• 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.,  03/06/11]

• 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.,  03/06/11]

• Ideal Diode Function -  This circuit uses a low power op amp and a p-channel FET to form a diode function with a very low 0. 05 volt voltage drop. With the selected FET, the circuit can handle up to 2 amps of current. Higher currents are possible with a FET with a lower channel . . . [Hobby Circuit designed by Dave Johnson P.E.,  01/22/08]

• 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.,  11/01/10]

• 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.,  02/03/13]

• 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.,  03/13/11]

• 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 second . . . [Circuit Solution by Dave Johnson P.E.,  05/07/06]

• 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.,  06/04/00]

• 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.,  06/06/00]

• Laser Burst Light Detector -  This circuit was originally designed to detect weak flashed of laser light bounced off of a fabric video projection screen. It was used as part of a firearm training system. It generates a 100mS output pulse whenever it detects a 3ms to 5ms laser burst, modulated at 40KHz. It is very sensitive and could be modified for long range laser communications.  . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/13/00]

• Laser Light Detyector-10Mhz to 20Mhz -  This circuit was originally designed to detect laser light pulses for an optical Ethernet communications system. It has good ambient light immunity . . . [Hobby Circuit designed by David Johnson P.E.,  06/14/00]

• LED/Laser Light Output Intensity Meter -  This circuit uses a large 1cm X 1cm silicon PIN photo diode and a transimpedance amplifier to measure the light power output of infrared and visible LEDs and laser diodes. It can be modified to produce almost any milliwatts to volts scale factor. It can b . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/08/00]

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

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.,  03/06/11]

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.,  03/06/11]

Ideal Diode Function -  This circuit uses a low power op amp and a p-channel FET to form a diode function with a very low 0. 05 volt voltage drop. With the selected FET, the circuit can handle up to 2 amps of current. Higher currents are possible with a FET with a lower channel . . . [Hobby Circuit designed by Dave Johnson P.E.,  01/22/08]

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.,  11/01/10]

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.,  02/03/13]

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.,  03/13/11]

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 second . . . [Circuit Solution by Dave Johnson P.E.,  05/07/06]

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.,  06/04/00]

IR Laser Light Detector -  Schematic only, no circuit description included. . .  [designer's name not included]

IR Proximity Detector -  The circuits on this page are for an Infrared Proximity Detector using the Vishay Electronics TSOP4830 "IR Receiver Modules for Remote Control Systems". Scroll down to view all the circuits. . . .  [from Rob Paisley's Model Train web site]

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.,  06/06/00]

Lamp Flasher -  Simple photo-sensitive circuit 3V battery supply. . .  [Flavio Dellepiane's web site]

Laser Burst Light Detector -  This circuit was originally designed to detect weak flashed of laser light bounced off of a fabric video projection screen. It was used as part of a firearm training system. It generates a 100mS output pulse whenever it detects a 3ms to 5ms laser burst, modulated at 40KHz. It is very sensitive and could be modified for long range laser communications.  . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/13/00]

Laser Light Detyector-10Mhz to 20Mhz -  This circuit was originally designed to detect laser light pulses for an optical Ethernet communications system. It has good ambient light immunity . . . [Hobby Circuit designed by David Johnson P.E.,  06/14/00]

Laser Pointer Train Detector  -  Light activated detector circuit for model train. . .  [Designed by Rob Paisley]

LDR light/dark activated relay Switch -  . . . 

LED Photo Sensor Circuit -  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. . .  [Bill Bowden]

LED/Laser Light Output Intensity Meter -  This circuit uses a large 1cm X 1cm silicon PIN photo diode and a transimpedance amplifier to measure the light power output of infrared and visible LEDs and laser diodes. It can be modified to produce almost any milliwatts to volts scale factor. It can b . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/08/00]

Light Activated Detector Circuit LM393/LM555 -  This page shows three circuits for using the 555 timer IC as a photocell controlled train detector. The circuit is shown driving light emitting diodes but any load of less than 200 milliamps could be used. Circuit for model railroad trains. . . .  [from Rob Paisley's Model Train web site]

Light Activated Relay -  This is same circuit as above with the addition of a photo resistor to trigger the flip flop instead of a push button. The bias resistor in series with photo resistor was chosen so that sufficient voltage is present at the base of the 2N3904 to supply current to the circuit in ambient lighting conditions. . .  [Circuit Designed by Bill Bowden]

Light Activated Relay with 555 IC -  This light activated relay circuit presented here uses the 555 timer IC and a light dependent resistor or LDR to form a light sensitive relay in an intruder alarm system or for switching on a lamp at Sun set and off at Sun rise. Potentiometer R1 value must be chosen and then adjusted that under normal conditions when the light. . .  [Circuit posted by Popescu Marian]

Light Activated Siren Circuit -  This light activated siren could make an unknowing “victim” wet his pants when turning on the lights in a dark room. This thing is LOUD! Power into the module is 3W and produces a 123db sound level from its 50mm diameter diaphragm. It wavers between 2kHZ and 4kHZ. An LDR senses ambient light level and switches on. . .  [Circuit posted by Jim Keith]

Light Dependent Resistor -  Find out more about LDRs and their use in renewable energy projects. . . .  [REUK-Renewable Energy UK website]

      PAGE   Next >>>>

Light Dependent Resistor Circuits / Photocell Circuits
Light Dependent Circuits:  # - C      D - H      I- N      O- Z