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Dimming 50W G5.3 Halogen Desk Lamp? How?

S

Sizz

Jan 1, 1970
0
Hi, I am currently building a desk lamp which requires some form of
dimming.
Specifications:
1x 12Volt Transformer (Suitable for dimming)
1x 50watt G5.3 Bulb

How can i create a dimming device which allows the user to dim the
halogen bulb which is suitable for them? Using a potentiometer? What
kind?

Any information regarding circuits/diagrams/material would be much
appreciated?

Thanks
 
H

Homer J Simpson

Jan 1, 1970
0
Sizz said:
Hi, I am currently building a desk lamp which requires some form of
dimming.
Specifications:
1x 12Volt Transformer (Suitable for dimming)
1x 50watt G5.3 Bulb

How can i create a dimming device which allows the user to dim the
halogen bulb which is suitable for them? Using a potentiometer? What
kind?

You can buy a transformer style dimmer off the shelf. They are designed to
provide symmetry.
 
R

Rich Grise

Jan 1, 1970
0
Hi, I am currently building a desk lamp which requires some form of
dimming.
Specifications:
1x 12Volt Transformer (Suitable for dimming)
1x 50watt G5.3 Bulb

How can i create a dimming device which allows the user to dim the
halogen bulb which is suitable for them? Using a potentiometer? What
kind?

Any information regarding circuits/diagrams/material would be much
appreciated?

I've heard it said that you shouldn't even try to dim a halogen bulb -
if it runs below operating temp, the filament vapor will condense on
the bulb envelope; I guess if you want to _permanently_ dim it, that'd
be OK.

Why not just replace the bulb with one that's not so bright?

You could also get some neutral-density filter plastic, but you have
to watch out for waste heat.

Good Luck!
Rich
 
S

Sizz

Jan 1, 1970
0
I've heard it said that you shouldn't even try to dim a halogen bulb -
if it runs below operating temp, the filament vapor will condense on
the bulb envelope; I guess if you want to _permanently_ dim it, that'd
be OK.

Why not just replace the bulb with one that's not so bright?

You could also get some neutral-density filter plastic, but you have
to watch out for waste heat.

Good Luck!
Rich

Hey Rich,

The only reason for dimming the halogen bulb is because different
people want different brightness levels whilst working. This lamp
would be for anyone as you are able to dim it to suit your needs.

Ive looked at several articles and i have mixed feelings about this
topic. Some people say it is possible and others say it isnt.

I need a simple solution which can be incorporated into a desk lamp (a
small unit)

Thanks
 
U

Ukaniu

Jan 1, 1970
0
Uzytkownik "Sizz said:
Ive looked at several articles and i have mixed feelings about this
topic. Some people say it is possible and others say it isnt.

look at graph showing lifetime of standard car halogen lightbulb. I think
there will be no problem with shortage of life with decreaseing voltage.
Especially when you do not dimm it more than 20-30%.

Lukasz
Cheers from Poland
 
P

Phil Allison

Jan 1, 1970
0
** Groper Alert !

Hi, I am currently building a desk lamp which requires some form of
dimming.
Specifications:
1x 12Volt Transformer (Suitable for dimming)
1x 50watt G5.3 Bulb

How can i create a dimming device which allows the user to dim the
halogen bulb which is suitable for them? Using a potentiometer? What
kind?


** A 240 volt, triac dimmer intended for transformer fed loads is what you
need.

On sale at any lighting supplier.

Millions in use - no problems with halogen bulbs.

Any information regarding circuits/diagrams/material would be much
appreciated?


** Best avoid any schematics that use a diac or neon bulb.

Such circuits do NOT work correctly with transformer fed lamps.

Schems using an opto isolator to drive the triac (eg the MOC3021) are likely
OK



......... Phil
 
A

Anthony Fremont

Jan 1, 1970
0
I've heard it said that you shouldn't even try to dim a halogen bulb -
if it runs below operating temp, the filament vapor will condense on
the bulb envelope; I guess if you want to _permanently_ dim it, that'd
be OK.

I don't know about that. My wife has two of these fire hazards. One has a
continuously variable dimmer knob, but the pot seems to have died in it.
The other has a three position switch allowing for two brightness levels.

I once heard something like you describe though, but IIRC they also said
that running it at full voltage again would restore the bulb. Anyone?
 
C

Charlie Edmondson

Jan 1, 1970
0
Anthony said:
I don't know about that. My wife has two of these fire hazards. One has a
continuously variable dimmer knob, but the pot seems to have died in it.
The other has a three position switch allowing for two brightness levels.

I once heard something like you describe though, but IIRC they also said
that running it at full voltage again would restore the bulb. Anyone?
I used a lot of these types of bulbs back in my college theatre days.
They work just find dimmed (all we ever did with them in the theatre)
but are best if they at least occasionally brought up to full brightness
and temperature.

Charlie
 
S

Sizz

Jan 1, 1970
0
I used a lot of these types of bulbs back in my college theatre days.
They work just find dimmed (all we ever did with them in the theatre)
but are best if they at least occasionally brought up to full brightness
and temperature.

Charlie

Yes, i've found these comments useful. Some people say it can be
dimmed, others say it shouldnt be dimmed.
Do i just use a potentiometer and connect it to the 12v supply?
Is there another way of dimming the halogen bulb using a potentiometer
and a resistor of some sort? What kind?
 
P

Phil Allison

Jan 1, 1970
0
"Sizz"

** Piisssssss Head.

Yes, i've found these comments useful. Some people say it can be
dimmed, others say it shouldnt be dimmed.
Do i just use a potentiometer and connect it to the 12v supply?
Is there another way of dimming the halogen bulb using a potentiometer
and a resistor of some sort? What kind?


** Hey, FUCKWIT !!

Go look up TRIAC DIMMER on Google.

And dam well read what is in replies even it is it NOT what you, in your
infinite ignorance, wanted to see.




....... Phil
 
D

Don Klipstein

Jan 1, 1970
0
I don't know about that. My wife has two of these fire hazards. One has a
continuously variable dimmer knob, but the pot seems to have died in it.
The other has a three position switch allowing for two brightness levels.

I once heard something like you describe though, but IIRC they also said
that running it at full voltage again would restore the bulb. Anyone?

There is no definitive answer to this.

I remember looking at some book in a university library over 20 years
ago, showing lots of graphs and equations expalining what supposedly
happens to the halogen cycle when a halogen lamp is dimmed.

Supposedly, dimming a halogen lamp slows down tungsten evaporation
more than it slows down the halogen's returning of tungsten to the
filament.

Now, for a couple things going wrong:

1) Dimming a halogen lamp is likely to not extend its life as much as
dimming a non-halogen one does. The ends of the filament are cooler, and
can be attacked by the halogen cycle, causing thin spots in the filament.
These "end notching" sites can have temperature overshoot during a cold
start. Soft starting can help here (and usually helps less with
non-halogen lamps, where most fatal filament thin spots usually have
excessive temperature in steady operation, and worsen at a rate
accelerating worse than exponentially).
Such filament end notches will worsen until failure occurs there one way
or another.
The bottom line is not dimming shortening life, but dimming extending
halogen lamp life less than it does with non-halogen lamps.

2) Halogen lamps could contain contaminants that do the halogen cycle in
reverse - transporting tungsten from the filament to the inner surface of
the bulb. Such bad stuff may slow down less from dimming than the proper
halogen cycle does. In such a case, dimming to the extent where a
contaminant's "reverse halogen cycle" outruns the normal one will cause
problems.

I suspect such problems are less with halogen lamps made by major brands
such as GE, Osram/Sylvania, Philips, Thorn and Ushio. I suspect that such
lamps will take mild to moderate dimming well and *usually* (maybe or
maybe not reliably) not blacken with severe dimming. No guarantee from me!

Now, for fixing blackened halogen lamps:

I hear that this works. I suspect it works only if the blackening is
simply tungsten, as opposed to an oxide (dusty grayish or colored). I
would also be a bit leery of doing this, since with full power operation
before the blackening is fixed the bulb can overheat. Every blue moon or
something like that, a halogen lamp somewhere explodes even if nothing
wrong is done, so I am leery of doing anything that increases stress on
them.

- Don Klipstein ([email protected])
 
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