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Dimming flourescents

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Jimmie

Jan 1, 1970
0
Recently installed some of thse flourescent bulb replacements. They work
great but they will not dim.They are at full brigtness no matter what the
setting of the dimmer is. What I expected was that the light would suddenly
come on as I turned it on at somewhere less than full on and go off before I
reached full off. They come on at full brightness with the dimmer just
barely on. My question, Am I saving eletricity by operating at nearly off
postion, doing damage to lamp, doing damage to the dimmer?

Jimmie
 
K

Ken

Jan 1, 1970
0
The said:
Without seeing your lights, and using mine for examples, they are
typically undimmible. Only special flourescents are dimmible. Also,
real warning, I believe dimming undimmible lights is a fire hazard.
So, read the instructions, and use the product safely.

hth,

tom @ www.WorkAtHomePlans.com

I always thought that fluorescent bulbs were gas and required a minimum
voltage to conduct. How do they dim a fluorescent bulb? Thanks.
 
J

John Gilmer

Jan 1, 1970
0
I always thought that fluorescent bulbs were gas and required a minimum
voltage to conduct. How do they dim a fluorescent bulb? Thanks.

It takes a little more engineering but it's quite possible to "dim" a
fluorescent lamp.

I don't know how "they" really do it, but a way to "dim" would be just to
replace a 40 watt ballast with a 20 watt ballast. The bulb would still
"see" the voltage needed to start but would only get HALF the current.

Likewise, it's possible to over drive a fluorescent lamp. Just replace a
40 watt ballast with something larger.
 
B

Bud

Jan 1, 1970
0
Dimming ballasts vary the current through the tube; the voltage is
substantially constant. Dimming ballasts keep the filaments at the end
of the tubes at full voltage while the arc current is lowered. One of
the problems with a non-dimming ballast is the filament voltage is
'dimmed' also.

Bud--
 
K

Ken

Jan 1, 1970
0
Bud said:
Dimming ballasts vary the current through the tube; the voltage is
substantially constant. Dimming ballasts keep the filaments at the end
of the tubes at full voltage while the arc current is lowered. One of
the problems with a non-dimming ballast is the filament voltage is
'dimmed' also.

Bud--

Ah, I did not think of limiting the current! Don't these lamps flicker
if they reduce the current? Or do they simply dim?
 
A

Andrew Gabriel

Jan 1, 1970
0
Ah, I did not think of limiting the current!

In many cases, it is done by rapidly chopping the current.
Actually, triac phase control dimmers can be used (and used
to be), but it's a bit more complicated than dimming a
filament lamp.
Don't these lamps flicker
if they reduce the current? Or do they simply dim?

They will flicker because when the current drops below a certain
level, there's not enough electron/ion bombardment to keep the
filaments hot enough to conduct into the gas fill by thermionic
emission. By separately heating the filaments, this problem is
resolved. Actually, running at reduced tube current without
separately heating the filaments, even before it's low enough
to cause flicker, will wear out the electron emitting coating on
the filaments much faster than running at the correct power
rating, contrary to what one might imagine.
 
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