Here's some background information for those who are curious:
The change from 2.5 to 2.6 was forced by the discovery (by somebody on the Forum) that the design of the Tenda HomePlug adapters had changed, and that the Tenda Revision 2.0 adapters would not fit on the V2.5 OROV Controller board. Yikes! Some quick E-mails to our Tenda rep revealed that yes, the design had changed, but somehow he hadn't notified us of this. We had some discussions here at OROV HQ whether or not to try to buy up a big stock of the old Tenda V1.1 adapters, since production and sales of the current ROV design were in full-swing, and we didn't want to perturb that. But after some head-scratching, we realized that we could modify the design of the Controller Board so that it was compatible with both the old and the new Tenda adapters.
So, off we went, updating the design of the electronics. The controller board schematic stayed mostly the same, but the layout of the central portion of the board changed significantly to allow the new adapters to plug in, while still keeping the pads for the old adapters. On the Tenda V2.0 design, the LEDs are on the power board rather than the logic board, so, since the ROV doesn't use this power board, we had to add some LEDs to the Controller board to show the status of the Homeplug adapter. We rolled a couple of other updates into the board as well- the holes for mounting the ESC power leads were opened up just a touch, there was some filtering added to the ESC current monitors, and the BB Cape ID EEPROM was added back in, in support of future auto-ID software.
In the end it all worked out OK- the boards are stuffed in a configuration where the Tenda V2.0 adapters plug right in, as before. If you have an old V1.1 adapter, you can still use it, but you have to unsolder a couple of headers, and stuff in a couple of sockets. The new LEDs work well at allowing you to see the status of the HomePlug adapter from outside the ROV. The 2.6 controller boards are 100% software-compatible with the old 2.5 controller boards.
The change in HomePlug adapter boards forced our hand in redesigning the top-side adapter as well. A number of folks had had problems putting together the V2.5 topside adapter, so, since we needed to build something with LEDs to display the topside adapter status, we decided to put together a complete board that eliminates all the soldering and fussing involved with putting together the topside adapter. This new board has a voltage regulator as well as the 3 status LEDs for the HomePlug adapter, and the tether connection is now made through some spring terminals rather than screw terminals. The Tenda HomePlug adapter plugs into this board similar to the way it does on the controller board. There's no soldering of any kind required.
So, while all this was going on, we were digesting the results of the open-water testing from Lake Tahoe in late October. The biggest takeaway was that our current main endcap design was just too twitchy for long-term use. The manufacturing tolerance stackup between the acrylic tube and the laser-cut endcaps was too wide for the O-ring to handle, even after fussing with Teflon tape, latex balloons, and the like. So Eric bit the bullet and redesigned the endcaps, changing the layer stackup in a way that allowed the O-ring to be greatly increased in diameter. There were also some changes made to the location of the wiring channel, that increase the strength of the endcaps.
The final changes that were made to OROV 2.6 involved simplifying the internal structure of the ROV. Some areas that required doublers of 1/8" acrylic were changed to a single piece of 1/4", which is significantly stronger, as well as not requiring any build time. The position of the motors was moved a bit as well, to try to improve the balance and the driveability of the ROV.
So, the 2.6 unit is easier to build, and more robust. What more can you ask for?
One of the objectives for our recent trip to the Sea of Cortez was to give the OROV 2.6 vehicles an extended test in sea water. More on that in some future blog posts, but the main thing we found out was that the new main endcap design is massively better than the older 2.5 design. So much so that we'll be offering new endcap kits to allow people to upgrade their older endcaps to the new style. No teflon tape, no latex balloons, it just pretty much works.