Ungrouped,High Quality Ungrouped,Ungrouped Details, CN Shenzhen Waweis Technology Co., Ltd. , https://www.laptopsasdapter.com
1 
Easy test of LED
First, the main features of LED (1) low operating voltage, some only need 1.5 - 1.7V to turn on the light; (2) small operating current, typical value is about 10O; (3) has a single guide similar to ordinary diode The electrical characteristics are only slightly higher in the dead zone voltage; (4) have the similar voltage regulation characteristics as the silicon Zener diode; (5) the response time is fast, the time from the voltage application to the light emission is only 1 to 10 ms, and the response frequency is up to 100Hz; the service life is long, generally up to 100,000 hours. Currently used LEDs have red and green phosphorescent (GaP) LEDs with a forward voltage drop of VF=2.3V; a red-emitting phosphorous arsenic (GaASP) LED with a forward voltage drop of VF = 1.5 - 1.7V; and yellow and blue LEDs with silicon carbide and sapphire, with a forward voltage drop of VF = 6V. Since the forward volt-ampere curve of the LED is steep, in the application, the current limiting resistor must be connected in series to avoid burning the tube. In the DC circuit, the current limiting resistor R can be estimated by the following equation: R = (E - VF) / IF In the AC circuit, the current limiting resistor R can be estimated by the following equation: R = (e - VF ) / 2IF, where e Is the effective value of the AC power supply voltage. Second, the test of LEDs In the absence of special equipment, LED can also be estimated with a multimeter (here MF30 multimeter as an example). First, place the multimeter in Rx1k or Rx100 and measure the forward and reverse resistance of the LED. If the forward resistance is less than 50kΩ, the reverse resistance is infinite, indicating that the tube is normal. If both the positive and negative directions are zero or both infinity, or the positive and negative resistance values ​​are relatively close, it indicates that there is a problem with the tube. Then, you must also measure the LED's illumination. Because the forward voltage drop is 1.5V or more, it can not be directly measured by Rx1, Rx1O, Rx1k. Although the R x1Ok file uses a 15V battery, the internal resistance is too high, and the tube cannot be turned on. However, the double table method can be used for testing. The two multimeters are connected in series and placed in the Rx1 gear. The total battery voltage is 3V and the total internal resistance is 50Ω. The operating current supplied to the L-print is greater than 10mA, which is enough to make the tube conduct light. If a tube does not illuminate during the test, there is a problem with the tube. For VF=6V LEDs, it can be tested with a 6V battery and a current limiting resistor.