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


Last Updated: November 30, 2017 10:29 AM

Circuits Designed by Dave Johnson, P.E. :

Safety LightMy 1200 square foot metal shop only has one small entrance door and no skylights.  If the lights are turn off while inside, there is not enough light to safely find the door to exit the building.  On a couple occasions, while I was quietly working at my test bench, my wife would walk into the shop, grab a garden tool and rush back out, turning off the lights and closing the door without thinking . . . Hobby Circuit designed by David Johnson P.E.-November, 2004

Salvaged Broken Solar CellsAs illustrated below, one way to salvage a large number of broken solar cells is to wire them in parallel, not in the more conventional series connection.  Broken cells of various sizes and shapes are grouped together into panels of about one quarter to on . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2012

Sensitive Modulated Light Receiver uses a Single ICThe 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 . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Shop Safety LightMy 1200 square foot metal shop only has one small entrance door and no skylights.  If the lights are turn off while inside, there is not enough light to safely find the door to exit the building.  On a couple occasions, while I was quietly working at my test bench, my wife would walk into the shop, grab a garden tool and rush back out, turning off the lights and closing the door without thinking . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2004

Simple Circuit for White LED Night LightThis simple circuit is designed to plug into a standard AC electrical outlet.  It uses four super bright white light emitting diodes (LED) in conjunction with a capacitor coupled full wave rectifier circuit. . . Circuit by David Johnson P.E.-July, 2003

Single IC forms Senesitive Modulated Light ReceiverThe 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 A. Johnson P.E.-June, 2000

Slotted Opto-Sensor used in 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 . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2000

Slotted-Type 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 . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Snow Depth AlarmThe design of this system alerts a snowplow driver when the snow depth has exceeded four inches.  A visible red LED packaged in a 10mm package is pulsed at a rate of about 50Hz with 10uS pulses.  Twenty four inches away a phototransistor detects the light from the LED.  The LED and the phototransistor are housed in a section of Ĺ inch PVC pipe, forming a waterproof seal. . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Solar Cell Test FixtureIf you are considering building your own solar panel, you might try building the solar cell tester shown below.  When constructing a solar panel it is important to make sure that all the solar cells used in the panel be closely matched for their short circuit . . . Hobby Circuit designed by David Johnson P.E.-November, 2007

Solar Insolation MonitorOwners of photovoltaic solar panels often like to monitor how bright the sunshine is.  They can use this information to gage how well their solar panels are doing.  On a typical clear day, the sun energy at sea level is about 1000 watts per square meter . . . Hobby Circuit designed by David Johnson P.E.-May, 2012

Solar Lithium Ion Battery Charger using LT1131I have been designing a number of solar powered devices lately.  Many of them use just a single 3.6v lithium ion battery.  These batteries like to be charged from a fixed 4.2v source with a charging current limited to about C/8, where C is the milliamp-hour rating of the part. . . Circuit by Dave Johnson P.E.-December, 2012

Solar Path Light ImprovementUse 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. . . Circuit by David Johnson P.E.-March, 2011

Solar Powered Cell Phone ChargerThe simple circuit below regulates the voltage from a 6v solar panel to a fixed +5v.  That voltage can be fed to any cell phone or USB connected portable device, to charge its battery.  The circuit uses a Reg113-5 voltage regulator from Texas Instruments. . . Circuit by David Johnson P.E.-January, 2011

Solar Powered Flood Light using NiMH
Cells
There are many solar powered garden lights available.  Most of the devices offered at the home improvement stores have very poor performance.  Their batteries are too small, the light launched is weak and the solar panels are undersized.  None of the devices I have tested would operate through a typical night. . . Circuit by David Johnson P.E.-December, 2013

Solar Powered Infrared 1W Security Camera IlluminatorMany security cameras are equipped with an array of infrared LEDs to illuminate an area in front of the camera with invisible light for night time surveillance.    However, there are times when a remote area, well away from the camera, needs additional infrared light.    The circuit below uses a modified solar powered path light to bathe a fairly large area with 850nm infrared light. . . Circuit by David Johnson P.E.-June, 2014

Solar Powered Lithium Ion Battery ChargerThe circuit below feeds a controlled current and voltage to a 3.6v lithium ion battery.  The current is limited to 300ma and the voltage is limited to 4.2 volts.  The circuit uses a LTC1734 IC from Linear Technology.  No diode is needed between the circuit a . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2007

Solar PV 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. . . Circuit by David Johnson P.E.-October, 2006

Solar-Powered Pump Motor ControllerA Discover Circuits visitor had a problem.  He needed a simple on/off controller for his solar powered water pump.  His system used two 12v 50 watt solar panels wired in series.  The power from the solar panels drove a submerged water pump.  However, during. . . Circuit by David A. Johnson P.E.-October, 2010

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 second . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2006

Transmitter for Line Powered Xenon FlashThis line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

TV-VCR Light Source 40Khz RepeaterThis 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 Dave Johnson P.E.-June, 2000

Ultra Low Power Detects Clear FluidUsing an ultra low power technique, 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 . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2005

Use Color Film Negative to Make an Optical FilterThis 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 Dave Johnson P.E.-January, 1998

Variable Isolated AC Voltage Spans 0VAC to 280VacI designed and built this circuit about 25 years ago.  It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC.  It provides complete isolation from the power line.  It uses two 1:1 isolation transformers that are wired in parallel. . . Circuit by Dave Johnson P.E.-July, 2000

Water Pump controlled by Solar PowerA Discover Circuits visitor had a problem.  He needed a simple on/off controller for his solar powered water pump.  His system used two 12v 50 watt solar panels wired in series.  The power from the solar panels drove a submerged water pump.  However, during . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2010

Xenon Flash Receiver-Pg2This is of the receiver circuit AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Xenon Lamp Flash Detector AmplifierThis circuit has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp.  When connected to a flip/flop it can serve as an on on/off Controller. . . Circuit by David A. Johnson P.E.-December, 2004


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

Safety Light -  My 1200 square foot metal shop only has one small entrance door and no skylights.  If the lights are turn off while inside, there is not enough light to safely find the door to exit the building.  On a couple occasions, while I was quietly working at my test bench, my wife would walk into the shop, grab a garden tool and rush back out, turning off the lights and closing the door without thinking . . . Hobby Circuit designed by David Johnson P.E.-November, 2004

Salvaged Broken Solar Cells -  As illustrated below, one way to salvage a large number of broken solar cells is to wire them in parallel, not in the more conventional series connection.  Broken cells of various sizes and shapes are grouped together into panels of about one quarter to on . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2012

SCC3 12V 20A Solar Charge Controller -  The SCC3 kit is the heart of a 12 Volt solar power system, it regulates the charging of batteries from photovoltaic    (PV) solar panels.  A charge controller is an essential part of any solar power system.  A 12 Volt solar power system can provide power to a wide variety of devices such as lighting systems, Ham and CB radios, car stereos, cell phone chargers, laptop computers, televisions, recording equipment, fans, water pumps and other 12V DC loads.  With the addition of a DC to AC inverter, the DC power can be converted to 120 Volts AC for running many household electronic devices. 
 __ Designed by G. Forrest Cook

Screamer Siren-Light Controlled -  This circuit will produce an ear-piercing scream, depending on the amount of light being detected by the Light Dependent Resistor.  __ 555-Timer

Sensitive Modulated Light Receiver uses a Single IC -  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 . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Shop Safety Light -  My 1200 square foot metal shop only has one small entrance door and no skylights.  If the lights are turn off while inside, there is not enough light to safely find the door to exit the building.  On a couple occasions, while I was quietly working at my test bench, my wife would walk into the shop, grab a garden tool and rush back out, turning off the lights and closing the door without thinking . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2004

Simple Circuit for White LED Night Light -  This simple circuit is designed to plug into a standard AC electrical outlet.  It uses four super bright white light emitting diodes  (LED) in conjunction with a capacitor coupled full wave rectifier circuit. . . Circuit by David Johnson P.E.-July, 2003

Simple Circuit light Sensoradapter for Oscilloscope -  This circuit is a simple visible light or IR detector for testing any equipment which outputs light. The circuit can be also used for measuring ambient light levels.  This circuit is based on one photodiode which is used in photocell mode so that the photodiode generates a voltage and current signal when it get light.   __ Designed by Tomi Engdahl

Simple Circuit 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

Simple Circuit Photodetector -  Iīve designed this simple circuit to test a photodetector.  I got the detector from an old 5 1/4" disk drive.  If you can get one, you will find two photodetectorts: one is used to sense the density  (double density or high density) 

Single IC forms Senesitive Modulated Light Receiver -  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 A. Johnson P.E.-June, 2000

Slotted Opto-Sensor used in 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 . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2000

Slotted-Type 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 . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Snow Depth Alarm -  The design of this system alerts a snowplow driver when the snow depth has exceeded four inches.  A visible red LED packaged in a 10mm package is pulsed at a rate of about 50Hz with 10uS pulses.  Twenty four inches away a phototransistor detects the light from the LED.  The LED and the phototransistor are housed in a section of Ĺ inch PVC pipe, forming a waterproof seal. . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Solar Cell Test Fixture -  If you are considering building your own solar panel, you might try building the solar cell tester shown below.  When constructing a solar panel it is important to make sure that all the solar cells used in the panel be closely matched for their short circuit . . . Hobby Circuit designed by David Johnson P.E.-November, 2007

Solar Insolation Monitor -  Owners of photovoltaic solar panels often like to monitor how bright the sunshine is.  They can use this information to gage how well their solar panels are doing.  On a typical clear day, the sun energy at sea level is about 1000 watts per square meter . . . Hobby Circuit designed by David Johnson P.E.-May, 2012

Solar Lithium Ion Battery Charger using LT1131 -  I have been designing a number of solar powered devices lately.  Many of them use just a single 3.6v lithium ion battery.  These batteries like to be charged from a fixed 4.2v source with a charging current limited to about C/8, where C is the milliamp-hour rating of the part. . . Circuit by Dave Johnson P.E.-December, 2012

Solar Path Light Improvement -  Use 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. . . Circuit by David Johnson P.E.-March, 2011

Solar Powered Cell Phone Charger -  The simple circuit below regulates the voltage from a 6v solar panel to a fixed +5v.  That voltage can be fed to any cell phone or USB connected portable device, to charge its battery.  The circuit uses a Reg113-5 voltage regulator from Texas Instruments. . . Circuit by David Johnson P.E.-January, 2011

Solar Powered Flood Light using NiMH
Cells
-  There are many solar powered garden lights available.  Most of the devices offered at the home improvement stores have very poor performance.  Their batteries are too small, the light launched is weak and the solar panels are undersized.  None of the devices I have tested would operate through a typical night. . . Circuit by David Johnson P.E.-December, 2013

Solar Powered Infrared 1W Security Camera Illuminator -  Many security cameras are equipped with an array of infrared LEDs to illuminate an area in front of the camera with invisible light for night time surveillance.    However, there are times when a remote area, well away from the camera, needs additional infrared light.    The circuit below uses a modified solar powered path light to bathe a fairly large area with 850nm infrared light. . . Circuit by David Johnson P.E.-June, 2014

Solar Powered Lithium Ion Battery Charger -  The circuit below feeds a controlled current and voltage to a 3.6v lithium ion battery.  The current is limited to 300ma and the voltage is limited to 4.2 volts.  The circuit uses a LTC1734 IC from Linear Technology.  No diode is needed between the circuit a . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2007

Solar PV 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. . . Circuit by David Johnson P.E.-October, 2006

Solar-Powered Pump Motor Controller -  A Discover Circuits visitor had a problem.  He needed a simple on/off controller for his solar powered water pump.  His system used two 12v 50 watt solar panels wired in series.  The power from the solar panels drove a submerged water pump.  However, during. . . Circuit by David A. Johnson P.E.-October, 2010

Sunrise Lamp using 120VAC 60 Watt Lamp -  In this circuit, a 120VAC lamp is slowly illuminated over a approximate 20 minute period.  The bridge rectifier supplies 120 DC to the MOSFET and 60 watt lamp.  A 6.2K, 5 watt resistor and zener diode is used to drop the voltage to 12 volts DC for the circuit power.  The bridge rectifier should be rated at 200 volts and __ Designed by Bill Bowden

Sunset Lamp -  LDR-based automatic lights flicker due to the change in light intensity at dawn and dusk.  So compact fluorescent lamps  (CFLs) are unsuitable in such circuits as flickering may damage the electronic...__ Electronics Projects for You

Sun-Up Alarm -  The SunUp Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on.  It can also be used to detect a light beam, headlights etc.  The circuit works as follows.  The phototransistor is very sensitive to light.   (Any phototransistor will work fine)  __ Designed by Randy Linscott

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 second . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2006

Transmitter for Line Powered Xenon Flash -  This line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

TV-VCR Light Source 40Khz Repeater -  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 Dave Johnson P.E.-June, 2000

Twilight Lamp Blinker -  During sunset or sunrise, the ambient light is not adequate to lead you through the open doorway or make your way around obstructions.  To avoid any mishap, here is a twilight...__ Electronics Projects for You

Twi-Light using White LEDs -  This sunlight-controlled lamp uses a light-dependent resistor  (LDR) as the sunlight sensor and a total of 25 high-brightness white LEDs.  Separate resistors are connected in series with each row of the...__ Electronics Projects for You

Ultra Low Power Detects Clear Fluid -  Using an ultra low power technique, 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 . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2005

Use Color Film Negative to Make an Optical Filter -  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 Dave Johnson P.E.-January, 1998

Variable Isolated AC Voltage Spans 0VAC to 280Vac -  I designed and built this circuit about 25 years ago.  It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC.  It provides complete isolation from the power line.  It uses two 1:1 isolation transformers that are wired in parallel. . . Circuit by Dave Johnson P.E.-July, 2000

Water Pump controlled by Solar Power -  A Discover Circuits visitor had a problem.  He needed a simple on/off controller for his solar powered water pump.  His system used two 12v 50 watt solar panels wired in series.  The power from the solar panels drove a submerged water pump.  However, during . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2010

Xenon Flash Receiver-Pg2 -  This is of the receiver circuit AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Xenon Lamp Flash Detector Amplifier -  This circuit has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp.  When connected to a flip/flop it can serve as an on on/off Controller. . . Circuit by David A. Johnson P.E.-December, 2004

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Light Dependent Circuits:  #'sD      E - L      M- Z


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