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How do I determine the voltage and necessary power supply for this bulb?

This bulb is a UVC low-pressure mercury vapor bulb used in my air purifier. It fits in a G23 Socket; normally I would expect a compact fluorescent bulb (G23) to have a ballast built in. This bulb is incandescent but it fits into a fluorescent socket. How do I drive this bulb, I'm assuming I need some sort of ballast?

Note: I believe this bulb is the old-style bulb which, according to some references, is considered incandescent but admit I do not know for sure. It does contain a filament.

enter image description here

An older design looks like an incandescent lamp but with the envelope containing a few droplets of mercury. In this design, the incandescent filament heats the mercury, producing a vapor which eventually allows an arc to be struck, short circuiting the incandescent filament.

  • from Wikipedia
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  • \$\begingroup\$ Re, "This bulb is a UVC low pressure mercury vapor bulb", and "This bulb is incandescent," Those two assertions can't both be true. Is it possible that you are seeing heated electrodes at either end of the tube, and mistaking those for incandescent filaments? \$\endgroup\$ – Solomon Slow Mar 23 '20 at 15:03
  • \$\begingroup\$ The bulb I’m referring to is an older style bulb which I believe is technically incandescent but I would defer to someone who is more knowledgeable. I will edit the question to be more accurate. \$\endgroup\$ – user379468 Mar 23 '20 at 15:08
  • \$\begingroup\$ Could you add a photo of this bulb? \$\endgroup\$ – rdtsc Mar 23 '20 at 15:16
  • \$\begingroup\$ Does Driving compact UV lamp with DC lead to anything useful for you? \$\endgroup\$ – Andrew Morton Mar 23 '20 at 17:39
  • \$\begingroup\$ It's essentially a fluorescent lamp, but without the fluorescent coating. The two wires are heaters, and fluorescent lamps also have them so that the lamp can be started from cols. \$\endgroup\$ – Simon B Apr 20 '20 at 7:42
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It looks like a fluorescent mercury bulb designed to output 254nm light with 5W. They are driven with AC current, but the actual control of that varies because temperature changes resistance. You can find many driver designs online, here is an example: https://www.electroschematics.com/fluorescent-light-driver/

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From wikipedia:

a bi-pin tube designed for conventional ballast, e.g. with G23 or G24d plug-in base (...) contains an integrated starter, which obviates the need for external heating pins but causes incompatibility with electronic ballasts.

This is just like a standard fluorescent fixture except the starter is inside the bulb and the two accessible pins are labeled 1 and 2 on the schematic below:

enter image description here

Source for the above picture explains how it works.

So you need a magnetic ballast, which is basically an inductor. Googling "G23 5W ballast" gives some useful links. Wire it in series with your 2-pin bulb.

Note: UV-C destroys DNA, it will make you blind, it gives sunburns and skin cancer, and it also destroys plastics which is probably why the plastic bulb base is protected by a metal sheath. Be very careful with it. Use only inside an enclosure. Just like a sunburn, effect becomes noticeable only after it is too late. You can get a high enough dose to go blind and only notice it later when the effects manifest. It's pretty treacherous.

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