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--- eeng:topics:photocells:start [2022/10/20 18:30] – [LUX] rolf
+++ eeng:topics:photocells:start [2023/11/22 01:07] (current) – [About LDR] rolf
@@ Line 1: / Line 1: @@
 ====== Photocells / Light Dependent Resistors (LDR) ======
+===== Lecture Slides =====
-| {{https://cdn.sparkfun.com//assets/parts/2/4/6/2/09088-02-L.jpg?300}} |
+  * {{ :eeng:topics:photocells:ldr_2022-09-22_v001_rb.pdf |}}
+===== About LDR =====
+| {{https://cdn.sparkfun.com//assets/parts/2/4/6/2/09088-02-L.jpg?200}} |
 | Fig.: A cadmium sulfide (CdS) photocell. \\ (Source: [[https://www.sparkfun.com/products/9088|SparkFun]]) |
@@ Line 13: / Line 18: @@
   - {{https://resources.perkinelmer.com/corporate/cmsresources/images/dts_photocellsa9050.pdf|Photocells A 9050, A 9060}}.
-=== High Variability ===
+==== Large Variance among specimen of the same product series ====
+The GL5528 datasheet from Sparkfun illustrates the broad performance variety between LDR of the same type:
+  * :!: https://cdn.sparkfun.com/datasheets/Sensors/LightImaging/SEN-09088.pdf
+==== LUX ====
+The light "intensity" illuminating the photocell is measured in **Lux**. This unit takes not just the physical light quantity but also the sensitivity of the human eye into account. It combines physics with physiology.
+"The lux (symbol: lx) is the **unit of illuminance, or luminous flux per unit area,** in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used as both the singular and plural form." (from [[https://en.wikipedia.org/wiki/Lux|Wikipedia]])
+==== High Performance Variability ====
 Do not trust the resistance-vs-lux curves too much. Adafruit states on its tutorial on Photocells for Arduino:
@@ Line 23: / Line 45: @@
 The [[http://cdn.sparkfun.com/datasheets/Sensors/LightImaging/SEN-09088.pdf|datasheet]] on GL5528 Photocell by **SparkFun** reflects these uncertainties.
-=== LUX ===
-The light "intensity" illuminating the photocell is measured in **Lux**. This unit takes not just the physical light quantity but also the sensitivity of the human eye into account. It combines physics with physiology.
-"The lux (symbol: lx) is the **unit of illuminance, or luminous flux per unit area,** in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used as both the singular and plural form." (from [[https://en.wikipedia.org/wiki/Lux|Wikipedia]])
 ===== LDR Voltage Divider Experiment with Arduino =====