Relay plays an important role in automatic systems. Mini Relay module can be used in many system.


- Dimension: 50×30mm.

- Voltage of controller: 3.3V÷5V.

- Voltage of relay: 12V.

- Type of relay: 220V – 10A.

Figure 1: Dimension of board



- VLR: Voltage of relay.

- VCC: Voltage of controller.

- CTRL: Control signal.

- GND: Ground.


- NC: Normally Closed.

- NO: Normally Open.

- COM: Common terminal


- POWER: Indicate power supply.

- SIGNAL: Indicate control signal. Control signal is high level, SIGNAL LED turns off. Control signal is low level, SIGNAL LED turns on.

3.Operating principle

Figure 2: Operating principle of relay module

When control signal is low level, diode in U1 enables, U1 operates. U1 allows the current to pass through, the transistor Q1 is in saturation mode, and relay switches its status from “NC” to “NO”. LED LD1 turns on. When control signal is high level, diode in U1 disables, U1 doesn’t operate. U1 permits the current to pass through, the transistor Q1 is in cutoff mode, and relay is in normal mode “NO”. LED LD1 turns off.


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