DC gas ionization lamp?

Fluorescent lamps will run on DC, but you of course need special current-limiting and starting circuitry to replace the ballast used on AC applications. It is not difficult if you use pre-heat type lamps; instant-start lamps are more challenging.

Exactly what are you trying to do? How much light do you need? How much lamp life?

Flourescent tubes will run on DC. The filaments are usually designed so that, on AC, they are heated by bombardment on one half-cycle when they are anodes and then have better emission properties when they are cathodes. If you run the tube in one direction only, you may have to consider heating the cathode from a small transformer.

The other problem with DC is that the tube will darken at one end after a few hour's use because the mercury ions all migrate to one end. You may need some sort of polarity reversal arrangement which operates from time to time.

In the days when DC mains was still common, they used a special switch for flourescent tubes, which reversed the polarity to the light fitting each time it was switched on.

I am looking for something like a common flourescent or neon tube, but one that runs on pure DC.

I don't mean it runs off an inverter but uses HVDC direct to the tube to maintain ionization of the gas.

An AC ignition voltage would be OK as long as the tube runs on DC once ignited.

I believe some cinema projection lamps do this, but they are far to powerful and expensive in terms of power supply and heat generated.

Color, wattage or gas content does not matter, but the tube must be cylindrical with diameter within the 10-30mm range. Length is not critical.

What would be the best off-the-shelf solution for doing this?

Much thanks,

David Masters

JKL Industries sells these by the bushel basket.

Otherwise, you are describing a NE-2 neon lamp.

"David Masters"

Obviously the ballast and starting set ups have to be redesigned to suit DC.

You can get small fluoro lamps (5 watt) only 10mm dia and about 150mm long from a lighting shop.

IIRC they run at about 150 volts and 30 mA.

What DC supply have you got ?

....... Phil

"BFoelsch"

.......... Phil ;-)

"Adrian Tuddenham"

Is this from personal knowledge ?

........... Phil

From reading up old textbooks to gain fundamental background knowledge.