<p>Thanks! I haven't disassebled an old school dimmer in a long time. The physics has changed<br>
Good description of why and how.</p>
<div class="gmail_quote">On Mar 31, 2011 10:38 PM, "Chris Ness" <<a href="mailto:luxomni@earthlink.net">luxomni@earthlink.net</a>> wrote:<br type="attribution">> On Mon, 2011-03-28 at 16:19 -0400, Jim Kinney wrote:<br>
> <br>>> <br>>> <br>>> <br>>> On Mon, Mar 28, 2011 at 3:53 PM, Greg Freemyer<br>>> <<a href="mailto:greg.freemyer@gmail.com">greg.freemyer@gmail.com</a>> wrote:<br>>> <br>>> dimmer's save electricity too unless you<br>
>> keep them at max. most of the time.<br>>> <br>>> <br>>> Not sure on that. Most dimmers are just a simple rheostat device<br>>> (voltage divider). They get pretty warm in use. Some are switches that<br>
>> vary the "on" time to keep the lamp lit. Those will save power. But<br>>> those also hum badly and provide some nasty noise back into the AC<br>>> line. Run a speaker cord near a dimmer and listen for the fun.<br>
>> <br>> <br>> NO! Most dimmers are not simple rheostat devices! They work on an<br>> entirely different principle, which is why they do not generally work<br>> with traditional (magnetic ballasted T-12) fluorescents. The dimmers<br>
> work with a diac/triac type device and a toroidal coil to distort the<br>> wave form of the AC current. Effectively, the voltage peak the same<br>> positive and negative cycles as before, but for a shorter period of time<br>
> during the 1/120th of a second that each half of the cycle is active.<br>> With an incandescent, the filament does not heat as much due to the<br>> shorter time and hence less light. On the other hand, a fluorescent tube<br>
> is 120 ≅200vac lightning bolts a second through a gas comprised of a<br>> mercury salt which is gaseous at room temperature (hence the 4vac<br>> heaters at each end). Dimming by reducing the duty cycle of the AC<br>
> allows the mercury to precipitate out of the gas after a short period of<br>> time and not conduct the electricity. (which will also happen if you do<br>> not make good connections with both pins)<br>> <br>> The new T-8 fluorescents and electronic ballasts have their own problems<br>
> with dimming.<br>> <br>> <br>> -- <br>> mailto:<a href="mailto:luxomni@earthlink.net">luxomni@earthlink.net</a> All jobs are equally easy to<br>> <a href="http://luxomni.blogspot.com">http://luxomni.blogspot.com</a> the person not doing the work.<br>
> <a href="http://www.flickr.com/photos/luxomni">http://www.flickr.com/photos/luxomni</a> Holt's Law<br></div>