Electronic Circuits and Tutorials
Electronics Schematics - L

Photocell / Light Dependent Resistor Circuits

24-Bit ADC Measures from DC to Daylight - DN219  Design Notes (Linear Technology)

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.

8 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.

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,

AN865: Sensing Light with a Programmable Gain Amplifier - Microchip Application Note Published 28-Mar-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…

Circuit rejects ambient light - EDN-Design Ideas

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.

Dark Activated 12v Power Supply Switch - Using an inexpensive phototransistor, this circuit switches 12v to 24v power to a load, whenever the sun goes down.

Dark activated switch - started this project with the idea to build a simple single-ended tube amplifier. I didn't have any experience with the construction of tube amps so I was looking for a beginner's project. Such a project should be simple (for easy debugging) and it should.

Dark Activated Switch (Andy Collinson) - This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer.

Dark Sensitive Switch - Dark Sensitive Switch is a simple project which operates a relay when the light falling on the LDR goes below a set point

Dark/Light Activated Relay - The potmeter adjust the trigger 'on' level.  The diode in the diagram shows to be 1N914.  This is ok if you have a light-duty relay, also the 1N914 is a signal diode so actually does not qualify.  Use a 1N4001 (Tony van Roon's or better) instead.  A couple of substitutes for the 2N2222 transistor are: NTE123A, ECG123A, PN100, etc. 

Dark-activated 230V Lamp - Compact circuitry using small-size parts only.  Can be wired in parallel to existing switches.

Dark-activated LED or Lamp Flasher - This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value.

Dark-activated switch needs only three components - EDN  Build a dark-activated switch with only a triac, a photocell, and a resistor.

Dark-Detecting LED Circuit - Here's a simple problem: "How do you make an LED turn on when it gets dark?" You might call it the "nightlight problem," but the same sort of question comes up in a lot of familiar situations-- emergency lights, street lights, silly computer keyboard backlights, and the list goes on. Solutions? Lots. The time-honored tradition is to use a circuit with a CdS photoresistor, sometimes called a photocell or LDR, for "light-dependent resistor."

Day/ Night/ 24 Hour Select Sensor

Digitally control room light intensity - EDN-Design Ideas: Many people favor different light and temperature settings for different rooms depending upon their mood or whether they are working or relaxing. The circuit in Figure 1 controls the intensity of the artificial light in a room and monitors the temperature of two zones. The two main circuit blocks are the PIC16C67 master controller and the ADT7516 temperature-sensor interface

Electronic Night Light

Feedback circuit enhances phototransistor's linear operation - EDN-Design Ideas: Bias-current compensation reduces ambient-light saturation effects.

Infrared Detection

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