Light Dependent Resistor

A light dependent resistor is also known as a photoresistor, or photoconductor.  A light dependent resistor is a resistor whose resistance decreases with increasing light intensity. 

If you need to know the specific science of a light dependent resistor, it kind of works like this:  photons absorbed by the light dependent resistor give bound electrons enough energy to enter the conduction band.  This creates electricity, and lowers resistance.  So, a light dependent resistor actually operates a lot like a semiconductor.  It is only referenced as a resistor in terms of usage. 

These photoresistors are used for street lights.  The light dependent resistor is basically keeping the power contacts apart, but it closed the contacts when its resistance is lowered (by the onset of night).  As you can see, this is a very practical application used in many different lighting mechanisms.  As you can imagine, the light dependent resistor is used primarily as a sensor mechanism for electronic devices.  There are countless imagineable ways of using these in the real world.  Some of them are even made so that they are potentiometers, and the user can change the resistance manually too.  These are handy for some devices. 

My brother is an electronics engineering graduate, and he knows a lot about electronic components and circuits.  He has constructed circuits that operate on light dependent resistor sensors, and he says that cadmium sulfide cells are the best because of how inexpensive they are.  Those are used in camera light meters, clock radios, alarms, and outdoor clocks.  There are also Lead Sulfide and indium antimonide photoresistors that are used for the mid infrared spectral region.  Photoconductors are used a lot in the fields of infrared astronomy, and infrared spectroscopy.  Some of the equipment would be impossible without them.

There are so many different applications that would be in trouble if we didn't have photoresistors.  A lot of equipment would be more expensive because it would need other means of achieving it's goals.  You wouldn't be able to get night-vision or infrared technology cheap anymore.  The real honest truth is that a photoresistor is a small circuit disguised as a component because it consists of a resitor, and conductor.  A lot of electronic nuts consider photoresistors to be the pinnacle of electronic achievement.

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