Waterproof circuit housing

Hey, I'm trying to replicate this fountain to some extent:

The candle has a hole through the center, water pumps up, out and down, and the candle glows from LEDs buried within. I have a good plan for how I want to make the circuit - just an AVR controlling 3 rgb LEDs. I will also use either a transformer/rectifier setup for 5v DC, spliced from the pump's AC line, or I may buy one of those switching supplies.

The LEDs I can bury in the wax, but everything else is pretty dangerous around water, the AC especially. What would be the best approach for this design? I've considered 3D printing the insides, I.e. one compartment for electronics, one for water. What's your take?


If I were doing this project I would power the LEDS from a 12v battery and solar panel. Zero risk of electrocution and you can assemble and test independently from the fountain.

If you are determined to to power them from the mains then I would put everything, including all electrical connections in a box and fill with marine potting compound. Don't improvise with Silicone caulk, epoxy or anything else that you can find at a hardware store - they just don't work long term.

Use a UL certified isolated power supply from a trustworthy electronics supplier. Don't use some random power supply you find on Ebay or Aliexpress.

De-rate the power supply as once potted it will run hotter.

Is potting compound cheap? It seems most sources start at $50.

look up pelican cases. they're the standard for waterproofing kit and make small hand sixed boxes which can be adapted to protect technology. Though because of changes in temp and atmospheric moisture i would think you will still have a problem with moisture build up over time. It might be better to simply make a ventilated but rain proof enclosure which would let air pass through so avoiding moisture. A material called Foamex is great for making enclosures. Its a PVC material that you will be able to buy from sign makers or even beg from a sign-makers scrap bin. It comes in various thicknesses 1mm, 2mm, 3mm etc, and can be glued with super glue and easily cut with a sharp blade and can be sanded to shape. Its also easy to paint with car type spray paint.

I'd be reluctant to put a 240ac powered device in the open unless abolutely necessary.

Buy a decent wall-wart, and power it with that.


Is potting compound cheap? It seems most sources start at $50.

Potting compound is expensive, however you can minimise usage by using an inert filler such as washed sand or aquarium gravel to fill the gaps between components.

The only parts that need to go into the wet area are the wires and leds, no?

If so, heat shrink and Elmer's Nano Glue or Gorilla Glue painted over then sprayed with water won't come off without a hell of a lot of effort. I'm assuming that the splices Wear rubber gloves when using that stuff.

Also look into 3M SkotchLok waterproof wire splices. They're an industry standard telecom splice that you don't strip the wires going in, a blade cuts the wires making contact and a bead of silicon glue seals them shut. It's considered permanent. A box of 50 runs about 25 cents each, not cheap but cheaper/quicker splicing CAT-5 than having a pro solder and heat shrink connections especially with hair thin wires. Downside, they may be too big to fit in your candle with 4-lead RGB leds to connect. A single CAT-5 cable has 8 wires, good for 2 RGB leds.

In fact, inside the candle wax you probably need no more than heat shrink tube and a little glue to wire the leds, it's not like the connections will be flexed is it?