What activates an Opto-isolated solid state relay?

• A. Voltage
• B. Current
• C. Light
• D. Temperature

Answer: (C)

An opto-isolated solid state relay operates through the use of an optocoupler, which is designed to isolate the input from the output while allowing control signals to pass through. This technology utilizes light as the medium of communication between its components. When a voltage is applied to the input side, it energizes an internal LED within the optocoupler, which emits light. This light, in turn, activates a photodetector component on the output side, allowing the relay to switch on or off without any direct electrical connection between the control side and the load side.

Therefore, light is the key element that activates the relay, making this option correct. Understanding how this isolation works is crucial for applications where you need to control high voltages or currents safely, as it protects sensitive components from electrical interference and surges that can arise in the output circuit.