This is a LOW Level 5V 8-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 equipped with high-current relays that work under AC 250V 10A or DC 30V 10A. It has a standard interface that can be controlled directly by micro-controller.

Features:

• Power Supply Voltage: 5VDC, 12VDC
  
• Current: Greater than 100mA
  
• Load: 250V 10A AC or 30V 10A DC
  
• Size: 134.6mm x 53.6mm x 19.5mm (LxWxH)
  
• Equipped with mounting holes around, hole diameter 3.1mm
  
• Relay Type: Single Pole Double Throw (SPDT)
  
• Optocoupler isolation, good anti-interference capability
  
• When input is at low level, the relay is off, and the indicator light is on.
• Standard interface that can be directly controlled by microcontroller (8051, AVR, PIC, DSP, ARM, MSP430, TTL logic)

Pinouts:
The module features a design that includes both input and output connections.

On the input side, where it receives the trigger signal, the connections typically include three or four pins, as outline din the relay module circuit diagram:

• VCC: This is the positive power supply input from the main control.
• GND: Ground connection.
• IN1~IN8: The signal input pins for the relays. When a low-level signal is input, the Normally Open (NO) contact of the relay connects with the Common (COM) terminal. 
• JD-VCC: This pin is for the relay's power supply. Connecting JD-VCC and VCC with a jumper cap indicates that the relay is powered by the main control board's power supply. Alternatively, an external power supply can be connected to this pin to power the relay. On the output side, the relay module has three connections:
• NO (Normally Open): This is the load connection when the relay is active (ON). In the off state, NO is not connected to the COM (Common) terminal. 
• COM (Common): This terminal serves as the common connection for both NO and NC (Normally Closed) pins.
• NC (Normally Closed): This is the default load connection, which is connected to the COM terminal when the relay is OFF or in its default state.