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2016 Extra Class study guide: E6F - Optical components

Posted: 24 Jan 2016 04:29 PM PST
http://feedproxy.google.com/~r/kb6nu...m_medium=email


Two questions—E6F13 and E6F14—about LCD displays were added to this
section. The other questions were unchangedDan

E6F: Optical components: photoconductive principles and effects,
photovoltaic systems, optical couplers, optical sensors, and optoisolators;
LCDs

The photovoltaic effect is the conversion of light to electrical energy.
(E6F04) In a photovoltaic cell, electrons absorb the energy from light
falling on a photovoltaic cell. (E6F12) The electrons then become free
electrons.

The most common type of photovoltaic cell used for electrical power
generation is silicon. (E6F10) The approximate open-circuit voltage
produced by a fully-illuminated siliconÂ*photovoltaic cell is 0.5 V. (E6F11)
The efficiency of a photovoltaic cell is the relative fraction of light
that is converted to current. (E6F09)

Photoconductivity is a similar phenomenon. Photoconductivity is the
increased conductivity of an illuminated semiconductor. (E6F01) The
conductivity of a photoconductive material increases when light shines on
it. (E6F02) A crystalline semiconductor is the material that is affected
the most by photoconductivity. (E6F06)

A device that uses the phenomenon of photoconductivity is the optoisolator.
The most common configuration of an optoisolator or optocoupler is an LED
and a phototransistor. (E6F03) Optoisolators are often used in conjunction
with solid state circuits when switching 120 VAC because optoisolators
provide a very high degree of electrical isolation between a control
circuit and the circuit being switched. (E6F08)

A similar device is the solid-state relay. A solid state relay is a device
that uses semiconductor devices to implement the functions of an
electromechanical relay. (E6F07)

Optical shaft encoders are another device that rely on photoconductivity.
An optical shaft encoder is a device which detects rotation of a control by
interrupting a light source with a patterned wheel. (E6F05) Optical shaft
encoders are used to detect when an operator turns a knob on an amateur
radio transceiver.

Liquid crystal displays

A liquid crystal display (LCD) is a display utilizing a crystalline liquid
and polarizing filters which becomes opaque when voltage is applied.
(E6F13) One thing that is true of LCD displays is that they may be hard to
view through polarized lenses. (E6F14)

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