Re: AC to DC question, old worklight

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "volitan712003"
<volitan@o...> wrote:

> There's a sign near the light that says to use a
> 24v, H3 Halogen bulb.
>
> David

Hi David:

Not to beat a dead horse, but I have designed several
high power, high reliability halogen bulb regulator
circuits for precision lighting applications in the
semiconductor test equipment industry. Here are a few
technical tidbits...

Halogen bulbs actually run better on AC. The quartz
bulb envelope will prematurely blacken with evaporated
tungsten at one end if DC power is used.

Bulb life depends on applied voltage... 10% overvoltage
cuts bulb life in half! 10% under doubles bulb life. But
20% under is very bad for life because the quartz envelope
gets too cold for proper "Halogen" operation. When this
happens, tungsten starts condensing on the inside of the
bulb and the filament evaporates away. When the bulb is
really hot (normal rated voltage applied) the tungsten can't
condense on the glass and actually re-forms back on the
filament... hence the increased lifetime even at very
white hot filament temperatures.

A good halogen bulb manufactuer (like Usheo) has this
kind of bulb data on line so you can check it out youself
to be sure that you are running the bulb under optimal
conditions.

Regards... Jeff