Dimmer Switch- Whats all the buzz amout.
Acutually, it’s more of a humming really.
I don’t know if it’s just me, or what. Do all dimmer switches cause a faint high pitch humming noise to come form the bulbs in the light fixture when the switch is in a dimming position. I know for sure that I am hearing this. I can’t be the only one, but sometimes if I mention it to someone else, they either say they don’t hear it, or that I should stop obsessing over it.
I will admit that I think I have a very acute sense of hearing, but it’s not like I’m superman…far form it. So I know this has to be a real thing.
Sometimes, it’s such a high pitch, it’s almost inaudible. You can hear it more on a subliminal level, if that makes any sense.
I assure you, I am more or less sane (I worry I might actually be the only one who notices this)
Can someone confirm this is a real thing, and if so, what causes it, and can it be “fixed” Is it just a cheap switch, or not the right type of bulbs?
I have a good feeling if I can get an answer anyplace, it will be here.
Replies
You've got a cheap dimmer there I'm guessing.
Old dimmers used variable resistors or rheostats to lower the light level, but this generated a lot of heat in the switch itself.
Newer dimmers use TRIACs to actually turn the switch on and off many times a second to achieve the lower light level. This can actually cause the filaments to vibrate in the bulbs especially at low light levels.
If the dimmer still buzzes when it's off, I'm guessing its the old model.
In any case, an upgrade to a better switch should cure the problem.
Edited 12/1/2005 1:12 pm ET by Thaumaturge
The switch is brand new. The humming is coming from from the bulbs, not the switch. It's not just isolated to this particular switch either.
>Newer dimmers use TRIACs to actually turn the switch on and off many times a second to achieve the lower light level. This can actually cause the filaments to vibrate in the bulbs especially at low light levelsVibrating filimants is making a lot of sense to me. In fact, I'm almost sure that's what it is. Sort of a high pitch mettalic twang type of noise. As I said the switch is brand new so just please clarify for me:Even though the switch I have is brand new, and most likely using the newer technology you mentioned, would upgrading to a better switch solve my problem. Or, would a different type of bulb be a solution. Different type of bulb = different type of filiment resulting in less of that vibrating?
shameless bump
Better dimmers use additional components to dampen the vibration effect caused by the TRIAC in the circuit.
Without getting too technical, here's what's happening. Okay, it's technical.
With AC power, the current direction changes 60 times a second - back and forth. This creates a sine wave varying from maximum positive voltage to zero and then to maximum negative voltage. Just imagine raising and lowering your hand from knee to shoulder and back again 60 times a second.
The TRIAC takes advantage of this "swing" and turns off the current to your lights as the AC current changes direction. Essentially, it switches off the negative or positive flow before it reaches zero. How soon it switches off the current each time determines the amount of current getting to your lights. (This is better than a rheostat wasting the extra voltage as heat)
Here's the rub. Your light bulbs have a filament in them which is essentially a tiny coil of wire. The wire acts like a tiny electromagnet. As the current in a dimmed circuit jumps from one level, to zero, and back, the little filament swings slightly back and forth due to the electromagnetism created. Since this is happening around 120 times a second, you get a little vibrating filament. The filament acts like a tiny version of the tweeter cone in your speakers and makes a sound.
More expensive dimmers can still use a TRIAC component but dampen the swings in current by using another component and technique that I'm guessing you don't want to hear about.
In short, it's cheaper to make a dimmer without the extra circuit/components and still dim lights. For most people, the frequency and volume of the resulting vibration is beyond their hearing and the ambient noise of the room.
The difference between a $25 dimmer and the $50 dimmer will most likely be the noise and the sexy controls. You might try different bulbs as well. Rough duty bulbs for instance use reinforced filaments that might offer some help. For my money though, I would change the dimmer and not have to worry about bulbs in the future.
Hope that helps.
Helps? Absolutely.
Don't worry about getting long winded with me. I love to know the how and why. Now I will read your response like two more times to absorb what I was unable to on the first pass. Thanks for taking the time to explain.
Glad to help.
I just re-read my explanation and realized what you really need is a picture.
Check the pics and info here:
http://home.howstuffworks.com/dimmer-switch2.htm
They're even more long-winded than I am. :-)
I hate to nitpick an otherwise excellent response (I gather you know your AC circuitry ;) ) but I don't believe rheostats or pots were ever used as household dimmers... If you can show me otherwise it'd be very interesting (could double as a toaster too I bet)
PaulB
> I don't believe rheostats or pots were ever used as household dimmers...
Certainly they weren't as widely used as today's triac dimmers. High end home screening rooms from the 1920's - 1960's likely would have used them, but the same makes and models as used theatrically. But we're talking the Pickfords and DeMille's here, not Joe Sixpack. I've also seen them in old TV online bays, where the electronic noise of triacs was unacceptable.
-- J.S.
I've seen rheostats used as dimmers in an old summer theatre I volunteered in as a kid John. Granted they were probably on the couple KW order but had handles the size of bus steering wheels and man oh man was that light "booth" toasty...
Still, I've never seen reference to them being used in any form residentially, but I'd love to see some reference if they were.
PaulB
I think that a common method for commercial/high end homes where variable reluctance transformers; IE there couple between the primary and secondary was changed. An autotransformer was one type, but I think that there where others where the either the core was moved or the relative position of the windings where changed.Another was magamps, magnetic amplifiers. They used magnetic cores that used a control winding that determined when the core would satsurate and "turn on". 40 years ago I could tell in detail how that worked, but it has been a while.Doing some googling I see that there was a common 3rd method used for stage light. Thyratrons, those where vacuum tube devices that have characteristics similar to SCR's.From the Penn State U theator lighting archives.http://www.theatre.psu.edu/facilities/lighting_archives/paper/sysdrawings.html
http://www.theatre.psu.edu/facilities/lighting_archives/dimmers.html
I've got an old one in a box around here somewhere...
Yes, it's capable of starting a nasty fire in the wrong application. That's why it's no longer in service. It was pulled out of a 100 year old house with equally scary wiring.
Scariest electrical thing I ever saw was in a 100 year old house also... Opened up a junction box and thought "what the heck.... did they encapsulate the wires in pitch?" then realized they were pounded into the box so tight they were essentially one solid mass...
A further little nit pick...actually the triac turns ON at a variable point on each AC half-cycle cycle and stays fully on till the end of each half-cycle.
Ooops I missed that Maggie ;) I always think of zero crossing but that's Quadracs isn't it? (realllllllllllllly stretching my memory here)
Ok, now you guys are just messing with my head (jk)
A triac is a quick little semiconductor switch which turns completely on when its control lead gets a pulse. You want to give it a good blast on the control lead or only a portion of the semiconductor gets turned on, and that portion will overheat and be damaged potentially (aka current hogging). So usually you put a device called a diac in series with the triacs control line and that ensures a good pulse gets to the triac. When the diac is packaged together in one package with the triac, it is called a Quadrac.Light dimmers work by varying the time on each half-cycke when the triac turns the load on. Since the repetative moments of turn-on have high current rush ( you are turning on the current when the voltace has climbed up the wave), you get noise---both audible and electrical noise.
Sometimes internal components are added to limit the hi-freq electrical noise, but I'm not sure you can minimize the lamp filiment flicker noise.
Ummmm yeah... I knew that Maggie (that is to say the parts I haven't forgotten ;) )
What I was trying to remember was whether you could have zero crossing with a triac or a quadrac was needed. Been a longggggggggg time...
Back to your regularly scheduled thread ;)
Maggie / Paul
That's precisely what I meant about getting too technical. :-)
I should have just posted "buy a new dimmer for no less than $45"
Thats why I have grown to love this forum. New dimmer switch is the way I'm going. At least now I have a good reason why I should spend twice as much. I know there usually is good reason, but it is sometimes hard to justify the expence, at least for me, when they look the same and I don't know what the real difference is.
Great post--informative.
There must be litterally tens of thousands of people wondering the same thing.
:-)
You are sane.
Is it a ceiling fan dimmer? They are different than light dimmers. Had a friend with the opposite problem... fan hummed because the dimmer was for lights. Changed to a fan dimmer and the hum disappeared.
Troy Sprout
Square, Level & Plumb Renovations
Good question. To be honest, I'm not sure. I bought it in one of those "supermarket sweep" style runs through HD where you play that game and see how fast you can get in and out of there with everything you needed. Wait...maybe I'm the only one who does that. =D Anyway, I'll check that out. But I suspect it's for lights. BTW what's the difference?
I know nuttin` about no dimmers.
What I do know is HD is the wrong place to be playing "supermarket sweep".
If there`s one store on earth where you need to take your time and read the product info to assure yourself you`re buying what you think you are....its Home Depot.
J. D. Reynolds
Home Improvements
I have a brand new one and it is doing the same thing
that "resistance" sound seems like it is consuming a lot of energy
make too many trips to places like HD - may take it back & trade for another & see what happens
Last year I installed a house full of dimmers and recessed cans (98 cans). The home owner got the first electric bill and switched the lights to the screw in flourescent type. He did this before I changed out the switches and the one in the basement screamed. I changed out the switch and the noise went away.