2-Channel 5V Relay Board with Optocoupler Isolation

This board lets a microcontroller switch mains-powered devices - lamps, pumps, small motors - that its own GPIO pins could never handle directly. Two SPDT relays, each rated for 10A at 250V or 15A at 125V, are triggered by a low-level 3.3-5V logic signal, so it works the same on a 5V Arduino or a 3.3V board like an ESP32 without extra driver circuitry.

The optocoupler on each channel is what makes the isolation real rather than nominal: it breaks the electrical connection between the low-voltage control side and the high-voltage switched side, so a fault on the load side has no path back into the microcontroller. A status LED per channel shows relay state at a glance, useful when debugging which channel actually fired.

Standard building block for home automation projects, appliance timers, and any control system that needs a microcontroller to turn a mains-powered device on and off safely.