​how to detect the discoloration LEDs?

how to detect the discoloration LEDs?

As shown in Figure 5-18,a circuit for detecting a discoloration light emitting diode (LEDs),a multimeter is placed in the RX10k2 block,and the two pin is connected.When the needle is swinging and having any light,the red pen is connected to a common electrode.

the red pen is connected to the common electrode,the black pen is replaced by an electrode,and the tube is emitting red light,and the black watch is connected to the red (R).

if the tube sends out green light,the black watch is connected to green (G).

the black pen is connected to red (R) and green (G) at the same time,and the tube should emit orange compound light.

During the above detection process,if a light-emitting diode is not lighted,it indicates that it is damaged.Such tubes can no longer be used as discolourable light emitting diodes.However,the undamaged LED can be used as a monochromatic light emitting diode.

what is a laser diode?

Semiconductor laser diode emitting red light when working,the wavelength is about 600nm, used in laser pointer,bar code reader,laser printer,CD and VCD machine and other circuits.

Semiconductor laser diode is the core device of laser head,and is widely used in CD and laser disc player.Figure 5-19 shows the symbols and internal structure of common laser diodes.It is seen from the figure that there are two diodes in the interior.LD is a laser transmitter tube,PD is a light power detection tube,and the negative feedback circuit can be used to automatically control the power of the laser diode.Common cathode is the most commonly used.Laser diodes are mostly double structured gallium arsenide three compound semiconductor laser diodes.It is a near infrared laser tube with a wavelength of about 780nm and a rated power of 3~5mW.The shape has two kinds of flat head and oblique head.For different circuits,the edge notch is a positioning mark,so as not to be wrong.The laser diode has the advantages of small volume,light weight,low power consumption,simple driving circuit,convenient modulation,mechanical shock and vibration resistance.But it is extremely sensitive to overvoltage,overcurrent and electrostatic interference.If used without attention,it will cause damage to the resonant cavity and cause permanent damage.