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What is LED?
A light-emitting diode (LED) is a semiconductor light source. LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates are also useful in advanced communications technology.
What is LED Blinking?
LED blinking is same as eye blinking. Close and open eyes is called an eye blink in same manner on-off-on (or off-on-off)transition of an led is an LED blink. If such process is done repeatedly it is said LED Blinking.
Why to do LED Blinking?
LED blinking is considered as the first project to learn any microcontroller interfacing. It is considered as âHello worldâ for embedded system.
LED blinking is also useful to make some indications (Slow blinking may be for normal operation and fast blinking may be used for a malfunction or faulty condition).
You can use LED for debugging your embedded applications.
In optical fiber and Infrared Communications LEDs are used as transmitter.
How to do LED blinking?
Here is a quick review about how you can do LED blinking.
LED Blinking Circuits
LED blinking with One transistor
LED blinking with one transistor
LED blinking with Two transistors
LED blinking with AC mains voltage
LED blinking with AC (mains) voltage
LED blinking circuit to blink led at Line voltage
LED Blinking with Solar Power (Infinity Blinker)
We have seen this circuit earlier. This circuit donât need any power source other than Solar power and as of now it is still working from last 5 years.
LED blinking circuit with solar power
LED Blinking with LM3909 IC
LED Blinking with 555 timer IC
to calculate timer time period have a look at 555 timer frequency calculator.
LED Blinking with Op-Amp
LED blinking circuit with Op-amp
LEDs that blink by themselves
Till now we have seen normal LEDs that behave normally so we need external circuit to make them blink, but here is an LED that Blinks  by itself you just have to apply DC voltages. Within the supply voltage range, no series resistor is required. These LEDs have a built-in blinking IC and have a blinking frequency from 3Hz to 1.5Hz.
How to connect LED with Microcontroller?
To connect LED with Microcontroller you have to put current limiting resistor, you can use this online LED Resistor calculator tool or you can use this awesome dial.  You can connect LED either in sink or source configuration.They are shown below.
Sink Or Source Logic Selection
LED Blinking with different Microcontrollers
LED Blinking With 8051 microcontroller
For more detail: A complete guide for LED Blinking
