Using Diodes as a photosensor

light intensity meter with diode

A photodiode is a PN junction or PIN structure that when light reaches the junction, it excites an electron thereby creating a free electron positively charged. This mechanism is also known as the photoelectric effect, common in transistors, diodes and ICs are made ​​of semiconductors, and contain PN junctions. Almost all of the potentially active constituents are a photodiode and may be used as a photosensor. The PN junction needs to be exposed to light, so to use a semiconductor diode as a light bulb must have a transparent glass, these diodes with these characteristics can be used to measure the light intensity.

Circuit diagram of a light intensity meter with diode.

Circuit diagram of a light intensity meter with diode

a test circuit diode light sensor

List of components:
D1 1n148 or any other photo-sensitive element
T1, T2 BC548 or similar
C1 680n
R1 2M

Above this circuit that is very popular, it works with LEDs, photodiodes and photo-resistors. V is a voltmeter which can be a multimeter.
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