![]() ![]() Unlike normal signal diodes that are made by doping Germanium or Silicon semiconductors, LEDs are made by doping semiconductor compounds - such as Gallium Arsenide (GaAs), Silicon Carbide (SiC), Gallium Phosphide (GaP), Gallium Indium Nitride (GaInN), Gallium Arsenide Phosphide (GaAsP), and Aluminium Gallium Phosphide (AlGaP). LEDs can be distinguished by the color they emit. Typically, the cathode of LED is indicated by a notch in the shell and/or by shorter lead at the cathode terminal. ![]() It’s the reason that light emitted from LED is brightest at the top of it.Īs LEDs resemble a monochromatic type of light, they have an extremely low heat emission that manifolds their efficiency in comparison to non-semiconductor light sources. Rather, the emitted light is reflected from the surrounding substrate base, such that when it leaves the diode it appears as a focused beam of monochromatic light. However, the junction does not produce much light. The PN junction of an LED is enclosed in a transparent epoxy-resin hard-plastic shell, which can be hemispherical, cylindrical, or rectangular. LEDs are constructed differently than typical signal diodes. As a result, no current flows through the diode and there’s zero light radiated from it. Also, the electrons in the N-type semiconductor are attracted to a positive potential widening or the depletion zone between the P-type and N-type semiconductors. In the reverse bias condition (when there’s a negative potential at the anode and a positive potential at the cathode of the diode), the holes in the P-type semiconductor are attracted to the negative potential. Therefore, in the forward bias condition, the LEDs radiate electrical energy in the form of light energy. When a forward bias voltage is applied (meaning, a positive potential at the anode and a negative potential at the cathode of the diode), electrons from the N-type semiconductor are exited and combine with holes from the P-type semiconductor - releasing energy in the form of monochromatic light.Īs the layer of semiconductor material in LEDs is extremely thin, the photons can escape through the junction and produce visible or infrared light. The P-type semiconductor material forms the anode and the N-type semiconductor material forms the cathode. Much like PN junction diodes, these are two-terminal devices. These diodes are made up of a very thin layer of heavily doped semiconductor material. And, when reverse voltage is applied, the current will be blocked. For example, when forward voltage is applied, a current will pass through LEDs. Light-emitting diodes, or LEDs, are semiconductor diodes that emit a narrow bandwidth of electromagnetic waves (either visible light, infrared light, or laser light) in forward bias condition. By driving digital output from Arduino UNO’s GPIO, we will build an LED driver. In this tutorial, we’ll go into more detail about the first one of these methods: digital output. Interfacing LED and driving digital output from a source is the “Hello World” of embedded systems.Īs discussed in the previous tutorial, a microcontroller interfaces and interacts with other electronic devices in five ways: In the previous tutorial, we discussed the basics about Arduino sketches, with a a quick Arduino language reference. ![]()
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