Dimmer Switches

Everything Else
21
Part of the issue is what dimmer you use. I use a dimmer in the main sound room without any issue whatsoever. It works because of the dimmer I use which is a higher end Lutron that says it is "quiet". Indeed, all dimmers work by chopping the waveform but the better ones have a reasonably large filter inside that reduces the harmonics to almost nothing.

Yes, but if it is constructed correctly they should come with a 'zero-crossing chip' meaning that the switching is done when the AC feed is zero (i.e. 60 times a second).

22
frode said: 'zero-crossing chip'

Hmmm. Wonder if these are available in the USA?
23
Gordon said: http://www.ee.teihal.gr/labs/electronics/web/downloads/Light_dimmer_circuits.pdf

This is quite an article. Interesting.

For those interested, it addresses why dimmers make noise and the ways to address this in the design of the dimmer.
24
frode said: . . . the switching is done when the AC feed is zero

All dimmers switch at the zero crossing; this is how they work. :)
25

Yup.

In between the As and the Cs

This is the “cause” of the problems.

26
frode said: . . . the switching is done when the AC feed is zero

All dimmers switch at the zero crossing; this is how they work. :)

In 2013 I have to agree to this.
Here is one circuit:
http://pdf.datasheetcatalog.com/datasheet/motorola/MOC3042.pdf
What confuses me is that it seems that it is a non-zero crossing principle that is used in dimmers (random phase triac controller). If it switches under load, then noise is inevitable.
27

I believe you are correct. I did some reading and found that a random phase triac controller does not detect zero crossing and can remain on as the phase changes. This would create more noise than zero crossing.



Thanks for bringing this up - neat stuff.