Question

Which of the following device provides isolation between the input circuit and output circuit?

• A. Photo transistor
• B. Opto-coupler
• C. LED
• D. Seven segment display

Hint:

Opto-couplers are like a "bridge made of light." Use them whenever you need to control a high-voltage motor circuit using a low-voltage microcontroller like an Arduino or PLC.

Answer 1

The Correct Option is B

In many electronic systems, it is necessary to transfer a signal from one part of a circuit to another while keeping them electrically isolated to prevent high voltages from damaging sensitive components or to eliminate noise. 1. Function of an Opto-coupler: An opto-coupler (also known as an opto-isolator) consists of an LED (light source) and a photosensor (like a phototransistor) encapsulated in a single package. The input signal triggers the LED, which emits light across an internal transparent gap. The photosensor on the output side detects this light and generates a corresponding electrical signal.

2. Electrical Isolation: Since the only link between the input and output is

light, there is no direct electrical connection. This "Galvanic Isolation" can often withstand thousands of volts between the input and output stages.

3. Why the others are incorrect:

• Photo transistor: This is just the receiving component; by itself, it doesn't provide the "coupling" from an input circuit.

• LED: This is just the light-emitting component.

• Seven segment display: This is an output device used to display numbers, not to isolate signals between circuits.