I honestly thought that this would not work because it is way too simple and easy for me to be the first person to think of it. (or at least the first person to publish) A normal scuba light will run you about $100-$150, renting one usually goes for between $9-$15.
I made a video podcast for the project below.
Please check out my other instructables as well.
Step 1: Materials
All you need for this project is:
LED Flashlight (I got 3 for $9 from Home Depot and made 2 dive lights) The lights should also have a push-button switch with a rubber seal and rubber seals at the threaded joints.
A drill with a small bit (I used a 3/64")
A small tupperware container
A small bottle of mineral oil (its a laxative so get it at a pharmacy for a few $)
Step 2: Theory
My idea was triggered by two things...
The first was the movie the Abyss. Remember when they were breathing an oxygenated liquid? This allowed them to go to incredible depths because liquids are not compressible like gasses are (see my video for a slightly more detailed explanation)
The second idea was from looking at pictures of people overclocking their computers. Basically they make their computers run faster than they are supposed to but this causes them to heat up and even melt. One way they combat the heat is to put the computer into an aquarium and fill it with mineral oil. The mineral oil does not conduct electricity or corrode components and just happens to be clear.
So if we can fill a flashlight or other device with oil, we can take the pressure off of the seals, the most work they will do is keeping the oil inside on the surface.
Step 3: Filling
The hardest part was getting access to the area between the LED's and the lens. I was starting to damage the aluminum trying to open it up so I just decided to drill through the back instead. I used a 3/64" bit and drilled two holes through the circuit board that holds the LED's. Be careful not to damage the copper traces or the LED's on the other side.
Now as I learned, mineral oil does not want to flow through a 3/64" hole. I came up with the idea of sticking the drill bit back in one of the holes and running it in reverse so it works like a pump. You will see air bubbles coming out of the other hole, when they stop coming out, there is no more air inside (provided you are holding it straight)
I put everything in the tupperware and poured the oil in. Make sure there are no trapped air bubbles as you start to re-assemble the light. When you are screwing the last part on; push and hold the button in to turn on the light. Otherwise, when you turn the last few turns on the threads, the rubber will start to push out like a balloon.
Once everything is together, wipe it off, rinse it off and put the remaining oil back into its container. (I spilled a bunch accidentally and still only used about 1/5th of the container.)
Now due to temperature changes the aluminum and oil will expand and contract very slightly which may cause some seepage. There also might be a bit of oil trapped in the grooves, threads and knurling. I didn't have a problem with the lights sitting for 2 weeks but I stuck them inside a ziplock during transportation to be safe.
Step 4: The Money Shot!
I was actually down below 95ft, but this is the deepest footage I took at about 88ft
The second light I made was mounted to my camera.
Thanks for reading!
If you have Ideas for other things you could take underwater like this, let me know in the comments, I'd like to try it! Next time I'm going to do a larger flashlight.
Before anyone says it! I don't think cameras will work well for a few reasons,
1) they are not sealed at all to begin with and would be hard to do so.
2) the index of refraction through the oil would be different than air which would screw up the way the lenses work.
3) the lenses have lots of little gaps inside that would be hard to purge of air.
4) waterproof housings are not that expensive considering what they protect.
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