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


Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

Micro Power 40Khz Burst Laser Diode DriverSome laser tag or simulated combat games can use this circuit to send short bursts of modulated laser light at the opponent's vest, equipped with a matching light receiver.  The circuit operates from three 1.5v cells (4.5v) that should provide enough energy. . . Circuit by David Johnson P.E.-June, 2000

Modified Cheap Solar LED Path LightModification of a typical solar path light with a standard 1000ma-hour NiMH
AAA cell.  I then replaced the small 4 cell solar panel with a larger 4 cell unit, which produced 150ma in the sun.  Next, I simply changed the 470uH coil on the circuit board to a 22uH coil.  The lower inductance increased the battery current to 40ma when the LED light was on, which translated to about 13ma LED current.  The light was much brighter. . . Circuit by David Johnson P.E.-October, 2012

Modified LED Night LightI bought some night lights a few months ago from Walmart here in Denver.  The devices were made by Elumina Lighting Technologies Inc.  (www.  eluminalighting.  com) , their model LED-6200A.  I think I paid about $15 for a pack of three lights.  I wanted a light . . . Hobby Circuit designed by David Johnson P.E.-May, 2007

Modulated Light Monitor #1This battery powered circuit will work from DC to 500KHz.  It is designed to connect to an oscilloscope to monitor the light level changes and modulated signals. . . Circuit by David Johnson P.E.-July, 2006

Modulated light receiver circuitThe circuit uses a very inexpensive C-MOS IC that is connected to a small photodiode.  Using a unique inductive feedback network, the circuit provides high sensitivity under high ambient light conditions.  It is a great circuit when you want to extend the range of an optical remote control transmitter. . . Circuit by David Johnson P.E.-June, 2000

Monitor Clear FluidsThis circuit detects when a clear fluid is inside a piece of clear plastic tubing.  It can be used for fluid level control and monitoring. . . Circuit by David A. Johnson P.E.-May, 2012

Night Light from White LEDAs many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components. . . Circuit by David A. Johnson P.E.-November, 2008

One-Watt White LED Night LightAs many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2008

Operation of Cascode Light ReceiversThis page provides a detailed explanation of how the modified cascode light receiver circuit operates.  The cascode technique in conjunction with an inductive load provides very high current to voltage conversion as well as very high speed . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Optical Fiber Receiver-5Mhz Broad BandThis circuit is a simple broad band light detector that uses a very inexpensive IC and a PIN photodiode that is packaged for use with plastic optical fibers.  It has a bandwidth from 1KHz to over 5MHz.  It is great for experimenting with various modulated . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Optical Filter using Color Film NegativeThis isnít an electronic circuit but the file shows the curve for an optical filter made from exposed color film.  The material blocks most visible light but is very transparent to 880nM infrared light.  Kodak 100ASA is exposed to "cool white" fluorescent light for about 5 seconds . . . Hobby Circuit designed by David Johnson P.E.-January, 1998

Optical Interrupter Draws MicroampsThis circuit is great for battery-powered systems that use slotted type optical interrupters.  It draws only 10uA from a 3v battery that should allow up to 5 years of operation from a lithium battery. . . Circuit by David A. Johnson P.E.-June, 2000

Optical RFID Test CircuitI designed this test the concept of using light techniques to send identification data instead of RF.. . . Circuit by David A. Johnson P.E.-February, 2002

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

Photovoltaic Solar Panels-Ideal Blocking Diode CircuitMost 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 David Johnson P.E.-March, 2011

PV Solar Cell Test FixtureThis is an illustration of a test fixture, which can be used to test individual solar cells for short circuit current.  Using a PIN photo diode and a control circuit, the solar cells can be tested under constant light level conditions . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2006

PV Solar Panels-Ideal Blocking Diode CircuitSolar 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 Johnson P.E.-March, 2011

Reduce voltage to Photovoltaic Solar Panel with Ideal DiodeSolar 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. . . Circuit by David Johnson P.E.-March, 2011

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.  Using the device, the remote can operate a TV or VCR over three times the normal distance. . . Circuit by David A. Johnson P.E.-June, 2000

RFID Test CircuitI designed this test the concept of using light techniques to send identification data instead of RF. . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002


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

Micro Power 40Khz Burst Laser Diode Driver -  Some laser tag or simulated combat games can use this circuit to send short bursts of modulated laser light at the opponent's vest, equipped with a matching light receiver.  The circuit operates from three 1.5v cells  (4.5v) that should provide enough energy. . . Circuit by David Johnson P.E.-June, 2000

Modified Cheap Solar LED Path Light -  Modification of a typical solar path light with a standard 1000ma-hour NiMH
AAA cell.  I then replaced the small 4 cell solar panel with a larger 4 cell unit, which produced 150ma in the sun.  Next, I simply changed the 470uH coil on the circuit board to a 22uH coil.  The lower inductance increased the battery current to 40ma when the LED light was on, which translated to about 13ma LED current.  The light was much brighter. . . Circuit by David Johnson P.E.-October, 2012

Modified LED Night Light -  I bought some night lights a few months ago from Walmart here in Denver.  The devices were made by Elumina Lighting Technologies Inc.   (www.  eluminalighting.  com) , their model LED-6200A.  I think I paid about $15 for a pack of three lights.  I wanted a light . . . Hobby Circuit designed by David Johnson P.E.-May, 2007

Modulated Light Monitor #1 -  This battery powered circuit will work from DC to 500KHz.  It is designed to connect to an oscilloscope to monitor the light level changes and modulated signals. . . Circuit by David Johnson P.E.-July, 2006

Modulated light receiver circuit -  The circuit uses a very inexpensive C-MOS IC that is connected to a small photodiode.  Using a unique inductive feedback network, the circuit provides high sensitivity under high ambient light conditions.  It is a great circuit when you want to extend the range of an optical remote control transmitter. . . Circuit by David Johnson P.E.-June, 2000

Monitor Clear Fluids -  This circuit detects when a clear fluid is inside a piece of clear plastic tubing.  It can be used for fluid level control and monitoring. . . Circuit by David A. Johnson P.E.-May, 2012

New Lightning Detector -  Especially built for the beginner __ Contact: Charles Wenzel of Wenzel Associates, Inc.

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

Night Light from White LED -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components. . . Circuit by David A. Johnson P.E.-November, 2008

Night Vision Enhancer -  Here is a simple green LED flashlight built around 555 timer IC (IC1) and powered from a 3V battery pack.  Green LED based flashlights are widely used by hunters and others in...__ Electronics Projects for You

Night-Light Uses a Photoresistor to Detect Dusk -  12/15/11Design Ideas: You can adjust this battery-powered circuit for different levels. __ Circuit Design by Chau Tran, Analog Devices, Malden, MA

Night-Vision Digital Goggle -  At night, on highways, the high-intensity light from the headlight of heavy vehicles blinds oncoming light vehicle drivers  (bike riders and car drivers) for a moment.  This is the main reason...__ Electronics Projects for You

One-Watt White LED Night Light -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2008

Operation of Cascode Light Receivers -  This page provides a detailed explanation of how the modified cascode light receiver circuit operates.  The cascode technique in conjunction with an inductive load provides very high current to voltage conversion as well as very high speed . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Optical Fiber Receiver-5Mhz Broad Band -  This circuit is a simple broad band light detector that uses a very inexpensive IC and a PIN photodiode that is packaged for use with plastic optical fibers.  It has a bandwidth from 1KHz to over 5MHz.  It is great for experimenting with various modulated . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Optical Filter using Color Film Negative -  This isnít an electronic circuit but the file shows the curve for an optical filter made from exposed color film.  The material blocks most visible light but is very transparent to 880nM infrared light.  Kodak 100ASA is exposed to "cool white" fluorescent light for about 5 seconds . . . Hobby Circuit designed by David Johnson P.E.-January, 1998

Optical Interrupter Draws Microamps -  This circuit is great for battery-powered systems that use slotted type optical interrupters.  It draws only 10uA from a 3v battery that should allow up to 5 years of operation from a lithium battery. . . Circuit by David A. Johnson P.E.-June, 2000

Optical RFID Test Circuit -  I designed this test the concept of using light techniques to send identification data instead of RF.. . . Circuit by David A. Johnson P.E.-February, 2002

Other Optical Sensors -  Cadmium-Sulfide photoelectric cells change resistance with changing light levels and are useable over a tremendous illumination range.  A simple CdS cell placed in the focal plane of a lens makes a telescopic 'electric eye' that can function at midnight or noon, with the appropriate circuitry.  To illustrate the idea, consider the antique from my school days shown below.  The box was for a famous cologne and the lens just perfectly projects images onto the photocell __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Photo Sensor -  Here's a circuit that takes advantage of the photo-voltaic voltage of an ordinary LED.  The LED voltage is buffered by a junction FET transistor and then applied to the inverting input of an op-amp with a gain of about 20.  This produces a change of about 5 volts at the output from darkness to bright light.  The 100K potentiometer can be set so that the output is around 7 volts in darkness and falls to about 2 volts in bright light __ Designed by Bill Bowden

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

Photovoltaic Solar Panels-Ideal Blocking Diode Circuit -  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 David Johnson P.E.-March, 2011

Porch Light Switch -  This circuit will activate a relay when light falls to a preset level.  Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer.   __ Designed by Andy Collinson

PV Solar Cell Test Fixture -  This is an illustration of a test fixture, which can be used to test individual solar cells for short circuit current.  Using a PIN photo diode and a control circuit, the solar cells can be tested under constant light level conditions . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2006

PV Solar Panels-Ideal Blocking Diode Circuit -  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 Johnson P.E.-March, 2011

Reduce voltage to Photovoltaic Solar Panel with Ideal Diode -  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. . . Circuit by David Johnson P.E.-March, 2011

Relay: Dark Activated -  This circuit switches a relay at dark via a Light Dependent Resistor or LDR for short.  The applications are numerous.  In my application, it switches on a light with an older type movement sensor and is mounted on the top corner of my workshop with the LDR __ Designed by Tony van Roon  VA3AVR

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.  Using the device, the remote can operate a TV or VCR over three times the normal distance. . . Circuit by David A. Johnson P.E.-June, 2000

RF Transmitter Light Sensing -  This transmitter is very simiilar to the Simplest RF Transmitter.   The only difference being the photoresistor placed in series with R1.   This could also be a thermistor or other variablwe resistance sensor. __ Designed by Tony van Roon  VA3AVR

RFID Test Circuit -  I designed this test the concept of using light techniques to send identification data instead of RF. . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

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

 


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