Putting LED near incadescent light source on lava lamp

Question

I am currently trying to modify a traditional lava lamp, to change the colour of light it emits, by placing an LED strip somewhere around the body, so it also lights the inside of the lamp.

My lava lamp is powered by a 25 watt incandescent lightbulb, which, as you may imagine generates quite a lot of heat. My question is, what is the maximum temperature my LED strip can take, whithout it seriously impacting longevity (I would like it to work for at least 2-3 years).

Is it even possible to do this?

Answer 1

The lava effect in the lava lamp is a kind of convection. It is driven by the heat of the incandescent lamp. You will need to replace the incandescent lamp with some kind of 25W heater that doesn't emit light in the first place.

While you are at it, you may want to add some ambient temperature correction for the heater power as most lava lamps don't work well when it is too hot or too cold around.

Having done that, diodes are easy. Most lava lamps work around 60C and most LEDs are pretty much OK at 60C as long as you drive them at 10-30% of their rated power. In general, lava lamps don't push the technology limits of the light intensity, so you should be pretty much OK with that.

(Why I think so: a lot of LEDs are rated for 80-120C crystal temperature, e.g. see a random LED datasheet here)

You can as well use some "fiber optics" (the "fiber" part may be 2-5mm diameter glass or transparent plastic sticks) and place the diodes well below the heater and carry the light where you need it. But it probably doesn't worth the hassle.

Answer 2

Is it even possible to do this?

Well, yes, but be prepared for very uninspiring results.

Normally, the liquid in a lava lamp is a single, fairly-bright color. This means that it absorbs most colors and only reflects over a fairly small range. Colored LEDs, of course, only emit light over a fairly small range, so for most colors put out by the LEDs the lava lamp globs will look pretty much black. Depending on the liquid used in the lava lamp, this may not be problem, but I'd strongly advise a quick test before you go to the trouble of building a complete assembly.

EDIT - Rather than saying black (which doesn't take into account light from the 25 W bulb), say rather that for most colors from the LED you probably won't see any effect, or only a very small effect, on the color of the blobs.