Flash-Triggered Pulse Stretcher Using Classic Monostable Circuit

This is a flash triggered (photo-driven) circuit which produce a pulse with constant predetermined wide. This circuit can be used to control any device which is required to be synchronized with optical trigger/flash light.  The pulse can be used to drive relay (after proper power buffering,  to drive other circuit logic, or electronic switch.  We call it a pulse stretcher […]

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Relay Circuit Detects Light Change

Configured with capacitive coupling (by inserting a small cap between photo-transistor and bipolar transistor), this relay circuit will respond only to rapid changes  in light while ignoring normal gradual changes in ambient light. Rapid changes can be produced by light interruption or turning on/off lamps, while gradual light changes can be produced by clouds or  sunrise.  Here is the schematic […]

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Light Level Droplets Detector

This is a circuit of Low-Light Level Drop Detector. This circuit utilize self-biasing configuration to detect small changes in light level. This circuit usually used in monitoring very low droplets rates. The collector of the transistor gives feedback that is used to stabilize the bias of the photodarlington. The effect on optical performance is reduced by a high base-source impedance […]

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Five-Decade Dynamic Light-Level Meter

This is a Portable light-level meter circuit with five-decade dynamic range. This uses  a single cell battery as the power supply. To calibrate this circuit, use an appropriate illumination, then adjust R2 so that the output equals the reference. To make this circuit give output meter follows standard light meter, adjust R2 and R6. Maybe there is an error at […]

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