We need to check parameters and Pin configuration carefully before replacing. Replacing without taking voltage, current and frequency parameters may lead to permanent damage. This setup is not feasible as microcontroller is sensitive device. The internal setup of two components can be seen below.
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When the IR led is powered the light from it falls on the transistor and it conducts. This IC is used to provide electrical isolation between two circuits, one part of the circuit is connected to the IR LED and the other to Photo-transistor. The digital signal given to the IR LED will be reflected on the transistor but there will be no hard electrical connection between the two.
This comes in very handy when you are trying to isolate a noisy signal from your digital electronics, so if you are looking for an IC to provide optical isolation in your circuit design then this IC might be the right choice for you. Out of which the Phototransistor mode is mostly used, so let us look at that mode first.
In the Photo-transistor mode we will not be using the base pin pin 6 of the transistor; we just have to connect the anode pin of the IR LED pin 1 to the logic input which has to be isolated and the cathode pin 2 of the IR led to the ground.
Then Pull high the collector pin of the transistor using a resistor here I have used 1K and connect the collector pin to the output of your desired logic circuit. The Emitter pin 4 is grounded.
This is where the isolation occurs. There pull-up resistor 1K acts as a load resistor. But when the Logic input is made high, this high voltage should be a minimum of 1.
This will short the collector and emitter and hence the Logic Output voltage will become zero. This way the logic input will be reflected at the logic output and still provides and isolation between the two. The complete working can also be understood form the GIF file above. Another important parameter to consider while using an Optocoupler, is the rise time tr and fall time tf.
The output will not get high as soon as the input logic is made low and vice versa. The below waveform shows the time taken for the output to transit from one state to another.
IC MCT2E PHOTOTRANSISTOR OPTOCOUPLER
Opto Couplers – Types & Applications