When I'm building something, I tend to make many small changes and improvements as I go along. I just finished assembling an OpenROV 2.6 kit, and in the process I made about a dozen or so little tweaks that made things nicer. It's not worth opening a forum topic to discuss each little item, so I thought I'd make a single topic where we can all share the little things we discover that make the kit assembly better. In time, many of these ideas will probably work their way into the "official" instructions for the kit.
In the current kit, the Contoller Board mounts directly to the E-chassis, with no spacers in between. If the mounting screws are overtightened, this can cause stresses on the board. I put some American #4 nylon washers between the Controller board and the E-chassis.
As was mentioned somewhere else on the forum, there is not much space in the 2.6 kit for the Ethernet RJ-45 plug to fit between the HomePlug adapter and the motor ESCs. We had to flip the orientation of the HomePlug adapters in the 2.6 kit due to design changes in the Tenda adapters, so we really weren't left with many choices here.
You can greatly ease the clearance problems by cutting down some of the excess shell on the RJ-45 connector. Just make sure you don't nick any of the wires in the process!
The long lead on the USB WebCam bothered me. A number of other people on the forum decided to shorten the cable by using a splice. This works fine, but I decided to do something different. I shortened the cable, but put a new USB plug (USB-A male) on the end of the cable. The new plug has a shorter strain relief, so it fits better in the limited space of the OROV E-chassis.
The connector I used was purchased from Digi-Key, part number was AE10637-ND.
Proper operation of the camera tilt servo depends upon smooth motion of the camera tilt platform. If the tilt platform binds, the plastic gears of the servo can strip, ruining the servo.
When I first mounted my camera on the tilt platform, I noticed some bowing of the platform:
It turns out that the white plastic blinders on the tilt platform stuck out the back side of the platform very slightly:
I ground those down with a Dremel tool to make sure that the camera would mount flat against the platform.
When the tilt platform was mounted in the E-chassis, I was not happy with the operation of the pivots. If I tightened the pivot screw/nut tight enough to keep the platform from flopping about, it bowed the camera tilt platform again. To make things work smoothly, I added some nylon washers to shim the mounting of the tilt platform. I used American #4 washers, you can use M3 as well.
Some washers in the servo mounting helped on the one side of the tilt platform mount:
And I used a very thin washer as a bearing of sorts on the other side:
With the washers in place, there is no bowing of the tilt platform whatsoever. Between this and shortening the camera USB cable, the tilt platform moves very smoothly over its entire range of motion.
For mounting the LEDs, I didn't like the procedure shown in the instructions. I mounted the LEDs on the camera tilt platform, but waited until after installing the camera to wire the LEDs together. There is just enough room on the side of the camera for one set of LED wires to sneak under the cable zip ties. They can then be trimmed to the correct length and soldered to the other LED module, leaving no loose cable.
To keep light from the LEDs from reflecting into the camera, I added some black velvet swatches to the white plastic blinders. The velvet needs to touch the outer acrylic tube without causing a lot of drag on the tilt mechanism- some experimentation and trimming is necessary.
As was noted in Kjetil's comment in this blog post, in the 2.6 kit the pins to which the Homeplug adapter mounts on the Topside Adapter and the Controller Board are a little too short. This will be fixed in the next production run of components, but if you have the current kit and are unhappy with the way things fit, you can desolder the current pins and install new ones.
The correct length for the pins is 0.320", as opposed to the "standard" mating length of 0.230".
Here's what happens to an existing topside assembly if you put pressure on the back side of the HomePlug adapter:
And here's the same thing with the longer pins installed:
Note: If you're unsure of your desoldering and soldering skills, this change may not be for you. Try working first on the topside adapter, which is a simple 2-layer board . The controller board is a 4-layer board, and if you rip out the plated-through holes, you will ruin the board.
Thanks for a lot of good tips.
When epoxying the props to the motor bells, the Dozuki instructions tell you to put the completed units on a wire shelf or rack of some kind while the epoxy is curing. I didn't have anything suitable around, but I did still have the foam that the Tenda Homeplug adapters came packed in. A little work with an awl:
And it becomes a perfect holder for the props while they cure:
My main tube was a couple of mm on the short side (it should be 180 mm long), but the fit of the end caps was very snug, so I didn't feel like replacing it with a different tube. When I put the whole assembly together, the combination of the wiring harness and the tabs on the end of the E-chassis tried to push the endcaps apart. This would have likely lead to a water leak at some point, no matter how carefully I fussed with things and adjusted things before each dive.
The fix was to grind off the tabs a bit on the end of the E-chassis- you can grind them down until the camera platform pivot screw has just a bit of clearance from the endcap when the whole assembly is put together.
When you first install the main tube endcaps together with the E-chassis, you should do a similar check to make sure that nothing is pushing the endcaps off of the main tube.
The Dozuki guide for ballasting your ROV hasn't been written yet, but we've found that with the Revision 2.6 OpenROV, the balance is really close is you just add 3 2-ounce river sinkers to the front M5 threaded rod, with the rod in the forward-most set of holes.
Here's what a river sinker looks like- they are available any place where fishing supplies are sold:
I wanted to move the forward M5 rod back one set of holes, so that it is not in the field-of-view of the camera. To mount the ballast weight forward on the unit, I mounted a 2-ounce river sinker on each side of the ROV at the forward mounting hole, using an M5-16 machine screw and a couple of nuts. The weight of the two screws and four nuts should be (I hope) about the same as if I had mounted a third sinker on the ROV:
These mods are great! ... I just had a thought: do you think grooves could be made across a diameter of a river sinker so that they could be put in front of the battery packs and held in place with the o-ring that goes around the pack? It seems like there would be a potential for the weights to fall off too easily this way, but if not, it would get the weight about as forward as it could be, and it would also help keep the battery endcaps on with more force.
Something to experiment with, perhaps...
I noticed the o-rings on my 2.5 build would not always make contact around 100% of the circumference. I started using a thin strip of self fusing silicone tape around the inside of the o-ring groove. The tape pushes the o-ring out to make good contact. Also the tape is silicone and seals with the o-ring quite well.
- silicone tape strip in o-ring groove
- self-fusing silicone tape wrapped around the outside of the end cap to add a redundant seal
Great suggestions walt. David asked that we post other tips here as well.
Tip is for Soldering the Topside Tenda Home Plug Adapter
1. put hot glue on the backside of the header pins prior to soldering
The hot glue helps dissipate the heat from soldering and prevents the header pints from breaking free of their mounting. I am a novice at soldering and these pins popped loose during soldering causing all my intermittent communications problems. I got a new Tenda adapter and used the hot glue technique and it worked!
Great tip Walt! Also on the 2.5 kit if you cut the pins too short you can remove the black spacer with needle nose pliers easily giving you enough pin to solder to. I found it difficult to re-solder these pins mine wouldn't bond to the board it was like I was stripping off the layer it mounted too. I found that putting a dab of hot glue on the back side of the header pins prior to soldering would prevent them from breaking free.
I did this too! Works great! Too bad the COB causes the batteries to be in the view as well. I painted the tops of my battery packs black to reduce glare at night. When looking at objects in the distance (at night) the auto-exposure tends to reduce brightness (and contrast) because of the battery pack glare. When you get close to something the lights light it up enough to tell the auto-exposure to change settings to see the scene. If the view is too dim the presence of the battery packs actually reduces visibility because of the glare.
Could just epoxy them on as part of the build.
Do you have a link for this silicone tape?
David Murphy commented on the problem with the teather on the sea of Cortez video. In those conditions there are many obstructions that the teather can get caught on as seen on the video. I have similiar conditions here except the water is much colder. I have purchased a floating line that the local fishermen use. The center of this line has a smaller rope which I used to pull in the teather (see picture). The boyancy is almost neutral in fresh water. I plan on attaching a float at the depth I plan to dive and to tow it around. That way I will be able to visually check where I am and as well if I get caught up I will be able to recover the float and to pull up on it without relying on the strength of the teather to recover it. I don't plan at this point of covering the whole teather but only the first 50 to 100 ft.,the rest I can afford to lose.
It doesn't really take much space on the spool.