The patch crystal diode is a p-n junction interface formed by the sintering of a p-type semiconductor and an n-type semiconductor. A space charge layer is formed on both sides of the interface to constitute a self-built electric field. In this paper, we mainly introduce the method of determining the positive and negative electrodes of SMD LEDs.

LED anode and cathode judgment methods are as follows:

1, using a multimeter to measure

When using a multimeter to detect the positive and negative polarities of SMD LEDs, use the “R*10k” position to detect them. The two pens and the two leads of the light emitting diodes are connected during detection. If the hand is deflected halfway, and there is a bright spot in the LED, it means that the SMD LED is connected in the forward direction.

2, observe the tube electrode

Observe the electrodes inside the tube, the smaller one is the positive electrode, and the larger one resembling a bowl is the negative electrode.

3, see the missing corner

In the LED energy-saving lamp lighting industry will often use 5050 SMD LED, this patch LED is a square, four right angles have a corner with a small missing corner, with a small corner of the end is the negative, the other One end is positive.

4, see the pin

The LED's pins are generally longer than the positive pole, and the negative pole's is relatively short.

The above is the method for determining the positive and negative polarities of SMD LEDs. After understanding the above knowledge, we can further understand the meanings of the electrical parameters of light emitting diodes, which we have described in detail in previous articles.