Jump to content

Buzz from when using dimmer switch


Recommended Posts

Hi Guys

Hope someone can shed light on buzz from dimmer switch

1. Tried two dimmer switches (major tech and wifi enable dimmer switch) get a weird buzz from the lights (LED GU10 Luceco Dimmable 8 connected in series)

2. When dimmer is on full power (no dimming) I hear no buzz

3. I can hear the earth leakage also buzzing when the lights are dimmed (AC DC Earth Leakage)

4. The lights are behind my inverter and weather I am using the inverter or eskom bypass I get the same buzz

5. The flickering was worse on the wifi dimmer switch


Its driving me nuts, should I move the led lights off earth leakage ? should I try another phase as the house is on 3 phase power ? Should I give up on my dream to control this lights remotely from google or phone ?



Edited by Treschen
Link to comment
Share on other sites

1 hour ago, Treschen said:

1. Tried two dimmer switches (major tech and wifi enable dimmer switch) get a weird buzz from the lights (LED GU10 Luceco Dimmable 8 connected in series)

Read up a bit on how dimmer switches work. They chop up the AC waveform and changes it into a kind of square wave with a leading or trailing sine-wave shape. Like this:


I stole that from here.

As you can see, both kinds chop some of the energy away, but they do it in different ways. It might help to figure out what kind of dimmer you have, and try the other kind.

Leading edge is cheaper to make (I think? Please correct me if wrong). You simply have a threshold voltage and you switch the TRIAC on hard when the threshold is exceeded. The level of dimming is adjusted simply by changing the threshold voltage. I believe leading-edge is also more prone to the buzzing effect (again, correct me if I am wrong).

Also, LED lamps sometimes have a poor power factor, meaning they do almost all the work on the leading edge. For example, here is a picture I made years ago of a Uniontech LED downlight (current is out of phase with the voltage cause I had the probe the wrong way round, just ignore that, the important part is that the current basically goes to zero by the time we're halfway through the voltage waveform):


Now imagine what happens if you use a leading-edge dimmer with a lamp that already does all the work on the leading edge. It's going to hammer like water in the pipes of an old house... 🙂


Link to comment
Share on other sites

4 hours ago, Treschen said:

So adding a capacitor should help with smoothing it out. 

I'm not sure what your plan is here. A capacitor is used with DC supplies to smooth things out, but on AC circuits it is only really used for a few things, 1) filter out a DC component and pass only the AC, and 2) create a phase shift, eg in single phase induction motors with an auxiliary/starter winding, 3) capacitive droppers, a small capacitor can be used to make a small non-isolated power supply directly from mains voltage. "Smoothing" isn't really a thing on AC.

The issue with leading-edge dimmers is that they cannot compensate for power factor. They work well with incandescent lamps where the power factor is 1, but for other loads a trailing-edge dimmer is better. Trailing edge dimmers also create less noise and also less radio noise. My guess is that your dimmers are all leading-edge.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...