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between exposure to light and the subsequent decrease in resistance, usually around 10 milliseconds. The lag time when going from lit to dark environments is even greater, often as long as one second. This property makes them unsuitable for sensing rapidly flashing lights, but is sometimes used to
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Photoresistors can be placed in streetlights to control when the light is on. Ambient light falling on the photoresistor causes the streetlight to turn off. Thus energy is saved by ensuring the light is only on during hours of darkness.
148:. The resistance range and sensitivity of a photoresistor can substantially differ among dissimilar devices. Moreover, unique photoresistors may react substantially differently to photons within certain wavelength bands.
235:. The photoresistor is facing rightwards and controls whether current flows through the heater which opens the main power contacts. At night, the heater cools, closing the power contacts, energizing the street light.
211:. The photoresistivity of any photoresistor may vary widely depending on ambient temperature, making them unsuitable for applications requiring precise measurement of or sensitivity to light photons.
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Photoresistors are also used in laser-based security systems to detect the change in the light intensity when a person or object passes through the laser beam.
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116:. A photoresistor can be used in light-sensitive detector circuits and light-activated and dark-activated switching circuits acting as a
124:(MΩ), while in the light, it can have a resistance as low as a few hundred ohms. If incident light on a photoresistor exceeds a certain
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and is not an efficient semiconductor (such as silicon is). In intrinsic devices, most of the available electrons are in the
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effect, as the oscillating light patterns control the level of signal running through the amplifier circuit.
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A photoelectric device can be either intrinsic or extrinsic. An intrinsic semiconductor has its own
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to control gain reduction. A common usage of this application can be found in many
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resistance. In the dark, a photoresistor can have a resistance as high as several
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390:"Photo resistor - Light Dependent Resistor (LDR) » Resistor Guide"
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The internal components of a photoelectric control for a typical USA
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photoresistors is severely restricted in Europe due to the
466:- detailing operation, structure and circuit information
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219:smooth the response of audio signal compression.
163:. Extrinsic devices have impurities, also called
214:Photoresistors also exhibit a certain degree of
144:partners) conduct electricity, thereby lowering
239:Photoresistors come in many types. Inexpensive
195:A photoresistor is less light-sensitive than a
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366:Electronic Devices: System and Applications
140:. The resulting free electrons (and their
132:absorbed by the semiconductor give bound
459:Connecting a photoresistor to a circuit
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318:photoconductors are among the best far-
191:Large CdS photocell from a street light
322:detectors available, and are used for
203:. The latter two components are true
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417:TO-18 photocells on ceramic substrate
183:Three photoresistors with scale in mm
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454:Using a photoresistor to track light
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368:. New Delhi: Delimar. p. 480.
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136:enough energy to jump into the
90:The symbol for a photoresistor
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364:Diffenderfes, Robert (2005).
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102:light-dependent resistor
30:Not to be confused with
27:Light dependent resistor
169:extrinsic semiconductor
464:Photoresistor overview
265:together with a small
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328:infrared spectroscopy
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205:semiconductor devices
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175:Design considerations
110:photo-conductive cell
480:Resistive components
275:light-emitting diode
288:The use of CdS and
263:dynamic compressors
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324:infrared astronomy
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394:resistorguide.com
308:indium antimonide
279:guitar amplifiers
114:photoconductivity
100:(also known as a
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78:Electronic symbol
71:Photoconductivity
63:Working principle
16:(Redirected from
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304:Lead sulfide
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223:Applications
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157:valence band
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249:nightlights
233:streetlight
209:PN-junction
32:Photoresist
474:Categories
435:17 October
415:"Silonex:
351:References
306:(PbS) and
197:photodiode
146:resistance
18:Photocells
271:neon lamp
134:electrons
126:frequency
399:19 April
334:See also
320:infrared
122:megaohms
490:Sensors
298:cadmium
296:ban on
283:tremolo
216:latency
165:dopants
161:bandgap
130:photons
65:
56:Passive
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429:(PDF)
422:(PDF)
273:, or
199:or a
108:, or
437:2013
401:2018
370:ISBN
326:and
294:RoHS
290:CdSe
142:hole
52:Type
269:or
106:LDR
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316:Cu
312:Ge
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
