Changes

Unfortunately, while this setup does allow for easy adjustment of the electrical supply, it is inefficient.  Much of the energy which would have gone through the controller is instead converted to heat.  This causes the output voltage drop desired, but most of the electricity is still being used, as it is converted into heat energy.  In some cases, this can also be a safety hazard since the heat can build up and potentially cause fire or other damage.<ref name="howstuffworks p1">http://home.howstuffworks.com/dimmer-switch1.htm</ref>

Unfortunately, while this setup does allow for easy adjustment of the electrical supply, it is inefficient.  Much of the energy which would have gone through the controller is instead converted to heat.  This causes the output voltage drop desired, but most of the electricity is still being used, as it is converted into heat energy.  In some cases, this can also be a safety hazard since the heat can build up and potentially cause fire or other damage.<ref name="howstuffworks p1">http://home.howstuffworks.com/dimmer-switch1.htm</ref>

===Switching circuit===

===Solid state (switching circuit)===

Rather than resisting the flow of electricity, switching circuit dimmers simply cycle the power on and off.  They work on [[alternating current]] by shutting of the flow every time the sine wave cycles to zero, then connecting it again a split second later. AC current completes sixty cycles per second, and in every cycle the sine wave comes to zero twice.  This means that 120 times every second, the first part of each positive and negative sine wave is "chopped" off.  The amount of the wave which is cut off can be adjusted, so that more or less of each wave can pass through.<ref name="howstuffworks 2">http://home.howstuffworks.com/dimmer-switch2.htm</ref><br />

Rather than resisting the flow of electricity, switching circuit dimmers simply cycle the power on and off.  They work on [[alternating current]] by shutting of the flow every time the sine wave cycles to zero, then connecting it again a split second later. AC current completes sixty cycles per second, and in every cycle the sine wave comes to zero twice.  This means that 120 times every second, the first part of each positive and negative sine wave is "chopped" off.  The amount of the wave which is cut off can be adjusted, so that more or less of each wave can pass through.<ref name="howstuffworks 2">http://home.howstuffworks.com/dimmer-switch2.htm</ref><br />

As portions of the waves are cut off, the net power allowed through is reduced.  Although this does cause the output to be inconstant, most people will not notice since it is so quick, the human eye, nerves, and brain can only process visual input at a limited speed. (This speed is not knows precisely, though some approximate that about 60 frames per second (FPS) can be processed, and others simply say that the processing rate is over 43 FPS.)<ref>https://tech.slashdot.org/story/14/12/24/1415207/human-eyes-oscillation-rate-determines-smooth-frame-rate</ref><ref>http://www.sciencedirect.com/science/article/pii/S0042698998003228</ref><ref>http://wolfcrow.com/blog/notes-by-dr-optoglass-motion-and-the-frame-rate-of-the-human-eye</ref>  However, some do actually notice this effect, and usually report that it is irritating.  Others report that light emissions which have been "dimmed" in the manner seem harsh, but cannot identify why.  (For this reason, some dislike the [[LED]] Christmas lights, and certain other such products.)

As portions of the waves are cut off, the net power allowed through is reduced.  Although this does cause the output to be inconstant, most people will not notice since it is so quick, the human eye, nerves, and brain can only process visual input at a limited speed. (This speed is not knows precisely, though some approximate that about 60 frames per second (FPS) can be processed, and others simply say that the processing rate is over 43 FPS.)<ref>https://tech.slashdot.org/story/14/12/24/1415207/human-eyes-oscillation-rate-determines-smooth-frame-rate</ref><ref>http://www.sciencedirect.com/science/article/pii/S0042698998003228</ref><ref>http://wolfcrow.com/blog/notes-by-dr-optoglass-motion-and-the-frame-rate-of-the-human-eye</ref>  However, some do actually notice this effect, and usually report that it is irritating.  Others report that light emissions which have been "dimmed" in the manner seem harsh, but cannot identify why.  (For this reason, some dislike the [[LED]] Christmas lights, and certain other such products.)<br />

   

So far, these systems do waste enough power to produce heat, but they are still improving. They also produce radio-frequency interference (RFI), although much of this can be filtered out, as is mandated in some places.<br />

===Coil-rotation transformer===

===Coil-rotation transformer===

   

   

===Autotransformer dimmer===

===Autotransformer dimmer===

Variable autotransformers (trademark "Variac") are very tolerant and reliable "dimmer" devices.  They and not significantly affected by how much power is drawn through them, so they are also very versatile.  However, theses also large and somewhat expensive, so they are rarely used for lighting today.  They are still used for some other purposes, however.  For example, some musicians use them not as much to reduce the voltage as to stabilize it.  These help deal with unreliable power sources (which sometimes provide too little voltage) and help remove electromagnetic interference and "noise."<ref name="mindspring.com">http://www.mindspring.com/~atlantatubeamp/id23.html</ref>

Variable autotransformers (trademark "Variac") are very tolerant and reliable "dimmer" devices.  They and not significantly affected by how much power is drawn through them, so they are also very versatile. The work by reducing the amplitude of the A.C. sine wave.<ref name="caseydiers.com">http://www.caseydiers.com/sinewavedimming.htm</ref> However, this reduction converts all of the unwanted power into heat, so it is inefficient. They are also large and somewhat expensive, so they are rarely used for lighting today.  Variacs are still used for some other purposes, however.  For example, some musicians use them not as much to reduce the voltage as to stabilize it.  These help deal with unreliable power sources (which sometimes provide too little voltage) and help remove electromagnetic interference and "noise."<ref name="mindspring.com">http://www.mindspring.com/~atlantatubeamp/id23.html</ref>

 

===Field effect transistor===

===Field effect transistor===

===CFL/LED dimmers===

===CFL/LED dimmers===

[[Fluorescent lightbulb|Fluorescent lights]] as well as LED (Light emitting diode) bulbs cannot be dimmed by a simple voltage reduction.  However, this does not mean that it is impossible.  In most cases, the bulbs themselves can (and must) control their brilliance.  Therefore, variable brightness bulbs or tubes must be installed into a "dimmer" system designed for them.  The user can then control brilliance easily, but the switch is simply telling the bulbs or tubes what to do.  The actual lights then adjust their output as requested.<ref>http://www.popularmechanics.com/home/how-to/a3886/how-to-use-a-dimmer-switch-with-cfls-and-leds-15882096</ref>

[[Fluorescent lightbulb|Fluorescent lights]] as well as LED (Light emitting diode) bulbs cannot be dimmed by a simple voltage reduction.  However, this does not mean that it is impossible.  In most cases, the bulbs themselves can (and must) control their brilliance.  Therefore, variable brightness bulbs or tubes must be installed into a "dimmer" system designed for them.  The user can then control brilliance easily, but the switch is simply telling the bulbs or tubes what to do.  The actual lights then adjust their output as requested.<ref>http://www.popularmechanics.com/home/how-to/a3886/how-to-use-a-dimmer-switch-with-cfls-and-leds-15882096</ref>

 

==Purpose==

==Purpose==

===Energy saving===

===Energy saving===