Led in the 1960s to the 80 's before the more than 10 years, the LED only red, yellow, green several colors, luminous efficiency is very low (only about 1 lm), the brightness is low, and the price is high, people just use it as the indicator of electronic products. From the development and application of LED, this period is the indication application stage of LED.
1 AC Power LED
As long as the circuit connected to the 220v/50hz AC power supply line, the LED will be lit, indicating that the power is connected. The resistance of the current limiting resistor R is 220v/if.
2 AC Switch Indicator
Using LED for incandescent lamp switch indicator circuit, when the switch off the lamp, the current through R, led and light bulb El Formation circuit, LED light, convenient for people in the dark to find the switch. At this point the current in the loop is very small, the bulb is not bright. When the switch is switched on, the bulb is lit and the LED goes out.
3 AC power outlet LED
Use two-color (common cathode) led for AC power outlet led circuit. The power supply of the socket is controlled by the switch s. When the red light is on, the socket is not electric;
4 Safety Tube Seat indicator
The LED is used as the circuit of the safety tube seat indicator of the factory equipment distribution box. When the safety tube is intact, the LED is not bright; when the fuse is fused, the LED is lit to indicate which fuse has been burnt and replaced. This is very convenient for the porcelain core type fuse which can not observe the good or bad with the naked eye.
5 LED Advertising Sign Lamp
6 LED monochrome or color display
The general monochrome display is used to display a single character, and the color display is used for outdoor large screen TV.
7 LED Street Lamp
8 LED car lights and led electric car lights