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Laser Pointer Train Detector: (added 8/03) |
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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.... |
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LDR
light/dark activated relay Switch: (Electronic circuit added 4/05) |
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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) |
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Light activated relay #1: (Electronic circuit added 4/05) |
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Light Activated Relay #2: (Electronic circuit added 4/05) |
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Light Detector #2: (Electronic Schematic / circuit added 4/02) |
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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) |
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Light Pollution Meter : (added 8/03) |
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Light Sensing RF Transmitter: (Electronic circuit added 7/03) |
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Light Sensor Adapter for Oscilloscope: (Electronic circuit added 4/05) |
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Light Sensor with Hysteresis: (Electronic Schematic / circuit added 4/02) |
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Light/Dark Detector: (Electronic Schematic / circuit added 4/02) |
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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) |
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Lightwave Component Analysis: Aligent Application Note (app note added 2/06) |
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LX1970 Visible
Light Sensor (AN-28): Application Note 28 from Microsem (app note added 6/06) |