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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

Master Category List - Dave's Circuits

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Optical / Light Sensor Circuits
Light Sensor Circuits designed by Dave Johnson:
Page 1,   Page 2,    Page 3,    Page 4,   Page 5,   Page 6

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


10Mhz to 20Mhz Light Receiver  -  Light power to volts conversion = APPROX. 15mV per microwatt at 850nM . . . [Circuit by David A. Johnson P.E.,  07/11/06]


12v Ė 24v AC and DC Day/Night Switch  -  The circuit uses a bridge rectifier circuit to convert AC into DC.  A 12v zener diode limits the operating voltage of the circuit to 12v.  A tiny Schmitt trigger inverter and a phototransistor detects the ambient light intensity.  If there is sufficient light, the inverter disables a push-pull oscillator circuit . . . [Hobby Circuit designed by Dave Johnson P.E.,  03/25/12]

1Khz to Over 70Mhz 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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/11/00]


1us Light Pulse Receiver  -  This circuit is designed to detect very weak light pulses lasting 1uS. It uses a tuned LC feedback network to provide high sensitivity while giving high ambient light immunity. A post voltage Amplifier is included with a gain of about X20 . . . [Hobby Circuit designed by David A. Johnson P.E.,  03/11/99]


1uS Light Pulse Receiver + Post Amp  -  This circuit is designed to detect very weak light pulses lasting 1uS. It uses a tuned LC feedback network to provide high sensitivity while giving high ambient light immunity. A post voltage Amplifier is included with a gain of about X20. The circuit is described in more detail in the receiver section of my Handbook of Optical Through the Air Communications.  Note: The LF357 op Amp is no longer available, this circuit is for reference only. . . . [Circuit by David Johnson P.E.,  03/11/99]


1W 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 David Johnson P.E.,  11/06/08]


20Mhz VCSEL 3mw Laser Test Circuit  -  This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL) that donít require light output control circuits. The circuit shows how to drive the device from a single high speed CMOS IC . . . [Circuit by David A. Johnson P.E.,  06/17/00]


24 Volt Day Night Switch  -  Many low voltage outdoor lighting systems use 24vac to power the devices.  The low voltage is much safer to use outside than standard 120vac or 240vac power systems.  The circuit below is designed to turn off power to outdoor lights during daylight and turn them back on at night . . . [Hobby Circuit designed by David A. Johnson P.E.,  12/26/10]


24v NiMH Battery Charger Using a 12v Solar Panel   -  A while back I received an email from a guy in the UK.  He wanted to use a small solar panel, designed to charge 12v lead acid batteries, but use it to charge a 24v battery pack.  His 24v battery pack used 20 AA size NiMH cells.  He went on to explain that his 20 cell NiMH battery pack was used very infrequently . . . [Hobby Circuit designed by David A. Johnson P.E.,  10/12/11]


2Mhz Broad Band Optical Fiber Receiver  -  If you need more sensitivity than the above circuit this circuit provides about ten times more gain. It too is designed around an inexpensive plastic optical fiber detector . . . [Hobby Circuit designed by David Johnson P.E.,  06/09/00]


30Khz Light Receiver Amp  -  This circuit uses NPN darlington transistor to Amplify the signal produced from short light flashes, as detected by a PIN photo diode.  The circuit draws only about 330uA from a 6v battery . . . [Circuit by David Johnson P.E.,  03/07/02]


3mw Laser Test-20Mhz VCSEL  -  This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL) that donít require light output control circuits. The circuit shows how to drive the device from a single high speed CMOS IC . . . [Hobby Circuit designed by David Johnson P.E.,  06/17/00]


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 . . . [Hobby Circuit designed by David A. Johnson P.E.,  06/04/00]


40Khz Laser Burst 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, . . . [Circuit by Dave Johnson P.E.,  06/13/00]


40Khz Light Detector With High Ambient Light Immunity  -  This circuit is designed for detecting infrared light modulated at around 40KHz.  Itís feedback scheme cancels much of the DC component from ambient light.  Itís conversion factor is about 100 millivolts per microwatt of 900nm light.  . . . [Circuit by Dave Johnson P.E.,  07/11/06]


40KHz Light Detector with Sunlight Immunity  -  This hobby 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 Dave Johnson P.E.,  07/11/06]


40KHz Light Receiver Front-End Circuit  -  This circuit uses a unique cascode Amplifier circuit to convert the current from a PIN photo diode to a current without any feedback network. It is very stable and very sensitive. This hobby circuit shown has the potential for a conversion factor of 10 volts per microwatt at 900nm. I included a simple JFET post-amplifier with a gain of about 20. . . . [Circuit by David Johnson P.E.,  06/14/00]


40KHz Modulated Light Detector  -  If you want even more sensitivity than the above circuit, try this design. When used with a one centimeter square photodiode, you can achieve a range of several hundred feet with a standard TV or VCR remote control module . . . [Circuit by Dave Johnson P.E.,  03/12/99]


40khz TV-VCR Light Source 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. Using the device, the remote can operate a TV or VCR over three times the normal distance . . . [Circuit by David Johnson P.E.,  06/04/00]


50Mhz Broad Band Optical Fiber Receiver Version A  -  If the above circuit it still too slow, you can try this circuit. What it lacks in sensitivity it makes up for in speed. The circuit attaches a plastic fiber optic PIN photodiode assembly to a small box containing a small 3v battery and a standard . . . [Circuit by David A. Johnson P.E.,  06/04/00]


5Mhz Broad Band  Optical Fiber Receiver  -  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 . . . [Circuit by Dave Johnson P.E.,  06/04/00]


8-Solar Cell Lithium Ion Battery Charger Version 2  -  Jim Wilber looked at my design for a battery charger and sent me some suggested changes.  He suggested using the LTC4412 ideal diode IC to switch off the current path from the solar cell to the battery in darkness.  He also noted that the 2.5v regulator from Seiko I had selected was no longer in production and suggested using the shunt reference . . . [Circuit by David Johnson P.E.,  05/21/13]


Air Transparency Monitor-Pg2  -  This is Page 2 of the receiver circuit AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER . . . [Circuit by David Johnson P.E.,  06/17/00]


Ambient Light Dectector with Compensation  -  These circuits were taken from a few application notes on infrared remote control devices. They use a current compensation method to separate the modulated light pulses from ambient light. They appear to have limited bandwidth and may only work at the 30K . . . [Hobby Circuit designed by David Johnson P.E.,  07/05/00]


Broad Band 2Mhz Optical Fiber Receiver  -  If you need more sensitivity than the above circuit this circuit provides about ten times more gain. It too is designed around an inexpensive plastic optical fiber detector . . . [Circuit by David Johnson P.E.,  06/09/00]


Broad Band 50Mhz Optical Fiber Receiver Version A  -  If the above circuit it still too slow, you can try this circuit. What it lacks in sensitivity it makes up for in speed. The circuit attaches a plastic fiber optic PIN photodiode assembly to a small box containing a small 3v battery and a standard . . . [Hobby Circuit designed by David A. Johnson P.E.,  06/04/00]


Broken Solar Panels  -  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 David A. Johnson P.E.,  01/01/12]


Cascode Light Receiver Circuit  -  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 . . . [Circuit by David Johnson P.E.,  02/15/02]


Cell Phone Solar Powered 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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  01/02/11]


Clear Fluid Detector #2  -  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 . . . [Circuit by Dave Johnson P.E.,  10/22/05]


Clear Fluid Monitor  -  An optical technique seemed like the best choice for this application.  The simple circuit below works well but only when the light detector can be shielded from bright ambient light.  A visible red LED launches light pulses through the side of the clear tubing and emerges at the opposite side.  A phototransistor forms a light detector.  The circuit takes advantage of the lens effect from any clear fluid inside the tubing.  When there is only air in the tubing, the light scatters and spreads out quickly before it reaches the phototransistor . . . [Circuit Solution by Dave Johnson P.E.,  05/01/05]


Color Film Makes 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 . . . [Circuit by David A. Johnson P.E.,  01/01/98]


Convert Solar Powered Light to Flasher  -  The circuit converts an off-the-shelf solar powered LED path light from producing a steady state light to one that produces a flash.  This circuit includes a tiny dual Schmitt trigger inverter IC which form the pulse generator and the daylight sensor circuit.  The circuit produces a positive pulse, which feeds the constant current LED driver circuit. . . . [Circuit by David A. Johnson P.E.,  03/02/10]


Day/Night Switch-24vac Powered  -  Many low voltage outdoor lighting systems use 24vac to power the devices.  The low voltage is much safer to use outside than standard 120vac or 240vac power systems.  The circuit below is designed to turn off power to outdoor lights during daylight and turn them back on at night . . . [Circuit by David A. Johnson P.E.,  12/26/10]


Detect Clear Fluid  -  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 Dave Johnson P.E.,  05/01/12]


Detect Short Xenon Lamp Flashes  -  This circuit uses a small 2.5mm square photo diode in conjunction with a 100mH coil to detect the short light flashes from a xenon lamp.  The coil makes the circuit immune to normal room lights.  Its 10mv sensitivity can detect light flashes from a range of over 100 feet. . . . [Hobby Circuit designed by Dave Johnson P.E.,  02/15/02]


Detects Xenon Lamp Flash  -  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 . . . [Hobby Circuit designed by David Johnson P.E.,  12/17/04]

 

Light Sensor Circuits designed by Dave Johnson:
Page 1,   Page 2,    Page 3,    Page 4,   Page 5,   Page 6

Optical / Light Sensor Circuits

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