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Sensors / Detectors: Light Detectors and Optical Sensors Page 1
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Light Detectors / Optical Sensors: #-C D-K L M-R S-Z
Last Updated on: Friday, February 05, 2010 10:05 AM

Circuits Designed by Dave Johnson, P.E. :

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.

1uS LIGHT PULSE RECEIVER PLUS 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.

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.

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.

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, modulated at 40KHz. It is very sensitive and could be modified for long-range laser communications.

40KHz Light Detector with Sunlight Immunity NEW
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. The light transmitter was positioned at a stationary position, while the matching receiver was mounted on the vehicle. The circuit has high ambient light immunity and in most cases, can operate in direct sunlight.

40KHz Light Detector with High Ambient Light Immunity
This circuit is designed for detecting infrared light modulated at around 40KHz. It’s feedback scheme cancels much of the DC component from ambient light. It’s conversion factor is about 100 millivolts per microwatt of 900nm light.

40KHZ LIGHT RECEIVER AMP
This circuit is similar to 30KHZ Light Receiver Amp but provides more gain and operates up to 40KHz. However it draws more power supply current.

40KHz LIGHT RECEIVER IS IMMUNE TO AMBIENT LIGHT
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.

40KHz MODULATED LIGHT DETECTOR
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. The 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.

AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER
I designed this circuit many years ago to monitor the quality of a mile long column of air for future optical communications experiments. The transmitter system (circuit 72 below) uses a powerful xenon flash in conjunction with a large 12 inch Fresnel lens at the transmitter end and a matching 12-inch lens with a PIN photo diode at the receiver. The receiver system was connected to a weather station and a computer to collect the changes in intensity of the light flashes under different weather conditions. It has the potential for a 30+-mile range. I have also used this system to conduct cloud bounce experiments.

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.

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 BNC plug. When the box is plugged into to the input of an oscilloscope with a 50-ohm termination resistor, it can detect light pulse frequencies beyond 100MHz.

BROAD BAND 5MHz 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 light sources.

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.

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.

Clear Fluid Detector
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.

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

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. ….(designed by David A. Johnson)

1us Light Pulse Receiver Plus 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. ….(designed by David A. Johnson)

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. ….(designed by David A. Johnson)

4 & 8 Infrared-Proximity Detectors (TSOP4830) - In this circuit the TSOP4830 is used as a sensitive infrared detector that does not require shielding from room lighting. The detector will work under almost any lighting condition from complete darkness to full sunlight….(added 08/08/08)

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, modulated at 40KHz. It is very sensitive and could be modified for long-range laser communications. ….(designed by David A. Johnson)

40kHz Light Detector With High Ambient Light Immunity - 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. The light transmitter was positioned at a stationary position, while the matching receiver was mounted on the vehicle. The circuit has high ambient light immunity and in most cases, can operate in direct sunlight.... ….(designed by David A. Johnson)

40kHz Light Detector with Sunlight Immunity - 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. …. ….(designed by David A. Johnson)

40kHz Light Receiver Amp - This circuit is similar to number 121 but provides more gain and operates up to 40KHz. However it draws more power supply current. ….(designed by David A. Johnson)

40kHz Light Receiver Is Immune to Ambient Light - 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. ….(designed by David A. Johnson)

40kHz Modulated Light Detector - 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. The 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. ….(designed by David A. Johnson)

5v Solar Charger - This project uses the 1.2v rechargeable battery and solar panel from a Solar Garden Light. These lights can be bought for less than $5.00 in most $2.00 shops or similar shops that sell general household items…..(diagram added 05/07)

741 Based Light Sensor - CdS photocell used for light/dark controlled relay (Tony van Roon's electronic design added 5/02)

8 Unit Photo Detector Circuit Board - There are two versions of the "8 Photo-Detector" on this page. Scroll down to view all of them. The circuit on this page is for a simple light detector circuit board that has 8 detectors that can be used with visible or infrared light systems. The detectors use LM339 voltage comparators as the active element. (train design added 04/05/06)

9v Powered Xenon Photoflash Controller - This 9v battery powered circuit is designed for remote control flash needs. A charge control circuit turns off the high voltage generator when the photoflash capacitor is fully charged. A neon lamp is included to indicate when the system is ready to flash. ….(designed by David A. Johnson)

Across The Track Infrared Detectors - This page presents information on infrared, 'Across The Track' train detection circuits. The circuits are designed around the LM339 comparator chip and can use a wide assortment of matched infrared, emitter / detector pairs….(diagram added 04/05/06)

Air Transparency Monitor, Xenon Flash Receiver - I designed this circuit many years ago to monitor the quality of a mile long column of air for future optical communications experiments. The transmitter system (circuit 72 below) uses a powerful xenon flash in conjunction with a large 12 inch Fresnel lens at the transmitter end and a matching 12-inch lens with a PIN photo diode at the receiver. The receiver system was connected to a weather station and a computer to collect the changes in intensity of the light flashes under different weather conditions. It has the potential for a 30+-mile range. I have also used this system to conduct cloud bounce experiments. ….(designed by David A. Johnson)

Air Transparency Monitor, Xenon Flash Receiver, Page 2 - This is Page 2 of the air transparency monitor receiver circuit. ….(designed by David A. Johnson)

AN-32 Optical Design Of Ambient Light Sensor - Application Note Microsemi 1404 (added 05/06/07)

AN865: Sensing Light with a Programmable Gain Amplifier - Microchip Application Note Published 28-Mar-03 (app note added 2/06)

Basic Infrared Light Train Detection - (circuit design added 8/03)

Battery Powered Sensor Detects Dangerous U Volt Radiation - 12/08/94 EDN-Design Ideas: The battery-powered circuit in Fig 1 detects 295-nm UV radiation, which is dangerous to eyes and skin. Be sure to protect yourself and your coworkers against this radiation. To operate device, press switch S1 and hold it closed for at least 2.2 sec. A start pulse applied to IC4 starts 2.2-sec measuring cycle. Pin 3 of IC4 resets 4040 binary.....(design idea added 3/03)

Block Occupancy Detector Helper Circuit information - This circuit would be used to hold a BLOCK OCCUPIED condition as a train passes out of the block even if the normal detector is not sensing a train….(added 07/03)

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. ….(designed by David A. Johnson)

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 BNC plug. When the box is plugged into to the input of an oscilloscope with a 50-ohm termination resistor, it can detect light pulse frequencies beyond 100MHz. ….(designed by David A. Johnson)

Broad Band 5mhz 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 light sources. ….(designed by David A. Johnson)

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. ….(designed by David A. Johnson)

Circuit rejects ambient light - 06/10/99 EDN-Design Ideas:.....(design idea added 2/06)

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. ….(designed by David A. Johnson)

Clear Fluid Detector-3 - 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. ….(designed by David A. Johnson)

Color Sensor - Colour sensor is an interesting project for hobbyists. The circuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected....added 10/05)

Light Detectors / Optical Sensors: #-C D-K L M-R S-Z