An ordinary LED lamp has two pins. Why does this LEDs have four pins?

 

Ordinary light-emitting diodes (LED lamps) have only two pins, one long pin and one short pin. The long pin is connected to the positive pole of the power supply and the short pin is connected to the negative pole of the power supply. In addition to this ordinary LED lamp with only two pins, have you ever seen an LED lamp with four pins? This led lamp is really available in the market. The physical picture is as follows. Since two pins are enough, why do you have four pins?

Although it has four pins, there are actually three LED beads in it. One pin is the common part of the three LED lamps, and the other three pins are the second pin corresponding to each LED lamp. This RGB LED lamp also has a common cathode and a common anode. For RGB LED lamps with a common anode, the longest of the four pins is the anode, that is, the positive pole connected to the power supply, The reference pictures are as follows.

If the red probe is connected to the anode of the common anode RGB LED lamp, and the black probe contacts any of the other three pins, if the LED lamp is normal, you will see that the LED lamp is illuminated, and the voltage drop at this time will be displayed on the multimeter, which is no different from the result of measuring ordinary LED lamps.
The LED light in the figure below emits red light after being powered on. If the red probe does not move and the black probe contacts the other two pins, you will find that it will also emit light of other colors. In fact, in addition to red, there are green and blue, which is why it is called RGB LED light. R represents red, It comes from the initial letter of the English word red (Chinese meaning: red); G stands for green, which comes from the initial letter of the English word green (Chinese meaning: green); B stands for blue, which comes from the initial letter of the English word blue (Chinese meaning: blue). 

 

If you observe the pressure drop during the measurement, you will find that it emits light of different colors, and the pressure drop will be different, as can be seen from the picture below. In fact, the light of these three colors is also the three primary colors of light. If two LED lights are lit at the same time, it can emit light of other colors. For example, if red and green LED lights are lit at the same time, it will emit yellow light. If three LED lights are lit at the same time, it will emit composite light: white light.

The designed four pin RGB LED lamp also has its advantages. By controlling these four pins, you can control the LED lamp to emit light of various colors. Of course, it must be troublesome to control it by hand, but it's not worth mentioning to leave it to the chip.
Of course, this method can also detect the quality of RGB LED lights. If it is found that the light of a certain color (red, green and blue) cannot be emitted during the detection process, the LED lights emitting that color are likely to be broken. For individuals, it can't be repaired. Just replace them with a new one, which is not expensive.