A test to see if ordinary LED lamps can be under-run like Dubai lamps to make them last longer with reduced intensity and heat.

To limit the current I used different values of series capacitor, which has a soft limiting effect, making it compatible with traditional capacitive dropper and linear regulator based lamps.

This technique does not work with some lamps with switchmode based power supplies. They will tend to strobe due to the way the circuitry works.

This project involves mains voltage, and suitable precautions should be taken during your experimentation.

The trickiest bit about making a Dooby lamp is finding a place to put the capacitor. In some capacitive dropper based LED lamps it's easy, since their covers may unclip allowing the original high value capacitor to be changed for a lower one. For other lamps like the glass filament styles the capacitor will need to be put inline external to the lamp. That could be in a lamp extender (if you can get one that is easy to open), in a ceiling rose, in the wiring box of a chandelier or in the lightswitch enclosure. Doing it at the lightswitch opens up the possibilities of letting the lamp be switched between full intensity mode or a lower security/night light mode. With two switches you could have the option of on, dim or off.

A benefit of using a capacitor is that it is a soft, efficient and low noise way of dimming to a fixed level. The power factor will generally be no worse than the original, and a suitably rated capacitor will be virtually indestructible in this application.

From my tests the following 400V AC capacitors worked well for a European 220-240V supply:-
470nF converted most lamps to approximately 2W
220nF converted most lamps to around 1W
100nF converted most lamps to around 0.5W
47nF was not measurable. Probably around 0.2W
22nF was not measurable. Probably around 0.1W
10nF (ceramic capacitor). Some lamps won't glow because they have an internal shunt resistor to avoid nuisance glowing due to capacitive switch-wire coupling. But others will glow at a surprising intensity for the tiny current. (I was really surprised at the intensity of some lamps.)

For 120V supplies the capacitors should be 250V AC film capacitors and the values may have to be higher - like 1uF or more. The capacitors are common and cheap, so they can be experimented with. They can be connected in parallel for higher capacitance.

I used a 1 Megohm resistor in parallel with the capacitors during my tests, as the capacitors can store a charge and may give a slight zap if not discharged. In final use the resistor can be soldered or twisted directly to the capacitor leads.

The capacitors will run cold and should be insulated properly if used behind switches or in junction boxes. That could be done with heatshrink sleeving.

Although the super low value capacitors like 22nF only made the lamps glow dimly, it makes them very suitable as directly viewed decorative lamps or for use as night lights, where very little light will be ample at night. With such low power the lamps can be left running continuously, as they will last a very long time and cost virtually nothing to run.