4-Channel 5V Relay Module with Optocoupler Isolation

Switching real-world loads safely from a microcontroller

This 4-channel relay module lets a low-power microcontroller such as an Arduino, AVR, PIC or ARM board switch much larger loads than its own pins could ever handle directly, controlling various appliances and other equipment that draw significant current. Each of its four channels is rated to switch up to AC250V at 10A or DC5V at 10A, which covers everything from small household devices to low-voltage DC motors and lighting circuits.

The key safety feature is optocoupler isolation on each channel, which uses light rather than a direct electrical connection to pass the switching signal from the microcontroller side to the relay coil side. That isolation protects the microcontroller from voltage spikes, back-EMF or any electrical fault on the switched load side of the circuit.

Design details

Relay operating voltage on the control side is 3.3V to 5V, so it works directly with both common logic levels without extra circuitry, and each relay includes both a normally closed and a normally open contact for wiring flexibility depending on whether a load should be on or off by default. A triode drive stage with a high-impedance controller pin and a pull-down circuit both help prevent the relay from triggering accidentally due to noise or a floating input.

Power supply and control status indicator lamps are built into the board, giving a quick visual check of which channels are active and whether the board itself is receiving power, useful when the module is tucked inside an enclosure with the relays' own clicking sound as the only other feedback.

Who it suits

Home automation projects, irrigation controllers, and any build needing a microcontroller to safely switch mains-level or higher-current DC loads will find this 4-channel isolated relay module a standard, well-protected way to do it.

Questions buyers ask

How many channels does it have?

4, each independently controllable.

What is the maximum load it can switch?

AC250V at 10A, or DC5V at 10A, per channel.

Why does it use optocoupler isolation?