dodgy but I just want someone to confirm it wouldn't work.

USB alone does not have a long enough range. (limited to 5meters) There are a few commercially available USB extenders on the market. The biggest drawback with this method, is the amount of cable you would need. You would need a dedicated Cat5 cable just to get the USB up to the surface. There are also some distance restrictions, depending on which extender you used.

Same again, could I just buy a couple of ethernet shields for arduino, and run a terminated cat5 between the two arduino's? What protocol would it be using if I did this? I assume it would still be RS232 but do they change the comms on the shields to improve distance? or is it the same as above?

Yup... pretty much same as above... this method would require a dedicated Cat5 cable...

I've already ordered 4 MAX485's so I can set up RS485 communication but don't want to over-complicate the project, if there is a simpler method. My main concern here is that the code will become unmanageable or too difficult and result in limiting my options later in the project.

I really recommend looking into the EasyTransfer library written by Bill Porter. I had a play with this over the weekend and was very impressed with how easy this made my communications. From what I understand, once I have this library up and running, I simply have to place the MAX488 chips in between the two arduinos to change from RS232 to full duplex RS485. This set up will require a total of 5 wires which leaves 3 wires free in my Cat5 tether for video transfer... I will be ordering my MAX488 chips today... so hopefully by next week I can confirm all this!

[Tal]

Hey Everyone,

Firstly, thanks for the feedback Ryan, and also a massive thanks to Deakel also for his posts and updates on his own project that have provided me with assistance.

Another brief update:

I have finally 'bit the bullet' and decided, as i alluded to in my previous post, to run 4mm shaft assembly ROV wide. So I've ordered the universal couplers (3.17mm - 4mm) and a left and right prop that fit the 4mm shaft. Unlike most I've seen, they have a 4mm shaft hole with a grub screw in the side, negating the need for a drive dog, tapped shaft, or prop nut. Let see how they look when they arrive though

After more thought, I ordered the Max488 chips for RS485 comms between the two arduino's. Yes, I had already ordered the Max485's, but they'll go into the drawer for some other project later down the track. I should have purchased the duplex in the first place. Also ordered a little voltage display for my test bed and a couple of micro servo's for tilt and pan of the camera.

Still waiting on the tap and die set to arrive in the post, along with the video balun's.

Probably the main progress I've been making is on educating myself.....definately something that I needed to do. I've been reading through everyone else's projects, watching you-tubes, done some basic electronics tutorials, and spent some more time going over Arduino code Tutorials. I've also dived into SketchUp8 and have been doing some of the basic tutorials to get my head around its use. I can't help but feel that my planning has been poor, but heaps of fun. I expect I'll save some time and money if I put some effort into planning. I don't like slaving over the laptop drawing what I've already made, when I could be working on the project, but I think it'll pay off in the long run.

Hope you are all doing well and having fun!

[scubersteve]

I have finally 'bit the bullet' and decided, as i alluded to in my previous post, to run 4mm shaft assembly ROV wide. So I've ordered the universal couplers (3.17mm - 4mm) and a left and right prop that fit the 4mm shaft. Unlike most I've seen, they have a 4mm shaft hole with a grub screw in the side, negating the need for a drive dog, tapped shaft, or prop nut. Let see how they look when they arrive though

Getting some traxxas villain ex props huh? I'm using the same ones on The Guppy.
They are decent little props and are pretty cheap although I haven't put them in the water yet.
Be warned though that they are threaded inside and must have the threads drilled, reamed, or ground out before they will fit on a 4mm smooth shaft.
I found a diamond dremel bit that was just the right diameter to grind them out. If you're going to do the same I suggest putting water down the bore before grinding. It speeds up the process considerably.

[Tal]

Thanks Scuba!

When I asked the lovely fellow whether the shaft diameter was 4mm he replied, "I am sorry I am unable to tell you this". So, considering the price, I bought them anyway So can I thread the end of my 4mm shaft? I've got a tap and die set on the way

[scubersteve]

You should be able to. Although I don't know how hard those shafts are.
If you can't, just grind the threads out with a dremel.
Do you have a dremel?

[Tal]

Thanks Scuba,

Yes, I do have a Dremel with a decent kit with all the usual bits, though it's not actually a 'Dremel' brand (sadly) but an inferior knock off. I wise man said to me a few years ago now, "Buy yourself a nice cheap [insert tool here], and if you break it then you have justified buying a more expensive one! If it sits on the shelf collecting dust, it doesn't matter that its a cheap one and you've saved money for the tools you really need".

In short, I've justified buying myself a new one although a new drill press, milling machine, metal lathe and a new workshop that looks like the one pictured by 'sthone' in the workshop forum are all on the list........lol

Back on topic, I've got a tap and die set coming so I'll see if I can put a thread on my drive shaft and see how it goes, or its out with the dremel.

Small update - it seems my ROV project is more about retail therapy than construction lately but, inspired by Deakel, I hunted down and purchased a digital compass circuit to add to my sensor collection. Looking forward to getting some of this stuff in the post.