What are the main parameters and types of LEDs and how to detect LED?

Last Update Time: 2018-12-14 13:55:28

1.The main parameters of LED.

The main parameters of LED include the maximum working current Im and the maximum reverse voltage Um. The maximum working current Im refers to the maximum forward current allowed by LED for long term normal operation. When using LED, the current in LED should not exceed this value, otherwise the LED will burn out. The maximum reverse voltage Um refers to the maximum reverse voltage that LED can withstand without breaking down.

The maximum reverse voltage Um of the LED is about 5V. In use, the LED should not bear the reverse voltage of more than 5V, otherwise the LED will be breakdown.

2.Type of LED

 LEDs made of different semiconductor materials can emit different colors of light, for example, phosphor LEDs emit green or yellow light, the gallium arsenide LED emits red light. LED is widely used in display circuit because of its advantages of low driving voltage, low power consumption, long life and high reliability. In recent years, energy-saving light bulbs made of high-brightness LED have been applied to automotive lighting and home interior lighting, and have a wide range of application prospects. The spectral range of the LED is relatively narrow, and the color of the light depends on the different compounds. LED is often used as a display device, in addition to a single use, it is often made into a seven-segment or matrix type, the working current of LED is generally a few milliamperes to more than ten milliamperes.


With the progress of technology, now there are two-color LED, color LED and self-flash LED come out, greatly enriching the LED family, making the application of LED more and more widely pan. The two-color LED is a reverse parallel package of two light emitting colors, common red and green, VD1 and VD2, when the working voltage is left and right negative the current passes through the VD1, making it red; when the working voltage is left negative right, the current passes through VD2, making it green.

The discolored LED is actually a tube core with two LED VD1 and VD2 in one shell, one is red, the other is green, the negative electrodes of the two tubes are connected together as two feet to ground, and the other two poles are : 1 feet and 3 feet.

When the working voltage of one foot is connected to the working voltage, the current passes through VD1 to make it glow red; when the 3-pin meets the working voltage, the current passes through VD2 to make it green; when the 1 and 3 feet are connected to the working voltage at the same time, the orange light is emitted by the LED; when the ratio of two current is different, the LED's luminous color changes between red, orange and green, and this is the working principle of the color change LED.


 The self-flashing LED is a special light emitting device, and the main difference between the self-flashing LED and the ordinary LED is that when the working voltage is added to the two ends of the LED, the rated working voltage is added, it can produce flashing light on its own, and the colors are red, orange, yellow and green, which have strong sense of vision and are widely used in various electric toys.

The self-flash LED is actually a combination of a CMOS integrated circuit and an LED. The CMOS integrated circuit includes an oscillator, a divider, and a driver. When connected with a DC power supply of 3 to 5 V, the oscillator can vibrate, and a fixed frequency in the range of 1.3 to 5.2 Hz is obtained after the frequency division, after amplification, the LED will emit flashing light.


3. Detection of LED

( 1 ) The pointer multimeter is transferred to RX 10k block with the pointer multimeter, and the red stylus and the black pen are respectively contacted with the measured diode pole ( black pen to positive, red pen and negative ), then the diode will shine, it is normal.

( 2 ) Digital multimeter is used to adjust the digital multimeter to the position of detecting diode, and the red pen and black pen are used to contact the two poles of the measured diode positive, black pen to negative ), when the diode will shine, it is normal.