The PC817 4-Channel Optocoupler Isolation Module uses light to safely pass signals between two separate electrical circuits. It protects weak parts, like a 3.3V or 5V micro-controller, from dangerous voltage spikes and noise coming from stronger external devices.

Input Signal Voltage: 3.6V to 24V DC
Output Voltage Range: 3.6V to 30V DC
Channels: 4 independent channels
Max Frequency: Up to 4 kHz (best for low-speed switching)
Jumpers: Onboard jumpers let you choose shared grounds or separate grounds. [1, 2, 3]

Voltage level shifting (e.g., matching a 24V industrial sensor to a 5V Arduino).
Noise reduction in motor drivers and switching circuits.
Protecting microcontrollers from high-voltage feedback