Build Blog for OpenROV #358 (aka "Little Boy Blue") - Post 5


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Greetings Citizen Explorers!


As mentioned in my last post several months ago, my blogging and building has gotten behind due to school commitments, so I’ll be playing catch up for a bit. If you need a quick reminder on my progress, just check out my previous posts below:


Post 1: Introduction

Post 2: Assembly of Inner Structure and End caps

Post 3: Assembly of Battery Packs and Thrusters

Post 4: Little Boy Blue Goes to the Atlanta Mini Maker Faire


Just to speed things up I’ll be highlighting the parts of the build I've had the most difficulty with:

(1) Step 8: Topside Tether Adapter

(2) Step 9: Potting the wire pass-throughs in the end caps...I’m woman enough to admit I messed this up two times, haha.

(3) Steps 11-13: Setting up the cape and software (which I will tackle in the next post).


And with that, let’s get started!



Step 8: Topside Tether Adapter


I realized I left a couple tools out of my list on Post 2 (link) - one being flush cutters. You can get a pair for about $8. BUY THESE. Don’t be clumsy like me and try to snip off connectors with an oversized tool, or you risk damaging other internal components. (http://www.adafruit.com/products/152)


The 22-gauge hookup wire can be purchased online here I managed to get some by buying double-stranded electrical wire from Home Depot and remove the internal wires. Or you can do it the easier way and buy some 22 gauge hookup wire from an electronics store or an online vendor like Adafruit Industries; they’re maker-friendly and have an awesome intro to electronics tutorial section.


Due to my unfamiliarity with handling delicate electronics, I frequently forget that touching the board could potentially cause static electricity to short out the board. Grasping the sides of the breadboard instead of touching things all willy-nilly like me should prevent this.



Step 9: Potting the wire pass-throughs in the end caps.


This step requires setting up the bundle of wires in a taught fashion so the pass-through hole in the acrylic end caps can be sealed shut with epoxy and hot glue. Anything that cantilevers over your table and end cap can be used to tie a string to the wire bundle and keep it vertical. I happened to have a music stand lying around so I adjusted the top of the stand until it hung over the table.



Trouble arose when it came time to apply the epoxy: the tutorial videos clearly and frequently stressed the importance of properly labeling all wires to their respective electronics, as well as to ensure the labels are visible after the wires are pulled through the end cap. Well, I forgot that important detail, and a couple labels got trapped - preventing me from knowing what wires belonged to what. I had to cut off the end cap and start over. Thankfully my college has several laser cutters so I was able to make new acrylic pieces.



My second attempt had better labeling, but I was overzealous with the hot glue along the outside of the end cap pass-through. The excess glue prevented the acrylic tube from properly sealing when connected to the end cap. I also had to re-solder new wire to extend the old wires, which was messy patchwork on my part; I plan to use butt splices next time around to ensure a neat and reliable connection between wires.



On a semi-related note, I saw these waterproof wire nuts at Home Depot. In the event of a leak within the e-chassis, these could be a good alternative to soldering together and coating the ESC wire bundles with liquid electrical tape.


That’s all for now! Blog Post #6 will cover cape and software shenanigans.


Leslie



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I moved a post to an existing topic: Build Blog for OpenROV #358 (aka “Little Boy Blue”) - Post 1


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