This is a 5V 4-channel relay or four channel relay module 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. Size: 75mm (Length) * 55mm (Width) * 19.3mm (Height) Weight: 61g PCB Color: Blue There are four fixed screw holes at each corner of the board, easy for install and fix. The diameter of the hole is 3.1mm High quality Songle relay is used with single pole double throw, a common terminal, a normally open terminal, and a normally closed terminal Optical coupling isolation, good anti-interference. Closed at low level with indicator on, released at high level with indicator off VCC is system power source, and JD_VCC is relay power source. Ship 5V relay by default. Plug jumper cap to use The maximum output of the relay: DC 30V/10A, AC 250V/10A Size: 75mm (Length) * 55mm (Width) * 19.3mm (Height) Weight: 61g PCB Color: Blue There are four fixed screw holes at each corner of the board, easy for install and fix. The diameter of the hole is 3.1mm High quality Songle relay is used with single pole double throw, a common terminal, a normally open terminal, and a normally closed terminal Optical coupling isolation, good anti-interference. Closed at low level with indicator on, released at high level with indicator off VCC is system power source, and JD_VCC is relay power source. Ship 5V relay by default. Plug jumper cap to use The maximum output of the relay: DC 30V/10A, AC 250V/10A