We should be never connected directly to the power supply because high amounts of current will flow through it and LED may be damage.Įach Light Emitting Diode has its own forward voltage drop across the PN junction. We should connect a resistor in series for current limited, which protects it from the excess current flow. It means LED positive terminal has to be connected to the power supply positive terminal and the negative terminal connected to the power supply negative terminal. Light Emitting Diode will be connected in a forward bias across the power supply. The relation is output light intensity being directly proportional to the forward current. Its output light intensity depends on the forward current passing through the LED. Light Emitting Diode is an output device, when current flow through it, then it emits light. Light Emitting Diode can be classified as two major categories of LEDs. The combinations of different types of materials can produce a unique wavelength of color. The color of light changes depends on the change in material. These semiconductor materials are Gallium Arsenide (GaAs), Gallium Phosphide (GaP), or Gallium Arsenide Phosphide (GaAsP). The different types of semiconductor materials combinations are used to manufacture LEDs. But, normal silicon diode is released energy in the form of heat. As a result, this energy released in the form of light. Initially, free electrons from the N-type region are in the conduction band but as they cross over into the P-type region, they release energy and fall into a hole in the valence band. When an LED is forward biased, then the free electrons from the N-type region gain enough energy to cross the junction and recombine with the holes in the P-type region. When the LED’s anode (positive) terminal is connected to the positive terminal of dc power supply and the cathode (negative) terminal is connected to the negative terminal of dc power supply then the PN junction is forward biased. The LEDs can emit light when it is in the forward bias condition. It allows the flow of current in the forward direction (forward biased) and blocks the current in the reverse direction (reverse biased). The LED Light Emitting Diode works like a regular diode. When free electrons and holes recombine with the opposite charge carriers in the active region, then energy release in the form of invisible or visible light. When the flow of current in the forward direction in LED (LED is forward biased), then the free electrons from n-type semiconductor and the holes from p-type semiconductor are pushed towards the active region. The active region also has known as the Depletion region. The N-type region has free elections, the P-type region has holes and the active region has both free electrons and holes. The top layer is called the P-type region, the Middle layer is called the active region and the last or bottom layer is called the N-type region. These three semiconductor material layers are made in three different regions. The construction of a light-emitting diode or LED is very simple to understand, it is made by depositing the three layers of semiconductor material on a substrate. This total mechanism is covered by a transparent solid and plastic epoxy resin hemispherical shaped shell body that protects the LED from atmospheric disturbances, vibrations, and thermal shock. So, there’s just a wire that connects it to the anode terminal through the post lead frame. But the semiconductor P-type region is placed at the top. a 65 mil pad gives 11 mils of annular ring.The semiconductor N-type region is placed at the bottom so it’s connected to the cathode terminal through Anvil lead frame. A number 57 drill is 0.043" which should be enough. See for example and part number SSL-LX3054LGD. ( typical LED is 0.5 mm or 0.020" square pin. Remember that a symbol file can't have any blank lines, so when you edit rgb-led.sym, make sure you haven't added a blank line to the end (like I did).
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