So, as I am experimenting with joystick control, I have decided to start brainstorming about how to waterproof the electronics. Any ideas? It will have to be able to go 15 ft. under water.
Thanks
Pelican cases are fantastic for rugged transport, and are super-water tight (they were originally made for divers). They come in all shapes and sizes, and even have pressure release valves to keep them from popping open when the local pressure changes. You might be interested in some of the “Micro” size cases, which have clear lids so you can see all the blinking lights inside. The downside is that they can get a little pricey, and you’re not going to find one at your local hardware store (of course you can order them online). They are very popular for electronics enclosures for underwater robots, as you can see in this video from the 2007 AUVSI International Autonomous Underwater Vehicle Competition.
On the other hand, if you watch the whole video, about 2/3 of the way through one of the organizers says:
What we were impressed with, the homeschool highschool team, the smirf team, they were working with almost a tupperware box, and we saw them on the dock open that thing 20 times or more, each time they made a run, and it stayed completely water-tight!
We’ve got other people that have, you know, ten thousand dollars of acrylic design and seals, and they fried!
So high-end tupperware is also definitely your friend.
Cheap RC boats aren’t very water-tight, but they slather all of their electronics in water-repelling grease, which makes things really messy and hard to change/repair, but at the same time is some sort of insurance against leaks into your waterproof chamber. Probably not worth it if you’ve got a good seal.
-Adam
Will the pelican cases allow wires to exit the case and stay watertight?
No, that’s the real trick. You’re going to have to make a hole in the case for whatever wires you use.
You can get special water-tight connectors like these that will make a seal around a flat hole you drill in the case, but those will cost a few bucks be a lot of work to assemble.
Alternatively you can drill a hole, pass your wires through it, then seal the hole back up with lots and lots of a good water-tight sealant like Marine Goop (which you should be able to find at a hardware/home improvement store). Make sure to secure the wire bundle to the case on both sides of this seal so that if the tether gets yanked on it doesn’t yank the goop out!
-Adam
While we were at the robotics competition last year, we saw some components encased in some kind of acrylic or plastic. Would that be feasible? It seems like the chips would overheat.
It’s possible, I’ve seen projects where people embedded electronics in clear casting resin, and I’ve seen some military robots with their circuit boards completely encased in bricks of epoxy. You’re right though, the real problem would be heat dissipation from the motor driver chips. It would depend on what kind of resin you were using, how thick it was, and how much power you put through the motor controller. The chips on your TReX Jr’s will shut down if they start to overheat, so I don’t think you would damage them, but you might find that they would only operate for a little while, then shut off.
I bet you could get away with just a well-sealed container, but if you want to do something like this I would suggest something like a soft polyurethane resin, or a 100% silicone sealant like DAP Aquarium sealant, which you should be able to find at a hardware store (like they use to seal/hold aquarium glass pieces together, water-tight indeed!). Essentially, if you use something flexible and rubbery, and you ever want/need to get the board out again (i.e. you discover its overheating all the time) you should be able to carefully cut and peel it out again.
If you encase it in something like epoxy, or an acrylic casting resin, and something goes wrong, you’re stuck, and you need to buy a new TReX!
-Adam
There will be an average of 1A per channel with peaks of about 1.5A. Do you think that will be ok temperature wise? It will be underwater most of the time. The water will probably be about 70-80*F.
Thanks
I belong to a group that sails r/c model submarines. The standard for them seems to be a length of plastic pipe/tube with plastic endcaps sealing with o-rings.
Ron