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Light Monitor Circuit - The circuit below takes advantage of a low power op amp with a “rail to
rail” feature. The single resistor R1 defines the light sensitivity of the circuit. The output voltage is
directly proportional to the intensity of light striking the small photodiode . . . [Hobby Circuit designed
by David A. Johnson P.E., 08/29/10]
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 . . . [Circuit by Dave Johnson P.E., 03/11/99]
Light
Receiver 30Khz 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 . . . [Hobby Circuit designed by
Dave Johnson P.E., 03/07/02]
Light
Receiver Front-End Circuit - 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. Note: The LF357 operational amplifier is no longer available this circuit is for reference only. . .
. [Hobby Circuit designed by David Johnson P.E., 03/12/99]
Light Receiver Works from 1Khz to
Over 70Mhz - 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 . .
. [Circuit by David Johnson P.E., 06/11/00]
Light
Receiver-10MHz to 20MHz - Light
power to volts conversion = APPROX. 15mV per microwatt at 850nM . . . [Hobby Circuit designed by David
Johnson P.E., 07/11/06]
Light Sensor Adapter for Oscilloscope - . . . [Designed by Tomi Engdahl]
Light to Frequency Converter - This circuit uses a CMOS version of the classic 555 timer, to form a
light intensity to frequency converter. A small PIN photo diode is used as the light detector. The pulses
produced are short, so in some applications you may want to stretch them or . . . [Hobby Circuit designed by
David Johnson P.E., 05/04/08]
Light/Dark 12V Switch - Often, for certain low voltage lighting systems; you would like to turn
off the lights during the bright light of the day. Most commercial day/night switches are designed for AC
lighting. The circuit below was designed for a 12v DC system. But, it could be modified for other voltage as
well. It uses an inexpensive phototransistor as the light detector. . . . [Circuit by David A. Johnson
P.E., 06/30/08]
Light/Dark Detector - This handy little circuit can tell the difference between darkness and
light, making it very useful for switching on and off signs, porch lights or other things when it gets dark
or light. . . . [Design by Aaron Cake]
Lightning Activated Camera Shutter Trigger - This circuit is used to trigger a camera's electronic shutter circuit
when a flash of lightning is present. This circuit would also work for photographing fireworks displays or
other events involving flashes of light. . . . [G. Forrest Cook]
Lightning Detectors - The following circuit is an improved version of my original Lightning
Detector designed to run on a 5 volt supply. . . [Circuit designed by Charles Wenzel]
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