Infrared light-emitting diodes are widely used in our daily life. Do you know how to judge the quality of infrared light-emitting diodes? Let's take a look at some ways to judge the quality of infrared light-emitting diodes!
Method 1:
The first step is to identify the positive and negative polarity of the pin. Infrared LED has two pins, usually, the long pin is positive and the short pin is negative. As the infrared LED is transparent, the electrode in the shell can be seen clearly. The wider and larger one is the negative electrode, while the narrower and smaller one is the positive electrode.
In the second step, put the multimeter in R*1K, and measure the forward and reverse resistance of the infrared light-emitting diode. Generally, the forward resistance should be about 30K, and the reverse resistance should be above 500K so that the tube can be used normally. The higher the reverse resistance is required, the better.
The measurement of the infrared light-emitting diode is different from that of an ordinary light-emitting diode. If the voltage used in the measurement is high, it will break down and cause a short circuit inside the device. For some infrared light-emitting diodes, it is not allowed to use the digital multimeter to measure the short-circuit gear directly, but only the X1K gear of the pointer meter. Correct measurement can show normal results.
Method 2:
To test the quality of the infrared light-emitting diode, we can test the positive and negative resistance of the common silicon diode.
Turn the multimeter to R*100 or R*1K, connect the black lead to the positive pole of the infrared light-emitting diode, connect the red lead to the negative pole, and the measured forward resistance shall be 20 ≈40K; connect the black lead to the negative pole of the infrared light-emitting diode, and connect the red lead to the positive pole, and the measured reverse resistance shall be more than 500K
Method 3: detect the infrared LED with Multimeter
The forward voltage drop of the LED is generally 1.3-2.5v. The R*10K range of the indicator multimeter can be used to measure the forward and reverse resistance of the LED.
Normally, the forward resistance is about 15 ~ 40K Ω (the smaller the value is, the better); the reverse resistance is greater than 500K Ω. If the positive and negative resistances are close to zero, it means that the inner part of the LED is damaged. If the positive and negative resistance values measured are infinite, it means that the diode has been opened and damaged. If the measured reverse resistance is far less than 500K Ω, it means that the diode has been damaged by leakage.
The infrared light emitted by the infrared light-emitting diode is invisible to human eyes. In addition to using the above method to judge whether the PN junction is good or not, it is better to prepare a photosensitive device (such as 2Cr, 2DR silicon photocell) as the receiver, and use a multimeter to measure the voltage changes at both ends of the photocell. To determine whether infrared light-emitting diode emits infrared light after adding appropriate forward current.
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