Changes

==Types==

==Types==

===Rheostat (variable resistor)===

===Rheostat (variable resistor)===

The first kind of dimmer switch made use of a variable resistor.  In this kind of device, a [[semiconductor]] strip is placed between two contact arms--one is stationary, one is adjustable.  The semiconductor permits the flow of electricity, but does resist it somewhat.  The stationary contact arm is placed at one end of the semiconductive strip, and the adjustable one is permitted to move across it.  When the latter arm is placed right near the stationary arm, electricity flows from one arm through a small amount of the semiconductor, and out to the other arm.  Since it only passes through a small amount of semiconductor, the power flow is minimally effected.  However, when the adjustable arm is moved down the strip, away from the stationary arm, the amount of semiconductor the power must flow through increases.  This prevents progressively more electricity from passing through, as the arms separate.<ref name="howstuffworks p1">http://home.howstuffworks.com/dimmer-switch1.htm</ref><br />

The first kind of dimmer switch made use of a variable resistor.  In this kind of device, a [[semiconductor]] strip is placed between two contact arms—one is stationary, one is adjustable.  The semiconductor permits the flow of electricity, but does resist it somewhat.  The stationary contact arm is placed at one end of the semiconductive strip, and the adjustable one is permitted to move across it.  When the latter arm is placed right near the stationary arm, electricity flows from one arm through a small amount of the semiconductor, and out to the other arm.  Since it only passes through a small amount of semiconductor, the power flow is minimally effected.  However, when the adjustable arm is moved down the strip, away from the stationary arm, the amount of semiconductor the power must flow through increases.  This prevents progressively more electricity from passing through, as the arms separate.<ref name="howstuffworks p1">http://home.howstuffworks.com/dimmer-switch1.htm</ref><br />

This simple system is then installed in a switch, where the user can easily move the adjustable arm.  The resulting supply is then connected to some device, usually a light bulb.  If the operator wished for a higher power supply, they can simply slide or twist the dimmer control to decrease the amount of semiconductor the energy must pass through.  If the operator wishes to reduce the electrical supply, the amount of used semiconductor can be increased, by sliding or twisting the control in the opposite direction.<ref name="howstuffworks p1">http://home.howstuffworks.com/dimmer-switch1.htm</ref><br />

This simple system is then installed in a switch, where the user can easily move the adjustable arm.  The resulting supply is then connected to some device, usually a light bulb.  If the operator wished for a higher power supply, they can simply slide or twist the dimmer control to decrease the amount of semiconductor the energy must pass through.  If the operator wishes to reduce the electrical supply, the amount of used semiconductor can be increased, by sliding or twisting the control in the opposite direction.<ref name="howstuffworks p1"/><br />

Another kind of Rheostat dimmer used salt water as a semiconductor, with metal contacts which could be adjusted so they were closer or farther away from each other.  As the distance between the contacts increased, the electricity needed to pass through more salt water, resulting in more being lost before it reached the other contact.  While also inefficient (and unsafe), this kind of dimmer was fairly easy to construct, although frequent maintenance was required due to the salt damage.<ref name="iawco.com">http://www.iawco.com/parlights/Downloads_files/strand/Dimming/Sinewave%20Dimmer%20Technology.pdf</ref><br />

Another kind of Rheostat dimmer used salt water as a semiconductor, with metal contacts which could be adjusted so they were closer or farther away from each other.  As the distance between the contacts increased, the electricity needed to pass through more salt water, resulting in more being lost before it reached the other contact.  While also inefficient (and unsafe), this kind of dimmer was fairly easy to construct, although frequent maintenance was required due to the salt damage.<ref name="iawco.com">http://www.iawco.com/parlights/Downloads_files/strand/Dimming/Sinewave%20Dimmer%20Technology.pdf</ref><br />

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"/>

===Autotransformer dimmer===

===Autotransformer dimmer===

[[File:Commercial variac red.jpg|thumbnail|150px|A Commercial Variac]]

[[File:Commercial variac red.jpg|thumbnail|150px|A Commercial Variac]]

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><ref name="iawco.com">http://www.iawco.com/parlights/Downloads_files/strand/Dimming/Sinewave%20Dimmer%20Technology.pdf</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="iawco.com"/><ref name="mindspring.com">http://www.mindspring.com/~atlantatubeamp/id23.html</ref>

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

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

===Other varieties===

===Other varieties===

Other varieties exist as well, each with strengths and weeknesses.  Over time, ways are being found to actually conserve the unwanted electricity, but this can result in other complications.  For example,  reverse phase control was found to be a fairly efficient method, but only works with resistive capacitive loads.  To many electronics such as fans, this kind of dimming technology would be destructive.<ref name="iawco.com">http://www.iawco.com/parlights/Downloads_files/strand/Dimming/Sinewave%20Dimmer%20Technology.pdf</ref>  Other varieties include Coil-rotation transformers and Field effect transistors.<ref>http://www.factsfacts.com/MyHomeRepair/DimmerSwitch.htm</ref>

Other varieties exist as well, each with strengths and weeknesses.  Over time, ways are being found to actually conserve the unwanted electricity, but this can result in other complications.  For example,  reverse phase control was found to be a fairly efficient method, but only works with resistive capacitive loads.  To many electronics such as fans, this kind of dimming technology would be destructive.<ref name="iawco.com"/>  Other varieties include Coil-rotation transformers and Field effect transistors.<ref>http://www.factsfacts.com/MyHomeRepair/DimmerSwitch.htm</ref>

==Purpose==

==Purpose==

===Extended device life===

===Extended device life===

While reduced voltage can be harmful to some electronics, others--mainly light sources--can actually be preserved by it.  In some cases, it helps to preserve lights by simply running them at a slightly reduced voltage.  In other cases, it helps them most of all if they are allowed time to warm up with a very low voltage running through them.  After doing this with halogen lamps, for example, it is much less harmful to them when full power is applied to them.

While reduced voltage can be harmful to some electronics, others—mainly light sources—can actually be preserved by it.  In some cases, it helps to preserve lights by simply running them at a slightly reduced voltage.  In other cases, it helps them most of all if they are allowed time to warm up with a very low voltage running through them.  After doing this with halogen lamps, for example, it is much less harmful to them when full power is applied to them.

==References==

==References==

{{reflist}}

{{reflist}}

[[Category:Electronics‏‎]]

[[Category:Electronics‏‎]]