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Light Dependent Resistor Circuits / Photocell Circuits
Light Dependent Circuits:  #'s - D      E - L      M- Z

 

Last Updated: November 21, 2017 05:47 AM

Circuits Designed by Dave Johnson, P.E. :

Eight-Solar Cell Lithium Ion Battery Charger Version 3A single lithium ion battery cell needs 4.2v from a current source to insure it is fully charged.  A solar panel with just enough individual cells wired in series to produce the needed voltage would be more efficient than one with more cells for a given surface area.  If you divide 4.2 by eight you come up with a figure of 0.525 volts. . . Circuit by David Johnson P.E.-May, 2013

FET Input High Speed Light DetectorThis circuit is yet another design that converts current from a PIN photo diode to a voltage.  It has a bandwidth that extends beyond 50MHz. . . Circuit by David A. Johnson P.E.-June, 2000

Fully Isolated 50/60hz Sync GeneratorThis circuit will produce a single pulse at the zero voltage cross points of the power line voltage.  An opto-coupler provides a very safe 5KV isolation . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

High Ambient Light Immunity Light Detector  - The circuit below was designed to turn on an external 12v relay, whenever it detects light from a nearby LED light source, modulated at 40KHz to 50KHz.   This circuit was originally designed to operate from a fast moving vehicle . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

High Speed Light Detector from FET InputThis circuit is yet another design that converts current from a PIN photo diode to a voltage.  It has a bandwidth that extends beyond 50MHz . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

High-speed 75MHz light receiverThis circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response.  It is designed around a PIN photo diode that is packaged for use with plastic optical fibers.  It can be used as an optical fiber receiver.  By using the open end of the optical fiber it can "sniff" out any modulated light signals. . . Circuit by David A. Johnson P.E.-June, 2000

Honeybee CounterI designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive.  The low power circuit uses a slotted opto-sensor to detect the passing bees.  The circuit advances an electronic counting. . . Circuit by David A. Johnson P.E.-July, 2000

Ideal Blocking Diode Circuit for Photovoltaic Solar PanelsMost photovoltaic solar panels are used to charge a battery during the daytime.  Nearly all panels come equipped with a blocking diode.  The diode prevents DC current from flowing backwards from the battery bank into the panel at night.  The usual blocking. . . Circuit by Dave Johnson P.E.-March, 2011

Ideal Diode for PV PanelsSolar panels usually include a diode at their outputs.  The diode prevents current from back feeding into the panel at night from the battery being charged by the panel.  But, this diode does waste some power and does reduce the available panel voltage . . . Hobby Circuit designed by David A. Johnson P.E.-March, 2011

Ideal Diode FunctionMost photovoltaic solar panels are used to charge a battery during the daytime.  Nearly all panels come equipped with a blocking diode.  The diode prevents DC current from flowing backwards from the battery bank into the panel at night.  The usual blocking . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2008

Improve Response Time of a Photo Transistor CircuitThis page shows different ways to improve the response time of a photo transistor circuit . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2010

Improved Solar LED Spot LightNearly all the Chinese made solar powered LED lights I see being sold at Lowe's and Home Depot home improvement centers are poorly designed.  Their solar panels and battery packs are all undersized.  The light from their Chinese made LEDs fade rapidly and the devices never make it through a complete night before the light dies. . . Circuit by David A. Johnson P.E.-February, 2013

Improved Solar Path LightThe circuit below was designed to replace the guts of an existing path light assembly with one which has a much better performance.  I suggest using a quality 10 cell solar panel with at least a 4 square inch area.  Buy a panel with solar panels that fills . . . Hobby Circuit designed by David A. Johnson P.E.-March, 2011

Indicates when it is Time to DustI thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough.  I have not yet built and tested this circuit completely but in concept it should work. . . Circuit by David A. Johnson P.E.-June, 2000

Indicates when it is Time to DustI have used the circuit below for many different applications, which require ultra low power drain.  It uses a single CA4013 flip/flop.  One section forms a pulse generator.  The generator produces 100uS pulses at a rate of about 1 per secondCircuit Solution by Dave Johnson P.E.-May, 2006

Infrared Remote Extender CircuitThis circuit is designed to be placed directly in front of a standard TV or VCR remote.  The exiting light pulses produced by the circuit match the pulses from the remote but are about 10 times more powerful . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

It's Time to Dust IndicatorI thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough.  I have not yet built and tested this circuit completely but in concept it should work . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Eight-Solar Cell Lithium Ion Battery Charger Version 3 -  A single lithium ion battery cell needs 4.2v from a current source to insure it is fully charged.  A solar panel with just enough individual cells wired in series to produce the needed voltage would be more efficient than one with more cells for a given surface area.  If you divide 4.2 by eight you come up with a figure of 0.525 volts. . . Circuit by David Johnson P.E.-May, 2013

Electronic Night Light -  This circuit for an electronic night light was submitted by Adam from Canada.  I have provided the notes __ Designed by Andy Collison

Feedback circuit enhances phototransistor's linear operation -  12-Oct-06 EDN-Design Ideas Bias-current compensation reduces ambient-light saturation effects.  A designer who uses a phototransistor to convert a modulated optical signal to an electrical signal frequently encounters problems when high-intensity background light saturates the phototransistor.  __ Designed by J Ferrer

Feedback enhances phototransistor's linear operation -  12-Oct-06 EDN-Design Ideas Bias-current compensation reduces ambient-light saturation effects __ Circuit Design by JC Ferrer and A Garrigós, University Miguel Hernandez, Elche, Spain

FET Input High Speed Light Detector -  This circuit is yet another design that converts current from a PIN photo diode to a voltage.  It has a bandwidth that extends beyond 50MHz. . . Circuit by David A. Johnson P.E.-June, 2000

Fully Isolated 50/60hz Sync Generator -  This circuit will produce a single pulse at the zero voltage cross points of the power line voltage.  An opto-coupler provides a very safe 5KV isolation . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

High Ambient Light Immunity Light Detector  -  The circuit below was designed to turn on an external 12v relay, whenever it detects light from a nearby LED light source, modulated at 40KHz to 50KHz.   This circuit was originally designed to operate from a fast moving vehicle . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

High Speed Light Detector from FET Input -  This circuit is yet another design that converts current from a PIN photo diode to a voltage.  It has a bandwidth that extends beyond 50MHz . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

High-speed 75MHz light receiver -  This circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response.  It is designed around a PIN photo diode that is packaged for use with plastic optical fibers.  It can be used as an optical fiber receiver.  By using the open end of the optical fiber it can "sniff" out any modulated light signals. . . Circuit by David A. Johnson P.E.-June, 2000

Honeybee Counter -  I designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive.  The low power circuit uses a slotted opto-sensor to detect the passing bees.  The circuit advances an electronic counting. . . Circuit by David A. Johnson P.E.-July, 2000

Ideal Blocking Diode Circuit for Photovoltaic Solar Panels -  Most photovoltaic solar panels are used to charge a battery during the daytime.  Nearly all panels come equipped with a blocking diode.  The diode prevents DC current from flowing backwards from the battery bank into the panel at night.  The usual blocking. . . Circuit by Dave Johnson P.E.-March, 2011

Ideal Diode for PV Panels -  Solar panels usually include a diode at their outputs.  The diode prevents current from back feeding into the panel at night from the battery being charged by the panel.  But, this diode does waste some power and does reduce the available panel voltage . . . Hobby Circuit designed by David A. Johnson P.E.-March, 2011

Ideal Diode Function -  Most photovoltaic solar panels are used to charge a battery during the daytime.  Nearly all panels come equipped with a blocking diode.  The diode prevents DC current from flowing backwards from the battery bank into the panel at night.  The usual blocking . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2008

Implement Photovoltaic-Module Simulator -  04/07/11  EDN-Design Ideas Use combinations of diodes to simulate photovoltaic cells.  Electronics engineers often use photovoltaic-module simulators to test dc/dc-power converters, inverters, or MPPT  (maximum-power-point-tracking) -control techniques.  The use of these simulators lets you work in the laboratory with predefined photovoltaic conditions, thus avoiding the drawbacks of real photovoltaic modules.  Various commercial simulators are available, but they are often expensive.   __ Circuit Design by José M Blanes and Ausiàs Garrigós, University Miguel Hernández, Elche, Spain

Improve Response Time of a Photo Transistor Circuit -  This page shows different ways to improve the response time of a photo transistor circuit . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2010

Improved Solar LED Spot Light -  Nearly all the Chinese made solar powered LED lights I see being sold at Lowe's and Home Depot home improvement centers are poorly designed.  Their solar panels and battery packs are all undersized.  The light from their Chinese made LEDs fade rapidly and the devices never make it through a complete night before the light dies. . . Circuit by David A. Johnson P.E.-February, 2013

Improved Solar Path Light -  The circuit below was designed to replace the guts of an existing path light assembly with one which has a much better performance.  I suggest using a quality 10 cell solar panel with at least a 4 square inch area.  Buy a panel with solar panels that fills . . . Hobby Circuit designed by David A. Johnson P.E.-March, 2011

Indicates when it is Time to Dust -  I have used the circuit below for many different applications, which require ultra low power drain.  It uses a single CA4013 flip/flop.  One section forms a pulse generator.  The generator produces 100uS pulses at a rate of about 1 per secondCircuit Solution by Dave Johnson P.E.-May, 2006

Indicates when it is Time to Dust -  I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough.  I have not yet built and tested this circuit completely but in concept it should work. . . Circuit by David A. Johnson P.E.-June, 2000

Infrared Remote Extender Circuit -  This circuit is designed to be placed directly in front of a standard TV or VCR remote.  The exiting light pulses produced by the circuit match the pulses from the remote but are about 10 times more powerful . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

It's Time to Dust Indicator -  I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough.  I have not yet built and tested this circuit completely but in concept it should work . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

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Light Dependent Circuits:  #'s - D      E - L      M- Z


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