l  Principle of infrared light emitting diodes

The common infrared light emitting diodes (abbreviated as infrared LED) have two kinds of dark blue and transparent, similar to ordinary light emitting diodes.

 Because the infrared light emitting diode usually uses a transparent plastic package, the electrode in the shell is clearly visible; the inner electrode is larger than the negative, and the narrower is the positive pole. The fully plastic encapsulated infrared light emitting diode has a small plane on the side, a negative electrode near the small plane, and a positive pole on the other.

The infrared LED operates under the forward voltage, the working voltage is about 1.4V, and the working current is generally less than 20mA. In the application, the finite current resistance should be set in the circuit.

In order to increase the distance of infrared ray, infrared LED usually operates in pulse state. When the infrared light emitting diode is used to transmit infrared to control the controlled device, there are corresponding infrared optical and electric converters in the controlled device, such as the infrared receiving diode, the photosensitive transistor and so on. In practice, photodiodes are usually used for infrared transmitting and receiving.

There are two ways to transmit and receive infrared light: one is direct radiation; the other two is reflective. The direct radiation means the light emitting light directly irradiate the receiving tube; the reflective finger light tube and the receiving tube are listed together. When the infrared light emitted by the light emitting tube meets the reflection, the receiver receives the reflected infrared ray to work.

l  Measure infrared light emitting diodes

When detecting infrared light emitting diodes, there is a big difference between the pointer type multimeter and the digital multimeter. The pointer type multimeter is placed in RX1kΩ the resistance value ( forward resistance ) of the black stylus connected to the positive pole and the red pen to the negative pole should be 20 ~ 40kΩ ( ordinary LEDs above 200 kΩ ), the resistance value ( reflection resistance ) of the black pen and the negative electrode and the red pen to the positive pole should be above 500 kΩ( close to the ordinary LEDs ).

The bigger the reflective resistance is, the better. The bigger the reflection resistance is, the smaller the leakage current is, the better the quality of the pipe is. If the reflection resistance is only tens of thousands of ohm, such a pipe is not available. If both the positive and negative resistance values are infinite or zero, it means that the inside of the measured infrared light emitting diode is broken or has been damaged. When measuring with the digital multimeter, the gear position is placed in the diode block, and the pressure drop value when the black pen is connected to the negative pole and the red pen is connected to the positive pole is 0.96 ~ 1.56V, the smaller the forward voltage, the better, that is, the starting voltage of the pipe is low. After adjusting the stylus, the number shown on the screen should be an overflow symbol " OL " or " 1 ".

If you want to know more, our website has product specifications for the infrared light emitting diodes, you can go to Allicdata Electronics to get more information.

Infrared (IR) Emitter 850nm:HIR19-21C/L11/TR8