Killing Halogen BUZZ Question
Gerald Fountain
dimmers, I wasn't able to find quite what I was looking for so I thought I
would post.
What is the easiest/best way to kill the 'buzz' of a halogen floor lamp
which is dimmed? I assume it has something to do with inductive load/triac
interactions but I was hoping for a simple circuit modification (or pointer
to more info). Currently the lamp I am using have a very simple switch
comprised of a triac (I assume), a cap, and a diode, all controlled by a
pot. The triac is coded 500F, BT138F, PHm930. The entire assembly is made
by (backwards UR) and is labeled "Dimmer Switch Incandescent Only" with the
numbers E115041, SC237 (120VAC, 60W~500W)
Any suggestions on how to modify/replace the switch to reduce or eliminate
the buzz? It can be *quite* annoying.
Jerry
--
Jerry Fountain | Laboratory for Fluid Mechanics, Chaos, and Mixing
g...@bart.chem-eng.nwu.edu | Northwestern University
(708) 491-3555 (Office) | Department of Chemical Engineering
(708) 491-3728 (FAX) | 2145 Sheridan Road, Evanston, IL 60208
Uwe Bonnes
In article <2mkgih$9...@news.acns.nwu.edu>, g...@casbah.acns.nwu.edu (Gerald Fountain) writes:
|> After looking for the FAQ and reading several postings about digital
|> dimmers, I wasn't able to find quite what I was looking for so I thought I
|> would post.
|>
|> What is the easiest/best way to kill the 'buzz' of a halogen floor lamp
|> which is dimmed? I assume it has something to do with inductive load/triac
|> interactions but I was hoping for a simple circuit modification (or pointer
|> to more info). Currently the lamp I am using have a very simple switch
|> comprised of a triac (I assume), a cap, and a diode, all controlled by a
|> pot. The triac is coded 500F, BT138F, PHm930. The entire assembly is made
|> by (backwards UR) and is labeled "Dimmer Switch Incandescent Only" with the
|> numbers E115041, SC237 (120VAC, 60W~500W)
|>
|> Any suggestions on how to modify/replace the switch to reduce or eliminate
|> the buzz? It can be *quite* annoying.
|>
Look carefully at the circuit. Parallel to the triac and with the main current path is a capacitor in the several hundred Nanofarad range (normally in series with with a resistor, both are called "snubber-circuit"). The capacitor must bear severe switching, and thus be qualified, which is a little more expensive, and so isn't done in most cases. Replace it with a qualified one ( in europe called "X2") with equal or better voltage rating and your problem should be gone.
Best regards
---
Uwe Bonnes b...@lte.e-technik.uni-erlangen.de
CC01...@brownvm.brown.edu
this topic brings up another question. Somewhere I saw stated,
somewhat contrary to what I expected, that Halogen bulbs
do not last as long when on a dimmer circuit. I suspect this
was a statement in error but would like to know for sure.
Also, my incandesent bulbs "buzz" when dimmed by a triac on
an 120 Volts AC line. I take this buzzing to be a mechanical
motion of the filament. Does this "buzz"ing have a negative
influence on the life expectancy of a "dimmed" bulb?
Thanks,
John
John Whitmore
Gerald Fountain <g...@casbah.acns.nwu.edu> wrote:
>
>What is the easiest/best way to kill the 'buzz' of a halogen floor lamp
>which is dimmed? I assume it has something to do with inductive load/triac
>interactions
>Jerry Fountain | Laboratory for Fluid Mechanics, Chaos, and Mixing
>g...@bart.chem-eng.nwu.edu | Northwestern University
The noise is caused by speaker-like motion of the filament
in the lamp. Some harmonic of the power frequency is introduced
by your dimmer that makes the adjacent coils of the filament
attract/repel at a mechanical resonance. You can experiment
with different bulbs, but the only way to kill the effect is
to use a non-distorting kind of dimmer (like a Variac autotransformer).
You will NOT like to hear the price of a 500W Variac, though
($70 and up), nor is it going to fit in a small control box.
And, the Variac is a transformer which will buzz
slightly...
John Whitmore
Robert Barbagallo
: Hi,
: Thanks,
: John
I work with high powered dimmers ie: 1.2kw and up. The buzz
comes from the inrush of current to the filament, the rise
time of the triac switching. This rise time has to be reduced,
the common way is to use a choke. For quiet dimmers you would
want a rise time of 400us to 550us at a 90 deg. firing angle.
A good source for these is Amecon in Calif.
Hope this helps.
Bob
v
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Dr. Finklestein
: In article <2mkgih$9...@news.acns.nwu.edu>,
: Gerald Fountain <g...@casbah.acns.nwu.edu> wrote:
: >
: >What is the easiest/best way to kill the 'buzz' of a halogen floor lamp
: >which is dimmed? I assume it has something to do with inductive load/triac
: >interactions
: [...] but the only way to kill the effect is
: to use a non-distorting kind of dimmer (like a Variac autotransformer).
: You will NOT like to hear the price of a 500W Variac, though
: ($70 and up), nor is it going to fit in a small control box.
: And, the Variac is a transformer which will buzz
: slightly...
You can do what they did at my old school and install a servo-controlled
Variac to dim the stage lights. You put the Variacs in the basement, and
just have a small slider in the lighting booth.
You could probably do this for maybe $600 per light, maybe less, if you buy
the parts surplus. Sure, it's a bit pricey, but think of COOL it would be
to have large racks of servo-controlled Variacs in your basement, especially
when the servo loops start oscillating...
mike
--
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mike bender | sun microsystems | 415-336-6353 | ben...@oobleck.eng.sun.com
The rip-off attitude of many today is "get somebody else to do your job for
you". This is very unprofessional and shows no pride of workmanship. It
demonstrates a deterioration in humanity in the past 30 years. -FRED BACH
--------------------------------------------------------------------------
Michael Stein
>>which is dimmed? I assume it has something to do with inductive load/triac
>>interactions
I haven't tried this, but wouldn't it be easier to just run the
lamps on variable DC? And you could get the DC via an
off-the-line switcher which switched above an audio rate...
Quiet... (try to avoid a fan..).
Robert Rolf
>: this topic brings up another question. Somewhere I saw stated,
>: somewhat contrary to what I expected, that Halogen bulbs
>: do not last as long when on a dimmer circuit. I suspect this
>: was a statement in error but would like to know for sure.
The reason the bulbs are called 'Halogen' is that they contain a Halogen
gas (Iodine if memory serves). Tungsten boils off the filament and
combines with the Halogen and then, later in the convection cycle, gets
redeposited on the hot filament. When the bulb gets dimmed, the
deposition instead occurs on the quartz housing, and unless that gets hot
enough, tungsten is not recycled back to the filament, reducing its life.
For this reason a lot of people don't dim their bulbs, they change the
size (wattage) of the lamp when setting up.
[rest of filtering discussion (and long PGP key. Setup a
fingerable .profile instead) Zapped]
John De Armond
>this topic brings up another question. Somewhere I saw stated,
>somewhat contrary to what I expected, that Halogen bulbs
>do not last as long when on a dimmer circuit. I suspect this
>was a statement in error but would like to know for sure.
It is in error. There is a shortening of life if the halogen bulb is
operated just a tad bit below its rated voltage. Under these conditions,
the temperature is still high enough to boil off the tungsten but not
high enough to cause the halogen chemistry to kick in. Lower the
temperature a bit more and the 13th power law kicks in (Westinghouse
determined that an ordinary incadescent lamp's life varies with the
13th power of applied voltage).
>Also, my incandesent bulbs "buzz" when dimmed by a triac on
>an 120 Volts AC line. I take this buzzing to be a mechanical
>motion of the filament.
True.
>Does this "buzz"ing have a negative
>influence on the life expectancy of a "dimmed" bulb?
No. The filiament is not hot enough to boil off tungsten atoms but is
hot enough to be ductile and therefore not fracture from the buzzing.
The only way to get rid of the buzzing is to use some dimming method that
does not distort the sine wave. Typical solutions include variable
autotransformers and magnetic amplifiers. None will fit inside an
outlet box, of course.
john
--
John De Armond, WD4OQC, Marietta, GA j...@dixie.com
Performance Engineering Magazine. Email to me published at my sole discretion
Suppose Clinton were choking on food and you were the only one present.
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CC01...@brownvm.brown.edu
>There is a shortening of life if the halogen bulb is
>operated just a tad bit below its rated voltage. Under these conditions,
>the temperature is still high enough to boil off the tungsten but not
>high enough to cause the halogen chemistry to kick in. Lower the
>temperature a bit more and the 13th power law kicks in (Westinghouse
>determined that an ordinary incadescent lamp's life varies with the
>13th power of applied voltage).
This is very interesting. I have 12 Volts halogen flashlight
that I use underwater. It draws 1.3 A. To save on the cost of
batteries I use eight 4Ah NiCad D-cells. The flashlight gets
turned on and/off a lot. To save the bulb from the inrush
current I mounted a HEXFET and some supporting electronics
to make it "soft-start". The HEXFET has a channel resistance
of 0.05 Ohm when ON so I loose 65 mV over the HEXFET.
Now I wonder if I do more damage than good to the bulb. I
haven't measured the operating voltage when using Alkalines
at a 1.3 Amps discharge current but it might very well be
above the approx. 10 V I get from the low-internal resistance
NiCads.
The question is, is it possible to quantify where
the different regions of halogen/tungsten operation are,
if not in terms of supplied voltage maybe filament temperature?
Thanks,
John
Greg Thoman
On a shorter note, if the bulb's glass isn't darkening due
to metal deposition, you're probably not doing any harm.
-----
Greg Thoman: The opinions expressed herein are mine alone, and I am
solely irresponsible for them.
Carl Kirchner
Newsgroup: sci.electronics
From: carl.k...@dscmial.com
C>This is very interesting. I have 12 Volts halogen flashlight
>that I use underwater. It draws 1.3 A. To save on the cost of
>batteries I use eight 4Ah NiCad D-cells. The flashlight gets
>turned on and/off a lot. To save the bulb from the inrush
>current I mounted a HEXFET and some supporting electronics
>to make it "soft-start". The HEXFET has a channel resistance
>of 0.05 Ohm when ON so I loose 65 mV over the HEXFET.
>Now I wonder if I do more damage than good to the bulb. I
>haven't measured the operating voltage when using Alkalines
>at a 1.3 Amps discharge current but it might very well be
>above the approx. 10 V I get from the low-internal resistance
>NiCads.
FWIT I know some makers of Halogen lights uses an inrush limiting
thermister for this purpose so assuming you are allowing the halogen
cycle to operate it, is probably not a problem.
Seems like you HEXFET is probably more efficient since it is essentially
out of the circuit when ON.