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I want to illuminate a aquarium using 2x 10W (12V) underwater LEDs (for aesthetic reasons and also to eliminate the cooling problem).

Can I submerge the LEDs directly while the LEDs are powered by a switching power supply? Is it safer if I use an isolated 12 volt DC power source?

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    \$\begingroup\$ The LED itself will (assuming it is constructed well enough) have no problems with being submerged in water. Your problem will be the LED's contacts. There will be 12 V between the contacts so Electolysis en.wikipedia.org/wiki/Electrolysis will take place. This will corrode the metal of the LEDs contacts and might dissolve certain metals in the water. But if you can prevent the LED's contacts from getting wet (that will be a challenge) then I see no issue. \$\endgroup\$
    – Bimpelrekkie
    Commented Jan 12, 2017 at 13:24
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    \$\begingroup\$ What's the lens made of? If it is they type with a clear rubbery looking material, it's not waterproof. \$\endgroup\$
    – Tom Carpenter
    Commented Jan 12, 2017 at 13:24
  • \$\begingroup\$ @TomCarpenter-oh... good to know! thanks. fortunately, it is not my case. usually this type of material is found at 20W+ LEDs. small power LEDs use hard plastic. \$\endgroup\$
    – IceCold
    Commented Jan 12, 2017 at 13:26
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    \$\begingroup\$ 20 watts to warm your fish up - better make sure you have tropical fish. \$\endgroup\$
    – Andy aka
    Commented Jan 12, 2017 at 13:39
  • \$\begingroup\$ A link to the device would prove useful. \$\endgroup\$
    – Andy aka
    Commented Jan 12, 2017 at 14:29

4 Answers 4

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I would put all the assembled LEDs in a small bucket of waterproof varnish for some hours, then let it dry before using.

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  • \$\begingroup\$ Hi Lionel. There might be a problem: the varnish will prevent heat dissipation. \$\endgroup\$
    – IceCold
    Commented Jan 13, 2017 at 12:36
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I used silicon tube for insulating a water warmer, try that and put some silicone gel on the end near the led to seal off the tube fron water.

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No voltage is safe underwater without waterproof insulation. If you let the water touch bare wires, they will be gone in a few hours due to electrochemical corrosion.

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  • \$\begingroup\$ I tried a to insulate the contact in plastic (glue gun) and it works. \$\endgroup\$
    – IceCold
    Commented Jan 12, 2017 at 13:25
  • \$\begingroup\$ @Silvester - "Works" for how long? Did you try it for hours/days/months? I'd still be worried about corrosion. \$\endgroup\$
    – Bort
    Commented Jan 12, 2017 at 13:25
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    \$\begingroup\$ Hot glue is kind of rubbish, but there are proper aquarium-safe sealants that could be used for this. \$\endgroup\$
    – pjc50
    Commented Jan 12, 2017 at 13:28
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    \$\begingroup\$ @Silvester I was expecting such a comment about 0V. Yes, corrosion slows down as the voltage decreases, but it never stops. Even without any voltage, most metals will corrode, and applying voltage only makes this worse. \$\endgroup\$
    – Dmitry Grigoryev
    Commented Jan 12, 2017 at 13:30
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    \$\begingroup\$ @Silvester did you want an answer to your question or did you just want to post snotty reply comments? \$\endgroup\$
    – user103993
    Commented Jan 13, 2017 at 12:36
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Water by itself isn't good conductor, but pretty much every bowl of water you use has additional chemical elements that might make it a better conductor. Gluing might be okay solution but if I were you I would find proper case. It might cost you, but at least IP67 case seems like an option to me

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  • \$\begingroup\$ Cases are big. I would like to 'hide' LEDs under rocks and stuff for dramatic effect. \$\endgroup\$
    – IceCold
    Commented Jan 12, 2017 at 13:32
  • \$\begingroup\$ Even distilled water will rust bare wires under 12V in a couple of days. (kind of proof) \$\endgroup\$
    – Dmitry Grigoryev
    Commented Jan 12, 2017 at 13:32
  • \$\begingroup\$ Yes, either use case or some material to make contacts safe or drop such ideas out of your head. \$\endgroup\$
    – Artūras Jonkus
    Commented Jan 12, 2017 at 13:40

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