This is a 4 Channel 5V Relay Module-channel relay interface board, and each channel needs a 15-20mA driver current. It can be used to control various appliances and equipment with large current. It is equiped with high-current relays that work under AC250V 10A or DC30V 10A. It has a standard interface that can be controlled directly by microcontroller.
From the picture below, you can see that when the signal port is at low level, the signal light will light up and the optocoupler 817c (it transforms electrical signals by light and can isolate input and output electrical signals) will conduct, and then the transistor will conduct, the relay coil will be electrified, and the normally open contact of the relay will be closed. When the signal port is at high level, the normally closed contact of the relay will be closed. So you can connect and disconnect the load by controlling the level of the control signal port.
VCC: Positive supply voltage
IN1–IN4: Relay control port
Connect a load, DC 30V/10A，AC 250V/10A
When the input terminals (IN1, IN2, IN3, IN4) are supplied with low level signals, you can see relay K1, K2, K3, K4 closed successively and repeat this cycle. In order to show its the ability of driving load more intuitively, two LEDs are connected to relay K1 and K2.
Build the circuit
|4 Channel relay shield||SunFounder uno R3|
Then upload the code. You should see the relays close one by one and the LED on the board and the LEDs connected to K1 and K2 light up or go out with the relays opened
You can use this 4-channel relay to drive some household appliances, such as table lamp, fan, etc.