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Ask MAKE is a weekly column where we answer reader questions, like yours. Write them in to becky@makezine.com or drop us a line on Twitter. We can’t wait to tackle your conundrums!


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Martin writes in:

Why do my incandescent light bulbs buzz when I’m using a dimmer switch? What can I do to stop it?

Household lights run on alternating current (AC), which can be seen as a sine wave on an oscilloscope. To decrease the brightness of the bulb, a dimmer switch takes chunks out of the sine wave. This essentially turns the bulb on and off around 120 times every second, depending on the dimmer swtting. Charging the bulb filament creates an electromagnetic field, and when this field is turned on and off so rapidly, the changing force can cause the filament to start vibrating in sync with the frequency of the ons and offs.

To stop the buzzing, you can try rough service light bulbs, which have the filament anchored in more than two places, unlike regular light bulbs. Think of the filament supports as legs on a table. Two legs would make for a wobbly table, but make that three or four legs, and you’ve got something more sturdy.

If it’s your dimmer that buzzes instead of your light bulbs, you may need a dimmer rated for a higher capacity. Try removing some of the light bulbs connected to the dimmer and see if it makes a difference. If the buzzing is quieter, you may need a stronger dimmer. Common triac-based dimmers are controlling the chopping up of that AC wave, and can also vibrate because of it. Some higher quality dimmers have filters in them to prevent that.

Some more reading on the subject:

Have you had to fix a noisy light problem in your house? Share with us in the comments.

This week’s Ask MAKE has been sponsored by Jameco Electronics.

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Becky Stern

Becky Stern is head of wearable electronics at Adafruit Industries. Her personal site: sternlab.org


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