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How to distinguish between emitter LEDs and receiver LEDs



Yesterday, a customer inquired about straw hat emitting diodes for use in night vision lights.

Based on the customer's needs, we further learned that what the customer needs is a receiving tube, because the receiving tube and the transmitting tube are collectively called infrared transmitting and receiving tubes in the industry. Their shapes are similar, so it's hard to tell which one is the receiving tube and which one is the transmitting tube.

Distinguish from appearance

The transparent colloid on the left is the transmitting tube, and the black colloid on the right is the receiving tube.

Infrared transmitting tube: Under normal circumstances, we can distinguish infrared transmitting tubes and infrared receiving tubes from their appearance. Infrared transmitting tubes are generally transparent, and the internal structure can be clearly seen.

The internal structure of infrared emission tubes is basically the same as that of light-emitting diodes, but the difference lies in their internal materials. And if it has not been used, we can also know its positive and negative poles, usually the positive pole, and the short leg is the negative pole.

Infrared receiving tube: Infrared receiving tube is an electronic component that converts infrared light signals into electrical signals. Most of the infrared receiving tubes are encapsulated in black opaque resin.

Infrared receiving tubes include infrared receiving diodes and infrared receiving transistors. The two-pin one is the infrared receiving diode, the long pin is the positive pole, and the short pin is the negative pole. The one with three pins is an infrared transistor. Infrared transistors can be divided into two types: NPN and PNP.

Use three-purpose meter to measure and identify

If both are transparent colloids, use them.

Then use instruments to measure and judge. Hailongxing Optoelectronics recommends using a three-purpose meter to measure and identify.

Three-purpose meter measurement and identification can use the Rxlk electrical barrier of the 500-type or other pointer-type three-purpose meter to measure the inter-electrode resistance of the infrared pair tube to identify the infrared pair tube.


Criterion 1: Change the test leads to measure when the end of the infrared tube is not exposed to light. The forward resistance of the emission tube is small and the reverse resistance is large. When the black test lead is connected to the positive electrode (long pin), the resistance is small. (1k-20k) is the launch tube. The receiving tube has large forward and reverse resistances.

Criterion 2: When the black test lead is connected to the negative electrode (short pin), the transmitter tube has the larger resistance. When the resistance is small and the pointer of the three-purpose meter changes with the intensity of the light, the receiver tube is the pointer that swings.


(1) When the black test lead is connected to the positive electrode and the red test lead is connected to the negative electrode, measure the forward resistance.

(2) High resistance means that the pointer of the three-purpose meter basically does not move.

receiver LEDs,emitter LEDs


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