Positive and negative judgment method of led lamp

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The principle of LED lights

  LEDs are light-emitting diodes and are new technologies developed in the mid-20th century. It relies on the energy generated by the electrons in the semiconductor heterojunction through the barrier to illuminate directly. Lamps made by LEDs do not generate heat due to the illuminating process, and the energy conversion efficiency is close to 100%, and the life is too long, which is the development direction of lighting technology.

The core portion of the   light emitting diode is a wafer composed of a p-type semiconductor and an n-type semiconductor, and a transition layer between the p-type semiconductor and the n-type semiconductor is referred to as a pn junction. In some PN junctions of semiconductor materials , the injected minority carriers recombine with the majority carriers to release excess energy in the form of light, thereby directly converting electrical energy into light energy. The PN junction is added with a reverse voltage, and minority carriers are difficult to inject, so they do not emit light. Such a diode fabricated by the principle of injection electroluminescence is called a light-emitting diode, and is generally called an LED. When it is in the forward working state (ie, the forward voltage is applied to both ends), when the current flows from the anode of the LED to the cathode, the semiconductor crystal emits light of different colors from ultraviolet to infrared , and the intensity of the light is related to the current.
 

  Positive and negative judgment method of led lamp

  The most direct way to determine the positive and negative LED lights is to look at the length of the pins: the length is "positive" and the short is "negative". The factory-made LEDs are long and short.

 

  If the diode is disassembled and the pins are cut to the same length, a multimeter can be used to distinguish between the "positive" and "negative" poles. Look for a mechanical multimeter with two 1.5v batteries in the table , hit the R×1 file of the measuring resistor , and put the test lead (stick) on the pin of the LED at the same time. If the LED is not bright, change it. The position of the bar is retested once, and the LED should be lit at this time. Then the pin that the black pen is connected to is the "positive" pole of the LED, and the foot touched by the red pen is "negative". If the position of the crown is changed and the second test is not lit, it means that the LED is bad.

  Similarly, a multimeter with R×10K file can also be used to measure and judge the polarity and quality of the LED. The need to pay attention to the position of the multimeter is placed in the RX100 or RX1k position. A 9v stacked battery, the RX1 file will burn out the LED under test.



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