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Electronic circuits and components * Course Index * Introduction * About the Author * About this Course * Feedback * Course Navigation * How to use this Course * TINA * Locktronics Fundamentals * Introduction: Fundamentals * Units and Multiples * Electricity * Electronic Principles * Electrical Circuits * Alternating Current * Assessment: Fundamentals Passive Components * Introduction: Passive Components * Resistors ## Resistor Specifications ## Examples: Resistor Specifications ## Preferred Values: Resistors ## Resistor Colour Code ## Examples: Resistor Colour Code Test ## BS1852 Resistor Coding ## Examples: BS1852 Resistor Coding ## Measuring Resistance ## Resistor Symbols ## Resistor Construction ## Resistors in Series ## Worksheet: Resistors in Series ## Resistors in Parallel ## Worksheet: Resistors in Parallel ## Resistance and Temperature ## Examples: Resistance and Temperature ## Positive Temperature Coefficient ## Negative Temperature Coefficient ## Thermistors ## Light Dependent Resistors * Capacitors * Inductors * Transformers * Batteries, Fuses, Lamps and Switches * Assessment: Passive Components Semiconductors * Introduction: Semiconductors * Diodes * Transistors * Logic Gates * Assessment: Semiconductors Passive Circuits * Introduction: Passive Circuits * Series and Parallel Connections * Kirchoff's Laws * Potential and Current Dividers * Passive Time Variant Circuits * Assessment: Passive Circuits Active Circuits * Introduction: Active Circuits * Power Supply Circuits * Operational Amplifier Circuits * Transistor Amplifier Circuits * 555 Timer Circuits * Assessment: Active Circuits Parts Gallery * Introduction: Parts Gallery * Passive Component Images * Semiconductor Images * Other Images * Quizzes |
(:Summary:Contains the 'action' links (like Browse, Edit, History, etc.), placed at the top of the page, see site page actions:) (:comment This page can be somewhat complex to figure out the first time you see it. Its contents are documented at PmWiki.SitePageActions if you need help. :) * Print (:comment (:if group Site,SiteAdmin,Cookbook,Profiles,PmWiki*:) (:comment delete if and ifend to enable backlinks:) * %item rel=nofollow class=backlinks accesskey='$[ak_backlinks]'% [[{*$Name}?action=search&q=link={*$FullName} | $[Backlinks] ]] (:ifend:) :) * Login Light Dependent Resistors<^< Thermistors | Course Index | Capacitors >^>(:nl:) (:video_flv-player Attach:ldr_3.flv width=352 height=288 params= startimage= Light dependent resistors (LDRs) use a semiconductor material (i.e., a material that is neither a conductor nor an insulator) whose electrical characteristics vary according to the amount of incident light. The two semiconductor materials used for the manufacture of LDRs are cadmium sulphide (CdS) and cadmium selenide (CdSe). These materials are most sensitive to light in the visible spectrum, peaking at about 0.6μm for CdS and 0.75μm for CdSe. A typical Cadmium Sulphide LDR exhibits a resistance of around 1MΩ in complete darkness and less than 1kΩ when placed under a bright light source. A typical application for such a component is in automatic lighting control. A small current is applied to the LDR and this produces a voltage drop which changes according to the level of incident light. The voltage from the LDR is passed to a transistor or operational amplifier stage which, in turn, operates a relay or solid-state switching device (such as a thyristor or triac). (:nl:)(:table style="clear:both":)
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