This is the first draft of the ROV's interior. Though the current production draft fits a bit tighter with the camera tilt servo and faceplate (which protects the raspberry pi from water drippings when you remove the dome), I think it gives you a pretty good idea of the hardware layout. You have a LiPo battery compartment down the center of the 3D printed "cradle" (out of view), which kind of acts like the interior's core. This fits a 2200mah 3S lipo, but let us know if you have any ideas on how to get a bigger battery in there!
Then we have a Raspberry Pi 3 Model B mounted forward of the LiPo compartment. This is positioned with the GPIO pins facing the rear dome. That makes it pretty difficult to accidentally unplug anything while you're getting set up for a dive.
On either side of the dome, we have our dual channel motor drivers. These communicate with the RPi via PWM from the GPIO pins. To make any changes to the GPIO setup, or add hardware, just unscrew the right-hand motor driver.
Neat layout. Then I think on the lower half of the sphere you have the tether penetration (RJ45) to the RPi and 8 o-ringed bolts penetrating the sphere which act as power posts for the thrusters to wire onto?
Yes, that’s exactly right! There is an epoxy-sealed RJ45 penetration into the bottom of the sphere, and the o-ringed bolts all conduct power to the thrusters. This is actually a photo of one of our original prototypes, so there are no wire penetrations in this image. I’ll take some pictures of the current version (Model C 0.1.0) for you soon so you can get a better look!
Here are those images!
Ethernet penetration:
This first one is a photo of the sphere's underside. You'll see the point where the ethernet enters the dome.
That's sealed very effectively by a spot of epoxy. The tight fit between the ethernet's wires and the penetration point make sure there's no flexure at all to pry away the epoxy seal.
O-ring seals:
The other penetration points (for the motors and start key) are sealed with o-ring screws as you said. These enter the sphere near the left and right flanks of the rear dome. This, along with a healthy coating of rubber cement, ensures that there's too much distance for them to create a short with the motor drivers.
Thanks for these. Very clear photo's and descriptions. Novel solutions to tether and external power supply.
Hi it’s really interesting and helpful answer but for the RJ can you think it’s be better enclose all cables one by one small hole are more easy for epoxy easy to filing ( I’m French sorry if my English is not perfect 🙂
Thanks for the comment!!
I think that's a pretty cool idea. I actually did consider using smaller self-sealing screws to serve as bulkhead penetrations for each Ethernet wire. However, that introduces a lot more potential spots where corrosion can set in if they're not sealed properly. To avoid problems with corrosion on the Ethernet wires, we decided to go with an epoxy seal around the wires themselves.
As far as one smaller hole for each wire, I'd be very interested to see how thatmight work. I personally feel a bit safer with one hole (fewer seals to break). But I do think you have a point, since a few well-sized holes probably would be even more secure. Definitely a good experiment to try!