Test method for led

Common led detection

1. Multimeter detection

Using pointer with x 10 k Ω block multimeter can roughly judge of light-emitting diodes (leds). Normal, the diode is proposed.theoretical Ω for decades to 200 k, reverse resistance value is ∝. If the forward resistance is 0 or infinity, and the reverse resistance is small or 0, damage occurs. This kind of detection method, cannot actually see glowing light situation, because x 10 k Ω block cannot provide larger forward current to the LED.

If there are two pointer multimeters (preferably the same model) can be better to check the led luminous condition. Connect the "+" terminal of one multimeter with the "-" terminal of the other meter with a wire. The remaining "--" pen is connected to the positive pole (P region) of the luminous tube under test, and the remaining "+" pen is connected to the negative pole (N region) of the luminous tube under test. Two pieces of multimeter Ω all buy x 10 block.

Under normal circumstances, after switching on, the light will normally shine. If the brightness is very low, not even light, can be both block multimeter to x 1 Ω block, if still very dark, not even light, it shows that the light emitting diode performance undesirable or damage. Should be paid attention to, can't start measuring is put two pieces of multimeter at x 1 Ω, in order to avoid too much electricity, damage the leds.

2. Measurement of external power supply

The photoelectric and electrical characteristics of leds can be measured more accurately with 3V voltage stabilizer or two tandem dry batteries and multimeters. If the measured VF is between 1.4 and 3V and the luminosity is normal, the luminescence is normal. If VF=0 or VF is approximately 3V and does not emit light, the luminescent tube is broken.

Infrared led detection

Because of the infrared light-emitting diode, it emits 1-3um of infrared light, which is invisible to the human eye. Usually, the emission power of a single infrared LED is only a few mw, and the intensity Angle distribution of infrared LED of different models is also different. The forward pressure drop of infrared LED is generally 1.3-2.5v. It is because the infrared light emitted by it cannot be seen by human eyes, so the detection method of visible light LED can only determine whether the positive and negative electrical characteristics of PN junction are normal or not, and cannot determine whether the luminous condition is normal or not. To this end, it is best to prepare a photosensitive device (such as 2CR, 2DR silicon photocell) as the receiver. Use a multimeter to measure voltage changes at both ends of a photocell. To determine whether the infrared LED emits infrared light with appropriate forward current.