Light Units: The total light energy output, or luminous flux (Φs), from a source can be measured in milliwatts (mW) or in lumens (1m), where 1 Im = 1.496 mW. The luminous intensity (Es) (also termed illuminance) of a Light Units … (Read More)

LED Seven Segment Display: The arrangement of a LED Seven Segment Display is shown in Fig. 20-6(a). The actual LED devices are very small, so, to enlarge the lighted surface, solid plastic light pipes are often employed, as shown. Any desired … (Read More)

Photoconductive Cell Construction and Working: Photoconductive Cell Construction and Working – Light striking the surface of a material can provide sufficient energy to cause electrons within the material to break away from their atoms. Thus, free electrons and holes (charge carriers) … (Read More)

Photodiode Operation and Characteristics: Photodiode Operation – When a pn-Junction is reverse biased, a small reverse saturation current flows due to thermally generated holes and electrons being swept across the junction as minority charge carriers. Increasing the junction temperature generates more … (Read More)

Solar Energy Conversion Diagram: The Solar Energy Conversion Diagram, or solar energy converter, is essentially a large photodiode designed to operate solely as a photovoltaic device and to give as much output power as possible. To provide maximum output current, solar … (Read More)

Phototransistor Working: A Phototransistor Working is similar to an ordinary BJT except that its collector base junction is constructed like a photodiode. Instead of a base current, the input to the transistor is in the form of illumination at the junction. Construction … (Read More)

Photodarlington Working: The Photodarlington Working shown in (Fig. 20-33) consists of a phototransistor connected in Darlington arrangement with another transistor. This device is capable of producing much higher output currents than a phototransistor, and so it has a greater sensitivity to … (Read More)

Optocoupler Circuit Operation: An Optocoupler Circuit Operation (optoelectronic coupler) is essentially a photo-transistor and an LED combined in one package. Figure 20-35(a) and (b) shows the typical circuit and terminal arrangement for one such device contained in a DIL plastic package. … (Read More)