View Full Version : Bulbs are humming

10-14-2008, 11:07 PM
Can anyone recommend a good dimmer that will not cause the bulbs that are being dimmed from humming/buzzing?

Bill Arden
10-15-2008, 02:30 AM
A fan dimmer might work.

10-15-2008, 06:25 AM
You may need to experiment. First, I assume thesee are not fluorescent bulbs.
The humming could just be the bulb...the filament vibrates. Try a different brand of bulbs. But also, it could be the dimmer....for example many dimmers alter the sign wave shape of the AC voltage, to reduce the wattage to the bulb. But the filament doesn't like that. You might need a more expensive dimmer....OR try the very inexpensive ones, OR try a fan speed controller.

10-15-2008, 07:29 AM
Some dimmers chop the top of the sine wave off to adjust the power going to the bulb. Rather than being an nice smooth curve, that abrupt off, then reverse causes the filaments to ring, or humm. Most manufacturers do a good job of supporting the filaments so they don't humm at 60Hz, but what now looks like a square wave and that abrupt chop excites them like hitting a tuning fork. Sometimes, rough-service bulbs (like those designed for a garage door opener) have the filaments better supported, and they don't humm. It's trial and error (which can get expensive!) to find a pair of bulbs and dimmer that minimize the problem.

10-15-2008, 05:22 PM
Can anyone recommend a good dimmer that will not cause the bulbs that are being dimmed from humming/buzzing?

I'd say they are about to fail, but how many of them hum?
All the same brand?
Do they hum at full intensity or low intensity?
A 60 Hz hum like you hear if you put your ear to a wall transformer, or a higher frequency?

Johnny C
10-20-2008, 05:57 PM
How about a little humor: The bulbs are humming because the don't know the words, just like a transformer! An oldy but goody. Some of us old guy still have a sense of humor, we don't have much more.

Bill Arden
10-20-2008, 08:40 PM
You could always use a variac :D

I once did a job for a company (back in the 90's) where I designed a fan motor controller that would drop whole half cycles so that the effective frequency would be dropped. It could only be set to a few different percentages due to the available patterns.

I'm guessing that is what some of the fan speed controllers do.