Prep for expansion?


#1

I am all assembled and bench tested on number 309. I have been holding off on potting the wire loom thinking about trying to prep for some of the upcoming changes and mods. Is there merit in potting in a few extra wires with the 2.4 design loom so additions can be made without drilling or having to get new build parts?

On the conference call video, Eric mentioned that he was posting links and such about the new projects and I cannot seem to find those anywhere on OpenROV.com or G+.


#2

Hi John:

Interesting timing on this. A couple of hours ago I sent Colin an E-mail suggesting that he address this issue in the instructions.

If you want to add sensors outside the E-chassis, you're going to need spare wires going through the potting. One of the things we're about to start playing with at OpenROV HQ is an externally-mounted I2C depth sensor, which will take 4 extra wires- power, ground, data, and clock. In a pinch you could do it with 3, by stealing the ground connection from the battery tubes.

I'm at the same spot as you in construction of the ROV, and hope to be potting stuff tomorrow. For my endcaps, I'm going to try to pot in 5 extra wires, so that every slot in the Molex connector is filled. 4 of these will be for external sensors as mentioned above, with one spare wire. For the hookups to the Molex connector, I'm going to have it fit the pinout used on the Power Distribution Board schematics (see here). The 5 extra wires won't be carrying a lot of current, so I'm just going to snip off some of the tether wire and use that.

I can only think of two downsides to adding the additional wires:

1.) The wire bundle needs to fit loosely enough through the hole in the endcap to allow the epoxy to flow and seal around all the individual wires.

2.) For the spare wires, I'm going to use some of the liquid electrical tape stuff on the exposed end of the wire, to keep water from wicking up between the wire and its insulation. Once the spare wires are hooked to a sensor, it will be sealed as needed.

Hope this helps. I'd certainly like to hear what others have done.

-Walt


#3

sounds like a good plan. I was thinking that the extra wires would be a bit of an issue with the existing loom so, I was thinking about potting them out the opposite end cap. May need to put in a different inline connector so that they don't hinder e-chassis removal. With the narrower endcaps on the 2.4 there is extra room to wrap in the extra length that would be needed.

I have not yet played around with I2C bus but as I understand you would be able to run a myriad of exterior items on a single setup of wires. I am waiting on shipment of some quite small form factor arduinos that I am planning on using to run payloads, either sensors or a buoy deployment package.