Monday, July 30, 2012

How Opto Coupler works? Animation

What is opto coupler?

 An opto-coupler is an optical link and it connects two circuits via this link.
The optical link is contained within a chip. A Light Emitting Diode inside the chip shines on a photo-diode, photo-transistor or other photo device. When the photo device sees illumination, the resistance between its terminals reduces. This reduced resistance can activate another circuit.  

Other Names: 

OPTO-ISOLATORS or PHOTO-COUPLERS.

Operation:

 The LED requires 1mA to 15mA.

What does this mean?

If the current-limiting resistor connected to the LED has a high value, only a small current will flow through the LED and it will not glow very brightly. (The LED is inside the chip - you cannot see it).
The transistor will not turn on very much and the resistance between the collector-emitter terminals will be fairly HIGH. The output voltage will remain fairly HIGH.
As the current through the LED increases, (the current-limiting resistor is reduced in value) the LED will glow brighter and the transistor will turn on harder. The output voltage in the diagram above will reduce.
If the current through the LED is allowed to rise and fall, the output voltage of the circuit above will fall and rise. In this way the opto-coupler will pass AUDIO.
If the current through the LED changes instantly from zero to say 15mA, the output will change from HIGH to LOW. This is the principle of SWITCHING or passing a DIGITAL SIGNAL


Hardwork Can Never Ever Fails...
Best luck...

 


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