Sensors: / Detectors: Light Detectors electronic circuits, Page 3 L


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Sensors / Detectors: Light Detectors and Optical Sensors Page 3
Sensors / Detectors -- Main Page
Light Detectors / Optical Sensors: #-C D-K L M-R S-Z
Last Updated on: Friday, August 29, 2008 02:34 PM

y Dave Johnson, P.E. :

LASER/LED 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 be connected to either a multi-meter or an oscilloscope.

LIGHT DETECTORS WITH AMIBIENT LIGHT 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 30KHz to 50KHz frequencies often used by TV and VCR remotes. I have not yet tested the circuits.

Light Intensity Monitor
For an on-going consulting project, I had to determine the light output decay time of different fluorescent lamps. I wanted to know how fast the light from a lamp dropped to a low level, after current was interrupted in the lamp. I used a high voltage transistor circuit to drive the lamps under test and used the hobby circuit below to measure the decay time. the hobby circuit was a simple PIN photo diode connected....

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 feed them through a flip/flop to produce a square wave signal. Although the circuit shown is designed for a 5v supply, it could operate from almost any voltage from 3v to 15v.

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.

Low power 100KHz Light Receiver
By starving a high speed logic inverter for current, this circuit can produce a sensitive 100KHz light receiver circuit, which is immune to ambient light, but only drawing 100 microamps from a 3 volt supply.

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

Laser Pointer Train Detector: (added 8/03)

Latching light detector is frugal with Power and parts: 09/26/02 EDN Design Ideas / (added 1/05) This idea demonstrates three uses for the humble LED. The circuit in Figure 1a forms a simple light detector that latches and turns on an LED when the ambient light exceeds a preset limit determined by potentiometer P1. LED D1 is both the indicator and the light detector. All junction diodes exhibit some degree of photosensitivity....

LDR light/dark activated relay Switch: (Electronic circuit added 4/05)

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... (Electronic circuit added 4/05)

Light activated relay #1: (Electronic circuit added 4/05)

Light Activated Relay #2: (Electronic circuit added 4/05)

Light Detector #2: (Electronic Schematic / circuit added 4/02)

Light Detector Circuit: Variable resistor R1 adjusts the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 resets the circuit. The output device may be a low power piezo buzzer. (added 2/06)

Light Pollution Meter : (added 8/03)

Light Sensing RF Transmitter: (Electronic circuit added 7/03)

Light Sensor Adapter for Oscilloscope: (Electronic circuit added 4/05)

Light Sensor with Hysteresis: (Electronic Schematic / circuit added 4/02)

Light/Dark Detector: (Electronic Schematic / circuit added 4/02)

Light-sensitive Alarm: The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright light and a high resistance in dim light..... (added 09/05)

Lightwave Component Analysis: Aligent Application Note (app note added 2/06)

LX1970 Visible Light Sensor (AN-28): Application Note 28 from Microsem (app note added 6/06)

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